# Smell when boiler runs?



## dave12345 (Feb 28, 2010)

Hi,

Looking for thoughts on this one. I have a New Yorker S176AP boiler and water baseboard heat. This unit also heats our hot water so it runs year round.

October 2008, shortly after my annual clean and service, I started occasionally smelling an odd smell over by the dryer, maybe 15 feet from the boiler. Mechanical oily burnt smell. Smell was so slight that just walking into the area would dissipate it. Smelled nothing unusual near the boiler. Cleaned the dryer of all lint, went so far as to replace the dryer vent. Smell got better and went away after a month. 

October 2009, shortly after my annual clean and service, the smell is back. Cleaned the dryer vents. Through process of elimination cleared the dryer of any culpability -- smell presented itself when the dryer had not been run in days. Chalked it up to the solvents from the cleaning burning off / running the heaters for the first time. Installed a carbon monoxide detector, nothing. Smell would come back on and off, getting weaker every time, until sometime in January I realized I couldn't remember the last time I had smelled it.

My wife complained of a smell in her sewing room, which is directly over the room with the boiler. Smelled like hot WD-40 to me. She had been running a brand new sewing machine for two days straight, and I had sprayed WD-40 on my snow thrower in the garage (not directly under this room, but close enough) so chalked it up to that. Installed a carbon monoxide detector in that room, nothing. She complained of it again today so I cranked the heat up a little more and waited in the room -- finally smelled it, right in the doorway. This position is on the next floor about three feet over from where we were smelling something in the laundry room. No idea if the two were related. The smell in the laundry room is definitely gone. Of course, it's colder out and heat rises, same smell just moved? I do not smell it _every_ time the boiler runs. I still do not smell anything unusual standing directly next to the boiler.

The chimney for the furnace runs through the sewing room and is ten feet to the right of the door. Do not smell anything unusual near the chimney. Hatch into the attic is here as well, do not smell anything.

Right now I'm thinking some sort of flue problem. Wouldn't that have shown up on the heater cleaning/inspection? I have a printout of the efficiency tests they did. I am having HVAC techs out tomorrow morning, will they be able to tell anything?

Thanks,
Dave


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## beenthere (Oct 11, 2008)

Hard to say if they would have caught it or not. Since it depends what is causing it. Since it sounds like its not always happening.

Could be just a slight mis-adjustment.

Was any thing else changed when you first noticed this in 2008? new windows, or a door replaced, caulked some windows, etc?


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## dave12345 (Feb 28, 2010)

beenthere said:


> Hard to say if they would have caught it or not. Since it depends what is causing it. Since it sounds like its not always happening.
> 
> Could be just a slight mis-adjustment.
> 
> Was any thing else changed when you first noticed this in 2008? new windows, or a door replaced, caulked some windows, etc?


Thanks. Don't mean to sound like I am trying to blame the HVAC guys, far from it, they have been incredible since I have moved into this house. I am just trying to understand the limits of what they can do since this is such a hard problem to nail down. Had them back out to look for the smell last year, nothing, had them out again for a bad pump.

Nothing has changed although it does seem to re-appear when the house is shut up for the winter. Probably it's always there but we only smell it now.


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## beenthere (Oct 11, 2008)

What can happen. is your house could be a little to tight for the burner to get enough combustion air.
or have enough air for dilution air for the barometric draft. And a bath fan, dryer, or cooking fan when it runs draws fumes out of the basement, or out of the barometeric damper.

The attic access. is it sealed tight? It can draw heated air out of the house. And that air could be being replaced with air from the chimney at times.


A mistake some techs make is calling a slight yellow spot, a zero smoke. Its not. its a sign of too much combustion air. And can cause an odor.


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## dave12345 (Feb 28, 2010)

Thanks beenthere, turned out the blower on the front had sucked up some dryer lint/dust/etc.


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## beenthere (Oct 11, 2008)

Keep us updated if it comes back.

I don't believe that was the problem. But I could be wrong.


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## dave12345 (Feb 28, 2010)

Well, Beenthere, you were right, it came back.

Had the heater company out again after my last post, they replaced a few parts, and the smell seemed to get better again and then return.

Called a chimney repair company out who diagnosed cracks in the liner. Saw them myself. Chimney was relined and rebuilt. Definitely was a liner issue there. Stuck a fan in the window to air the room out for a day or two, but the smell came back.

Called the heater company out again, they put a smaller nozzle on the heater and dialed down the gallons per minute or whatever it is, adjusted the draft, got the heater down to 1ppm CO in the pipe. This was Friday afternoon. Noticed the smell still Friday afternoon and Saturday morning (but I had not made an attempt to air out the room) but by Saturday night, the smell was gone.

Smell came back tonight.

Any ideas? Can this all still be residual from the chimney liner cracks somehow?

To answer your question about the attic, no, the attic hatches are not sealed tight. There are two and they both open into that room. There is also an attic fan. The thing I can't understand is that the smell is nowhere near the attic hatches and there is no smell in the attic. The smell is near the doorway somewhere between 1-3 feet off the floor. Sometimes you even have to bend over to smell it. If you go into the room below the smell, nothing, not even up by the ceiling.


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## beenthere (Oct 11, 2008)

Try taping off your attic access hatches. See if that helps.


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## dave12345 (Feb 28, 2010)

OK will do.

I stood in the room while the boiler ran last night and I noticed the smell didn't start until about 30-60 seconds _after_ the boiler shut down. Does that indicate anything to you?


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## beenthere (Oct 11, 2008)

Could be that as the boiler and chimney cools down. that the draft in the chimney decreases enough. That the stack effect in the house begins to pull back through the chimney, and up through the attic hatches.


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## natemare13 (Nov 11, 2013)

@dave12345 I know this is an old thread but I have the EXACT same issue. tons of service calls, such an ellusive smell, issue. Still no resolution. You nailed it on the head when you said you actually smell is 30-40 sec after the boiler shuts off. Were you able to solve this issue? How? I am going around in circles with techs and chimney guys. lots of money spent, still same issue. If you're still around, an update to your story would help me tremendously. Many thanks...


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## dave12345 (Feb 28, 2010)

10k later, never resolved to my satisfaction.

The original smell in the sewing room, the thing that kicked off the whole chimney relining debacle, was identified and was nothing to do with the HVAC.

I believe relining the chimney made the whole situation worse. Now I had a 7 inch chimney restricted down to 6 inches. Technically this was within spec but now I took whatever issue I was having with draft and making the boiler work harder to breathe to boot. The smell immediately by the heater was constant. I had the relining company out again. His first solution was to redo the flue pipe coming out of the boiler so there was no right angle. After that change I found that the flue door would pop when the boiler shut down and bang open with a big puff of air. Had the chimney guy back out for that one and his solutions was to glue to the flue shut.

So, he was fired. Had my HVAC guys who service the boiler back and they had it down to insanely low PPM on the CO so I just let it go.

I think where I went wrong was allowing myself to get talked out of insulating the chimney. When I was researching the relining to begin with I read a lot of conflicting opinions in regards to whether the liner had to be insulated or not. The chimney guy said no, so I went with him. I think this was a mistake. The liner cools faster than the old clay did and the cooling kills the draft, especially when the boiler is shut down. I think this was my issue.

In 2011 I had an oil tank issue and found out I could go natural gas, so I did. The new gas boiler only needs a 6 inch flue and has a mechanical switch that opens and closes the flue. I thought my smell issues were over.

Wrong.

Still smelled. HVAC guys claimed it was pipe dope burning off.

Had a new chimney company out to check things out. They told me the first guy did it all wrong and it had to all be torn out and redone and that the liner type was wrong -- then wrote me an estimate to replace the liner with the same kind of liner.

So they were thrown out.

Third chimney company came in and said the original guy did everything just as should be but yes it should be insulated. They did vermiculite insulation for me. Made no difference for the smell.

Eventually (like a year later) the pipe dope did all burn off and the smell did go away.

I still have some kind of issue down there. It's odd, all the way at the opposite end of the laundry room there is a spot I can stand and smell that same exhaust kind of smell. Always in the same spot and only in the fall/winter when the heat comes on, not during the rest of the year when he boiler only does my hot water. This smell was the same from the gas boiler or the oil. I can only assume there is some other cause for this and hope it's not serious.

My observations over the years have been that the popping of the flue and/or the smell coming to the room after shut down tends to happen in the summer, usually August. The smell at the other end of the room is all heating season long. I have smoke detectors and CO detectors installed closer to the boiler than they should be as well as in the rest of the house and none had ever chirped.

My advice would be to look into one of those mechanical flues and then just let it go. They also sell these venturi chimney caps that are supposed to help with draft. I never tried one but they looked like the would help. Good luck!

Oh and look for OTHER CAUSES. The original smell? The screen door insert for my storm door. I stored it in the laundry room off season. The screen was made of some kind of petroleum product plastic material and was giving off the odor. Why did it travel to the sewing room? Because as I was digging around in the laundry room to find the source of the smell I temporarily moved stuff stored in the laundry room up to the sewing room/spare junk room. Finally figured it out by accident but not after countless HVAC calls and one visit from an electrician.


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## natemare13 (Nov 11, 2013)

dave12345 said:


> 10k later, never resolved to my satisfaction.
> 
> The original smell in the sewing room, the thing that kicked off the whole chimney relining debacle, was identified and was nothing to do with the HVAC.
> 
> ...



Can't thank you enough for your time many years later updating your story to help me out. I'll remove all items from that area and then investigate the use of any new pipe dope or similar product that may have been used during a recent (6mo?) boiler maintenance. Then, I'll check the flu for clay or insulated liner. I think I have clay. Finally, I'll have a look into the mechanical flu door. 

Again, many thanks for your time.


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## yuri (Nov 29, 2008)

Do either of you have a floor drain near in that area. If it dries up you may be getting a sewer gas smell ( just trying to be helpful ). I tell my customers to pour water and bleach in there to kill the bacteria and then flush it and add water with a bit of cooking oil so it does not dry out. These suspicious smells sometimes are plumbing related. Sometimes the plumbing stack freezes or won't draw properly and you can get sewer gas smells even in the kitchen. Stack may be plugged/plugging up on the roof from bird nests etc. I get lots of gas smell calls and many turn out to be floor drains or even a hole in a stack or drain pipe can let out gas smell. had one from a kitchen sink drain where the pipe rotted away behind the sink.


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