Coleman natural gas furnace 7966A856 is 20 years old.

[techman1]

I know that I should replace this furnace, even though I am having no problems with it. I am worried about burn through in the heat exchanger allowing carbon monoxide into the house.

The parts of the heat exchanger that I can see without removing covers look quite well and very little rust specks. I will remove more covers to see what I can see (like the bear who went over the mountain).

How long would you expect that one of these furnaces could last? No problems with the central air either.

OK, now for the weird part. I have a degree in heating and air conditioning. I don't use it because I don't work in that field. I do pull the cover off the front of the burn chamber, wire brush and vacuum it, and adjust or replace the thermocouple position and pilot light height. I remove the blower, clean the squarrel cage, blow dust off the windings, and oil the bearings annually.

What should I look for as the safety of the heat exchanger?

Thanks.

New to the forum.

Ken

[Robert]

Hi Ken,

First off and you probably know this, the only effective way to inspect it is through combustion analysis and testing.

You can look for rust spots, cracks/seams, loose rivets.

Best to heat up and then carefully inspect, the heat will expand cracks and make them more visible.


Do a smoke test , watch for burner and pilot flame to dance.


Black soot around registers and/or ductwork insides.



Thanks for inquiring,
Robert