New Evaporator Coils necessary for new Condenser ?

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My mom's 22 year old 4 Ton 10-seer Carrier A/C condenser is shot. Her furnace is relatively new.
She wants to replace the old unt with a new Puron Carrier 4 ton condenser.
One HVAC company is saying that they do not install new evaporator coils because it is unnecessary, and the efficiency will be around 12 or 13 if the old coils are used with a 15 seer unit. They say they have never had a problem with leaving the old evaporator coils in.
Another HVAC company is saying that it is important to install new coils because the efficency won't be good, and also the unit will be under more stress with the old coils and will likely only last for 4 years.
Which of the two is correct?
Thanks,
J.
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Neither of them are correct. The coils *MUST* be replaced when switching to R-410a(Puron). R-410a and R-22 are not compatable at all, nor are the oils, and R-410a operates at much higher pressures than R-22....yet another reason to change the coils. BTW, did you know that the manufacturers will *NOT* stand behind their warranties if a correctly matched coil is not used with the new condenser??
I would suggest that you get a properly matched system from and have it installed by a *COMPETENT*, licensed, insured, professionally trained HVAC technician. and don't walk, but run away from those two companies. Don't forget to get that 10 year parts and labor extended warranty with the new correctly matched system. Also demand a copy of the ARI Certificate of Performance for the new system. If they can't or won't give you one, then show them the door.
FWIW, I would not put Carrier in my home on a bet.
http://www.consumerreports.org/cro/appliances/heating-cooling-and-air/gas-furnaces/furnaces-repair-history-205/overview/
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You might still be able to get an R-22 instalation done. We had a compressor failure a few years ago and our HVAC just replaced the outside unit for less than $2000. It's only a 5 year guarantee but the man who did the work is very good and very careful.
If you can't just replace the "outside unit" and/or your HVAC isn't up to just replacing the compressor you may be stuck with replacing just about everything but the thermostat and the blower housing.
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Just wait till Bubba hears that you're not replacing the thermostat. OOOHH... I don't want to be here.... oh, yah, maybe I do?
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Christopher A. Young
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Would you buy a new Honda and have them put the radiator from your 1986 Oldsmobile in it to save a few bucks? The high efficiency systems are designed to work as a complete package. Have the coil and the lines replaced with new.
As another poster already suggested, I would find a contractor that will do a load calculation to confirm the size unit that is needed and not just assume that what is there now is correct. She can save quite a bit on the system and the cost to run it by ensuring that the system is sized properly.
Steve B.
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Carrier... lol Nuff said...
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the
Beside the previous comments, a 22 year old coil is a leak waiting to happen.
HankG
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It's likely to outlast the new coil... That said... you still have to install a new coil.
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Bottoms up I guess float the oil out the top with the calgon shit spose take your time...soak it...$$$=hours
still that old coil is gonna be all stiff an brittle and inadequately rated as to test and working pressure while any of the new one will be dual rated--(duh for lower pressure r22) as well as being listed for the higher pressures you'll encounter w / 410
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wrote:

Even if it did work the seer increase you get from a new coil will make a major difference in your electric bill, and that you want. Have you checked how much you will save. do so, charts might be at Carrier. But one more point in upgrading you may not need 4 ton, but maybe 3 ton,[ im just guessing here] did anybody do a load calculation or point that out to you. You have 10 seer, probably its 9 seer by now, its an energy hog, 15 seer is a big saver in electric costs. If it didnt run nearly constantly on the hottest days, you might have been oversized before. You need a load calculation in writing.
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A heat load such as manual J is critical to be sure the correct size unit is installed. One of the items in a J is a blower door test. This can be critical as one can guess at the ACH (Air Changes per Hour) but I do not know anyone that can get this GUESS correct every time. Test do not GUESS. Another test that is critical is the duct leakage. Id say 1 of 20 homes we test have duct leakage high enough our equipment cannot test it. Things such as building cavities used for ducts, a common practice in many areas of the country during certain years. So that 15 SEER can be compromised and a larger unit will be needed. Tight ducts can be more important than a high efficiency unit.
Be sure dampers are installed in all ducts to balance the unit.
Andy
Think Whole House Performance, its the right thing to do
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I agree with Noon-air. They should put in a high efficiency evap coil, even if you're staying with R-22 refrigerant. You MUST replace the if you're moving to R410. If the first company is an authorized dealer for a name brand company, they could lose their dealership for recommending a hair brained combination like that.
The second company is correct that you need to install a matching coil. Most of the high efficiency coils are oversized and then use a thermostatic expansion valve to squeeze the most efficiency out of them. However, if that's the way you go, make sure the blower motor can provide the increased airflow demanded by the oversized coil. Otherwise you'll get freeze up in humid weather.
Bottom line is you want a matched system.
You also need to change out the line set for the new refrigerant.
On Tue, 06 May 2008 17:50:41 GMT, " snipped-for-privacy@verizon.net"

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Sounds like you have some really interesting HVAC techs, there. Mix Puron and R-22? Not a good idea. If it works at all, it won't work for long.
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Are you visiting the area Stormy??? Sounds like something you'd do...
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Katy-West Houston Air had written this in response to http://www.thestuccocompany.com/hvac/Re-New-Evaporator-Coils-necessary-for-new-Condenser-31920-.htm :
Mixing R-22 and R410A is serious invitation for trouble. Once Mineraloil mixes with the Polyolester oil you can just about guarantee compressor failure after compressor failure. Using the old lineset is OK, but they MUST be flushed with RX-11, and no chinching. We use a minimum of 1 can per system after an inital high pressure nitrogen purge to insure all of the old oil is stripped from the lines. We then follow up with a second high pressure dry nitrogen purge to help remove any RX-11 liquid that may be present in the lines and provide about a 2 hour vacuum to the system. ------------------------------------- KJPRO wrote:

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wrote:

Am I missing something on AC operation and sizing? I know from the many points of what has been said, he needs to replace the coil to. But couldnt his old 10 seer be actualy running at 8, won`t he save near 50% on his electric bill with a complete 15 Seer unit, yes. So if that is the case couldn`t a 2-2.5 ton work and a 4 ton unit be way oversized making the house uncomfortable and the extra cost a waste?. Of course he also needs pros, not hacks to bid, and do a load calculation in writing.
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The SEER rating has nothing to do with the units capacity. It just takes more energy to move the same amount of heat.
Thing of SEER as MGPs, the fuel costs the same and has the same octane, but one car uses more to travel the same distance.
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I'm left wondering. In this age of escalating energy prices, who in their right mind would ever want to use a 22 year old evaporator that they acknowledge,will turn a new 15 seer system into a 12 seer one?
And if you do, and two years later the compressor fails, who will warranty it?
As someone previoulsy said, it's like replacing all of a car then shoving a radiator from a 22 year old junker into it.
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Not a lot of peaple post HERE so they have to make the most of the one's that do.
Anybody want a 9 Lobe 7 Flute 300 Ton Frick Screw for $10 Come's with 5 Tons of NH3 and a free EVAPORATOR COIL ( NEW ONE ) Very usefull for holding down the roof in a cyclone ( 3 Ton Weight )
The Interpretation of all the Complex technical terms USED IS THEY WANT YOU TO BUY A NEW ONE

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Telstra wrote:

Hi, Rule of thumb, you always use matched set. Older coil may die soon(spring a leak) or if you want to reuse it, it needs flushing with special chemical which is very expensive. (R22 and Puron oil is different) Most techs does not want to do this. Also Puron runs at higher pressure. Proper thing to do is to replace line set, coil and use transfer valve. For more expert advice go to forum at www.hvacmechanic.com I am not a tech. Just alert consumer.
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