Heat Pump Purchase

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dfin
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Heat Pump Purchase

Post by dfin »

Replacing an older heat pump and air handler (full electric). Have a quote for Lennox ML14XP1 single stage (Merit series economy line) vs Carrier 25HCE4 two stage (Performance series mid line). Carrier option is approximately $4,000 higher. Anyone have any input whether the two stage is worth the additional cost? Located in Jersey where we pretty much get both extremes (hot and cold).

Thanks
Valuethinker
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Re: Heat Pump Purchase

Post by Valuethinker »

dfin wrote: Wed Jun 23, 2021 7:50 am Replacing an older heat pump and air handler (full electric). Have a quote for Lennox ML14XP1 single stage (Merit series economy line) vs Carrier 25HCE4 two stage (Performance series mid line). Carrier option is approximately $4,000 higher. Anyone have any input whether the two stage is worth the additional cost? Located in Jersey where we pretty much get both extremes (hot and cold).

Thanks
There is an HVAC Forum which is apparently quite helpful (but does not allow discussion of costs/ quotes). Main question is whether there has been a "Manual J" calculation which ensures your HP is not oversized.

It seems like a big jump in price (I am not US based). SEER rating though may be quite different? New Jersey has relatively high electricity prices by US standards, so there will be a payback (I assume it's a very long payback, but there will be one ie the net cost of this is less than $4000).

If I was planning to be in the house for less than 5 years I might take the cheaper option (or at least consider it) depending on what my portfolio looked like relative to my financial goals. 5 years or more I would probably take the more expensive option and "earn" a return on the higher energy efficiency - but more importantly on comfort. A cheaper model will probably have cheaper components - there's no way around that - although how much cheaper (re reliability) I don't know.

I think of my parents (in the same house for 60 years) and the philosophy of "do it once, do it right" worked for them, even though I am certain they never intended to live there so long .

I think the majority of people here (I might even say the vast majority) find that the 2 speed ones (with variable speed fans) are more comfortable in the climate of the USA east of the Mississippi. That is where humidity is the predominant experience alongside heat. Since it's actually the humidity that makes you uncomfortable, the ability to run on a quieter, lower speed, still pulling the humidity out, leads to much greater comfort (rather than cycling too hot/ too cold).
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galawdawg
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Re: Heat Pump Purchase

Post by galawdawg »

Can I recommend you get a quote for a York system from a York Certified Comfort Expert dealer? We recently replaced a heat pump with a York unit. It was comparable in price to the least expensive Trane and Lennox systems but had better specifications, was a 15.75 SEER unit (rather than 15 SEER) and came with a full ten (10) year parts and labor manufacturer warranty.
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hand
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Re: Heat Pump Purchase

Post by hand »

I'd also take a look at parts availability for the manufacturers in question - a warranty isn't much use if there are no replacement parts on hand.
brianH
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Re: Heat Pump Purchase

Post by brianH »

dfin wrote: Wed Jun 23, 2021 7:50 am Replacing an older heat pump and air handler (full electric). Have a quote for Lennox ML14XP1 single stage (Merit series economy line) vs Carrier 25HCE4 two stage (Performance series mid line). Carrier option is approximately $4,000 higher. Anyone have any input whether the two stage is worth the additional cost? Located in Jersey where we pretty much get both extremes (hot and cold).

Thanks
2 stage is worth extra cost, but maybe not that much. If the brand was the same, the cost is usually like $1000-1500 more for a 2-stage unit, which is probably worth it for NJ area.

On the days where it's not so hot, the unit can run in stage 1 (like 60-70% of full stage 2 capacity), which allows it to dehumidify better, and reduces wear on the compressor. For both heat and cool, you want the unit to run as long as possible (in stage 1) instead of slamming on/off as it might if it was running at full capacity.
Big Dog
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Re: Heat Pump Purchase

Post by Big Dog »

brianH wrote: Wed Jun 23, 2021 8:35 am
dfin wrote: Wed Jun 23, 2021 7:50 am Replacing an older heat pump and air handler (full electric). Have a quote for Lennox ML14XP1 single stage (Merit series economy line) vs Carrier 25HCE4 two stage (Performance series mid line). Carrier option is approximately $4,000 higher. Anyone have any input whether the two stage is worth the additional cost? Located in Jersey where we pretty much get both extremes (hot and cold).

Thanks
2 stage is worth extra cost, but maybe not that much. If the brand was the same, the cost is usually like $1000-1500 more for a 2-stage unit, which is probably worth it for NJ area.

On the days where it's not so hot, the unit can run in stage 1 (like 60-70% of full stage 2 capacity), which allows it to dehumidify better, and reduces wear on the compressor. For both heat and cool, you want the unit to run as long as possible (in stage 1) instead of slamming on/off as it might if it was running at full capacity.
Agree with the 2nd stage. Makes the house more comfortable as it can run in stage 1 when its only moving the temp 1-2 degrees to maintain temp. Air circulates more often, albeit slowly, and temperature and humidity is better balanced.
tibbitts
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Re: Heat Pump Purchase

Post by tibbitts »

dfin wrote: Wed Jun 23, 2021 7:50 am Replacing an older heat pump and air handler (full electric). Have a quote for Lennox ML14XP1 single stage (Merit series economy line) vs Carrier 25HCE4 two stage (Performance series mid line). Carrier option is approximately $4,000 higher. Anyone have any input whether the two stage is worth the additional cost? Located in Jersey where we pretty much get both extremes (hot and cold).

Thanks
That seems like a lot extra for the 2-stage. To me part of the advantage would be that you can over-size the 2-stage. I didn't think about that and so my 2-stage almost always runs however I long I program in stage 1 and then has to resort to stage 2 - for a long time. Maybe part of the cost difference accounts for upsizing.
hicabob
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Re: Heat Pump Purchase

Post by hicabob »

Get lots of quotes. When I got quotes the best one had the 2 stage at about $600 more than single and variable was about $1200 more than single. I went for the 18.5 SEER variable speed handler+pump. Variable speed is really nice for comfort and efficiency.
The other quotes had the few thou differences between the good/better/best. It's not that big a deal to run motors at variable speeds nowadays and shouldn't cost 1000's more.
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dfin
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Re: Heat Pump Purchase

Post by dfin »

Thanks all for the great insights
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tcassette
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Re: Heat Pump Purchase

Post by tcassette »

hicabob wrote: Wed Jun 23, 2021 8:54 am Get lots of quotes. When I got quotes the best one had the 2 stage at about $600 more than single and variable was about $1200 more than single. I went for the 18.5 SEER variable speed handler+pump. Variable speed is really nice for comfort and efficiency.
The other quotes had the few thou differences between the good/better/best. It's not that big a deal to run motors at variable speeds nowadays and shouldn't cost 1000's more.
This. I went for the second from top of the line American Standard variable speed HP with a further down the line variable speed air handler. Note that a variable speed system will typically require a communicating thermostat which is a few hundred $ more expensive than a regular programmable one.
meebers
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Re: Heat Pump Purchase

Post by meebers »

5 years ago, I went with a 4 ton heat pump high seer, variable speed compressor and variable speed air handler from Trane with a communicating thermostat. I am in central Florida and very seldom does the compressor go over 60%. Lot of times it is @ 20%. We have had thunderstorms all week , 90+ F temps outside and the indoor humidity is 48%. Average bill is ~ $150/month with 2300 Sqft. If I am outside, you cannot hear it running, sometimes check the fan and confirm it is running.
Last edited by meebers on Wed Jun 23, 2021 7:43 pm, edited 1 time in total.
Normchad
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Re: Heat Pump Purchase

Post by Normchad »

Lots of people will tell you to get 2 speed or variable speed for the comfort of it.

I’m not one of them. I’ve only ever had bottom of the line, builder grade stuff. So when it came time to replace mine, that’s what I bought. It’s perfectly comfortable for me..

Whatever you buy, it will be much better than what you are replacing. So it’s reallly a questioner how much better will it be.
Valuethinker
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Re: Heat Pump Purchase

Post by Valuethinker »

Normchad wrote: Wed Jun 23, 2021 7:41 pm Lots of people will tell you to get 2 speed or variable speed for the comfort of it.

I’m not one of them. I’ve only ever had bottom of the line, builder grade stuff. So when it came time to replace mine, that’s what I bought. It’s perfectly comfortable for me..

Whatever you buy, it will be much better than what you are replacing. So it’s reallly a questioner how much better will it be.
A lot depends on where you live.

The more humid the climate in summer, the greater the improvement in comfort arising from variable speed configurations.
andypanda
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Re: Heat Pump Purchase

Post by andypanda »

We had a Lennox variable system put in 2 years ago. The XP-20 is variable (30 or 35% up to 100% in 1% steps) and so is the air handler. The air temp stays at whatever the thermostat is set on and you don't know it's blowing unless you are standing a foot away from an outlet.

Last week we rented a very nicely renovated cottage on the Outer Banks of NC. We've stayed there before in years past, but this time the temp swings were annoying. The ecobee thermostat was set on 73 and when the air temp reached 73 the system stayed off until the inside temp hit 75 a couple of hours or so later. Later in the week when the outdoor temp got into the low 90s it would swing between the set point of 73 and 76. Back and forth, up and down. It worked like our old one-speed system worked.

I like our slow and steady variable speed system. I don't wake up in the middle of the night either a little warm or reaching for the sheet because the air is blowing hard for an hour.

Yes, our Lennox system cost a great deal and I never suggest that anyone spend that much. Part of the reason it works so well is that we had the old duct board and flex ducts torn out and large diameter insulated galvanized steel ducts installed in the crawl space.
talzara
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Re: Heat Pump Purchase

Post by talzara »

dfin wrote: Wed Jun 23, 2021 7:50 am Replacing an older heat pump and air handler (full electric). Have a quote for Lennox ML14XP1 single stage (Merit series economy line) vs Carrier 25HCE4 two stage (Performance series mid line). Carrier option is approximately $4,000 higher. Anyone have any input whether the two stage is worth the additional cost? Located in Jersey where we pretty much get both extremes (hot and cold).
Neither system makes sense for New Jersey, a heating-dominated climate where the winter design temperature is 15°F.

American heat pumps perform poorly at low temperatures. According to the performance curve in the specifications, the Carrier 25HCE4 only delivers its rated capacity at 52°F. Performance drops to 73% of rated capacity at 32°F, and only 51% of rated capacity at 15°F.

Electricity in New Jersey costs 16 cents per kWh, which is 5 times the cost of natural gas and 1.7 times the cost of propane. At those prices, electric heat strips are economically infeasible for supplemental heating. It costs less to operate a gas furnace for supplemental heat, even if you have to burn propane.

If you want to stay all-electric, it'll cost a lot less to operate low-temperature mini-splits from Fujitsu, Mitsubishi, and other Asian manufacturers. They have heat pumps that can deliver their rated capacity down to 0 degrees Fahrenheit. They'll cost a lot more to install, but you were willing to spend an extra $4,000 just to upgrade to two-stage. Switching to mini-splits is a much better way to spend $4,000.
talzara
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Re: Heat Pump Purchase

Post by talzara »

Valuethinker wrote: Wed Jun 23, 2021 8:00 am It seems like a big jump in price (I am not US based). SEER rating though may be quite different? New Jersey has relatively high electricity prices by US standards, so there will be a payback (I assume it's a very long payback, but there will be one ie the net cost of this is less than $4000).
It's unlikely that there will be a payback.

There is a loss of efficiency from short-cycling, but it's greatly exaggerated. Air conditioners approach their maximum efficiency at just 10 minutes of runtime.

The cycles have to be very short to earn back $4,000.
brianH
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Re: Heat Pump Purchase

Post by brianH »

talzara wrote: Thu Jun 24, 2021 12:46 pm Neither system makes sense for New Jersey, a heating-dominated climate where the winter design temperature is 15°F.

American heat pumps perform poorly at low temperatures. According to the performance curve in the specifications, the Carrier 25HCE4 only delivers its rated capacity at 52°F. Performance drops to 73% of rated capacity at 32°F, and only 51% of rated capacity at 15°F.

Electricity in New Jersey costs 16 cents per kWh, which is 5 times the cost of natural gas and 1.7 times the cost of propane. At those prices, electric heat strips are economically infeasible for supplemental heating. It costs less to operate a gas furnace for supplemental heat, even if you have to burn propane.
There are too many assumptions here to make that blanket statement. Heat strips are inexpensive to add (assuming the circuits are run), and require zero maintenance. Adding a separate furnace (and propane tank if no natural gas) is a huge upfront cost, and that furnace requires separate maintenance. Propane costs are highly variable, and often spike 2-3x in the dead of Winter.

If the HP is sized properly, and the house is well-insulated and tight, it may need very little supplemental heat from the strips.

I agree that it's almost impossible to beat the current cost of natural gas for heating, but that assumes you have it available and that it doesn't get taxed in the near future. The writing is on the wall that residential natural gas is going to be phased out over the next few decades, likely by dramatically taxing its use.
talzara
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Re: Heat Pump Purchase

Post by talzara »

brianH wrote: Thu Jun 24, 2021 1:06 pm There are too many assumptions here to make that blanket statement. Heat strips are inexpensive to add (assuming the circuits are run), and require zero maintenance. Adding a separate furnace (and propane tank if no natural gas) is a huge upfront cost, and that furnace requires separate maintenance. Propane costs are highly variable, and often spike 2-3x in the dead of Winter.

If the HP is sized properly, and the house is well-insulated and tight, it may need very little supplemental heat from the strips.
The problem in New Jersey is that the heating load is double the cooling load. The winter design temperature is 15°F, and the summer design temperature is 90°F.

New Jersey is a heating-dominated climate. Newark gets 4,700 heating degree-days per year, but only 1,200 cooling degree-days. You need almost four times as much heating as cooling.

To use zero supplemental heat, you'd need a heat pump rated for 200% of the heating load, so it can deliver 100% of the design heating load. Then it would be hugely oversized in summer at 400% of the cooling load. Even then, the heat pump would have a low COP at low temperatures. You'd also pay more for a heat pump that's twice the size.

If you size it to 200% of the cooling load, then it would be rated at 100% of heating load, and it can only deliver 50% of the heating load at the winter design temperature. That leaves about 1600 degree-days to be delivered through supplemental heat. At 8 BTUs per square foot per degree day, a 2000 square foot house would need 256 therms of supplemental heat, or 7500 kWh. At 16 cents per kWh, it would cost $1,200 per year just for supplemental heat! The heat pump itself adds a couple of thousand dollars on top of that.

The numbers just don't work out in New Jersey's climate when you're paying 16 cents per kWh. You're either oversizing or undersizing the heat pump. There's no sweet spot, like there is in Georgia or Florida. American heat pumps are squeezed from one side by Asian mini-splits, and they're squeezed from the other side by gas furnaces.
brianH
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Re: Heat Pump Purchase

Post by brianH »

talzara wrote: Thu Jun 24, 2021 2:43 pm The numbers just don't work out in New Jersey's climate when you're paying 16 cents per kWh. You're either oversizing or undersizing the heat pump. There's no sweet spot, like there is in Georgia or Florida. American heat pumps are squeezed from one side by Asian mini-splits, and they're squeezed from the other side by gas furnaces.
And yet, in nearby and similar-climate Philadelphia, I see plenty of houses running only electric (HP+strips.) Mostly the conventional, central-split variety. There's no question that many of the Asian mini-split systems have much higher efficiencies and better output in sub-zero temps, but somehow, many houses in the coastal Mid-Atlantic get by just fine on conventional HPs.
bi0hazard
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Re: Heat Pump Purchase

Post by bi0hazard »

Some thoughts, running 3 hvac units:

- anecdotally Lennox is low quality and Carrier is great. I have both.

- I go for lower grade units since I usually can’t justify increased price by energy cost saving . But then again, I’m “frugal”.

- It is very important to have a good warranty on the product and company that is large enough to service 24/7 without hassle if needed. Larger hvac companies warranty parts longer than manufacturer warranty. So, IMO it is better to pay extra to have a well established hvac company do this job, rather than a single man operation.
Disclaimer: I'm not very smart, and this is just my hypothesis.
tibbitts
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Re: Heat Pump Purchase

Post by tibbitts »

talzara wrote: Thu Jun 24, 2021 12:50 pm
Valuethinker wrote: Wed Jun 23, 2021 8:00 am It seems like a big jump in price (I am not US based). SEER rating though may be quite different? New Jersey has relatively high electricity prices by US standards, so there will be a payback (I assume it's a very long payback, but there will be one ie the net cost of this is less than $4000).
It's unlikely that there will be a payback.

There is a loss of efficiency from short-cycling, but it's greatly exaggerated. Air conditioners approach their maximum efficiency at just 10 minutes of runtime.

The cycles have to be very short to earn back $4,000.
This might also have something to do with the architecture of the system, and obviously local electricity rates. I have a bottom-floor condo where I'm very comfortable with a single-speed system. On the other hand, with my house, you really never want the air to go off, because the ducts will heat up to well over 100F, and you're going to blow all that hot air back into your house. Yes, the ducts are all insulated, but extreme attic heat will overcome any reasonable amount of insulation in a very short time. Maybe some of the same issues exist for heat as well as cooling.
mgensler
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Re: Heat Pump Purchase

Post by mgensler »

+1 we are in the process of installing Fujitsu mini splits. They output 100% of the rated BTU at -15 degrees F. No need for backup heat.
talzara wrote: Thu Jun 24, 2021 12:46 pm
dfin wrote: Wed Jun 23, 2021 7:50 am Replacing an older heat pump and air handler (full electric). Have a quote for Lennox ML14XP1 single stage (Merit series economy line) vs Carrier 25HCE4 two stage (Performance series mid line). Carrier option is approximately $4,000 higher. Anyone have any input whether the two stage is worth the additional cost? Located in Jersey where we pretty much get both extremes (hot and cold).
Neither system makes sense for New Jersey, a heating-dominated climate where the winter design temperature is 15°F.

American heat pumps perform poorly at low temperatures. According to the performance curve in the specifications, the Carrier 25HCE4 only delivers its rated capacity at 52°F. Performance drops to 73% of rated capacity at 32°F, and only 51% of rated capacity at 15°F.

Electricity in New Jersey costs 16 cents per kWh, which is 5 times the cost of natural gas and 1.7 times the cost of propane. At those prices, electric heat strips are economically infeasible for supplemental heating. It costs less to operate a gas furnace for supplemental heat, even if you have to burn propane.

If you want to stay all-electric, it'll cost a lot less to operate low-temperature mini-splits from Fujitsu, Mitsubishi, and other Asian manufacturers. They have heat pumps that can deliver their rated capacity down to 0 degrees Fahrenheit. They'll cost a lot more to install, but you were willing to spend an extra $4,000 just to upgrade to two-stage. Switching to mini-splits is a much better way to spend $4,000.
Designairohio
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Re: Heat Pump Purchase

Post by Designairohio »

mgensler wrote: Thu Jun 24, 2021 6:37 pm +1 we are in the process of installing Fujitsu mini splits. They output 100% of the rated BTU at -15 degrees F. No need for backup heat.
talzara wrote: Thu Jun 24, 2021 12:46 pm
dfin wrote: Wed Jun 23, 2021 7:50 am Replacing an older heat pump and air handler (full electric). Have a quote for Lennox ML14XP1 single stage (Merit series economy line) vs Carrier 25HCE4 two stage (Performance series mid line). Carrier option is approximately $4,000 higher. Anyone have any input whether the two stage is worth the additional cost? Located in Jersey where we pretty much get both extremes (hot and cold).
Neither system makes sense for New Jersey, a heating-dominated climate where the winter design temperature is 15°F.

American heat pumps perform poorly at low temperatures. According to the performance curve in the specifications, the Carrier 25HCE4 only delivers its rated capacity at 52°F. Performance drops to 73% of rated capacity at 32°F, and only 51% of rated capacity at 15°F.

Electricity in New Jersey costs 16 cents per kWh, which is 5 times the cost of natural gas and 1.7 times the cost of propane. At those prices, electric heat strips are economically infeasible for supplemental heating. It costs less to operate a gas furnace for supplemental heat, even if you have to burn propane.

If you want to stay all-electric, it'll cost a lot less to operate low-temperature mini-splits from Fujitsu, Mitsubishi, and other Asian manufacturers. They have heat pumps that can deliver their rated capacity down to 0 degrees Fahrenheit. They'll cost a lot more to install, but you were willing to spend an extra $4,000 just to upgrade to two-stage. Switching to mini-splits is a much better way to spend $4,000.
Fujitsu also makes a full size air handler that can be connected to a mini split outdoor unit.
Inverter technology, super efficient and dependable
Ken
Valuethinker
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Re: Heat Pump Purchase

Post by Valuethinker »

talzara wrote: Thu Jun 24, 2021 2:43 pm
brianH wrote: Thu Jun 24, 2021 1:06 pm There are too many assumptions here to make that blanket statement. Heat strips are inexpensive to add (assuming the circuits are run), and require zero maintenance. Adding a separate furnace (and propane tank if no natural gas) is a huge upfront cost, and that furnace requires separate maintenance. Propane costs are highly variable, and often spike 2-3x in the dead of Winter.

If the HP is sized properly, and the house is well-insulated and tight, it may need very little supplemental heat from the strips.
The problem in New Jersey is that the heating load is double the cooling load. The winter design temperature is 15°F, and the summer design temperature is 90°F.

New Jersey is a heating-dominated climate. Newark gets 4,700 heating degree-days per year, but only 1,200 cooling degree-days. You need almost four times as much heating as cooling.

To use zero supplemental heat, you'd need a heat pump rated for 200% of the heating load, so it can deliver 100% of the design heating load. Then it would be hugely oversized in summer at 400% of the cooling load. Even then, the heat pump would have a low COP at low temperatures. You'd also pay more for a heat pump that's twice the size.

If you size it to 200% of the cooling load, then it would be rated at 100% of heating load, and it can only deliver 50% of the heating load at the winter design temperature. That leaves about 1600 degree-days to be delivered through supplemental heat. At 8 BTUs per square foot per degree day, a 2000 square foot house would need 256 therms of supplemental heat, or 7500 kWh. At 16 cents per kWh, it would cost $1,200 per year just for supplemental heat! The heat pump itself adds a couple of thousand dollars on top of that.

The numbers just don't work out in New Jersey's climate when you're paying 16 cents per kWh. You're either oversizing or undersizing the heat pump. There's no sweet spot, like there is in Georgia or Florida. American heat pumps are squeezed from one side by Asian mini-splits, and they're squeezed from the other side by gas furnaces.
I had not considered that OP would be using Heat Pump to heat as well as cool.

Normally if you have access to Natural Gas, it is a far cheaper way to heat the house/ heat hot water. CO2 is an issue - I burn about 6 tonnes pa. There are offset programmes, but I don't have a lot of confidence in the ones I have seen.

You are right that the Japanese seem to have far better HPs for heating purposes.
Valuethinker
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Re: Heat Pump Purchase

Post by Valuethinker »

brianH wrote: Thu Jun 24, 2021 3:19 pm
talzara wrote: Thu Jun 24, 2021 2:43 pm The numbers just don't work out in New Jersey's climate when you're paying 16 cents per kWh. You're either oversizing or undersizing the heat pump. There's no sweet spot, like there is in Georgia or Florida. American heat pumps are squeezed from one side by Asian mini-splits, and they're squeezed from the other side by gas furnaces.
And yet, in nearby and similar-climate Philadelphia, I see plenty of houses running only electric (HP+strips.) Mostly the conventional, central-split variety. There's no question that many of the Asian mini-split systems have much higher efficiencies and better output in sub-zero temps, but somehow, many houses in the coastal Mid-Atlantic get by just fine on conventional HPs.
Do these houses not have gas furnaces? Are there parts of Philadelphia which just don't have gas?
brianH
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Re: Heat Pump Purchase

Post by brianH »

Valuethinker wrote: Fri Jun 25, 2021 5:04 am
brianH wrote: Thu Jun 24, 2021 3:19 pm And yet, in nearby and similar-climate Philadelphia, I see plenty of houses running only electric (HP+strips.) Mostly the conventional, central-split variety. There's no question that many of the Asian mini-split systems have much higher efficiencies and better output in sub-zero temps, but somehow, many houses in the coastal Mid-Atlantic get by just fine on conventional HPs.
Do these houses not have gas furnaces? Are there parts of Philadelphia which just don't have gas?
I'm mostly referencing the Philly suburbs. Oil is still pretty popular out here, because NG infrastructure isn't everywhere, and propane tends to be more expensive than areas in the Midwest and South (probably due to its lack of popularity.)

The local electric utility played a big part in all-electric houses. They used to have a special 'heating' rate where over 700kWh in a month got a significant price break. Of course, they eliminated that program about a decade ago, screwing over many homes that relied on baseboard heaters!

Nevertheless, many homes have moved away from oil to just heat pumps.
blueberrypi
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Re: Heat Pump Purchase

Post by blueberrypi »

I notice most of the new construction in my area (Maine) also uses mini splits, despite the cold winters here. Mitsubishi Hyper-Heat is what I've had in my apartment this past year. I am totally sold on it and would happily pay to have one installed were I to buy a place that wasn't equipped.
talzara
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Re: Heat Pump Purchase

Post by talzara »

brianH wrote: Thu Jun 24, 2021 3:19 pm And yet, in nearby and similar-climate Philadelphia, I see plenty of houses running only electric (HP+strips.) Mostly the conventional, central-split variety. There's no question that many of the Asian mini-split systems have much higher efficiencies and better output in sub-zero temps, but somehow, many houses in the coastal Mid-Atlantic get by just fine on conventional HPs.
Philadelphia pays 15 cents per kWh for electricity. The numbers don't work out there either.

It's common to find inefficient HVAC systems in American houses. Usually it's because the owners cannot wait to recoup the up-front costs in lower operational costs. If it takes 8 years to earn a payback, but the owners plan to move in 5 years, they'll install a lower-cost system that has higher operational costs.

Also, not every HVAC contractor installs Asian mini-splits. They may never have been offered as an option.
talzara
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Re: Heat Pump Purchase

Post by talzara »

tibbitts wrote: Thu Jun 24, 2021 6:29 pm This might also have something to do with the architecture of the system, and obviously local electricity rates. I have a bottom-floor condo where I'm very comfortable with a single-speed system. On the other hand, with my house, you really never want the air to go off, because the ducts will heat up to well over 100F, and you're going to blow all that hot air back into your house. Yes, the ducts are all insulated, but extreme attic heat will overcome any reasonable amount of insulation in a very short time. Maybe some of the same issues exist for heat as well as cooling.
It actually works the other way. When the ducts run through the attic, a two-stage air conditioner will gain more heat from the attic than a single-stage air conditioner.

Since the air is traveling at a lower velocity in first stage, it will pick up more heat as it's passing through the attic ductwork. A single-stage system will shut off, allow the ducts to approach the attic temperature, and then send a blast of cold air through the ducts at high velocity. It doesn't get a chance to pick up as much heat.

The Florida Solar Energy Center has done several studies of air conditioner sizing. A right-sized unit is better than an oversized unit, but the improvement is smaller when the ducts are in the attic:
... right-sizing yielded 4.2% and 5.9% annual cooling energy savings for attic ducts and indoor ducts, respectively.

https://publications.energyresearch.ucf ... 040-15.pdf
When the ducts are especially leaky, a smaller unit can actually increase the amount of energy used. This happens when the duct gains are larger than the improvement to compressor efficiency:
We conclude from the three analysis methods that the new downsized system increased daily space cooling energy use by 8 to 18%. The most likely explanation for the poorer performance of the new air conditioner system is that with the greater runtime of the new air-conditioning system, that duct leakage and conduction to the attic duct system is placing a considerable additional load on the AC system and, in the case of any supply leaks, loss of conditioned air.

https://publications.energyresearch.ucf ... 641-06.pdf
This is what makes HVAC so hard. Your intuition doesn't work for thermodynamics. You have to take measurements and do calculations to find out what's actually happening.
Valuethinker
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Re: Heat Pump Purchase

Post by Valuethinker »

brianH wrote: Fri Jun 25, 2021 7:55 am
Valuethinker wrote: Fri Jun 25, 2021 5:04 am
brianH wrote: Thu Jun 24, 2021 3:19 pm And yet, in nearby and similar-climate Philadelphia, I see plenty of houses running only electric (HP+strips.) Mostly the conventional, central-split variety. There's no question that many of the Asian mini-split systems have much higher efficiencies and better output in sub-zero temps, but somehow, many houses in the coastal Mid-Atlantic get by just fine on conventional HPs.
Do these houses not have gas furnaces? Are there parts of Philadelphia which just don't have gas?
I'm mostly referencing the Philly suburbs. Oil is still pretty popular out here, because NG infrastructure isn't everywhere, and propane tends to be more expensive than areas in the Midwest and South (probably due to its lack of popularity.)

The local electric utility played a big part in all-electric houses. They used to have a special 'heating' rate where over 700kWh in a month got a significant price break. Of course, they eliminated that program about a decade ago, screwing over many homes that relied on baseboard heaters!

Nevertheless, many homes have moved away from oil to just heat pumps.
Thank you. All makes sense.

If you don't have natural gas, then going from oil to a Heat Pump makes sense, probably.

Getting away from electric baseboard definitely does.
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dfin
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Re: Heat Pump Purchase

Post by dfin »

Just returned to this thread after starting it a week ago. It's been interesting reading through all the posts. I've also been to a couple other HVAC forums and there doesn't appear (at least from my perspective) that there is any one answer.

So let me ask a somewhat different question. I "believe" I'm leaning towards a single stage unit vs two stage. To reiterate, we currently have a 2.5 ton heat pump in a 2,100 sq ft home in NJ and natural gas is not available.

I've had 4 contractors out thus far. Related to the single stage, 3 of the 4 have suggested 3 ton (not sure they have done manual J load calc but I'm thinking not). The 4th contractor has done load calc and says the 2.5 is ok.

Could a 3 ton really cause any issues? I realize bigger isn't always better here but I'm thinking (layman here) that the increase would be more positive than negative and this is the one opportunity I have to "enhance" what I have now. I'm thinking since I'm not looking to increase size dramatically it would probably be fine? Again layman here...

Thanks,
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Nate79
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Re: Heat Pump Purchase

Post by Nate79 »

dfin wrote: Thu Jul 01, 2021 9:42 am Just returned to this thread after starting it a week ago. It's been interesting reading through all the posts. I've also been to a couple other HVAC forums and there doesn't appear (at least from my perspective) that there is any one answer.

So let me ask a somewhat different question. I "believe" I'm leaning towards a single stage unit vs two stage. To reiterate, we currently have a 2.5 ton heat pump in a 2,100 sq ft home in NJ and natural gas is not available.

I've had 4 contractors out thus far. Related to the single stage, 3 of the 4 have suggested 3 ton (not sure they have done manual J load calc but I'm thinking not). The 4th contractor has done load calc and says the 2.5 is ok.

Could a 3 ton really cause any issues? I realize bigger isn't always better here but I'm thinking (layman here) that the increase would be more positive than negative and this is the one opportunity I have to "enhance" what I have now. I'm thinking since I'm not looking to increase size dramatically it would probably be fine? Again layman here...

Thanks,
How did your existing 2.5ton system handle this heat wave we just got on the East Coast (I'm just south of you in Delaware)?
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dfin
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Re: Heat Pump Purchase

Post by dfin »

Able to maintain 70 or 72 downstairs with a 5 - 7 higher temp upstairs. Humidity mid 50s to 60s. Can maintain 68 in the winter but system runs much more in cold temp.
andypanda
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Re: Heat Pump Purchase

Post by andypanda »

The question according to the pros on HVAC-Talk would be if your ductwork can handle 3 tons and all that extra air. Actually, they'd start by asking if your ducts are large enough for the 2.5 tons you have now. The fan can only move so much air per minute or hour through the ducts. Trying to move more strains the blower. And then there's the whole issue of the size of your returns. You have to have enough ductwork to get that air back to the air handler. Too many restrictions makes for a lot of noise, etc.

Other things I've learned on that site include, "Two stories, two systems" because it's hard to push air uphill and if you zone then each zone needs to be able to handle the blower output, etc., so you're back to the duct work. If your downstairs is cold and not calling for air, can the upstairs zone handle what the system produces?

Luckily we were dealing with one story and I went with an all-variable system to help deal with central Virginia humidity and prevent temp swings in the house by having a steady, slow flow of conditioned air.

No, the system isn't saving us any money in the sense that it's paying for itself with the savings, but we like it. Let's see, if you save $50/month year round and you paid $19k for the new ducts and heat pump and you're 70, how long is the payback period? :) Answer: the payback is daily comfort.
talzara
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Re: Heat Pump Purchase

Post by talzara »

dfin wrote: Thu Jul 01, 2021 10:30 am Able to maintain 70 or 72 downstairs with a 5 - 7 higher temp upstairs. Humidity mid 50s to 60s. Can maintain 68 in the winter but system runs much more in cold temp.
You have a humidity problem. Manual J targets 50% relative humidity, and 55% is allowed in very humid climates. 60% relative humidity is too high.

Oversized air conditioners are worse at dehumidification. You already have a humidity problem at 2.5 tons, and you'll have an even worse problem at 3 tons. However, system sizing takes a back seat to finding out where the humidity is coming from. Are there air leaks? Is the basement wet? Are the ducts running through the attic?
dfin wrote: Thu Jul 01, 2021 9:42 am I've had 4 contractors out thus far. Related to the single stage, 3 of the 4 have suggested 3 ton (not sure they have done manual J load calc but I'm thinking not). The 4th contractor has done load calc and says the 2.5 is ok.
Since the 4th contractor is the only one who did a load calculation, this is the only one you should trust.

The problem with HVAC is that there are so many details to distract the consumer from what really matters. First, you asked about two-stage systems. However, you were setting dollar bills on fire in winter by running electrical resistance heat strips at 16 cents per kWh. Now, you're asking about increasing system size. However, you actually have a humidity problem.

It's easy to sell the consumer on equipment features. It's hard to sell proper system design.
talzara
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Re: Heat Pump Purchase

Post by talzara »

andypanda wrote: Thu Jul 01, 2021 12:11 pm The question according to the pros on HVAC-Talk would be if your ductwork can handle 3 tons and all that extra air. Actually, they'd start by asking if your ducts are large enough for the 2.5 tons you have now. The fan can only move so much air per minute or hour through the ducts. Trying to move more strains the blower. And then there's the whole issue of the size of your returns. You have to have enough ductwork to get that air back to the air handler. Too many restrictions makes for a lot of noise, etc.
The average residential HVAC system in the United States has:
  • An oversized air conditioner
  • Undersized ducts
  • Undersized return ducts compared to the supply ducts
  • No balancing dampers
  • No return visit from the HVAC contractor to commission the system after the house has been completed
It's no wonder that so many people have problems with climate control.
andypanda wrote: Thu Jul 01, 2021 12:11 pm Luckily we were dealing with one story and I went with an all-variable system to help deal with central Virginia humidity and prevent temp swings in the house by having a steady, slow flow of conditioned air.
Two-stage and variable-speed systems will reduce humidity in partial-load conditions. They do not help at full load.

The OP said that humidity was "mid 50s to 60s" during a heat wave. Yesterday, the high temperature in Newark, NJ was 102°F, and the high dewpoint was 73°F. This was above the design temperature but at the design dewpoint. Under those conditions, the relative humidity might creep up to 55%, but 60+% is too much.
brianH
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Re: Heat Pump Purchase

Post by brianH »

andypanda wrote: Thu Jul 01, 2021 12:11 pm The question according to the pros on HVAC-Talk would be if your ductwork can handle 3 tons and all that extra air.
Absolutely. The basic metric is 400 cubic feet per minute of air, per ton. That is a LOT of air, and systems are particularly sensitive to undersized returns, which most houses have.

Undersized duct work can lead to icing over in the summer and high head pressures and shutdown in heat mode. In addition, if you have electric heat strips, those require a certain amount of airflow so they don't get too hot and burn out.
Valuethinker
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Re: Heat Pump Purchase

Post by Valuethinker »

dfin wrote: Thu Jul 01, 2021 9:42 am Just returned to this thread after starting it a week ago. It's been interesting reading through all the posts. I've also been to a couple other HVAC forums and there doesn't appear (at least from my perspective) that there is any one answer.

So let me ask a somewhat different question. I "believe" I'm leaning towards a single stage unit vs two stage. To reiterate, we currently have a 2.5 ton heat pump in a 2,100 sq ft home in NJ and natural gas is not available.

I've had 4 contractors out thus far. Related to the single stage, 3 of the 4 have suggested 3 ton (not sure they have done manual J load calc but I'm thinking not). The 4th contractor has done load calc and says the 2.5 is ok.

Could a 3 ton really cause any issues? I realize bigger isn't always better here but I'm thinking (layman here) that the increase would be more positive than negative and this is the one opportunity I have to "enhance" what I have now. I'm thinking since I'm not looking to increase size dramatically it would probably be fine? Again layman here...

Thanks,
An oversized AC cycles too much and is uncomfortable. You don't want to oversize (although an undersize would probably be worse).
Topic Author
dfin
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Re: Heat Pump Purchase

Post by dfin »

brianH wrote: Thu Jul 01, 2021 7:33 pm
andypanda wrote: Thu Jul 01, 2021 12:11 pm The question according to the pros on HVAC-Talk would be if your ductwork can handle 3 tons and all that extra air.
Absolutely. The basic metric is 400 cubic feet per minute of air, per ton. That is a LOT of air, and systems are particularly sensitive to undersized returns, which most houses have.

Undersized duct work can lead to icing over in the summer and high head pressures and shutdown in heat mode. In addition, if you have electric heat strips, those require a certain amount of airflow so they don't get too hot and burn out.
I just measured the duct work that the air handler goes into and it's 20 x 8 rectangular. From what I can find that's 750 cfm (I think). Would those dimensions stand for the entire house? Anything we can take away from this?
tibbitts
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Re: Heat Pump Purchase

Post by tibbitts »

talzara wrote: Fri Jun 25, 2021 2:45 pm
tibbitts wrote: Thu Jun 24, 2021 6:29 pm This might also have something to do with the architecture of the system, and obviously local electricity rates. I have a bottom-floor condo where I'm very comfortable with a single-speed system. On the other hand, with my house, you really never want the air to go off, because the ducts will heat up to well over 100F, and you're going to blow all that hot air back into your house. Yes, the ducts are all insulated, but extreme attic heat will overcome any reasonable amount of insulation in a very short time. Maybe some of the same issues exist for heat as well as cooling.
It actually works the other way. When the ducts run through the attic, a two-stage air conditioner will gain more heat from the attic than a single-stage air conditioner.

Since the air is traveling at a lower velocity in first stage, it will pick up more heat as it's passing through the attic ductwork. A single-stage system will shut off, allow the ducts to approach the attic temperature, and then send a blast of cold air through the ducts at high velocity. It doesn't get a chance to pick up as much heat.
I wouldn't have thought the efficiency would have been more with single stage cycling on and off, so that's interesting, although in terms of the comfort I was addressing, in practice it's not as comfortable to have the blast of hot air followed (after a long wait) by cold air blowing on me periodically at higher velocity. So most people would want to avoid that if possible.

This year has been a completely different experience for me with my two-stage with attic ducts than any year in recent memory. So far there hasn't been anywhere the same amount of hot weather that was very common in previous years. In previous years I simply didn't have enough cooling capability, and if I let the cooling get behind at all (like during the 4-7pm high-rate period, or when I'd be gone all day with the temperature set up a little) it would run at maximum and not catch up until midnight if then. With the temperatures this year I'd like to have a stage 1.5, since 1 might never get the house down to the temperature I want (I have it set for about 20min run time before 2 starts), but 2 blows a annoying hard sometimes and then shuts off completely. But overall this year I'd say my 3t unit is about right, whereas in every previous year in memory it wasn't enough.
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