Boiler Chimney Venting

[camdids]

Just started to get a problem and thought I would throw it out there and see what you think.
Had my Boiler set up for 15 years. No issues. But in the last few days I have been getting exhaust fumes seeping into my living room from my Fire Place. My chimney has Two Flues, one for the Boiler and the other is the Fire PLace where I have a Pellet stove Insert. The Boiler Vent just goes into the Flue in the basement, but does not extend any further up.(pic). I'm assuming there are obviously cracks and gaps between the flues letting the fumes through. Taking the repair of the Chimney would be very expensive, could I have the Boiler Vent Pipe extended up further, to take care of the issue. The current pipe from the Boiler is 7inches.

 

[begreen]

Definitely have both flues cleaned and inspected. If there are cracks, add a liner.

But maybe this could be downdraft? Is the house all closed up for running air conditioner(s)? Does the problem only occur when something is exhausting from the house like a stove fan, bath fan or dryer? If yes, leave a window cracked open about an inch and see if that stops the problem.

One thing to look at is the chimney flue tops. Are the chimney terminations (caps) at the exact same height? If yes, extend the fireplace flue, but not the boiler flue by about 12"- 18".

 

[camdids]

Thanks for the reply.
That may be a good point with the Air Conditioners. I only started noticing it about a week ago. I have some space fans blowing air around as well. I will do some testing.
The Chimney has a Complete Cover over Both Flues. The Fireplace Flue has a complete Pellet Stove Liner through. The Flue to the Boiler does not have its own cap. Have not had this happen before and have had the smae boiler venting since it was installed 15 years ago. I was assuming there are some cracks at the level around the fireplace.

 

[camdids]

Spoke to my Chimney Proffesional. he is telling me that the Boiler is struggling for air and is therefore sucking and causing the fumes to vent through the living room fireplace. This only occurs when all windows are shut and the Air Conditioner in the window in the kitchen(open Plan) next room is on. I also have portable Fans around the first floor area to help circulate the cold air from the kitchen. I admit to doing some testing , but nothing too scientific.
Is he onto something or is he blowing smoke up my chimney? :lol: