Replace A coil or whole system?

10726 Views 8 Replies 7 Participants Last post by Mercenary, Jul 23, 2009

Mercenary

Discussion Starter · Jul 17, 2009 (Edited)

Background, I worked in home remodeling for over 3 years, plus general contracted my own house. That's on top of being a DIYer for 30+ years. So I'm pretty familar with most of this stuff.

I moved from Chicagoland to the DC area (lost all my previous contractor contacts) and am in an 8 year old townhouse. The HVAC is GOODMAN, we all know how good that is. The AC was working reasonably when I bought the place but this season it is out. I've had it checked and it appears that there is a leak somewhere in the A coil. They pressurized with nitrogen, to find the leak. The freon is gone.

So, do I get the A coil replaced and system recharged knowing that there is a goodman compressor sitting outside? I've had a few quotes to do so but they seem high. I figure it's less than a half day work plus the coil ($250 retail on line) and Freon. Not sure what that should cost. I don't want to scrap the compressor if it's still got useful life, that's not good for the environment either.

I've been told Freon is being phased out which fuels my delima. Prices for the gas and replacement parts will go up as they aren't made any more.
I've been told I can't upgrade the AC to take advantage of the current tax breaks because my furnace doesn't have a variable speed motor and I can't reach the required efficency without replacing the furnace (because of the motor).
I've been told that Goodman furnaces have a tendency to fail in the heat exchanger department. I had 2 Amanas in my previuos house (didn't know Goodman made them until later) and neither had a heat exchanger problem in 15 years of service. Sure ignitors went, a controller went in one and the blower motor in the other, none of those were Goodman quality issues in my book.

Swapping out the whole HVAC system is costly and I don't know if I'd ever see a payback from an efficency standpoint. It's an 90+ furnace, I only have 1,600 sq/ft to heat/cool.

I've got quotes for replacing/upgrading the whole AC system, the current system is 1.5 ton and probably 8 SEER (so the salesmen that want to replace it tell me. Is there a place I can find out?). My quotes are for 14 SEER systems, also 1.5 ton. Don't know if I could/should go to 2 ton since I have a 3 story townhouse and getting cooling up to the top floor is a challenge. The ducts also run in unheated space in the attic. All the sales guys just see the current size and quote me a replacement of the same size. They don't seem to feel an evaluation is necessary.

I was thinking if the whole system was dead I'd go with the higest efficency possible, but then started rethinking this and was wondering if there is a sweet spot where spending more on the HVAC plant doesn't really gain you enough savings to pay the higher equipment cost. I'm wondering about this since I'm guessing that if I upgrade the AC now and the furnace goes a few years down the road, I don't want to be regretting the effeciency of my AC and I won't want to have to upgrade it again.

I'm willing to spend the money, but want to do it smartly. One last tidbit is that I don't see any moves in the foreseable future. But you know how that goes.

Argh.

Any real insight would be appreciated.

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Home Air Direct

· #2 · Jul 17, 2009

Depends on the outcome you really want. I am not a Goodman fan, but in their defense, the compressor that is sitting outside is probably a Copeland, like almost everything else on the market.

If you are needing to go on the cheap, change out the coil (though with an 8 SEER you will not have a matched system and this could be a problem)

If it were me, I would at the least, change out the AC system, and a 13 SEER or 14 SEER will be your "sweetspot" or best bang for your buck in relation to outlay of cash versus payback over time.

Plug your numbers in here to see a simple payback calculator.
http://www.acdoctor.com/cooling_calculator.php

Good Luck

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Dave Carney

· #3 · Jul 17, 2009

My Goodman heat pump (which runs 9 months a year here in the dust bowl), is 14 1/2 years old, and while the system is leaking some R22 now, after all this time, the pressures indicate the compressor is still in fine shape. In your case, with an 8 year old unit, I, like you would be inclined just to change the A coil, because that compressor probably has a lot of years left, or alternatively, I change the whole thing, including the furnace and take the tax credit. I'll do that next year, with another Goodman setup.

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yuri

· #4 · Jul 17, 2009 (Edited)

As much as I hated the older Goodman stuff my company sold, the new Goodman is fine. They upped their standards/took over Amana which always was good. R22 will be available for the next 10 yrs at a higher cost but I would probably change the coil if they are ABSOLUTELY sure that is the problem. You may have a 10 SEER system. If they are guessing it is the coil then a new system may be a better idea. Goodman used Copeland compressors and so do the other major companies. A new furnace with ECM motor will give you better airflow upstairs as they can provide .8"WC pressure vs the .5"WC of a standard PSC motor and they will provide it constantly as the filter gets dirty (within reason). A proper heat/cooling load calculation is absolutely necessary and you can DIY. http://www.hvac.cc/
I still prefer Lennox over Goodman and would use a Rheem B4 a Goodman but that is my preference.

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kenmac

· #5 · Jul 19, 2009

replaced a bristol compressor on a 12 year old goodman today with a copeland.. The guy didn't have the $$$ to replace air handler, condenser, evap coil... I wouldn't say goodman is junk... They have a large share of the market... You can't stay in business installing junk

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Mercenary

Discussion Starter · #6 · Jul 22, 2009

yuri said:
As much as I hated the older Goodman stuff my company sold, the new Goodman is fine. They upped their standards/took over Amana which always was good. R22 will be available for the next 10 yrs at a higher cost but I would probably change the coil if they are ABSOLUTELY sure that is the problem. You may have a 10 SEER system. If they are guessing it is the coil then a new system may be a better idea. Goodman used Copeland compressors and so do the other major companies. A new furnace with ECM motor will give you better airflow upstairs as they can provide .8"WC pressure vs the .5"WC of a standard PSC motor and they will provide it constantly as the filter gets dirty (within reason). A proper heat/cooling load calculation is absolutely necessary and you can DIY. http://www.hvac.cc/
I still prefer Lennox over Goodman and would use a Rheem B4 a Goodman but that is my preference.

Thanks all. I'll check out the load calculator. I'll also see if I can find te SEER on the compressor. Not 1 of 4 contractors did anything but look at the current system. The first vendor I had out sent 1 crew that checked the system and found the lack of Freon. The second crew came out and pressurized the system with nitrogen and said it was leaking in the A-Coil. I was there, his detector went off when he stuck it near the coil. The guy said something about capilary tubes standing in water and corroding. The next guy didn't retest but he guessed the leak was probably in the coil, suspected an issue with the manufacturing when they press the fins on the copper pipe. Both theories sounded reasonable, both and the location of the leak point to the coil.

Weather hasn't been too beastly so far this summer, only 1-2 nights we wished we had AC. We'll be gone for 2 weeks in August.

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hvac122

· #7 · Jul 22, 2009

As far as a new unit goes make sure a manual J is run especially if you want to increase tonnage. The ducts were most likely sized for 1.5 ton and if the third floor is the problem cooling a larger unit will have shorter run times so it could make matters worse.

If the evap coil is bad then there is not to much of a problem changing it. We do it all the time. The main drawback that I see is that if the compressor goes out next year you will need to buy another coil with the new system. Its a crap shoot.

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hennyh

· #8 · Jul 22, 2009

If the system is only 8 years old and had previously been performing fine, then I'd simply repair or replace the coil. After that the system could go on for another decade or more.

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Mercenary

Discussion Starter · #9 · Jul 23, 2009

hennyh said:
If the system is only 8 years old and had previously been performing fine, then I'd simply repair or replace the coil. After that the system could go on for another decade or more.

This is the way I was leaning...

hvac122 said:
As far as a new unit goes make sure a manual J is run especially if you want to increase tonnage. The ducts were most likely sized for 1.5 ton and if the third floor is the problem cooling a larger unit will have shorter run times so it could make matters worse.

If the evap coil is bad then there is not to much of a problem changing it. We do it all the time. The main drawback that I see is that if the compressor goes out next year you will need to buy another coil with the new system. Its a crap shoot.

This is my major concern.

I don't think the builder spent too many brain cells on sizing. The unit next door to mine has the exact same equipment and 20% more sq/ft. When his AC runs, it does so non stop and still he complains that there isn't enough cooling on the upper floor. I used the simple sizing calculator at http://www.acwholesalers.com/ and it says I should have a 3 ton system.

Is the calculator on the pay site more accurate? (Costs $49) Will it help me determind proper duct size? I could increase ducts to the lower 2 floors, but am fairly screwed to bump up the ducts to the 3rd. The Attic has flex and I'm sure it's very lossy but am open to suggestions there if I make some major changes.

These guys have complete systems that cost significantly less than what I'm being quoted for AC alone. If I dropped one of these systems in and had to pay a tech $500 to attach the lineset and charge, I'd still come out ahead. Plus I would qualify for the Obama tax insentive.

Sorry to be a pain, just looking to learn and make the best of a bad situation.

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