Change in chimney draw after converting oil to gas
We have a standard 1949 house with a brick firebox and chimney. We never had issues with the chimney draw until we converted to oil hot water burner to a high effciency gas unit. Initially the change in draw was not too severe, and we would just sometimes get a smoky smell the day after a fire.
Christmas day we went to have a fire and had a serious negative draw and the house filled with smoke. I should have guessed as the lighter didn’t even want to stay lit when in the firebox.
I initially suspected the gas boiler installation, or the new kitchen vent hood, but have changed my mind. We have had fires, with little issue, since both installations – aside form the smoky after-smell.
To do some investigation, I placed crepe paper strips in front of the firebox to watch the airflow as I tried various things. The kitchen vent fan and gas boiler do aggravate the situation, but there seems to be a random component. It’s almost as if the wind/direction is affecting our draw, now.
Sometimes with the furnace and fan off, I still get a serious negative draft, and sometimes it seems fine. This is making me wonder if it might be related to the new chimney cap/flue, which was installed with the gas boiler to keep the stacks (chimney and gas boiler) at the proper relative heights.
We had to get a chimney sweep in to clear our chimney of a bird’s nest (apparently the new chimney cap is not enclosed) before we tried any fires this season.
Currently I am suspecting the chimney cap, but calls to BGE Home (the installer) have led to the usual denials about their installation. Any suggestions would be helpful. Thanks.
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Chimney Draw
If you can't get BGE Home to do anything about you problem, I would suggest that you get someone else, you could have an extreme safety Issue!
Several things are not clear. First, I'm assuming from your post that the chimney you're talking about is for a wood fireplace, and is not in any way connected to the furnace flue. Is this correct?
Is the new boiler a "condensing" unit with plastic flue out the sidewall? Your mention of "high efficiency" would suggest this, but then you say there's a "stack" for the boiler.
Was anything changed with regard to "makeup air" for the new boiler, vs the old. Code generally requires a makeup air feed from outside (or the attic in earlier codes) into the furnace room when using a conventional flue (vs "condensing") unit.
From the sound of it, though, you're simply having cold flue problems. (Though precisely why is a good question that I can't answer.) Well before you start a fire cold air gets moving down the fireplace flue, and once it starts it's self-sustaining, since cold air is heaver than warm. In such conditions it's impossible to start a fire without warming the flue first. What I do with our fireplace is to wad up some newspaper and jam it into the damper area. Set that alight and it generates enough heat fast enough that it gets forced up the chimney and gets a draft started. Then the fireplace can be lit. (Caution: Don't use too much newspaper or large wads of burning paper will be carried up the flue and out onto the roof and other areas.)
RE: Change in chimney draw after converting oil to gas
It is a condensing boiler with an external vent to the side of the house.
It is a chimney for a wood fireplace, but I mis-spoke. It is the gas water heater that also vents up the chimney, and they replaced the chimney cap/flue to make sure the heght of the water heater exhaust was sufficient to prevent the exhaust gas coming back in the chimney - if I remember right. The gas water heater vent shares the physical chimney structure, using (I assume) some sort of separate flue pipe.
There was nothing done for makeup air that I am aware of.
I agree that it sounds like cold flue issues, but why are we having cold flue issues all of a sudden? Could the chimney cap or the damper (which is at the top of the chimney, but was not changed since we bought the house) make this dramatic of a change?
I have no problem hiring someone, but who do I look for (certainly not a chimney sweep company) to investigate/fix this?
Thanks
Ah, so previously the boiler was exhausting up a stack parallel to and in the same masonary structure as the fireplace flue? But now it's only the water heater using that stack?
The old boiler was keeping the chimney warm -- even with separate stacks there was enough heat transfer to keep the fireplace flue warm. The chimney's no longer being warmed by the boiler, and hence you get the cold flue situation.
RE: Change in chimney draw after converting oil to gas
Thanks DanH! So easy even an electrical engineer come wannabe woodworker half-a**ed DITer can understand.
I guess we'll have to live with the newspaper in the chimney trick until we contact a chimney guy and see if we can effect a more permanent solution (to prevent the smoky smell the day after the fire).