Author Topic: HVAC problem - smoke in house  (Read 1001 times)

cfabe

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HVAC problem - smoke in house
« on: January 30, 2012, 12:11:48 PM »
Had a problem this morning, I think I figured out the cause but would like to hear other's opinions.

We woke to the smoke alarms going off at 4:30 this morning. There was faint smoke in the house, and a smell similar to burning plastic - but a little different. I did the rounds and determined the house was not on fire, then tried to locate the source of the problem.

Everything electrical checked out, felt for heat and tested for operation all outlets, switches, appliances. I had immediately shut down the furnace and the bathroom electric heated floor, so turned each of those back on, they operated normally and did not generate smoke. I went outside to check the wood boiler, and found the fire I set last night had gone out. This meant the propane furnace would have fired at about 4am when the thermostat kicks back up to morning temp. This would have been the first time the furnace fired on propane in 1-2 weeks.

So, I pulled the panels off the furnace and ran it through an ignition cycle. Everything was normal. Then I noticed that the blower motor run capacitor was leaking, had leaked enough fluid to spread across the bottom of the blower compartment. This is a 92% Goodman furnace, 4 years old, mounted in downdraft position. I think what may have happened is the fluid from the capacitor had leaked down into the heat exchanger, then when the propane fired for the first time in a while, it burned/smoked it off. I scraped up some of the fluid, sticky white pasty stuff, and burnt it off with a torch, we thought the smell was similar to what we smelled in the house.

Does this sound plausible? It's the only possible source/cause I can come up with. I'll be replacing the capacitor today, but just wanted to see if this was possible or anyone had seen this happen before.

Scout26

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Re: HVAC problem - smoke in house
« Reply #1 on: January 30, 2012, 01:24:57 PM »
280, Jim, and Nick to the White Courtesy Phone please.   Jim, Nick, Nick and 280; The White Courtesy Phone.
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cassandra and sara's daddy

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Re: HVAC problem - smoke in house
« Reply #2 on: January 30, 2012, 01:39:35 PM »
nice job of trouble shooting
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Brad Johnson

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Re: HVAC problem - smoke in house
« Reply #3 on: January 30, 2012, 03:28:19 PM »
Sounds like the start capacitor is toast just like you diagnosed.  Only four years old and it's not still under warranty?

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280plus

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Re: HVAC problem - smoke in house
« Reply #4 on: January 30, 2012, 03:58:26 PM »
Sounds like you're on the right track. Replace the capacitor and go from there. Funny it would leak after only 4 years. Is it bulging and misshapen?
Avoid cliches like the plague!

cfabe

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Re: HVAC problem - smoke in house
« Reply #5 on: January 30, 2012, 06:10:11 PM »
Well, replaced the cap and it's doing okay so far. Just a hint of smoke smell left over that seems to have dissipated.

The cap was not bulged or anything. I think the leak was due to how it was mounted. It passed through a hole in sharp sheetmetal, with a couple of screws clamping the lip of the cap to the sheet metal, which dug into the sides of the can for grip. The new one is zip-tied in place instead.

never_retreat

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Re: HVAC problem - smoke in house
« Reply #6 on: January 30, 2012, 10:26:39 PM »
Defiantly sounds like burnt cap juice. It will take a while to get that stink out of the house.
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280plus

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Re: HVAC problem - smoke in house
« Reply #7 on: January 30, 2012, 11:09:39 PM »
Well, replaced the cap and it's doing okay so far. Just a hint of smoke smell left over that seems to have dissipated.

The cap was not bulged or anything. I think the leak was due to how it was mounted. It passed through a hole in sharp sheetmetal, with a couple of screws clamping the lip of the cap to the sheet metal, which dug into the sides of the can for grip. The new one is zip-tied in place instead.
Good, as long as it wasn't overheating due to an issue with the motor which is what the bulging would mean. One thing though, zip ties have a bad habit of dry rotting and falling apart in about 3 years so you night want to find a better way to mount it.  ;)
Avoid cliches like the plague!

geronimotwo

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Re: HVAC problem - smoke in house
« Reply #8 on: January 31, 2012, 09:46:39 AM »
the aviation world has some great wire clamps of any size made with rubber abrasion protection already installed.
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