Forced air furnace - fix or replace

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cadreamer2015
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Forced air furnace - fix or replace

Post by cadreamer2015 »

Our natural gas forced air furnace isn’t working reliably. We had an HVAC company out on Friday and they say it’s a bad circuit board in the controller. They didn’t have the correct unit on the truck. They say it will be about $600 to replace the circuit board and maybe $200 or $300 more if they also have to replace the pressure switch. The furnace is 20 years old and was probably builder standard grade. We live in San Diego county so no super heating load in the winter, but we’d like to have heat! I think it’s size is 75,000 BTU/hr. I’ve read on line (mostly on HVAC company websites) that a forced air furnace should last 15-30 years. The rough estimate to install a completely new furnace is $4,000-$6,000 depending on quality.

So the question is: should we attempt to fix the furnace with a replacement control board, or bite the bullet and get a new furnace, which will be more efficient and have a warranty of some sort? We will probably stay in the house at least another 10 years.
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inverter
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Re: Forced air furnace - fix or replace

Post by inverter »

In San Diego, I would be moving to a heat pump as soon as you can. Much more efficient than traditional A/C and furnace, especially given your climate. If it's a reasonably efficient furnace, I would try and buy time until you can replace the entire system.
JoinToday
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Re: Forced air furnace - fix or replace

Post by JoinToday »

inverter wrote: Sun Oct 24, 2021 10:44 am In San Diego, I would be moving to a heat pump as soon as you can. Much more efficient than traditional A/C and furnace, especially given your climate. If it's a reasonably efficient furnace, I would try and buy time until you can replace the entire system.
1. Is the OP looking for just a heater, or heater + AC? Maybe no need for AC is coastal SD, but it might be nice if inland SD.

2. Electricity cost in Los Angeles (where I live) is expensive. When I looked at mini-split, my estimate was that heating with electricity/heat pump was twice as expensive as natural gas -- maybe my estimates (or my memory) is wrong.

3. I replaced my control board on my heater. I don't remember it being too expensive (but my labor was free) or too difficult. But I has some of the drain hoses plugged which affected the pressure switch operation.
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BolderBoy
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Re: Forced air furnace - fix or replace

Post by BolderBoy »

cadreamer2015 wrote: Sun Oct 24, 2021 10:41 amSo the question is: should we attempt to fix the furnace with a replacement control board, or bite the bullet and get a new furnace, which will be more efficient and have a warranty of some sort? We will probably stay in the house at least another 10 years.
I was faced with this same scenario a year ago. My 19 y/o, 80% GFA, croaked and it was the circuit board. I elected to replace the furnace with a similar, new model for about $4k. No problems and no regrets.

I live in a completely different climate than yours. The heat pump suggestion above may be a better choice for you.
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Big Dog
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Re: Forced air furnace - fix or replace

Post by Big Dog »

Depends on where in SD. If coastal, and no/little need for ac, then I'd just repair. New, efficient furnaces are nice, but any possible savings payback for coastal SoCal is many years. (Heating demand for coastal SoCal is not much.)

OTOH, if SD County means inland, where you use a lot of ac, then I'd look to a heat pump.
talzara
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Re: Forced air furnace - fix or replace

Post by talzara »

cadreamer2015 wrote: Sun Oct 24, 2021 10:41 am The rough estimate to install a completely new furnace is $4,000-$6,000 depending on quality.

So the question is: should we attempt to fix the furnace with a replacement control board, or bite the bullet and get a new furnace, which will be more efficient and have a warranty of some sort? We will probably stay in the house at least another 10 years.
Big Dog wrote: Sun Oct 24, 2021 11:17 am Depends on where in SD. If coastal, and no/little need for ac, then I'd just repair. New, efficient furnaces are nice, but any possible savings payback for coastal SoCal is many years. (Heating demand for coastal SoCal is not much.)
At these prices, there will never be a payback on a new furnace.

North County San Diego isn't that cold. Carlsbad only needs 1,700 degree-days of heating each year. At an average efficiency of 8 BTUs per sqft per degree-day, a 2,000 sqft house with an 80% efficient furnace would only use 340 therms per year. At $1.50 per therm, that's only $510 of natural gas per year.

Upgrading from an 80% efficient furnace to a 95% efficient condensing furnace would only save $81 per year. A $6,000 furnace will take 74 years to earn a payback, so it will fail before it pays for itself.

There are universal control boards that can handle many different models of furnace. The important thing is to match the voltage so you don't burn out the igniter. A 20-year-old furnace might be using an 80 V igniter, so it might be easier to buy a 120 V control board and upgrade the igniter.
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Re: Forced air furnace - fix or replace

Post by talzara »

inverter wrote: Sun Oct 24, 2021 10:44 am In San Diego, I would be moving to a heat pump as soon as you can. Much more efficient than traditional A/C and furnace, especially given your climate. If it's a reasonably efficient furnace, I would try and buy time until you can replace the entire system.
JoinToday wrote: Sun Oct 24, 2021 11:02 am 2. Electricity cost in Los Angeles (where I live) is expensive. When I looked at mini-split, my estimate was that heating with electricity/heat pump was twice as expensive as natural gas -- maybe my estimates (or my memory) is wrong.
Heat pumps are much more efficient in that climate, and they will put less CO₂ into the atmosphere. However, at California electricity prices, heat pumps cost much more to operate than natural gas furnaces. Not twice as much, but about 50% more.

SDG&E's residential tariffs are:
Electricity costs 7 times as much as natural gas. Mini-split heat pumps should be able to achieve a COP of about 4 in that climate, which will not be enough to offset the price advantage of natural gas. Even with an 80% efficient non-condensing gas furnace, it will still cost less to heat with natural gas.

My last post calculated a heating bill of $510 per year for an average 2,000 sqft house in Carlsbad with an 80% efficient natural gas furnace.

Using a mini-split at a COP of 4, the same house will use 1,992 kWh per year, or $797 of electricity at an average of 40 cents per kWh.
Big Dog wrote: Sun Oct 24, 2021 11:17 am Depends on where in SD. If coastal, and no/little need for ac, then I'd just repair. New, efficient furnaces are nice, but any possible savings payback for coastal SoCal is many years. (Heating demand for coastal SoCal is not much.)

OTOH, if SD County means inland, where you use a lot of ac, then I'd look to a heat pump.
At these prices, it makes sense to install a furnace even if you also install an air conditioner.

The OP was quoted $4,000 for the lowest-cost gas furnace. Since it costs $287 less to operate each year than a heat pump, the furnace will pay for itself in 14 years.

The payback period will be shorter if natural gas prices fall relative to electricity prices. It will be longer if natural gas prices rise.
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cadreamer2015
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Re: Forced air furnace - fix or replace

Post by cadreamer2015 »

Thank you all for the very helpful and interesting replies. Some additional information:

The repair tech tried a "universal" control board in our furnace but this did not solve the problem. Hence the idea to try to get the specific control board for this furnace.

We live in coastal SD county. Last year we used about $400 of gas for home heating (not including the usual hot water and cooking usage). We already have central A/C but we only use it about a week per year or less. We have rooftop PV solar. So if we were to go with a heat pump we could probably add additional panels on our roof (there is room both on the roof and in our inverter).
Last edited by cadreamer2015 on Sun Oct 24, 2021 1:30 pm, edited 1 time in total.
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adamthesmythe
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Re: Forced air furnace - fix or replace

Post by adamthesmythe »

I would repair. A natural gas furnace of that age could easily last another 10 years. Or more.

I would consider replacement only if you wanted to add AC.
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Re: Forced air furnace - fix or replace

Post by Big Dog »

talzara wrote: Sun Oct 24, 2021 1:03 pm
inverter wrote: Sun Oct 24, 2021 10:44 am In San Diego, I would be moving to a heat pump as soon as you can. Much more efficient than traditional A/C and furnace, especially given your climate. If it's a reasonably efficient furnace, I would try and buy time until you can replace the entire system.
JoinToday wrote: Sun Oct 24, 2021 11:02 am 2. Electricity cost in Los Angeles (where I live) is expensive. When I looked at mini-split, my estimate was that heating with electricity/heat pump was twice as expensive as natural gas -- maybe my estimates (or my memory) is wrong.
Heat pumps are much more efficient in that climate, and they will put less CO₂ into the atmosphere. However, at California electricity prices, heat pumps cost much more to operate than natural gas furnaces. Not twice as much, but about 50% more.

SDG&E's residential tariffs are:
Electricity costs 7 times as much as natural gas. Mini-split heat pumps should be able to achieve a COP of about 4 in that climate, which will not be enough to offset the price advantage of natural gas. Even with an 80% efficient non-condensing gas furnace, it will still cost less to heat with natural gas.

My last post calculated a heating bill of $510 per year for an average 2,000 sqft house in Carlsbad with an 80% efficient natural gas furnace.

Using a mini-split at a COP of 4, the same house will use 1,992 kWh per year, or $797 of electricity at an average of 40 cents per kWh.
Big Dog wrote: Sun Oct 24, 2021 11:17 am Depends on where in SD. If coastal, and no/little need for ac, then I'd just repair. New, efficient furnaces are nice, but any possible savings payback for coastal SoCal is many years. (Heating demand for coastal SoCal is not much.)

OTOH, if SD County means inland, where you use a lot of ac, then I'd look to a heat pump.
At these prices, it makes sense to install a furnace even if you also install an air conditioner.

The OP was quoted $4,000 for the lowest-cost gas furnace. Since it costs $287 less to operate each year than a heat pump, the furnace will pay for itself in 14 years.

The payback period will be shorter if natural gas prices fall relative to electricity prices. It will be longer if natural gas prices rise.
yes, no question that natural gas is cheaper to heat, and that is why I recommended repairing the existing furnace for coastal communities.. But if inland, the HP will save an air conditioning costs in the summer as it is more efficient than a standard compressor, correct? So it becomes an economic tradeoff: higher heating costs with an HP, but ac savings in the summer. (ignoring environmental benefits)

btw: I cannot foresee CA regulators allowing natural gas or electricity prices to fall.
Last edited by Big Dog on Sun Oct 24, 2021 3:12 pm, edited 1 time in total.
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Re: Forced air furnace - fix or replace

Post by iamblessed »

My furnace had a board go out. I bought a used tested board(brand name) on ebay and put it in myself. It was not hard to do. The board cost about $60.
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illumination
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Re: Forced air furnace - fix or replace

Post by illumination »

I bet the actual cost of that circuit board is under $100 and takes 15 minutes to replace.
Might want to open it up, take a picture and find and install yourself.
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Watty
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Re: Forced air furnace - fix or replace

Post by Watty »

cadreamer2015 wrote: Sun Oct 24, 2021 10:41 am We will probably stay in the house at least another 10 years.
To me that would tend to favor going on and replacing it. Even if you can fix it now the odds if it lasting another 10 years is not that great.

Be sure to get half a dozen bids though. The last time I replaced HVAC equipment the bids varied dramatically for similar equipment from different companies.
Last edited by Watty on Sun Oct 24, 2021 4:05 pm, edited 1 time in total.
Uniballer
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Re: Forced air furnace - fix or replace

Post by Uniballer »

Diagnosing a pressure switch problem is not rocket science, either, if you have any troubleshooting ability and a few tools.

Check the hoses and fittings to be sure they are not plugged. Watch the pressure switch contacts with a test light or meter. It is awfully easy to find and order replacement parts online compared to 30 years ago.

EDIT: I replaced the 22yo Amana high efficiency furnace in my house last year because it was dripping condensate all over the place and I could no longer get the plastic parts to repair it.
Last edited by Uniballer on Sun Oct 24, 2021 5:14 pm, edited 2 times in total.
Gryphon
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Re: Forced air furnace - fix or replace

Post by Gryphon »

You might also want to take a look at the circuit board & see if you can spot the problem, if you're at all handy with electronics. You might find it's an easy fix.

About 6 or 7 years after I bought my house, the furnace suddenly quit working one day (in February, of course) - the blower motor wouldn't come on. It didn't appear to be a motor problem, as the motor wasn't getting any AC voltage when the furnace tried to turn on. I spent a Saturday afternoon driving around to various repair shops looking for a replacement board without success. I went home & started trying to figure out how I could wire in a manual switch for the motor to get me through the weekend when I noticed a few connections on the board that didn't appear to be soldered. They turned out to be the main connections for the relay controlling the blower. I resoldered them & I was back in business. (The same thing happened again after another 6 or 7 years; I replaced the furnace before a third occurrence).

I never did figure out exactly what was happening to the solder connections - my best guess is some sort of arcing was sometimes occurring when the relay turned off and that was gradually eating away the solder. But in retrospect I was glad I couldn't find a replacement board.
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Re: Forced air furnace - fix or replace

Post by cockersx3 »

iamblessed wrote: Sun Oct 24, 2021 3:11 pm My furnace had a board go out. I bought a used tested board(brand name) on ebay and put it in myself. It was not hard to do. The board cost about $60.
That happened to me as well. In my case the HVAC we called to initially troubleshoot the problem (blower motor not turning on) said the exact same thing as the OP mentioned - replacement will cost >$1000, so I should just look at replacing. Of course, he was more than happy to work me up a quote.

I located the circuit board in the unit within about 5 mins of him leaving, and was able to find a replacement on Amazon for like $60. Took all of about 30 minutes to install - just pulled off all of the electrical connectors on the old board (after taking lots of pictures!), removed the two screws holding the board in, and installed the new board and plugged everything back in.

Long story short - OP should look at the furnace themselves and see if a) the board is easy to find, and if so b) try to locate a replacement themselves. I wouldn't replace an entire furnace just because the motherboard failed.
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Re: Forced air furnace - fix or replace

Post by talzara »

cadreamer2015 wrote: Sun Oct 24, 2021 1:29 pm The repair tech tried a "universal" control board in our furnace but this did not solve the problem. Hence the idea to try to get the specific control board for this furnace.
Since the universal board did not fix it, the problem is probably somewhere else. You have not described the problem or identified the model of furnace, so there's no information to go on.

Furnaces are not that complex, especially builder grade units. Universal boards can do everything that most OEM boards are doing. There's a universal board for most systems: spark ignition, hot surface ignition, 80 V, 120 V, one-stage, two-stage. It's only really the modulating furnaces that have to use an OEM board.

You may want to get a second opinion from a different HVAC technician. There were several air conditioning threads over the summer where the first HVAC tech couldn't figure out the problem, but the second tech did.
cadreamer2015 wrote: Sun Oct 24, 2021 1:29 pm We live in coastal SD county. Last year we used about $400 of gas for home heating (not including the usual hot water and cooking usage). We already have central A/C but we only use it about a week per year or less. We have rooftop PV solar. So if we were to go with a heat pump we could probably add additional panels on our roof (there is room both on the roof and in our inverter).
Based on those numbers, even 75,000 BTU/h is too big for the house. A 4-ton heat pump (48,000 BTU/h) could probably handle the heating load with some resistive backup.

A solar system allows you to avoid the electric utility's distribution costs. However, your heating load will be highest at night, when the sun is not shining. Even on the time-of-use tariff, SDG&E still charges 28.0 cents per kWh for winter off-peak usage.
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Re: Forced air furnace - fix or replace

Post by talzara »

Watty wrote: Sun Oct 24, 2021 3:56 pm
cadreamer2015 wrote: Sun Oct 24, 2021 10:41 am We will probably stay in the house at least another 10 years.
To me that would tend to favor going on and replacing it. Even if you can fix it now the odds if it lasting another 10 years is not that great.
This is a furnace, not an air conditioner.

A 20-year-old air conditioner is likely to be on its last legs.

A 20-year old furnace should be able to last another 10 years. Furnaces are much simpler than air conditioners. It's only when the heat exchanger fails that they become too costly to fix.
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illumination
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Re: Forced air furnace - fix or replace

Post by illumination »

cockersx3 wrote: Sun Oct 24, 2021 5:05 pm
iamblessed wrote: Sun Oct 24, 2021 3:11 pm My furnace had a board go out. I bought a used tested board(brand name) on ebay and put it in myself. It was not hard to do. The board cost about $60.
That happened to me as well. In my case the HVAC we called to initially troubleshoot the problem (blower motor not turning on) said the exact same thing as the OP mentioned - replacement will cost >$1000, so I should just look at replacing. Of course, he was more than happy to work me up a quote.

I located the circuit board in the unit within about 5 mins of him leaving, and was able to find a replacement on Amazon for like $60. Took all of about 30 minutes to install - just pulled off all of the electrical connectors on the old board (after taking lots of pictures!), removed the two screws holding the board in, and installed the new board and plugged everything back in.

Long story short - OP should look at the furnace themselves and see if a) the board is easy to find, and if so b) try to locate a replacement themselves. I wouldn't replace an entire furnace just because the motherboard failed.

I've found HVAC to be one of the sleaziest trades. So many stories like this.
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Re: Forced air furnace - fix or replace

Post by talzara »

iamblessed wrote: Sun Oct 24, 2021 3:11 pm My furnace had a board go out. I bought a used tested board(brand name) on ebay and put it in myself. It was not hard to do. The board cost about $60.
illumination wrote: Sun Oct 24, 2021 3:51 pm I bet the actual cost of that circuit board is under $100 and takes 15 minutes to replace.
Might want to open it up, take a picture and find and install yourself.
cockersx3 wrote: Sun Oct 24, 2021 5:05 pm I located the circuit board in the unit within about 5 mins of him leaving, and was able to find a replacement on Amazon for like $60. Took all of about 30 minutes to install - just pulled off all of the electrical connectors on the old board (after taking lots of pictures!), removed the two screws holding the board in, and installed the new board and plugged everything back in.
The OP's board has already been replaced with a universal board, and that did not solve the problem.

Unless the OEM board is doing something that the universal board can't do, replacing the board should've fixed it or at least changed the symptoms. However, it is possible that the tech installed an incompatible board or did not install it correctly. It's also possible that there's something wrong with the wiring, so a new board will behave exactly the same as the old board.

The OP has not described the actual problem with the furnace, so we don't have any idea what might be happening.
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Re: Forced air furnace - fix or replace

Post by talzara »

Big Dog wrote: Sun Oct 24, 2021 2:55 pm But if inland, the HP will save an air conditioning costs in the summer as it is more efficient than a standard compressor, correct?
The OP said the house was on the coast. However, your statement is not correct. Heat pumps are no more efficient than air conditioners.

An American heat pump is just an air conditioner with some parts added to run in reverse. When used for cooling, it performs as well as or worse than the same model of air conditioner. Compare the Trane heat pump brochure with the Trane air conditioner brochure (page 5):
  • XV20i: heat pump 21 SEER, AC 22 SEER
  • XV18: heat pump 18 SEER, AC 18 SEER
  • XL18i: heat pump 18 SEER, AC 18 SEER
  • XL16i: heat pump 17 SEER, AC 17 SEER
  • XR17: heat pump 17.25 SEER, AC 18 SEER
  • XR16: heat pump 17 SEER, AC 17 SEER
  • XR14: heat pump 14.5 SEER, AC 16 SEER
The Asian HVAC manufacturers design their mini-splits as heat pumps first. They have exactly the same efficiency when run as air conditioners. Compare the equivalent heat pumps and air conditioners in the Mitsubishi M-series catalog (page 4):
  • MUY-GL09NA heat pump 24.6 SEER, MUZ-GL09NA AC 24.6 SEER
  • MUY-GL12NA heat pump 23.1 SEER, MUZ-GL12NA AC 23.1 SEER
  • MUY-GL15NA heat pump 21.6 SEER, MUZ-GL15NA AC 21.6 SEER
  • MUY-GL18NA heat pump 20.5 SEER, MUZ-GL18NA AC 20.5 SEER
  • MUY-GL24NA heat pump 20.5 SEER, MUZ-GL24NA AC 20.5 SEER
By the way, the catalogs show that a mid-range Mitsubishi performs about as well as a top-end Trane. Mitsubishi's top-end model has a SEER of 33.1!
Last edited by talzara on Mon Oct 25, 2021 8:12 pm, edited 1 time in total.
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Re: Forced air furnace - fix or replace

Post by illumination »

talzara wrote: Sun Oct 24, 2021 5:25 pm
iamblessed wrote: Sun Oct 24, 2021 3:11 pm My furnace had a board go out. I bought a used tested board(brand name) on ebay and put it in myself. It was not hard to do. The board cost about $60.
illumination wrote: Sun Oct 24, 2021 3:51 pm I bet the actual cost of that circuit board is under $100 and takes 15 minutes to replace.
Might want to open it up, take a picture and find and install yourself.
cockersx3 wrote: Sun Oct 24, 2021 5:05 pm I located the circuit board in the unit within about 5 mins of him leaving, and was able to find a replacement on Amazon for like $60. Took all of about 30 minutes to install - just pulled off all of the electrical connectors on the old board (after taking lots of pictures!), removed the two screws holding the board in, and installed the new board and plugged everything back in.
The OP's board has already been replaced with a universal board, and that did not solve the problem.

Unless the OEM board is doing something that the universal board can't do, replacing the board should've fixed it or at least changed the symptoms. However, it is possible that the tech installed an incompatible board or did not install it correctly. It's also possible that there's something wrong with the wiring, so a new board will behave exactly the same as the old board.

The OP has not described the actual problem with the furnace, so we don't have any idea what might be happening.

It really just screams to me that there's an incompetent tech involved. They should be able to troubleshoot if the circuit board is at fault before even replacing. So then they replace with a universal circuit board, and it still doesn't fix it, but they still think a factory one might resolve it (for $600) or it could also be a pressure switch? How about getting out your multimeter and figuring it out first before installing all of these parts?

I don't know what's going on, but my shoot from the hip is that's a relatively easy and cheap fix on a simple, 20 year old gas furnace, but the outfit would rather sell them a whole new system (which will absolutely never pay for itself). The OP says their gas bill for the entire year in CA is $400, no way would I change anything.
Californiastate
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Re: Forced air furnace - fix or replace

Post by Californiastate »

Repair the existing furnace. My existing furnace is approaching 30 years old. I won't be replacing it until my condenser/compressor give up the ghost. Then I'll go to a variable speed system. Until then I'd put $1k into repairs on the furnace.
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Re: Forced air furnace - fix or replace

Post by Trader Joe »

cadreamer2015 wrote: Sun Oct 24, 2021 10:41 am Our natural gas forced air furnace isn’t working reliably. We had an HVAC company out on Friday and they say it’s a bad circuit board in the controller. They didn’t have the correct unit on the truck. They say it will be about $600 to replace the circuit board and maybe $200 or $300 more if they also have to replace the pressure switch. The furnace is 20 years old and was probably builder standard grade. We live in San Diego county so no super heating load in the winter, but we’d like to have heat! I think it’s size is 75,000 BTU/hr. I’ve read on line (mostly on HVAC company websites) that a forced air furnace should last 15-30 years. The rough estimate to install a completely new furnace is $4,000-$6,000 depending on quality.

So the question is: should we attempt to fix the furnace with a replacement control board, or bite the bullet and get a new furnace, which will be more efficient and have a warranty of some sort? We will probably stay in the house at least another 10 years.
Fix the furnace. Do not get a new furnace.
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Re: Forced air furnace - fix or replace

Post by rivercrosser »

Right now HVAC dealers are having problems getting parts and equipment here in MO. My whole system got hit by lightning back in Aug. They could get a board but not the motor. After a closer look it was so bad the insurance investigator recommended replacement of everything. I wanted to go back with the same brand but they never could get a system in comparable to what I had. We went without AC all this time. With cold weather coming I finally went with a different brand. Got it all installed last Monday. Was a large dealer that had stocked up on equipment. But even he was starting to have problems getting equipment. They had the furnace I wanted. The AC unit I wanted was out of stock. Didn't know when he would get one in. Ended up with a dual fuel system. He gave me the heat pump for the same price as a regular ac unit and I'll get a rebate that way. Insurance paid for a similar system to what I had so I spent a good bit out of pocket but I have a nicer system now.
Last edited by rivercrosser on Mon Oct 25, 2021 1:11 pm, edited 1 time in total.
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Re: Forced air furnace - fix or replace

Post by Hockey10 »

rivercrosser wrote: Mon Oct 25, 2021 11:23 am Right now HVAC dealers are having problems getting parts and equipment here in MO.
Same thing going on in my area. Recently needed a replacement part for my furnace, as it was not working. HVAC company told me part was on backorder and had no idea when it would come in. About a week later, they managed to find the part and fix the furnace. Just glad this happened in Oct and not Jan/Feb.
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Re: Forced air furnace - fix or replace

Post by skis4hire »

If you do end up replacing the unit, I would also advocate for a heat pump.

The upside that I did not see discussed above is an increase in comfort. A modulating heat pump with variable blower will keep the temperature of your house much more consistent and you won't 'feel' the heat coming on/turning off with large changes in air movement because it will instead run longer at lower air flow.

[OT comments removed by admin LadyGeek]
talzara
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Re: Forced air furnace - fix or replace

Post by talzara »

illumination wrote: Sun Oct 24, 2021 6:36 pm It really just screams to me that there's an incompetent tech involved. They should be able to troubleshoot if the circuit board is at fault before even replacing. So then they replace with a universal circuit board, and it still doesn't fix it, but they still think a factory one might resolve it (for $600) or it could also be a pressure switch? How about getting out your multimeter and figuring it out first before installing all of these parts?
Yes, it sounds like the OP hired a parts changer. There are a lot of them in the residential HVAC industry.

Furnaces are not that complex. The control logic is described in detail in the service manual. As the furnace goes through each step, you can follow along in the manual and find out exactly which step is failing.
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Re: Forced air furnace - fix or replace

Post by talzara »

rivercrosser wrote: Mon Oct 25, 2021 11:23 am Right now HVAC dealers are having problems getting parts and equipment here in MO. My whole system got hit by lightning back in Aug. They could get a board but not the motor. After a closer look it was so bad the insurance investigator recommended replacement of everything. I wanted to go back with the same brand but they never could get a system in comparable to what I had. We went without AC all this time.
There are universal motors, too.

Furnaces are not that complex. The manufacturers are buying from the same suppliers, and you can replace most of the furnace with non-OEM parts.

Air conditioners are much more complex than furnaces. Even a refrigerator is harder to repair than a furnace.
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Re: Forced air furnace - fix or replace

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Re: Forced air furnace - fix or replace

Post by rivercrosser »

talzara wrote: Mon Oct 25, 2021 8:39 pm
rivercrosser wrote: Mon Oct 25, 2021 11:23 am Right now HVAC dealers are having problems getting parts and equipment here in MO. My whole system got hit by lightning back in Aug. They could get a board but not the motor. After a closer look it was so bad the insurance investigator recommended replacement of everything. I wanted to go back with the same brand but they never could get a system in comparable to what I had. We went without AC all this time.
There are universal motors, too.

Furnaces are not that complex. The manufacturers are buying from the same suppliers, and you can replace most of the furnace with non-OEM parts.

Air conditioners are much more complex than furnaces. Even a refrigerator is harder to repair than a furnace.
It was variable speed motor on a modulating furnace. Not sure if they make a universal one it. It was pretty messed up. Burnt the ground wires off in two places at the furnace and burnt a wire off out at the condenser disconnect. Got the board in the condenser. Had burn marks in serveral places. Repair was not an option.
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