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Furnace Cleaning


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I called this company to clean my furnace as I haven't done it since I bought this house about three years ago, and I was not familiar with the process. The guy who come to do the job opened the covers, inspected with a flash light and said "holy shit, it is full of carbon". I was surprised as I didn't see any black carbon but there was some white, ash like dust on inside walls. So I asked Do you mean this white dust ? " Yeah that is not dust, that is carbon". Then he opened the little window to inspect the heat exchanger and said A/C coil is completely plugged and he said the furnace is poorly maintained and is in very bad shape and he cannot safety this, and this is very unsafe. I tried to explain that I didn't ask for a safety but I called you to clean the furnace. Then he said according to the company policy he has to inspect the furnace first and if he can pass the safety, he will clean and tune up the furnace and issue the safety, but in this case he cannot do anything as it is in bad shape. He said it will cost about $1800 to repair this and he recommended to buy a new one at $3500 as this is about 15 years old and a mid efficiency one. He didn't do any cleaning and even didn't worry to paste a duct tape over the inspection window but charged me for the service.

As I was not convinced about what he said, and also he didn't do the job, I searched internet and started to clean it by myself. I cleaned both chambers using a vacuum cleaner and It took me only five minutes to remove the plugged dust layer from the cooling coil. This guy didn't do that, and he even didn't advice me how to do that if it is not his job.

I called an expert to get advice about the things I didn't know.

Any way now my question is how do I verify the furnace is safe and in good order ? It was always working fine, and it doesn't make sense to me why he said the furnace is so bad and need $1800 worth of repairs. ( Still I have to clean the blower). What is that white dust ?

I have attached a picture of the white dust and of the plugged cooling coil.

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Can you post some establishing photos of the furnace that show it's location and the exhaust vent configuration?

With that much crud built up on the A-coil it's a wonder the thing ran at all. It must have short cycled like crazy because without any air flowing through it the furnace would have reached it's high set quickly and shut down. Heating a house like that would be like walking five miles while taking three steps forward and two steps back all the way.

AC in Manitoba? Whodda thunkit?



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That looks like dust on the cooling coil. Maybe check if any returning air flow is bypassing the air filter because the cooling coil seems to be doing double duty as filter.

I don't see any rust on the cooling coil drain pan. Corrosion begins quickly on new coils and old coils are badly corroded, unless this pan is plastic. Is it?

Jim isn't exaggerating the draft issue. I wouldn't turn that furnace on before you post the photos Mike requested.

Your 'serviceman' sounds like a couillon. He's probably doing approximately what his boss wants him to do but only approximately and he's got an awful bedside manner. I wouldn't hire such a guy.


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Thanks for the comments. Mike here is photos. Exhaust vent go up and with two 90 bends connected to the flue.

Actually air flow was not totally blocked. May be the crud worked as an extra filter. Anyway I cleaned them all. I checked with a candle flame & couldn't find any back draft. I am going to change the exhaust vent as it shows signs of corrosion. Anything else I should do until I replace this furnace.

One more question. If condensate get collected inside the vent, it has no way to go. Shouldn't there be a drain ? There are kind of two traps one shown in the picture and the other at the bottom of flue. I mean flue pipe is bottom capped and vent line is connecting like a T. so water can remain at the bottom. Isn't that bad ?

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