IR cam pics of hot spots in gas furnace

[Chris Bernhardt]

I have been scanning furnaces looking for anomalies like these. This was the first time I found something interesting. The furnace is in a crawlspace and is an 1978 lennox model.

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View of right side furnace

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IR view of right side of furnace

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IR view of back of furnace.

Chris, Oregon

[hausdok]

That furnace is at about 150% of its normally expected service life. Does it have a pilot light? If so, that may be where the hot gas from the pilot turns on it's way to the flue.

Hot spots on the cabinet typically indicate a crack in the exchanger, but that's only 88 degrees. Is that with the furnace running? If so, I don't think it's being caused by a crack. Maybe there's something wedged in there.

That's a less-than-ideal environment for a furnace to be operating at 1-1/2 times service life.

I'd bet it's about time for replacement.

ONE TEAM - ONE FIGHT!!!

Mike

[Chris Bernhardt]

It was retro fitted with an automatic pilot. My bad I should have scanned it before I turned it on. I will do that from now on.

I scanned it after the first couple of minutes but took the pics after about 10 minutes of operation. The contrast increased between the two times but I agree it usually is hotter where there is a cracked heat exchanger. I didn't take a physical measurement of the temperature nor did I try and calibrate the camera. I would't take the indicated temperature as real.

Chris, Oregon

[kurt]

That's interesting, because I was trying to figure out what could be learned from those images.

That series Lennox is old enough to have some burned out turns in their little curvaceous heat exchanger, no?

What sorts of variables would affect IR used to analyze furnace condition? How might one go about it?

[Chris Bernhardt]

What sorts of variables would affect IR used to analyze furnace condition? How might one go about it?

The metal and glossyness of the finish tends to play havoc. Making sure you scan it before you turn it on would be helpful, duh. Comparing the performance of similar models.

Concerning comparing similar models, I have scanned this model several times and never found this anomaly. But what do I know.

Even if I hadn't IR'd it, I would still be telling the client it's ancient and to have a follow up by an HVAC tech and to be prepared to replace at any time.

Chris, Oregon

[ghentjr]

I think that Lenox had a flat steel back that was prone to cracking. It did not have the typical ported exchanger. What I would take away from the back photo is a failed exchanger.