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Old 02-07-2019, 05:23 AM   #1
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Replace both A/C unit and gas furnace?


I have a town home that is about 17 years old. It is central air. Located in Virginia, USA. The furnace is gas. Last summer, the A/C unit was on its last leg, thus we would be replacing it for this coming summer.

During this winter, my gas furnace and the blower kept up quite nicely with the cold months. We didn't see any problems with the gas furnace and the blower at all. The only thing that I wish my blower would do is that it would be quieter.

--

So my dilemma is:

should I go ahead and replace the entire system (A/C unit, gas furnace, blower) to a new, more efficient system, and maybe quieter blower?

Or should I only replace the A/C unit and wait for when the blower and/or the gas furnace to die, and replace those?

Or should I replace the A/C unit and the blower? I would ask for a new blower that is quieter and run on brushless motor.

--

The HVAC contractors advice to replace the entire system. He gave quite a logical reason behind his decision. He explained that since the system is quite old, replace the entire system at this point would help save cost and time. Vs having to replace just the A/C unit now, and then some how 2 years down the line either the gas furnace or the blower dies, and then they have to come out again to replace those.

While I think that his reason is sound, I am also caution that he does profit more for replacing the entire system then just the A/C unit.

--

Thus I am here seeking your opinion. What do you think my best option is? Do you think the HVAC contractors gave the best advice for my situation?

--

Thank you.
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Old 02-07-2019, 08:45 AM   #2
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Re: Replace both A/C unit and gas furnace?


I would replace both. Generally you get a better package price. That can save you $3-500 versus doing them separately.

You also have about 5% inflation yearly so the furnace will cost more in the future.

You may get lucky and the furnace lasts another 3-5 years but if not then the first repair will be $300-1000 depending on what the part is.

Fan motors do not use brushes. The ECM variable speed motors are heavier and smoother and are somewhat quieter. However once they get up to speed the air noise from the vents is the same.
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Old 02-07-2019, 09:05 AM   #3
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Re: Replace both A/C unit and gas furnace?


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Originally Posted by yuri View Post
I would replace both. Generally you get a better package price. That can save you $3-500 versus doing them separately.

You also have about 5% inflation yearly so the furnace will cost more in the future.

You may get lucky and the furnace lasts another 3-5 years but if not then the first repair will be $300-1000 depending on what the part is.

Fan motors do not use brushes. The ECM variable speed motors are heavier and smoother and are somewhat quieter. However once they get up to speed the air noise from the vents is the same.
************************************************
[QUOTE=yuri However once they get up to speed the air noise from the vents is the same.[/QUOTE]
************************************************** *

Isn't that the truth. A niece has a large 2 story house with 1 big ole unit and the return air grill is near the floor in the kitchen dining area. It sounds as if a hurricane is approaching and the motor couldn't be heard if we desired to because of air noise.
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Old 02-07-2019, 09:06 AM   #4
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Re: Replace both A/C unit and gas furnace?


You mentioned a new motor would be quieter. What is loud now? Do you get a lot of airflow noise while the unit runs?
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Old 02-07-2019, 09:42 AM   #5
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Re: Replace both A/C unit and gas furnace?


If you can afford the cost for a complete system... one and done!
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Old 02-07-2019, 04:34 PM   #6
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Re: Replace both A/C unit and gas furnace?


Due to the often greater height of new A/C coils, and the shorter new furnaces, it would be better to replace both at the same time.
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Old 02-07-2019, 05:25 PM   #7
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Re: Replace both A/C unit and gas furnace?


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Due to the often greater height of new A/C coils, and the shorter new furnaces, it would be better to replace both at the same time.
I was going to say that.

You end up with a neater job and maybe less chance of rattles. Having to retrofit ACs coils into existing plenums is not always easy.
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Old 02-10-2019, 02:35 AM   #8
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Re: Replace both A/C unit and gas furnace?


Quote:
Originally Posted by 012abc View Post
I have a town home that is about 17 years old. It is central air. Located in Virginia, USA. The furnace is gas. Last summer, the A/C unit was on its last leg, thus we would be replacing it for this coming summer.

During this winter, my gas furnace and the blower kept up quite nicely with the cold months. We didn't see any problems with the gas furnace and the blower at all. The only thing that I wish my blower would do is that it would be quieter.

--

So my dilemma is:

should I go ahead and replace the entire system (A/C unit, gas furnace, blower) to a new, more efficient system, and maybe quieter blower?

Or should I only replace the A/C unit and wait for when the blower and/or the gas furnace to die, and replace those?

Or should I replace the A/C unit and the blower? I would ask for a new blower that is quieter and run on brushless motor.

--

The HVAC contractors advice to replace the entire system. He gave quite a logical reason behind his decision. He explained that since the system is quite old, replace the entire system at this point would help save cost and time. Vs having to replace just the A/C unit now, and then some how 2 years down the line either the gas furnace or the blower dies, and then they have to come out again to replace those.

While I think that his reason is sound, I am also caution that he does profit more for replacing the entire system then just the A/C unit.

--

Thus I am here seeking your opinion. What do you think my best option is? Do you think the HVAC contractors gave the best advice for my situation?

--

Thank you.

If you can afford to replace one by paying someone, then I bet you could DIY and get a whole new system for the price you were going to pay to replace part of it. Once I had my furnace installed by a tech that went through 2 packs of cigs in my garage, and wrapped electrical tape around insulation on the PVC vents haphazardly, I vowed never to pay someone to install my furnace again. If you read up on the process, take your time, you cam do a much better job than someone who is on the clock to git-er-done.. I had success with the hybrid install approach, I buy the gear after ample research, I do the heavy lifting and the time-consuming duct work, then I call in a pro to do the things I can't or don't want to do, like brazing and charging, and handling the refrigerant.. Just an option.. You can install a really nice furnace with heat pump for about 4000 if you do it yourself.
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Old 02-10-2019, 02:40 AM   #9
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Re: Replace both A/C unit and gas furnace?


Quote:
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What is loud now? Do you get a lot of airflow noise while the unit runs?
Thanks for pointing this out. I will investigate.
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Old 02-10-2019, 02:11 PM   #10
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Re: Replace both A/C unit and gas furnace?


I disagree with the majority this time.

I don't see much value in changing a furnace that's working under 20 years old and in good condition unless it's to accomplish something else like reducing utility bills or improving comfort.

You're talking spending thousands of dollars before you need to, to gain what? Some furnaces can last 25 years, just need to get the heat exchanger and other parts checked off season each year so you don't get caught having to make a snap decision in winter.

There's a push in every industry to sell new stuff prematurely - it's more profitable than maintaining, repairing and optimizing what's already there. The quality of the new stuff keeps on going down.

Heck, if the existing a/c isn't leaking refrigerant and has a good compressor, it may be worth keeping. The new ones use thinner copper* and I believe there are class action lawsuits going on against the manufacturers due to leak problems. The parts are mostly made in third world countries and break just after the warranty period.

*Costs less in materials, they can get the same heat transfer with smaller coils.

As far is doing just the a/c goes:


They can most likely change the coil and there should be space unless you go for a higher seer unit. (which needs a matched furnace with the right blower motor anyhow - in which case, change the furnace)

When the furnace goes, they can leave the coil and just build a transition.

Not as pretty but it can work.
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I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.

Last edited by user_12345a; 02-10-2019 at 02:19 PM.
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Old 02-10-2019, 02:47 PM   #11
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Re: Replace both A/C unit and gas furnace?


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Originally Posted by user_12345a View Post
I disagree with the majority this time.

I don't see much value in changing a furnace that's working under 20 years old and in good condition unless it's to accomplish something else like reducing utility bills or improving comfort.

You're talking spending thousands of dollars before you need to, to gain what? Some furnaces can last 25 years, just need to get the heat exchanger and other parts checked off season each year so you don't get caught having to make a snap decision in winter.

There's a push in every industry to sell new stuff prematurely - it's more profitable than maintaining, repairing and optimizing what's already there. The quality of the new stuff keeps on going down.

Heck, if the existing a/c isn't leaking refrigerant and has a good compressor, it may be worth keeping. The new ones use thinner copper* and I believe there are class action lawsuits going on against the manufacturers due to leak problems. The parts are mostly made in third world countries and break just after the warranty period.

*Costs less in materials, they can get the same heat transfer with smaller coils.

As far is doing just the a/c goes:


They can most likely change the coil and there should be space unless you go for a higher seer unit. (which needs a matched furnace with the right blower motor anyhow - in which case, change the furnace)

When the furnace goes, they can leave the coil and just build a transition.

Not as pretty but it can work.

I was reading this thread and thinking 'yikes'; my condensing gas furnace and a/c are 27 years old!


I get it inspected annually and my service shop says the newer ones will probably be more electrically efficient but, to me, the replacement cost has to be considered in one-time today's dollars. If the heat exchanger or control board packs it in I'll replace and, of course, I run the risk of this happening in February, but such is life. If I get a few grand burning a hole in my pocket, I'll proactively replace.
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Old 02-10-2019, 03:58 PM   #12
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Re: Replace both A/C unit and gas furnace?


the newer ones can really improve comfort if you go 2-stage and downsize if oversized and use the right thermostat type. continuous operation in extreme cold is very nice, as comfortable as radiant.
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Old 02-10-2019, 05:42 PM   #13
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Re: Replace both A/C unit and gas furnace?


Quote:
Originally Posted by user_12345a View Post
I disagree with the majority this time.

I don't see much value in changing a furnace that's working under 20 years old and in good condition unless it's to accomplish something else like reducing utility bills or improving comfort.

You're talking spending thousands of dollars before you need to, to gain what? Some furnaces can last 25 years, just need to get the heat exchanger and other parts checked off season each year so you don't get caught having to make a snap decision in winter.

There's a push in every industry to sell new stuff prematurely - it's more profitable than maintaining, repairing and optimizing what's already there. The quality of the new stuff keeps on going down.

Heck, if the existing a/c isn't leaking refrigerant and has a good compressor, it may be worth keeping. The new ones use thinner copper* and I believe there are class action lawsuits going on against the manufacturers due to leak problems. The parts are mostly made in third world countries and break just after the warranty period.

*Costs less in materials, they can get the same heat transfer with smaller coils.

As far is doing just the a/c goes:


They can most likely change the coil and there should be space unless you go for a higher seer unit. (which needs a matched furnace with the right blower motor anyhow - in which case, change the furnace)

When the furnace goes, they can leave the coil and just build a transition.

Not as pretty but it can work.

Considering that 14SEER is the min in the OPs state. A new coil won't be nearly as short as the OPs current one. So there will be duct alterations to change out just the A/C. If the furnace last 5 more years, the manufacturer may or may not still make replacement heat exchangers for it. Might have to wait a few days for a replacement heat exchanger if they are still made.


Once someone replaces a heat exchanger on their dime. Then as other parts go out. They are almost forced to keep on repairing the old furnace, to justify the money they spent on replacing the heat exchanger. So good money after bad money.


Then when they finally get tired of the old furnace breaking down. They end up paying more for the new furnace, and the duct alterations to match up to the new A/C they got 5 or 10 years ago. Costing them far more money over all, than if they had just replaced the furnace at teh same time.
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Old 02-10-2019, 07:03 PM   #14
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Re: Replace both A/C unit and gas furnace?


Quote:
If the furnace last 5 more years, the manufacturer may or may not still make replacement heat exchangers for it. Might have to wait a few days for a replacement heat exchanger if they are still made
No one in the right mind would replace a heat exchanger on a unit near or above 20 years old, especially if out of warranty for the reasons you stated.

But op's furnace is still okay - presumably.

It could last years more without breakdowns or require minor stuff that's cheap as long as the repairs are diy, no labour charge.

The greatest disadvantage of keeping it is the risk of getting caught without heat for a bit if it cracks during the season and it takes a while to get the unit replaced.

Without seeing it there's no way to know if a new coil will fit without major alterations or not. I'm also sure the heights vary depending on the manufacturer and the required width, with the wider coils being shorter.
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I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
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Old 02-11-2019, 09:01 PM   #15
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Re: Replace both A/C unit and gas furnace?


If the noise from the blower (furnace) is objectionable, you should consider a 2 stage system (furnace and AC). These run mostly on low stage and are quieter, dehumidify better, and are more comfortable thsn their single stage counterparts.
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