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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 22021
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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I have a residential water boiler heating system. As we've

Customer Question

I have a residential water boiler heating system. As we've started it up this season we get a mix of gas/plastic burning smell. It doesn't smell like the normal "burn off the dust" smell we normally smell at the start of the winter season.
So far I've had a tech over. He's okay. I live in a small town so I don't have many option. He suggested it was a back draft and that maybe there was an obstruction. I looked and I can see no obstruction from the flue. I opened up the end piece at the 90 and there was a lot of soot. I cleaned it out and replaced it, but still the same smell.
I opened up the boiler and it was amazingly dirty. There appears to be a lot of lint type stuff all over the metal pieces. I carefully cleaned it off and I noticed that there are two metal bars that hang down. One hangs down fine and the other appears to have "fallen." It;s also got some insulation/line looking dust.
Could this be the cause of the smell?
Submitted: 1 year ago.
Category: HVAC
Customer: replied 1 year ago.
I should not that when he did a backdraft test (match) he didn't think it was the problem. It appears to be pulling everything up just find. I've tested with matches and candles and see no evidence of any draft coming back. I've also checked from both ends and I can't see any obstruction. That is why I think his initial thought was correct. That it was drafting just fine.So while there might be a leak, it really doesn't appear to be a problem at the flue or stack.My biggest concern is that metal bar which is just leaning while the other is hanging. I wonder if that piece, along with all the dust and lint looking stuff is the culprit.
Customer: replied 1 year ago.
But when I open the main box area, the smell isn't coming from that area. It's coming from much higher. Where the vent goes into the beginning of the flue stack.Any ideas?
Expert:  HVAC Guru replied 1 year ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset I am just one of the techs on here and I try to get to as many customers as I can and I just picked up your question now. Please give me time to respond sometimes I get your replies late so there may be a significant delay in responses. Please be patient and often I will ask you questions to narrow down the issue to get is diagnosed correctly.

Can you take a picture of what you are talking about and upload it here?

Customer: replied 1 year ago.
Here are the photos. Let me know if you need a photo of the outside. The small doesn't seem to be coming from the burner area but a little higher.
Expert:  Rick replied 1 year ago.

Sorry for the delayed response. It sounds like the heat exchanger (the area above the burners probably cast iron) is clogged. The jacket and draft hood will need to be removed as well as the burners (which should also be cleaned) and the inside of the boiler brushed and vacuumed out. This is potentially a hazardous condition and you really shouldn't use the boiler until you can get this professionally cleaned. Gas boilers should never produce soot. It's an indication that there's not enough air for combustion. This could be a matter of opening the shutters on the ends of the burners or you may need to get some fresh air into the boiler room