Oil Boiler Exhaust Smell

Hi -

I have a 30 year old Weil Mclain oil boiler that has started making exhaust fumes that come up into the living room (which is directly above the boiler).

I have already had a contractor come out twice to service the boiler (and the boiler has received yearly tune-ups, although I suspect they were not high quality - they did not mention replacing the filter or nozzle or anything like that). Originally the exhaust smell only happened occasionally and only at night - it would smell for a minute after the boiler kicked in and then go away. I thought perhaps the cool night air was causing insufficient draft and the initial exhaust was not going up the chimney.

Then my boiler died (circulator was running, but burner not functioning), so I called the contractor for a restart. He bled the fuel line and go it going again. I mentioned the exhaust smell, and the guy said he adjusted the air/fuel mix to be less rich and then left - but when the boiler kicked back in it smelled worse than before and was smelling every time it turned on.

I had them come back out, the guy tried sealing the venting more thoroughly, and messed with the air/fuel mixture more. I suspect he didn't really know what he was doing, though, since he puttied over the view port (I guess to seal up all possible leaks?) Also, I didn't think the air/fuel mixture should be that important to an exhaust smell - regardless of how clean it is burning, I shouldn't have odors coming into the house, right?

For now I just have a table fan on the floor next to the boiler pushing the exhaust out the cellar door.

So, any thoughts on what is causing the smell? Happy to provide more information. On a related note, if anyone knows a contractor in the DC area who knows their stuff when it comes to oil boilers, please let me know.

 

Welcome to the forums.

We're not an Angies list for contractors. You'd have to ask around or check with Angies list.

The smell you are experiencing..... is that just as strong in the basement or do you only smell it upstairs ?

 

When you write that the boiler has received yearly tune-ups did that include a thorough cleaning every time?

You most likely have a draft problem and that is most likely caused by dirty firesides on the boiler or a defective chimney. You can have a chimney sweep do a cleaning and inspection of the chimney to determine if the problem is the chimney. If the chimney checks out okay then it is the boiler gas passages that are severely fouled.

 

PJ - The smell is stronger in the basement, less intense upstairs.

Furd - The tuneup checklist on my receipt includes a vacuum and a cleaning of the chimney base, but they didn't actually use the checklist so i'm not sure what has been done. On the older receipts, the draft is noted as .04 over the breaching and .02 over the fire, if that is useful information.

 

I'm not a pro on this, but I do burn oil and these units need more than a new air filter each year. Oil filter, thorough cleaning (and I mean thorough) and a new nozzle and related adjustments. It is also state law here that all tune-ups provide a printout (or equivalent) of the resulting performance of the boiler. What you have described sound way short of a proper tune-up which should be done each year, not just after it dies.

Check with your oil delivery company, they may have service or be able to recommend someone. If they are the ones who came out, change oil companies.

Bud

 

Bud,
You mentioned according to a receipt you had a .02 over the fire & a .04 at the breech. Those are good numbers and what it says is that the boiler is not plugged and your chimney works fine, that is if the numbers were legit.
You should have other numbers also. Stack temp., smoke test, co2 reading. This should all be on a sheet and these can only be obtained with the proper equipment.
It sounds like you have a combustion (fuel/air) mixture problem.
The only way way to set these burners properly is with a combustion anylizer test kit, which should be part of any tuneup.
There are particular settings that are required to make this run right. The fact that it's worese now than it was before and it ran fine for years is pointing to the service you're receiving.
If they don't at least bring out the test kit and set it up right, I would look for someone else.
It doesn't sound like a major problem, just human error.
By the way you probably have a WM P368, which is what I still have in my house since 1984 and still runs fine so don't let them tell you it's the boiler unless it's leaking.
Good Luck,

 

What about outside?

When the boiler is firing and you are in the vicinity of the chimney, do you smell the exhaust then?

 

Do you have a barometric draft regulator on the smoke pipe, often they will open past there maximum travel and stay there , the -.02 over fire pressure will be lost and go to a + pressure which will allow fumes to enter the building.

 

Some more information: I bought this house in 2013 - had no trouble with exhaust smell last winter, though it was much much colder. Had a tuneup done last year and this year, they didn't write anything down on the receipts except the date and a part number they replaced (I'm guessing a filter or nozzle, it was the same part both years).

Previous owners said they did yearly checkups, but don't know where the receipts for those are. The most recent tune-up receipt above the boiler besides mine is from 2001, which does have the draft numbers, stack temp, C02, etc.

It is a WM P366-W. Not sure of the age, oldest receipt above the boiler is from 1985.

NJ - I raised the temperature so the boiler would fire and stood outside by the chimney, but I don't smell anything there - the chimney is contained within the house, though (runs through the living room). I will say that having the fan running to push the air out the open cellar door has greatly improved the smell (although there is still a faint odor) - this indicates to me that the smell is coming from the boiler itself, not through a crack in the chimney lining.

Saves - I do have a draft regulator. Not sure if it is set properly, though - there is rust on the counterweight so I doubt it was adjusted on the recent service calls (although I'm not sure if they checked the draft - they didn't mention that, only messing with the combustion mixture and double checking the venting)

 

That's not really where I was going with my line...

If the boiler is really running poorly, for example, if there is unburnt fuel, soot, etc, it will be heavy and sink to the ground after it comes out the chimney instead of rising... and it will smell like a bus depot outside, downwind from the chimney.

 

Ah, now I read you. I have not noticed any smell outside the house.

Another detail that I thought might be relevant - the living room does not smell when I come downstairs in the morning. The system runs for 45 minutes or so to get back up to the daytime temperature, and has usually finished shortly before I come down.

So I am guessing it does not continuously produce foul odors, only around start-up (which have faded by the time I come down).

 

Do you see soot around the boiler , inside the draft regulator, were the smoke pipe connects to the boiler , evidence of heat or soot above flame inspection hole. When the burner is on does the heat come out the flame inspection port when it is opened, if it does there pressure build up in the firing chamber. check this on burner start up with the back of your hand , be carful not to get burnt. The teck may have changed the nozzle to a larger size or increased the amount of air through the burner and now the heat exchanger is over loaded with excess exhaust,

 

It could be possible that the startup is poor. Perhaps delayed ignition... and it's 'blowing back', or 'puffing' out the damper opening for a few seconds when it starts.

As has been said, most likely nothing that a PROPER TUNE UP would not solve.