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mystar 03-10-2012 03:21 PM

Furnace problem - Heat Exchanger???
beenthereView Public ProfileFind More Posts by beenthereAdd beenthere to Your Contacts Today, 08:19 PM #28 mystar

Join Date: Mar 2012
Posts: 1 Gas furnace Carrier 58MCA120

My furnace seems to be working fine but I smell an odor. Called the gas company and they tested for gas. No gas. There was a Carbon Monoxide level of 30 ppm. There was also water at the bottom of the furnace which I have never seen before. We called the HVAC guy and he told us he could not tell if it was the heat exchanger. He said that it looked very rusty but the flames did not seem to go all over the place. This is what I can remember from the conversation.

He then went outside and said that they way the air was flowing into the pipes that go outside that the furnace pipe was going directly into the pipe for the water tank that comes back into the basement.

He did cut a hole into the furnace to look at the heat exchanger and he said that it did not look like it was cracked.

Basically he could not figure out was was wrong. He did all kinds of testing. He also put a camera down the pipe outside and said he could not see anything.

As of now we really have no idea what the problem is. I do not want to keep paying for service calls.

Carbon Monoxide is nothing I want to play with.:( I did see on the Carrier site my model number is on there for a heat exchanger problem. Does this sound like that?

beenthere 03-10-2012 03:28 PM

Could be. The secondary restricting can cause it to over heat.

mystar 03-10-2012 03:38 PM

He did not say it was over heating... He could not figure out where the Carbon Monoxide was coming from. The only thing he said it could be was the two vents outside that the air was flowing from the funace vent into the water tank vent. We unplugged the water tank and pluggged up the pipe. Turned the furnace back on and the carbon monoxide level was down to 12 PPM. But, I do need to be able to use my hot water... Do you think this guy just did not know what he was doing...:yes: ????

beenthere 03-10-2012 03:48 PM

Probably doesn't know well enough how to check things.

If the exhaust from the furnace is coming back in the water heater vent. then why is the room in a negative pressure for this to happen? This is something he should have looked for.

how 03-10-2012 03:52 PM

The only reason why a HWT vent would be pulling down outside air would be from a strong low pressure zone in your furnace area. Is there a fresh air supply for the tank?
The CO from your HWT alone could give you 30 ppm if that vent is downdrafting!
What kind of HWT system do you have?
The fact of the leaking water, the smell. and the 30 ppm does suggest a furnace heat exchanger problem.

Tator1076 03-10-2012 04:23 PM

You sure the 2nd heat exchanger plastic cover is not cracked? I had found them cracked and water leaking out of them on corners.

mystar 03-10-2012 05:17 PM

I called the guy back and he said that he checked the 2nd heat exchanger and it was not cracked. He did say the heat exchanger it self looked really rusty and old for the age of the furnace. :eek:

Also there is no fresh air suppy for the hot water tank that I can see... Not for sure!

beenthere 03-10-2012 06:52 PM

How big is the room the furnace and water heater are in.

mystar 03-11-2012 09:43 AM

About a 2000 square ft basement. Ranch style home. Completly unfinshed.

beenthere 03-11-2012 09:51 AM

That is big enough. Is the furnace's air filter panel sealed, or can it pull air from the basement.

mystar 03-11-2012 02:33 PM

Not sealed. It can pull air from the basement. Not alot. We could seal it with duct tape if this is an issue.

how 03-11-2012 04:26 PM

Did you have a dryer on (or any other large fan or fireplace operating) that might have pulled replacement air down the HWT vent when the test was going on?
The air cracks in your return air plenum would have to be pretty large in a well sealed basement to overcome the HWT vent.

beenthere 03-11-2012 06:11 PM

Air filer bracket should always be sealed so as not to pull air from the basement.

how 03-11-2012 06:30 PM

Testing for spillage from the hot water vent is as easy as turning on the furnace and holding a flame or anything that makes smoke (cigarette/incense) beside the opening of the HWT draft diverter. Make sure all the doors and windows are closed in the basement during testing.
Test that for a 5 minutes minutes and then turn up the temp on the HWT to start that running as well while that furnace is still running to retest the combination of both appliances running. If the flame or smoke angles away from the draft diverter during testing then you have a venting problem.
If are back to the heat exchanger problem.

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