[Replacing HVAC - considering heat pump]

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MortgageOnBlack
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[Replacing HVAC - considering heat pump]

Post by MortgageOnBlack »

[Moved into a new thread from: Heat pumps --admin LadyGeek]

Our furnace and AC are almost 20 years old. The original install was not done too well (return duct was overlapping the filter :shock: and other issues that I have repaired myself (control board, flame igniter, flame sensor). It i still trucking along and I believe I'll get one more winter out of it, but I am considering replacing this system during the slow season in spring or next Fall.

I'm looking into an American Standard furnace, but am considering using a Heatpump for the AC (and possibly supplement the heat? Not sure).

Bumping this thread to see if any other bogleheads are shopping around for HVAC and for what setup.
Valuethinker
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Re: Heat pumps

Post by Valuethinker »

MortgageOnBlack wrote: Mon Nov 29, 2021 9:50 pm Our furnace and AC are almost 20 years old. The original install was not done too well (return duct was overlapping the filter :shock: and other issues that I have repaired myself (control board, flame igniter, flame sensor). It i still trucking along and I believe I'll get one more winter out of it, but I am considering replacing this system during the slow season in spring or next Fall.

I'm looking into an American Standard furnace, but am considering using a Heatpump for the AC (and possibly supplement the heat? Not sure).

Bumping this thread to see if any other bogleheads are shopping around for HVAC and for what setup.
Knowing where you are located makes a big difference.

If you live in Wisconsin or Minnesota, say, then your HP is going to need a backup. Whether electric bar or gas/propane.

My relation, on an exposed ridge in S-Central Ontario (so warmer, probably, most days than WI by at least 10 degrees F), had a Ground Source HP (geothermal). 1970s home but not well insulated or airtight (I think the walls were R12 - despite the energy crisis on the 1970s, home manufacturers were slow to upgrade their kit designs).

The GSHP served admirably well for 25 years post installation. Their backup was a glass-doored wood fireplace, with a huge central chimney & hearth. Kept the fire going 16 hours a day plus glowing at night, heated the rock.

They retired there and the air conditioning was extremely useful w the very hot summers & heat waves that have become normal. Medical advice was not to have too big a gap from outside temp so they kept it in the high 70s.

If you live in coastal California, or indeed any of the south eastern US States, an ASHP should provide more than adequate heating in winter & cooling in summer, assuming efficient ductwork & correctly sized. If you live in the Midwest or North East, it might not.
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Re: Heat pumps

Post by MortgageOnBlack »

Valuethinker wrote: Tue Nov 30, 2021 5:52 am
MortgageOnBlack wrote: Mon Nov 29, 2021 9:50 pm Our furnace and AC are almost 20 years old. The original install was not done too well (return duct was overlapping the filter :shock: and other issues that I have repaired myself (control board, flame igniter, flame sensor). It i still trucking along and I believe I'll get one more winter out of it, but I am considering replacing this system during the slow season in spring or next Fall.

I'm looking into an American Standard furnace, but am considering using a Heatpump for the AC (and possibly supplement the heat? Not sure).

Bumping this thread to see if any other bogleheads are shopping around for HVAC and for what setup.
Knowing where you are located makes a big difference.

If you live in Wisconsin or Minnesota, say, then your HP is going to need a backup. Whether electric bar or gas/propane.

My relation, on an exposed ridge in S-Central Ontario (so warmer, probably, most days than WI by at least 10 degrees F), had a Ground Source HP (geothermal). 1970s home but not well insulated or airtight (I think the walls were R12 - despite the energy crisis on the 1970s, home manufacturers were slow to upgrade their kit designs).

The GSHP served admirably well for 25 years post installation. Their backup was a glass-doored wood fireplace, with a huge central chimney & hearth. Kept the fire going 16 hours a day plus glowing at night, heated the rock.

They retired there and the air conditioning was extremely useful w the very hot summers & heat waves that have become normal. Medical advice was not to have too big a gap from outside temp so they kept it in the high 70s.

If you live in coastal California, or indeed any of the south eastern US States, an ASHP should provide more than adequate heating in winter & cooling in summer, assuming efficient ductwork & correctly sized. If you live in the Midwest or North East, it might not.
We are in Colorado. Summers have been getting quite hot, but we do get freezing temperatures every year(this year hasn't been too many though)
IMD801
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Re: Heat pumps

Post by IMD801 »

Lee_WSP wrote: Sun Jan 03, 2021 1:31 pm
Not my area of expertise, but my reasoning is that since the air heat pump doesn't work or work well below 40 degrees anyway, I don't think there's a difference when heating. When it kicks into using the alternative heating method otoh....

That said, I'm in Phoenix, my heating costs are probably less than most people's electricity bill. Summer otoh... Ugh
This is a commonly repeated and incorrect statement about heat pumps I heard from several HVAC companies until I found a knowledgeable one and did some of my own research. The performance of modern heat pumps down to extremely cold temperatures is outstanding. Our new unit has backup electric heat that will turn on at 10F if needed but the heat pump is actually capable of working way below that. The efficiency is quite high until 10-15F and even then not too bad. (Daikin VRV system, air source)
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Lee_WSP
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Re: Heat pumps

Post by Lee_WSP »

IMD801 wrote: Tue Nov 30, 2021 11:13 am
Lee_WSP wrote: Sun Jan 03, 2021 1:31 pm
Not my area of expertise, but my reasoning is that since the air heat pump doesn't work or work well below 40 degrees anyway, I don't think there's a difference when heating. When it kicks into using the alternative heating method otoh....

That said, I'm in Phoenix, my heating costs are probably less than most people's electricity bill. Summer otoh... Ugh
This is a commonly repeated and incorrect statement about heat pumps I heard from several HVAC companies until I found a knowledgeable one and did some of my own research. The performance of modern heat pumps down to extremely cold temperatures is outstanding. Our new unit has backup electric heat that will turn on at 10F if needed but the heat pump is actually capable of working way below that. The efficiency is quite high until 10-15F and even then not too bad. (Daikin VRV system, air source)
If they're in the ground, they certainly function, but in Arizona the coils kick on at about forty degrees. Modern ones may be better. I don't know.
talzara
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Re: Heat pumps

Post by talzara »

IMD801 wrote: Tue Nov 30, 2021 11:13 am This is a commonly repeated and incorrect statement about heat pumps I heard from several HVAC companies until I found a knowledgeable one and did some of my own research. The performance of modern heat pumps down to extremely cold temperatures is outstanding. Our new unit has backup electric heat that will turn on at 10F if needed but the heat pump is actually capable of working way below that. The efficiency is quite high until 10-15F and even then not too bad. (Daikin VRV system, air source)
Lee_WSP wrote: Tue Nov 30, 2021 11:37 am If they're in the ground, they certainly function, but in Arizona the coils kick on at about forty degrees. Modern ones may be better. I don't know.
These are air-source heat pumps, so they are not in the ground, nor do they stop working at 40°F. In fact, they work better in Arizona than in New England because the air is dry, so they will waste less energy on defrosting.

The word that you missed is "Daikin." This is a large Japanese HVAC manufacturer. In fact, it's the largest HVAC manufacturer in the world.

Asian low-temperature heat pumps are designed as heat pumps first. They are designed to achieve 100% of rated heating capacity down to 5°F, and some of the high-end ones can achieve 100% of rated capacity below 0°F. They are then run in reverse for air conditioning, which makes them oversized in heating-dominated climates, so most of them have inverter-driven motors to operate at partial capacity.

American heat pumps are designed as air conditioners first, and they are run in reverse for heating. The heating capacity is usually specified at 47°F, and performance drops off rapidly at lower temperatures. It is not unusual to be putting out less than 25% of rated capacity at 5°F.

Daikin owns Goodman. Take a look at Daikin's global website to see where its American subsidiary actually stands:
A unitary lineup is offered in the North American residential market.

https://www.daikin.com/products/ac/lineup/duct_unitary
"Unitary" is what Daikin calls conventional American ducted heat pumps. They're not sold in South America, Europe, Asia, Africa, or Oceania. Nobody would buy them because they'd just buy real Daikin heat pumps.

The American HVAC manufacturers have held on because of cheap energy, established construction methods, and an entrenched contractor base. They are far behind the Asian HVAC manufacturers on technology.
Last edited by talzara on Wed Dec 01, 2021 4:37 pm, edited 1 time in total.
inverter
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Re: Heat pumps

Post by inverter »

IMD801 wrote: Tue Nov 30, 2021 11:13 am This is a commonly repeated and incorrect statement about heat pumps I heard from several HVAC companies until I found a knowledgeable one and did some of my own research. The performance of modern heat pumps down to extremely cold temperatures is outstanding. Our new unit has backup electric heat that will turn on at 10F if needed but the heat pump is actually capable of working way below that. The efficiency is quite high until 10-15F and even then not too bad. (Daikin VRV system, air source)
Completely agree. I also found a very knowledgeable installer who did a Manual J for us and we also went with a Daikin VRV system. More info here: viewtopic.php?p=6307966#p6307966

Doing it again, I would start with a home energy audit and blower door test.
Turbo29
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Re: Heat pumps

Post by Turbo29 »

Lee_WSP wrote: Tue Nov 30, 2021 11:37 am
IMD801 wrote: Tue Nov 30, 2021 11:13 am
Lee_WSP wrote: Sun Jan 03, 2021 1:31 pm
Not my area of expertise, but my reasoning is that since the air heat pump doesn't work or work well below 40 degrees anyway, I don't think there's a difference when heating. When it kicks into using the alternative heating method otoh....

That said, I'm in Phoenix, my heating costs are probably less than most people's electricity bill. Summer otoh... Ugh
This is a commonly repeated and incorrect statement about heat pumps I heard from several HVAC companies until I found a knowledgeable one and did some of my own research. The performance of modern heat pumps down to extremely cold temperatures is outstanding. Our new unit has backup electric heat that will turn on at 10F if needed but the heat pump is actually capable of working way below that. The efficiency is quite high until 10-15F and even then not too bad. (Daikin VRV system, air source)
If they're in the ground, they certainly function, but in Arizona the coils kick on at about forty degrees. Modern ones may be better. I don't know.
No heat strips on my heat pump (Phoenix) nor most people I know around here. Has always heated just fine even in the rare times we had lows in the high 20's. It ran noticeably longer but still heated.
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rivercrosser
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Re: Heat pumps

Post by rivercrosser »

I wasn't considering a heat pump. My whole system got wiped out by lightning back in Aug. Had a propane modulating furnace and regular single speed split ac. Wanted to go back with Lennox equipment and maybe upgrade the AC to a variable compressor. Lennox dealer couldn't find the furnace I wanted so I ended up with the Carrier dealer. He didn't have the AC unit I was interested about in stock. He ended up offering me a heat pump for the same price as a regular AC unit and I was able to get a $500.00 rebate from the power company so it was a no brainer. He said the only difference is the outside unit has a reversing valve in in. Right now, I have it set up to run on the heat pump above 35 and gas below 35. Install guys said the heat pump would work down to 10 degrees or lower but I'm trying to save some wear and tear on it. It's the best system Carrier makes, fully variable, modulates up and down. I was surprised how warm of air the heat pump puts out. Works really good. Be interesting to see how warm of air it puts out in really cold weather. The only thing I don't like about the heat pump vs. the gas heat is the blower is a little louder when its running at 100% capacity. The heat pump needs more airflow for the indoor coil (same as AC in summer) than when on gas heat. When not bringing up the room temp from a setback and just maintaining the set temp it doesn't run at 100% much. I've used the system for the whole month of November now, mostly on the heat pump so I'm anxious to see how much electric it used for the month.
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Re: Heat pumps

Post by bradinsky »

We have a Carrier heat pump & variable speed air handler installed in 10/2015 & a Bosch inverter heat pump paired with an American Standard variable speed air handler installed 5/2019. I love the Bosch heat pump set up & it takes a lot of self control to keep from replacing the Carrier unit with a Bosch. The Bosch puts the Carrier unit to shame. It cools well & never has had any issues keeping up with the northern Ohio winters.

FWIW, Carrier Corporation used to be owned by United Technologies & was spun off into an independent, free standing company (CARR) in 2020. Not owned by Daiken.
Valuethinker
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Re: Heat pumps

Post by Valuethinker »

MortgageOnBlack wrote: Tue Nov 30, 2021 9:22 am
Valuethinker wrote: Tue Nov 30, 2021 5:52 am
MortgageOnBlack wrote: Mon Nov 29, 2021 9:50 pm Our furnace and AC are almost 20 years old. The original install was not done too well (return duct was overlapping the filter :shock: and other issues that I have repaired myself (control board, flame igniter, flame sensor). It i still trucking along and I believe I'll get one more winter out of it, but I am considering replacing this system during the slow season in spring or next Fall.

I'm looking into an American Standard furnace, but am considering using a Heatpump for the AC (and possibly supplement the heat? Not sure).

Bumping this thread to see if any other bogleheads are shopping around for HVAC and for what setup.
Knowing where you are located makes a big difference.

If you live in Wisconsin or Minnesota, say, then your HP is going to need a backup. Whether electric bar or gas/propane.

My relation, on an exposed ridge in S-Central Ontario (so warmer, probably, most days than WI by at least 10 degrees F), had a Ground Source HP (geothermal). 1970s home but not well insulated or airtight (I think the walls were R12 - despite the energy crisis on the 1970s, home manufacturers were slow to upgrade their kit designs).

The GSHP served admirably well for 25 years post installation. Their backup was a glass-doored wood fireplace, with a huge central chimney & hearth. Kept the fire going 16 hours a day plus glowing at night, heated the rock.

They retired there and the air conditioning was extremely useful w the very hot summers & heat waves that have become normal. Medical advice was not to have too big a gap from outside temp so they kept it in the high 70s.

If you live in coastal California, or indeed any of the south eastern US States, an ASHP should provide more than adequate heating in winter & cooling in summer, assuming efficient ductwork & correctly sized. If you live in the Midwest or North East, it might not.
We are in Colorado. Summers have been getting quite hot, but we do get freezing temperatures every year(this year hasn't been too many though)
I think a good ASHP - talzara mentions Daikin brand - should serve you well (if natural gas is not an option**). Once you get below c 15F, it will be electric bar, so it's helpful to have a backup (such as a good airtight wood stove or fireplace -- although I understand that air pollution control rules ban these in many jurisdictions in CO?). But if your electricity rates are not too high, and your home is well insulated + had a blower test and rectifications for air leaks, then electric bar for some days of the year is not the worst thing.

The problem in Ontario is humidity, not heat per se. That said, inland British Columbia (which has a similar geography and climate to Colorado) was nearly 110 degrees in the "heat dome" this summer. That possibility was not in my high school geography textbooks ...


Winters can be cold -- can get below 0 F in southern Ontario. Depends how far you are from Lake Erie & Lake Ontario. But it's mostly temperatures in the 20 to freezing range, but with wind chill a lot lower. Not a dry cold like they get in the Prairies so it's damp and it gets into you. Much warmer than Minneapolis (for sure) or Wisconsin (probably).

GSHPs work very well - perfect technology. ASHPs I don't think are a "thing" *except* on commercial buildings (where they might not have a gas connection). Propane is of course common. Don't know about fuel oil (there must still be people in rural areas who use it).


** you can check your utility's mix of fuel sources. Generally electricity is cleaner than natural gas BUT not always depending on mix. The relevant numbers are per kwhr 1 kg for coal, 550g for NG, 0 (by assumption) for wind/ hydro/ solar/ nuclear. Balance that off against 230 g/ kwhr of heat from a high efficiency furnace (because it doesn't lose all the energy trying to generate electricity - a coal fired plant is c 35% efficient, a gas fired one is c 50-55%; whereas your furnace can be mid 90%s efficient).

(in terms of local air pollution, gas is worse than electricity, of course; but cleaner than wood or coal & probably propane (not sure on that latter). Natural gas burn emits no sulphur dioxide, no particulates (PM2.5 size and below turn out to be the worst thing for health there is in air pollution terms) and some nitrous oxides).

Also, you have to think about what the mix will be in 10 years (your utility probably has some web pages on its future energy system plans, or your Public Utility Commission).
WhyNotUs
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Re: Heat pumps

Post by WhyNotUs »

I ended up buying a heat pump just to check out the technology. I bought a Mr Cool 3rd Gen. E Star unit for a 700 sf space. It comes with pre-charged lines for possible homeowner installation. It was about $1700 plus $150 for line set covers. I had a friend help me and it took about 5 hours to do the install for each of us. Part of that time was reading the instructions and watching videos and figuring out how to make a 90 degree turn around a corner of the house without kinking the line. Cutting the hole in the house was a little bit dramatic but it all worked out in the end. If I ever had to install another one it would go faster but I would still want 2 people.

In about a year I will have a sense of savings. A comparable Mitsubishi unit installed by a local contractor was $5,000 and that was not going to work for me, even with rebates.
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talzara
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Re: Heat pumps

Post by talzara »

bradinsky wrote: Tue Nov 30, 2021 7:51 pm We have a Carrier heat pump & variable speed air handler installed in 10/2015 & a Bosch inverter heat pump paired with an American Standard variable speed air handler installed 5/2019. I love the Bosch heat pump set up & it takes a lot of self control to keep from replacing the Carrier unit with a Bosch. The Bosch puts the Carrier unit to shame. It cools well & never has had any issues keeping up with the northern Ohio winters.
The Bosch IDS series (Inverter Ducted Split) is fully modulating in 1% increments.

Carrier only released a fully modulating heat pump in 2018: its top-of-the-line Infinity Greenspeed series. The next step down is the 5-stage Infinity VS, and it goes all the way down to single stage.
bradinsky wrote: Tue Nov 30, 2021 7:51 pm FWIW, Carrier Corporation used to be owned by United Technologies & was spun off into an independent, free standing company (CARR) in 2020. Not owned by Daiken.
I have edited my post to say that Daikin owns Goodman. The point is that American residential heat pumps are so far behind the state-of-the-art that Daikin will not distribute its own subsidiary's products outside North America.

However, Carrier also realizes that it is behind. Carrier sells ductless mini-splits in the United States: https://www.carrier.com/residential/en/ ... s-systems/

It's not American technology inside, though. It's Chinese. Carrier mini-splits are manufactured in a joint venture with Midea, which is the 3rd largest HVAC manufacturer in the world.
rivercrosser
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Re: Heat pumps

Post by rivercrosser »

I'm an hour away from St. Louis. I've never seen a Bosch or Daiken unit around here. I'm sure there's some but if you want someone local for quick service its pretty muwch Lennox or Carrier. A few other brands but one man operations. The local Carrier dealer has a really good reputation, does a lot more installs than anyone else around here. I was going to go with the Carrier 5 speed unit but he didn't know when he was going to get any in. Said it was a popular model. Ended up with the Greenspeed unit. Had to add some money to my insurance settlement but now that I have it I'm satisfied.
talzara
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Re: Heat pumps

Post by talzara »

rivercrosser wrote: Wed Dec 01, 2021 8:25 pm I'm an hour away from St. Louis. I've never seen a Bosch or Daiken unit around here. I'm sure there's some but if you want someone local for quick service its pretty muwch Lennox or Carrier. A few other brands but one man operations. The local Carrier dealer has a really good reputation, does a lot more installs than anyone else around here. I was going to go with the Carrier 5 speed unit but he didn't know when he was going to get any in. Said it was a popular model. Ended up with the Greenspeed unit. Had to add some money to my insurance settlement but now that I have it I'm satisfied.
Asian mini-splits are more common on the East Coast and the West Coast, especially in New England where many houses use hydronic heating.

Bosch has even more limited distribution. The Bosch USA website lists only two contractors within 25 miles of St. Louis that install HVAC systems. One of them is an error because it's a water heater company, and the other one is an HVAC company that only mentions American brands on its website. It may only install one Bosch unit per month. Bosch is a lot more popular in New York City.
Valuethinker
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Re: Heat pumps

Post by Valuethinker »

talzara wrote: Thu Dec 02, 2021 4:36 pm Bosch is a lot more popular in New York City.
Cultural convergence?

Bosch is the quintessential middle (upper middlesy) class appliance brand in the UK (I'd call it "the John Lewis market" - that's the largest chain of department stores, definitely not as upmarket as Nordstrom). And they own one of the largest brands of gas boilers (Worcester-Bosch)-- used w hydronic heating.

Heat Pumps I don't know what the brands are. Commercial equipment, it's all Japanese.
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Re: [Replacing HVAC - considering heat pump]

Post by TheGreyingDuke »

I volunteer as an Energy Navigator in Central NY; there is a big push to electrify everything and cold-climate, ASHP are definitely part of the mix. They have the capacity to handle temperatures to -13F, although the COP goes way down. Mostly Asian brands (Japan,Korea,with China beginning to have an impact)

The consumers most satisfied with the technology are those who had no access to natural gas (so heated with propane or oil),a forced air system, well insulated homes, and access to reasonably priced electricity.

On the other end of the satisfaction would be folks with natural gas access and an existing hydronic system.They were spending more and the quality of the heat was not up to that of a hydronic system,especially true of they had pipes buried in a slab. Of course the AC was a big plus.
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bluegill
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Re: [Replacing HVAC - considering heat pump]

Post by bluegill »

I live in the TN river valley. Electricity is relatively cheap here. TN Valley Authority electricity. Most homes have Heat Pumps with natural gas furnace in this area. I avoid brands that restrict access to repair parts. These companies sell parts only to Authorized dealers/repairmen. Goodman brand is manufactured in this area and parts are not restricted. My son went to HVAC school. Quality of installation is much more important the quality of hardware. Recommendation: Variable speed air handler is more comfortable and quieter than single speed air handler. It worth the money to pay for variable speed air handler.
Valuethinker
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Re: [Replacing HVAC - considering heat pump]

Post by Valuethinker »

TheGreyingDuke wrote: Fri Dec 03, 2021 6:42 am
On the other end of the satisfaction would be folks with natural gas access and an existing hydronic system.They were spending more and the quality of the heat was not up to that of a hydronic system,especially true of they had pipes buried in a slab. Of course the AC was a big plus.
This is really interesting.

Here (UK & Europe) the *best* setup for heat pumps (geothermal or air) is said by conventional wisdom to be underfloor heating (pipes in a concrete floor slab, typically). Forced air heating systems are pretty rare in residential homes in NW Europe, I would think (but common in commercial premises).

But the way the HP is used changes from a gas or oil furnace. "Low and slow" not "hot and fast". The slab has thermal mass, and with a well calibrated HP, which has a lower output water temperature than a gas boiler/ furnace, it takes much longer to get to the desired temperature. Thus: run the HP all the time, targetting the desired temperature. It will get there, and then stay there (assuming the house is otherwise well insulated). The result is a nice even heat - not the hot spots and cold spots that rads typically bring.

Is it possible that that adjustment in operating behaviour has just not been made? (Thinking of, for example, your posting from US DOE regarding nighttime setbacks (basically not to do them with HPs?).
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TomatoTomahto
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Re: [Replacing HVAC - considering heat pump]

Post by TomatoTomahto »

Valuethinker wrote: Fri Dec 03, 2021 7:58 am
TheGreyingDuke wrote: Fri Dec 03, 2021 6:42 am
On the other end of the satisfaction would be folks with natural gas access and an existing hydronic system.They were spending more and the quality of the heat was not up to that of a hydronic system,especially true of they had pipes buried in a slab. Of course the AC was a big plus.
This is really interesting.

Here (UK & Europe) the *best* setup for heat pumps (geothermal or air) is said by conventional wisdom to be underfloor heating (pipes in a concrete floor slab, typically). Forced air heating systems are pretty rare in residential homes in NW Europe, I would think (but common in commercial premises).

But the way the HP is used changes from a gas or oil furnace. "Low and slow" not "hot and fast". The slab has thermal mass, and with a well calibrated HP, which has a lower output water temperature than a gas boiler/ furnace, it takes much longer to get to the desired temperature. Thus: run the HP all the time, targetting the desired temperature. It will get there, and then stay there (assuming the house is otherwise well insulated). The result is a nice even heat - not the hot spots and cold spots that rads typically bring.

Is it possible that that adjustment in operating behaviour has just not been made? (Thinking of, for example, your posting from US DOE regarding nighttime setbacks (basically not to do them with HPs?).
I love our GSHP, but this is one of the few things I don’t care for. We have forced air delivery for our GSHP, as it was a retrofit. Since heat rises, dammit, our desire for a very cold bedroom (top floor) to sleep in means that I have to carefully manage the thermostat time settings (I have 4 daily times available) and it never quite satisfies. I should be embarrassed at the waste, but sometimes during the shoulder seasons I run the AC for our bedroom while running heat for the downstairs.

NB: for those considering forced air HPs, your ducts might not be optimal in retrofits. We redid many of our ducts, as “low and slow” wasn’t what they were set up for. It’s a great opportunity to add more returns, which many contractors (willfully) ignore since most consumers just pay attention to supply registers.
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sully45
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Re: Heat pumps

Post by sully45 »

That MrCool kit does look really slick. Being up north I'll definitely want a unit rated to -20F so I'll have to look around. It would be awesome if the industry did their best to simplify install for homeowners.

Our home energy auditor let me in last year that (I think Mitsuibuishi?) was working on a heat pump that was integrated into the hot water as well. Giving you a 'free' heat pump water heater (with an outdoor coil). Additionally in summer the waste heat from the AC can be dumped into the hot water instead of out doors.
Valuethinker
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Re: Heat pumps

Post by Valuethinker »

sully45 wrote: Fri Dec 03, 2021 10:13 am That MrCool kit does look really slick. Being up north I'll definitely want a unit rated to -20F so I'll have to look around. It would be awesome if the industry did their best to simplify install for homeowners.

Our home energy auditor let me in last year that (I think Mitsuibuishi?) was working on a heat pump that was integrated into the hot water as well. Giving you a 'free' heat pump water heater (with an outdoor coil). Additionally in summer the waste heat from the AC can be dumped into the hot water instead of out doors.
Heat Pump water heaters are pretty standard and widely available. Main issue is Natural Gas and electricity prices are so low in most North American jurisdictions that they are not worth installing (they may also be less reliable). (I pay roughly 2-2.5x average US retail electricity price and probably more than that in natural gas price - this is in England).

But the technology you describe is standard in "indirect" heating systems which are the (overwhelming?) norm in NW Europe (where HPs are used - most homes probably use gas, oil or propane in rural areas, wood in Scandinavia). i.e. the same heat source ("boiler" or HP) serves both a hot water rad circuit and hot water heating for cooking/ bathing.

Not sure about Japan (the home of the high performance HP) but I suspect so. So it won't take much tweaking for Mitsubishi to offer it in the USA -- it already exists.
talzara
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Re: [Replacing HVAC - considering heat pump]

Post by talzara »

Valuethinker wrote: Fri Dec 03, 2021 7:58 am
TheGreyingDuke wrote: Fri Dec 03, 2021 6:42 am
On the other end of the satisfaction would be folks with natural gas access and an existing hydronic system.They were spending more and the quality of the heat was not up to that of a hydronic system,especially true of they had pipes buried in a slab. Of course the AC was a big plus.
This is really interesting.

Here (UK & Europe) the *best* setup for heat pumps (geothermal or air) is said by conventional wisdom to be underfloor heating (pipes in a concrete floor slab, typically). Forced air heating systems are pretty rare in residential homes in NW Europe, I would think (but common in commercial premises).
They're not using heat pumps with radiant floor heating. They're replacing hydronic boilers with forced-air heat pumps. Having 80°F air blow past your skin at high speed is much less comfortable than having warm air gently rising from a 110°F floor.

Air-to-water heat pumps are very hard to find in the United States. The hydronic market is so small that the Asian HVAC manufacturers don't even sell their air-to-water heat pumps here. There are a couple of American companies that make air-to-water heat pumps for commercial installations and custom homes, but they are very expensive.

The HVAC industry in North America is very different from the rest of the world. That's how the American HVAC manufacturers fell so far behind the state-of-the-art. They grew fat and lazy selling to the American market, while the rest of the world moved on.
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Re: [Replacing HVAC - considering heat pump]

Post by twh »

MortgageOnBlack wrote: Mon Nov 29, 2021 9:50 pm [Moved into a new thread from: Heat pumps --admin LadyGeek]

Our furnace and AC are almost 20 years old. The original install was not done too well (return duct was overlapping the filter :shock: and other issues that I have repaired myself (control board, flame igniter, flame sensor). It i still trucking along and I believe I'll get one more winter out of it, but I am considering replacing this system during the slow season in spring or next Fall.

I'm looking into an American Standard furnace, but am considering using a Heatpump for the AC (and possibly supplement the heat? Not sure).

Bumping this thread to see if any other bogleheads are shopping around for HVAC and for what setup.
As at least one person mentioned, there are dual-fuel units. It can run on natural gas or electric heat pump and the thermostat decides which depending on how you set it. Might be a good idea, especially in CO, as more or more stuff is getting solar panels. And, if gas or electric prices spike crazy you can change it around.
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Re: Heat pumps

Post by talzara »

sully45 wrote: Fri Dec 03, 2021 10:13 am Our home energy auditor let me in last year that (I think Mitsuibuishi?) was working on a heat pump that was integrated into the hot water as well. Giving you a 'free' heat pump water heater (with an outdoor coil). Additionally in summer the waste heat from the AC can be dumped into the hot water instead of out doors.
Mitsubishi already makes an air-to-water heat pump. It's been available in Australia since at least 2016: https://www.mitsubishielectric.com.au/a ... rk-web.pdf

The other Asian HVAC manufacturers have also been making air-to-water heat pumps for years. They just don't sell them in the United States because the hydronic market is too small.

If Mitsubishi Electric releases its air-to-water heat pump in the United States, hopefully the other Asian HVAC manufacturers will follow.
Valuethinker wrote: Fri Dec 03, 2021 11:30 am Heat Pump water heaters are pretty standard and widely available. Main issue is Natural Gas and electricity prices are so low in most North American jurisdictions that they are not worth installing (they may also be less reliable). (I pay roughly 2-2.5x average US retail electricity price and probably more than that in natural gas price - this is in England).
This is another case where the United States is different from the rest of the world.

American "heat pump water heaters" draw heat from the air inside your house (sometimes a basement or garage). The Asian HVAC companies make air-to-water heat pumps, which draw heat from the air outside the house.
Last edited by talzara on Fri Dec 03, 2021 2:14 pm, edited 1 time in total.
ktdintex
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Re: [Replacing HVAC - considering heat pump]

Post by ktdintex »

My RV has two heat pumps for AC and heating. They work great as long as it isn't too hot (above 90 degrees) or cold (below 40's). However, outside those ranges, they really struggle to cool and heat.

Our pool also has a huge heat pump, which also acts like a chiller. Exact same experience - works well within a middle temperature range but not outside that.

Personally, I'm not a fan.
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illumination
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Re: [Replacing HVAC - considering heat pump]

Post by illumination »

I'd stick with a gas furnace for winters in Colorado.

I personally just prefer how the heat feels from a gas furnace as opposed to the "clammy" feeling a heat pump provides in a cold climate. I have a vacation house in a climate very similar to Denver, there's no way I'd ditch the gas furnace for an electric only heat pump.

In terms of utility costs between the two, there's a a lot of factors, but I'd be willing to pay the extra if it came down to that (but I would wager an "average" central air heat pump though is more expensive to operate and has less service life than a gas furnace in colder climates)
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Re: [Replacing HVAC - considering heat pump]

Post by jharkin »

It’s funny that these heat pump threads keep popping up me every time the same people insist they don’t work below 40.

That is 1980s thinking that is simply NOT true anymore. Mitsubishi, Fujitsu, Daikin and others all make cold climate heat pumps that provide full rated BTUs down to -15F and partial heat even lower.
If your contractor tells you you need to switch to backup heat at 40, or even 30, you need to fire them and find a contractor that actually knows what they are talking about.

I installed a 2.5 T Mitsubishi hyper heat ducted unit to supplement my propane hot water baseboard. It’s been down to 24F already and it’s not even running full time, house feels more comfortable than with the baseboard and my propane usage seems to be cut in half. Electric has gone up for sure but won’t know how much until next bill, thoug I don’t think it will be even as bad as the the 30 year old AC it replaced was in summer.
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Re: [Replacing HVAC - considering heat pump]

Post by Valuethinker »

talzara wrote: Fri Dec 03, 2021 1:31 pm
Valuethinker wrote: Fri Dec 03, 2021 7:58 am
TheGreyingDuke wrote: Fri Dec 03, 2021 6:42 am
On the other end of the satisfaction would be folks with natural gas access and an existing hydronic system.They were spending more and the quality of the heat was not up to that of a hydronic system,especially true of they had pipes buried in a slab. Of course the AC was a big plus.
This is really interesting.

Here (UK & Europe) the *best* setup for heat pumps (geothermal or air) is said by conventional wisdom to be underfloor heating (pipes in a concrete floor slab, typically). Forced air heating systems are pretty rare in residential homes in NW Europe, I would think (but common in commercial premises).
They're not using heat pumps with radiant floor heating. They're replacing hydronic boilers with forced-air heat pumps. Having 80°F air blow past your skin at high speed is much less comfortable than having warm air gently rising from a 110°F floor.

Air-to-water heat pumps are very hard to find in the United States. The hydronic market is so small that the Asian HVAC manufacturers don't even sell their air-to-water heat pumps here. There are a couple of American companies that make air-to-water heat pumps for commercial installations and custom homes, but they are very expensive.

The HVAC industry in North America is very different from the rest of the world. That's how the American HVAC manufacturers fell so far behind the state-of-the-art. They grew fat and lazy selling to the American market, while the rest of the world moved on.
Thank you for explaining. That's much clearer.

Does the Canadian market parallel the US market?** I would presume it did so but I don't think you'd ever build a house in Canada without some kind of furnace arrangement -- except on the West Coast (but not inland BC). Ground Source HPs are a thing, and there was a subsidy in some provinces during the 1990s. But it's pretty niche. My relative who had a farm house (not very well insulated 1970s A Frame) kept her electric baseboard heaters, but said later that was unnecessary. The (glass door sealed) wood fireplace in a huge central stone hearth was all the backup heat needed.

Due to the prevalence of hydro power and the lack of local natural gas resources, Quebec still has a lot of electric resistance heating as the primary heating system, unbelievably. But electricity rates are very low.


** Google says there are A to W ASHP in Canada (which I think you mentioned)

https://plumbingandhvac.ca/residential- ... eat-pumps/

https://hydrosolar.ca/blogs/news/heat-p ... r-lifespan (useful advice on system installation)
https://hydrosolar.ca/collections/hydro ... -heat-pump (Hydro Solar brand of ATW)
https://cdn.shopify.com/s/files/1/0010/ ... 4542340756 (says COP of 1.3 at -5 degrees F)


https://www.subzeroheat.ca/air-to-water ... eat-pumps/

https://www.nrcan.gc.ca/energy-efficien ... -pump/6817
NRCan has developed an Air-Source Heat Pump Sizing and Selection Guide. This guide, along with a companion software tool, is intended for energy advisors and mechanical designers, and is freely available to provide guidance on appropriate sizing.
Canada has officially gone metric so there would be a need to convert units. However the climate of southern Ontario, for example, is very similar to the climate of upstate NY. Prairie Provinces to the US Dakotas, etc.

https://www.achrnews.com/articles/14359 ... can-market

tells me that "the market is well advanced in Canada and Germany".
The Environmental Protection Agency (EPA) bestowed the Energy Star® Emerging Technology Award to ATW heat pumps last year. The technology has continued to improve as it makes new inroads in the North American market. More widely used in Asian countries such as China and Japan, the systems also have a strong market in Germany and Canada. The North American market is slowly catching up as contractors embrace the coefficient of performance (COP) race developing in regard to energy savings and environmentally friendly heating and cooling technology.
Divided into two primary types — monobloc and split system — ATW systems are ideally suited for low-temperature delivery such as radiant floor heating applications that do not require temperatures over 120°F.

The monobloc system is self-contained with pre-charged refrigerant.

...

“The cabinet-like unit should be elevated above the ground at least one foot, especially in a deep snow area,” he said, during the Coffee with Caleffi™ webinar Applying Air-to-Water Heat Pumps in Hydronic Systems. “You don’t want snow covering where the unit fans are, and by getting them up off the ground by at least a foot, conditions for the unit improve as far as grass clippings, leaves, and bugs not getting into the systems.”

The second type of ATW heat pumps is a split system. Schramel said that split types mostly resemble ATA heat pumps in that they couple an outdoor condensing unit with an indoor unit consisting of a coaxial coil commonly found in geothermal systems.

“The advantage of split type systems is that the contractor can use his preferred brand of condenser in either single-speed or variable speed heat pumps,” he explained.

Siegnthaler noted that typically the compressor is in the outdoor unit of a split system but cautioned that this is not always the case. A refrigerant lineset and electricity must be run between the indoor and outdoor units. There isn’t a danger of water freezing, however, as there is no water in the outdoor unit and no need for antifreeze.
Heat Distribution Systems
Heat pump systems generally supply a greater volume of airflow at lower temperature compared to furnace systems. As such, it is very important to examine the supply airflow of your system, and how it may compare to the airflow capacity of your existing ducts. If the heat pump airflow exceeds the capacity of your existing ducting, you may have noise issues or increased fan energy use.

New heat pump systems should be designed according to established practice. If the installation is a retrofit, the existing duct system should be carefully examined to ensure that it is adequate.
Important advice, I think.
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Re: [Replacing HVAC - considering heat pump]

Post by talzara »

Valuethinker wrote: Sun Dec 05, 2021 6:23 am Does the Canadian market parallel the US market?**
Yes, it does. Most of the Asian HVAC manufacturers treat the US and Canada as a single market.
Valuethinker wrote: Sun Dec 05, 2021 6:23 am https://www.achrnews.com/articles/14359 ... can-market

tells me that "the market is well advanced in Canada and Germany".
The market may be "advanced" compared to the United States, but Canada is not Germany. 100,000 air-to-water heat pumps are installed each year in Germany, which is a large enough market for the Asian HVAC manufacturers to sell to: https://heatpumpingtechnologies.org/wp- ... 210907.pdf
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Re: [Replacing HVAC - considering heat pump]

Post by twh »

I know Bosch is big in ground source heat pumps.
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Re: [Replacing HVAC - considering heat pump]

Post by finite_difference »

jharkin wrote: Sat Dec 04, 2021 4:14 pm It’s funny that these heat pump threads keep popping up me every time the same people insist they don’t work below 40.

That is 1980s thinking that is simply NOT true anymore. Mitsubishi, Fujitsu, Daikin and others all make cold climate heat pumps that provide full rated BTUs down to -15F and partial heat even lower.
If your contractor tells you you need to switch to backup heat at 40, or even 30, you need to fire them and find a contractor that actually knows what they are talking about.

I installed a 2.5 T Mitsubishi hyper heat ducted unit to supplement my propane hot water baseboard. It’s been down to 24F already and it’s not even running full time, house feels more comfortable than with the baseboard and my propane usage seems to be cut in half. Electric has gone up for sure but won’t know how much until next bill, thoug I don’t think it will be even as bad as the the 30 year old AC it replaced was in summer.
I expect my NG forced-air furnace to die in about 5-10 years. The warm air is nice but it needs to be paired with a steam humidifier since otherwise the air gets really dry. Upstairs we have a Carrier American-style heat pump that uses electric strips when it gets cold outside. It also makes a lot of noise when it goes into its defrost cycle.

For the Japanese heat pumps, are they more energy efficient than a regular American-style heat pump? Are they quieter? Is the only issue that they cost quite a bit more to install?
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Re: [Replacing HVAC - considering heat pump]

Post by Williams57 »

illumination wrote: Sat Dec 04, 2021 1:07 pm I'd stick with a gas furnace for winters in Colorado.

I personally just prefer how the heat feels from a gas furnace as opposed to the "clammy" feeling a heat pump provides in a cold climate. I have a vacation house in a climate very similar to Denver, there's no way I'd ditch the gas furnace for an electric only heat pump.

In terms of utility costs between the two, there's a a lot of factors, but I'd be willing to pay the extra if it came down to that (but I would wager an "average" central air heat pump though is more expensive to operate and has less service life than a gas furnace in colder climates)
Denver isn't really a cold climate though. Not anymore at least.
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Re: [Replacing HVAC - considering heat pump]

Post by Valuethinker »

finite_difference wrote: Mon Dec 06, 2021 10:47 pm
jharkin wrote: Sat Dec 04, 2021 4:14 pm It’s funny that these heat pump threads keep popping up me every time the same people insist they don’t work below 40.

That is 1980s thinking that is simply NOT true anymore. Mitsubishi, Fujitsu, Daikin and others all make cold climate heat pumps that provide full rated BTUs down to -15F and partial heat even lower.
If your contractor tells you you need to switch to backup heat at 40, or even 30, you need to fire them and find a contractor that actually knows what they are talking about.

I installed a 2.5 T Mitsubishi hyper heat ducted unit to supplement my propane hot water baseboard. It’s been down to 24F already and it’s not even running full time, house feels more comfortable than with the baseboard and my propane usage seems to be cut in half. Electric has gone up for sure but won’t know how much until next bill, thoug I don’t think it will be even as bad as the the 30 year old AC it replaced was in summer.
I expect my NG forced-air furnace to die in about 5-10 years. The warm air is nice but it needs to be paired with a steam humidifier since otherwise the air gets really dry. Upstairs we have a Carrier American-style heat pump that uses electric strips when it gets cold outside. It also makes a lot of noise when it goes into its defrost cycle.

For the Japanese heat pumps, are they more energy efficient than a regular American-style heat pump? Are they quieter? Is the only issue that they cost quite a bit more to install?
I *think* what Talzara is saying is yes, they are more efficient *as heaters*. US HPs are basically air conditioning units, run in reverse. This works in the south eastern USA (where the main demand is AC & the winters are usually mild) or Pacific NW but not so well outside that. Certainly the Coefficients of Performance [= kwhr of heat moved/ kwhr of electricity used or (heat output in BTU/hr)/ (electrical input x 3.413)] of the Japanese HPs seem to be much higher at low temperatures (sub 32 F).

However the problem will be getting contractors who can install and service Japanese brands - given the US brands (Carrier & Lennox & Goodman?) are so dominant? But one of the brands (Goodman?) is owned by a Japanese firm.

On quiet the technical specifications sheets will give you the DB. I assume your concern is DB from the outdoor unit? It is possible to have a box with sound baffles installed around the outside unit - that will reduce the sound by about 10 DB I think? (remembering that DB is a log scale that is a big reduction).

My parents' house in North America, the furnace and AC are not quiet. That seems to be the norm?
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Re: [Replacing HVAC - considering heat pump]

Post by Valuethinker »

talzara wrote: Mon Dec 06, 2021 8:48 pm
Valuethinker wrote: Sun Dec 05, 2021 6:23 am Does the Canadian market parallel the US market?**
Yes, it does. Most of the Asian HVAC manufacturers treat the US and Canada as a single market.
Valuethinker wrote: Sun Dec 05, 2021 6:23 am https://www.achrnews.com/articles/14359 ... can-market

tells me that "the market is well advanced in Canada and Germany".
The market may be "advanced" compared to the United States, but Canada is not Germany. 100,000 air-to-water heat pumps are installed each year in Germany, which is a large enough market for the Asian HVAC manufacturers to sell to: https://heatpumpingtechnologies.org/wp- ... 210907.pdf
Thank you, that is interesting.
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Re: Heat pumps

Post by firebirdparts »

IMD801 wrote: Tue Nov 30, 2021 11:13 am This is a commonly repeated and incorrect statement about heat pumps I heard from several HVAC companies until I found a knowledgeable one and did some of my own research. The performance of modern heat pumps down to extremely cold temperatures is outstanding. Our new unit has backup electric heat that will turn on at 10F if needed but the heat pump is actually capable of working way below that. The efficiency is quite high until 10-15F and even then not too bad. (Daikin VRV system, air source)
I agree with this. Economically, There is likely not a temperature in practice where its' "cheaper" to turn a new heat pump off. If you live in the Yukon Territory, then fine, the bulk of your annual heating degrees would likely be stage 2. In a reasonable climate, there will be a point at which you need more capacity, and lo-and-behold, heat pumps have had stage 2 heating forever. They've always had that as an option. I live in Tennessee and I actually put a cut-off swich in stage 2 and leave it off even when defrosting. I'm cheap.

So a heat pump with stage 2 as the gas furnace would be awesome. I would love to have that, but we don't have access to gas on my street. Unfortunately there is beginning a big energy crisis which will likely last a long time during the life of these new systems, but if you have both forms of heat, you can choose to use whatever is cheaper.

A second consideration is that the price difference between a heat pump and A/C must be pretty small if you do it right. So any reasonable person would think about if I spend $500 on this, do I get the $500 back some time, and that's a pretty low bar.

I am a fan of American Standard FWIW.
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Re: Heat pumps

Post by jharkin »

firebirdparts wrote: Tue Dec 07, 2021 7:55 am
I agree with this. Economically, There is likely not a temperature in practice where its' "cheaper" to turn a new heat pump off. If you live in the Yukon Territory, then fine, the bulk of your annual heating degrees would likely be stage 2. In a reasonable climate, there will be a point at which you need more capacity, and lo-and-behold, heat pumps have had stage 2 heating forever. They've always had that as an option. I live in Tennessee and I actually put a cut-off swich in stage 2 and leave it off even when defrosting. I'm cheap.
The cool thing is that you dont have to take your installers word for htis, its easy to calculate. All you need to do is look up the rating sheets of your heat pump and whatever the alternate heating is, and your cost of fuel/electricity.

For the math, the delivered heat is as follows, just divide that by you $ per unit energy:
electric resistance heat is 3412 BTU/hr per kWh
Heat pump is 3412x[COP] BTU/hr per kWh
Natural gas is 100,000x[AFUE] BTU per therm
Fuel oil is 140,000x[AFUE] BTU per gallon
Propane is 91,500x[AFUE] BTU per gallon


Example calculation:
I pay $2.95/gallon for propane and $0.227/kWh all in for electric.

My standard heat is a propane fired modulating/condensing hot water baseboard system. Its 95% efficient on mild days when its in condensing mode, and 85% efficient on really cold days.
So on a mild day 91500 X 95% / $2.95 = 29466 BTU/$
And on a cold day 91500 X 85% / $2.95 = 26364 BTU/$

My new Mitsubishi SUZ-KA30NA hyper heat pump has ratings of COP 3.9 @ 47F, COP 2 @ 17F, COP1.75 @ 5F, COP 1.7 @ -13F
At 47F 3412 x 3.90 / $0.227 = 58620 BTU/$
At 17F 3412 x 2.00 / $0.227 = 30061
At 5F 3412 x 1.75 / $0.227 = 26303
At -13F 3412 x 1.70 / $0.227 = 25552

So comparing the above numbers to the propane numbers, my crossover point where propane becomes cheaper is around 7-10F. The HVAC heating design temp in my climate zone is 8F, so in practice I can pretty much just leave the heat pump on and forget it.

There are real world nuances however and if you want to be precise you have to measure actual real time fuel use - the numbers above I have been told don't account for the energy cost of defrost cycles, and the COP numbers are all at max load (and the pump is probably more efficient at part load)

If your backup heat is electric resistance there is NEVER a crossover point other than the point here your heating load exceeds hte HP capacity, as by definition resistance heat is COP 1.0 and will always be less efficient than the HP.
firebirdparts wrote: Tue Dec 07, 2021 7:55 am A second consideration is that the price difference between a heat pump and A/C must be pretty small if you do it right. So any reasonable person would think about if I spend $500 on this, do I get the $500 back some time, and that's a pretty low bar.

I am a fan of American Standard FWIW.
+1 When I got quotes to replace my old failing AC, a heat pump was only about 1k more than a Carrier AC only replacement. The cold climate (Hyper Heat) version of the heat pump was only $750 more than the standard version. I calculate the heat pump upgrade will save mea at least $1000/yr in propane so it pays off in a single season.
Last edited by jharkin on Tue Dec 07, 2021 11:35 am, edited 1 time in total.
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Re: [Replacing HVAC - considering heat pump]

Post by illumination »

Williams57 wrote: Tue Dec 07, 2021 12:00 am
illumination wrote: Sat Dec 04, 2021 1:07 pm I'd stick with a gas furnace for winters in Colorado.

I personally just prefer how the heat feels from a gas furnace as opposed to the "clammy" feeling a heat pump provides in a cold climate. I have a vacation house in a climate very similar to Denver, there's no way I'd ditch the gas furnace for an electric only heat pump.

In terms of utility costs between the two, there's a a lot of factors, but I'd be willing to pay the extra if it came down to that (but I would wager an "average" central air heat pump though is more expensive to operate and has less service life than a gas furnace in colder climates)
Denver isn't really a cold climate though. Not anymore at least.

This doesn't really make sense to me.
If you're talking about global warming, we're talking about a 1 degree difference over the last 100 years.
https://climate.nasa.gov/vital-signs/gl ... mperature/
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Re: [Replacing HVAC - considering heat pump]

Post by Williams57 »

illumination wrote: Tue Dec 07, 2021 10:27 am
Williams57 wrote: Tue Dec 07, 2021 12:00 am
illumination wrote: Sat Dec 04, 2021 1:07 pm I'd stick with a gas furnace for winters in Colorado.

I personally just prefer how the heat feels from a gas furnace as opposed to the "clammy" feeling a heat pump provides in a cold climate. I have a vacation house in a climate very similar to Denver, there's no way I'd ditch the gas furnace for an electric only heat pump.

In terms of utility costs between the two, there's a a lot of factors, but I'd be willing to pay the extra if it came down to that (but I would wager an "average" central air heat pump though is more expensive to operate and has less service life than a gas furnace in colder climates)
Denver isn't really a cold climate though. Not anymore at least.

This doesn't really make sense to me.
If you're talking about global warming, we're talking about a 1 degree difference over the last 100 years.
https://climate.nasa.gov/vital-signs/gl ... mperature/
I've lived in Denver since 2006 and it doesn't feel like a cold climate anymore. It finally cooled down two days ago, but before it was in the 60s. I don't like it, too warm. I understand this is not factual.
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Re: [Replacing HVAC - considering heat pump]

Post by illumination »

jharkin wrote: Sat Dec 04, 2021 4:14 pm It’s funny that these heat pump threads keep popping up me every time the same people insist they don’t work below 40.

That is 1980s thinking that is simply NOT true anymore. Mitsubishi, Fujitsu, Daikin and others all make cold climate heat pumps that provide full rated BTUs down to -15F and partial heat even lower.
If your contractor tells you you need to switch to backup heat at 40, or even 30, you need to fire them and find a contractor that actually knows what they are talking about.

I installed a 2.5 T Mitsubishi hyper heat ducted unit to supplement my propane hot water baseboard. It’s been down to 24F already and it’s not even running full time, house feels more comfortable than with the baseboard and my propane usage seems to be cut in half. Electric has gone up for sure but won’t know how much until next bill, thoug I don’t think it will be even as bad as the the 30 year old AC it replaced was in summer.

But an "average" central air heat pump in most homes needs "help" when it gets below 40 degrees outside. Most all electric ones have an electric resistance coil that turns on for "Aux" heat. It's incredibly inefficient when running that way. Even modern heat pump manufacturers have this as a disclaimer.

A heat pump with a gas furnace (dual fuel) makes a lot of sense if you already have nat gas. I can't imagine someone not going in that direction if you have any sort of cold winter.

Mini splits are a different set up, most people don't want to convert over from central air with ductwork to a home full of minisplits in every room. But they can do a better job at lower temps and are more efficient.
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Re: [Replacing HVAC - considering heat pump]

Post by jharkin »

illumination wrote: Tue Dec 07, 2021 10:40 am
But an "average" central air heat pump in most homes needs "help" when it gets below 40 degrees outside. Most all electric ones have an electric resistance coil that turns on for "Aux" heat. It's incredibly inefficient when running that way. Even modern heat pump manufacturers have this as a disclaimer.

What are you basing this "average" on? Personal experience or something stated online (possibly by a contractor trying to upsell?).

If a proper Manual J calculation was done and the heat pump sized to the design heat loss of the building it should not need any help, period. And in the real world few contractors take the time to do a proper Manual J and just size by outdated rules of thumb from a time when homes had far less insulation and most real world heat pumps are oversized.

My install is a classic example. 2800 sq on 2 levels. First floor (1400) was a 2.5T AC unit from 1993. I just had it replaced and contractor spec'd a 2.5T (30,000) BTU replacement - and it holds full rated output to 5F, and about 80% of crated capacity at -13. I know this is way oversized but I let him install it anyway as a lot of that heat rises up to the second floor by convection and will help offset the other zone- Im hoping to offset at least 60% of my whole house propane use.

House total design day heat loss I estimate at around 40,000 BTU/hr at 5F, reverse engineering from the last 2 years of fuel use and HDD information. So I suspect that even at zero the heat pump will have capacity to spare for the first floor. Empirical findings so far seem to support that as its been down close to 20F and it was still only running at about a 50% duty cycle on low fan.


All these outdated "rules of thumb" and assumptions about heat pumps need to die if we are going to convince the majority of homeowners to move off fossil fuel heating. Some interesting reading:
https://www.greenbuildingadvisor.com/ar ... s-of-thumb (ts about AC, but similar calcs are used for heat)
https://www.greenbuildingadvisor.com/ar ... -minnesota (if this house can do it, anybody can)
and so on. Spends some time reading GBA, Buildingscience.com, etc and you will find a ton of good info.
vg55
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Re: [Replacing HVAC - considering heat pump]

Post by vg55 »

I just purchased and installed two HEIL air source heat pumps to replace 2 end of life compressors and to reduce reliance on fossil fuel. At the moment, i have an outside monitor that will force a change over from heat pump to oil heat at 35F. It all appears to be working fine and so I will soon lower the set point to 30F. Unfortunately, I cant seem to locate any heating efficiency information on these units, so in the absence of information am conducting a trial by error approach. If anyone has insight on the HEIL NXH5 units - I would appreciate your thoughts.

I am pleased that my solar array is keeping up with the heating of the house during daylight hours. While both ASHP units were working, i checked and the solar array was still sending excess power to the grid.
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illumination
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Re: [Replacing HVAC - considering heat pump]

Post by illumination »

jharkin wrote: Tue Dec 07, 2021 11:53 am
illumination wrote: Tue Dec 07, 2021 10:40 am
But an "average" central air heat pump in most homes needs "help" when it gets below 40 degrees outside. Most all electric ones have an electric resistance coil that turns on for "Aux" heat. It's incredibly inefficient when running that way. Even modern heat pump manufacturers have this as a disclaimer.

What are you basing this "average" on? Personal experience or something stated online (possibly by a contractor trying to upsell?).

It's coming right from the manufacturer's of heat pumps.

AT WHAT TEMPERATURES ARE HEAT PUMPS MOST EFFECTIVE?
The heat pump is most effective on its own at temperatures around 25 to 30 degrees Fahrenheit. At that point, either a gas furnace or an air handler with supplemental electric heat will kick in to help heat your home.


https://www.trane.com/residential/en/re ... r-my-home/
aquaman
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Re: [Replacing HVAC - considering heat pump]

Post by aquaman »

jharkin wrote: Tue Dec 07, 2021 11:53 amAll these outdated "rules of thumb" and assumptions about heat pumps need to die if we are going to convince the majority of homeowners to move off fossil fuel heating.
In another thread on this topic, I asked whether the heat pump manufacturers have they done anything yet about their comfort. I know that it at least used to be that heat pumps produced 82F to 92F air, which felt cold and uncomfortable in the winter, as it's below our body temperature of 98.6F. These temperatures would obviously still warm things up, but the air itself felt very uncomfortable. I don't know, however, if the newest heat pumps still work the same.

Natural gas furnaces produce 130F to 140F air, which always feels nice and warm, as it's significantly above our body temperature.

In that thread, I was told that the newest heatpumps still work the exact same way, but that you can slightly alleviate the discomfort by running the blower at a lower speed. If so, that's not really an attractive option for quite a few reasons.

In other words, energy efficiency is obviously important, but so is comfort. Yet, an overwhelming majority of the posts in this thread focus solely on the energy efficiency without mentioning anything about the comfort drawbacks that people would have to accept from heat pumps.
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illumination
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Re: [Replacing HVAC - considering heat pump]

Post by illumination »

aquaman wrote: Tue Dec 07, 2021 3:53 pm
In other words, energy efficiency is obviously important, but so is comfort. Yet, an overwhelming majority of the posts in this thread focus solely on the energy efficiency without mentioning anything about the comfort drawbacks that people would have to accept from heat pumps.
Exactly.

I have two houses, one with an all electric heat pump and one with a natural gas furnace combo. The gas furnace is a MUCH better experience for comfort in the winter. Warms the place up much faster and I also find I don't need to keep the temp on as high a setting for everyone to be comfortable.

But I would also bet a natural gas furnace is cheaper to run in the winter for most people than an "all electric" central heat pump, just like it's usually cheaper to run natural gas for a water heater. But some states/utilities handle things differently.
finite_difference
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Re: [Replacing HVAC - considering heat pump]

Post by finite_difference »

illumination wrote: Tue Dec 07, 2021 10:27 am
Williams57 wrote: Tue Dec 07, 2021 12:00 am
illumination wrote: Sat Dec 04, 2021 1:07 pm I'd stick with a gas furnace for winters in Colorado.

I personally just prefer how the heat feels from a gas furnace as opposed to the "clammy" feeling a heat pump provides in a cold climate. I have a vacation house in a climate very similar to Denver, there's no way I'd ditch the gas furnace for an electric only heat pump.

In terms of utility costs between the two, there's a a lot of factors, but I'd be willing to pay the extra if it came down to that (but I would wager an "average" central air heat pump though is more expensive to operate and has less service life than a gas furnace in colder climates)
Denver isn't really a cold climate though. Not anymore at least.

This doesn't really make sense to me.
If you're talking about global warming, we're talking about a 1 degree difference over the last 100 years.
https://climate.nasa.gov/vital-signs/gl ... mperature/
That’s global temperature, which is different than local temperature. Raising the temperature of the entire Earth by 1 degree Celsius (almost 2 degrees Fahrenheit) doesn’t sound like much. That’s a crazy amount of energy though.

From your link: Earth’s surface continues to significantly warm, with recent global temperatures being the hottest in the past 2,000-plus years.

Nineteen of the hottest years have occurred since 2000, with the exception of 1998, which was helped by a very strong El Niño. The year 2020 tied with 2016 for the hottest year on record since record-keeping began in 1880.


For local extreme highs, see for example (can plug-in Denver):

https://www.nytimes.com/interactive/201 ... etown.html

They need to do something like that for tracking mild winters.
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finite_difference
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Re: [Replacing HVAC - considering heat pump]

Post by finite_difference »

illumination wrote: Tue Dec 07, 2021 4:08 pm
aquaman wrote: Tue Dec 07, 2021 3:53 pm
In other words, energy efficiency is obviously important, but so is comfort. Yet, an overwhelming majority of the posts in this thread focus solely on the energy efficiency without mentioning anything about the comfort drawbacks that people would have to accept from heat pumps.
Exactly.

I have two houses, one with an all electric heat pump and one with a natural gas furnace combo. The gas furnace is a MUCH better experience for comfort in the winter. Warms the place up much faster and I also find I don't need to keep the temp on as high a setting for everyone to be comfortable.

But I would also bet a natural gas furnace is cheaper to run in the winter for most people than an "all electric" central heat pump, just like it's usually cheaper to run natural gas for a water heater. But some states/utilities handle things differently.
A natural gas (methane) forced air furnace needs a steam dehumidifier to be comfortable. Otherwise the air gets way too dry. The heat pump is perfectly comfortable and dries out the air much less. (I could see it being uncomfortable if you are warming up a cold house though.)

I think NG prices have been low but are subject to much more volatility than electric prices. Recently I think NG has gone up quite a bit, but the savings you’ll get also depends on also how much you’re paying for electricity.

I do agree that radiant heat is the most comfortable one though. So we need a heat pump that heats up water and circulates it through the house? Rather than slightly warm air blowing on your face.
The most precious gift we can offer anyone is our attention. - Thich Nhat Hanh
mervinj7
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Re: [Replacing HVAC - considering heat pump]

Post by mervinj7 »

finite_difference wrote: Tue Dec 07, 2021 6:01 pm I do agree that radiant heat is the most comfortable one though. So we need a heat pump that heats up water and circulates it through the house? Rather than slightly warm air blowing on your face.
A heat pump water heater for radiant floor heating is totally possible! A more ideal one would use a geothermal heat pump. I've only ever seen it in one house, so they are not common as far as I know.

https://www.arcticheatpumps.com/radiant ... -pump.html
adamthesmythe
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Re: [Replacing HVAC - considering heat pump]

Post by adamthesmythe »

illumination wrote: Tue Dec 07, 2021 10:40 am
jharkin wrote: Sat Dec 04, 2021 4:14 pm It’s funny that these heat pump threads keep popping up me every time the same people insist they don’t work below 40.

That is 1980s thinking that is simply NOT true anymore. Mitsubishi, Fujitsu, Daikin and others all make cold climate heat pumps that provide full rated BTUs down to -15F and partial heat even lower.
If your contractor tells you you need to switch to backup heat at 40, or even 30, you need to fire them and find a contractor that actually knows what they are talking about.

I installed a 2.5 T Mitsubishi hyper heat ducted unit to supplement my propane hot water baseboard. It’s been down to 24F already and it’s not even running full time, house feels more comfortable than with the baseboard and my propane usage seems to be cut in half. Electric has gone up for sure but won’t know how much until next bill, thoug I don’t think it will be even as bad as the the 30 year old AC it replaced was in summer.

But an "average" central air heat pump in most homes needs "help" when it gets below 40 degrees outside. Most all electric ones have an electric resistance coil that turns on for "Aux" heat. It's incredibly inefficient when running that way. Even modern heat pump manufacturers have this as a disclaimer.

A heat pump with a gas furnace (dual fuel) makes a lot of sense if you already have nat gas. I can't imagine someone not going in that direction if you have any sort of cold winter.

Mini splits are a different set up, most people don't want to convert over from central air with ductwork to a home full of minisplits in every room. But they can do a better job at lower temps and are more efficient.
I was unpersuaded by the postings about newer heat pump designs which contained claims rather than explanation. The same thing was true about links from heat pump manufacturers. However I HAVE managed to turn up one link with real technical content that provides a justification for believing that improved designs, capable of useful operation at lower temperatures, are practical.

(https://www.energy.gov/sites/default/fi ... 042314.pdf)

Briefly, it appears that higher operating pressures, obtained either with multiple compressors or oversized compressors, will push the temperature at which COP is usefully high to lower outside air temperatures. This means that the outside temperature at which supplementary heat is required will be reduced (and also the electric power consumption for a particular outside air temperature will be reduced).

The price of this improvement would be presumably higher cost (larger or more compressors) and increased complexity. Possibly also increased repair cost if higher pressure is associated with more frequent leaks.

Now this does not change the fact that there is some outside temperature at which it becomes more economic to use supplementary natural gas heat or an even lower temperature where it becomes economic to use supplementary electric heat. It just reduces the range where supplementary heat will be needed.

A brief comment about WHY low temperatures are a problem. Thermodynamics says that a heat pump can have a COP > 1 (that is, it can output more heat that the amount of electrical power input). But the COP for a given refrigeration cycle decreases as the temperature difference between inside and outside increases. The amount of heat required increases with the temperature difference. So there will exist a critical temperature where a heat pump will not be able to keep up without supplementary heat.
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Re: [Replacing HVAC - considering heat pump]

Post by RetiredAL »

adamthesmythe wrote: Tue Dec 07, 2021 6:27 pm
illumination wrote: Tue Dec 07, 2021 10:40 am
jharkin wrote: Sat Dec 04, 2021 4:14 pm It’s funny that these heat pump threads keep popping up me every time the same people insist they don’t work below 40.

That is 1980s thinking that is simply NOT true anymore. Mitsubishi, Fujitsu, Daikin and others all make cold climate heat pumps that provide full rated BTUs down to -15F and partial heat even lower.
If your contractor tells you you need to switch to backup heat at 40, or even 30, you need to fire them and find a contractor that actually knows what they are talking about.

I installed a 2.5 T Mitsubishi hyper heat ducted unit to supplement my propane hot water baseboard. It’s been down to 24F already and it’s not even running full time, house feels more comfortable than with the baseboard and my propane usage seems to be cut in half. Electric has gone up for sure but won’t know how much until next bill, thoug I don’t think it will be even as bad as the the 30 year old AC it replaced was in summer.

But an "average" central air heat pump in most homes needs "help" when it gets below 40 degrees outside. Most all electric ones have an electric resistance coil that turns on for "Aux" heat. It's incredibly inefficient when running that way. Even modern heat pump manufacturers have this as a disclaimer.

A heat pump with a gas furnace (dual fuel) makes a lot of sense if you already have nat gas. I can't imagine someone not going in that direction if you have any sort of cold winter.

Mini splits are a different set up, most people don't want to convert over from central air with ductwork to a home full of minisplits in every room. But they can do a better job at lower temps and are more efficient.
I was unpersuaded by the postings about newer heat pump designs which contained claims rather than explanation. The same thing was true about links from heat pump manufacturers. However I HAVE managed to turn up one link with real technical content that provides a justification for believing that improved designs, capable of useful operation at lower temperatures, are practical.

(https://www.energy.gov/sites/default/fi ... 042314.pdf)

Briefly, it appears that higher operating pressures, obtained either with multiple compressors or oversized compressors, will push the temperature at which COP is usefully high to lower outside air temperatures. This means that the outside temperature at which supplementary heat is required will be reduced (and also the electric power consumption for a particular outside air temperature will be reduced).

The price of this improvement would be presumably higher cost (larger or more compressors) and increased complexity. Possibly also increased repair cost if higher pressure is associated with more frequent leaks.

Now this does not change the fact that there is some outside temperature at which it becomes more economic to use supplementary natural gas heat or an even lower temperature where it becomes economic to use supplementary electric heat. It just reduces the range where supplementary heat will be needed.

A brief comment about WHY low temperatures are a problem. Thermodynamics says that a heat pump can have a COP > 1 (that is, it can output more heat that the amount of electrical power input). But the COP for a given refrigeration cycle decreases as the temperature difference between inside and outside increases. The amount of heat required increases with the temperature difference. So there will exist a critical temperature where a heat pump will not be able to keep up without supplementary heat.
+1
I looked at data for Mitsubishi 36,000btu a couple of weeks ago, and is showed that BTU output drops to 22,000 by 25F, long before it switches to resistive electric. As for the statement of full output at a way low temp, I guess that is technically correct, they just don't mention that "full output" has a temperature curve below a certain temp.
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