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Vaandjay 12-19-2010 09:04 AM

How to check secondary heat exchanger on Carrier SXC?
First, I'll admit that unlike many people here, I do not have great DIY skills. I can disassemble things but getting them to work is another issue.

Anyhow, our 1992 Carrier SXC definitely has a crack in the primary heat exchanger, so it will be replaced shortly no matter what. When the Carrier contractor was here, he pointed out the visible vertical crack on the primary exchanger and left. At the time, I didn't think of checking the secondary too. After reviewing info on the lawsuit against Carrier for failing secondary heat exchangers, I see that Carrier gives a credit to replacement buyers with failing secondary heat exchangers if they previously had a model covered by the lawsuit.

Is there a way to check for clear problems with the secondary heat exchanger? Problems I've noticed with the furnace--besides the limit switch cutting off frequently/overheating burner box/fan constantly running even after burners cut off--include (1) exhaust smell sort of like a mix of gas/rotting animal, (2) water on the bottom corners of the top section of the furnace, which has caused the frame to rust in places.

Also, each winter the past two or three, I got into the habit of having to reset the furnace a few times. I considered this a normal, infrequent situation; the burner box never overheated those times, nor did the fan run constantly after the burners went off. Finally, I had to replace the circuit board due to rust (about five years ago).

So, if I go with a Carrier again, if my secondary heat exchanger has been failing or failed (along with the primary), I'd ask for the credit. If it isn't I wouldn't. Thanks for any advice.

yuri 12-19-2010 09:40 AM

Are you paying for the labor to install the primary heat ex and how much? If you can remove the blower and crawl in and see water stains on the secondary it may be leaking (may be stained from an overflow from the A/C too). It is difficult to remove the blower and cond trap w/o damaging the trap/hoses so you may want to think twice. The tech can check the secondary when doing the primary but you will have to pay him for what he does either way. Best to get advice from him on what to do. Get him to check the secondary B4 he starts dismantling the primary etc so you can stop the job if it is shot.

Vaandjay 12-19-2010 10:31 AM

Tech came once already
No, I won't have the primary replaced because the labor is not covered on that. When the tech came out, he saw that crack, told me to stop using the furnace, took measurements so his boss could give a bid, and left.

Only afterwards did I realize that there was the potential for a credit on a replacement Carrier furnace if the secondary heat exchanger was failing or had failed.

yuri 12-19-2010 11:27 AM

I would find out how much the Carrier credit is. If it is under $500 you may have to pay him $100-200 to come check the secondary. Net savings $300. If you want to stay with Carrier, fine as they are not bad units. I would not pay the $600 and up in labor to replace the primary as the secondary could go soon. If you want to go with Lennox or another brand then save the $100-200 and just buy a new one. At that age I would buy a new furnace and not repair it as the next items to go will be: pressure switches, gas valve, inducer motor etc and it is a $$ pit to keep going for a few yrs until you get tired of repairing it and being without heat etc. Most of my customers won't spend $1000 repairing a furnace after 15 yrs old. Average life is 20.

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