Last summer I installed a gable vent attic fan, all summer long I smelled smoke, I couldn't understand why now. It had never happened before. Just recently it became warm enough for that fan to kick on again, and I smelled the smoke again. I deducted that it was probably creating a negative air pressure in the house and drawing from whereever it could, namely the fireplace flue. I shut the damper, which did some good, but not completely. Is there anything more I can do to seal off that fireplace when not in use?

I have a Trane XE90 power fan assisted exhaust furnace. I noticed that condinsate water is collecting in what appears to be the heat chamber and dripping down into the fan box. I have checked the condinsate drain on the exhaust fan and note that it is open and draining. So are all the other drains. The furnace is an updraft unit located in the basement in an open finished room. The furnace is not enclosed. Where is it coming from and what is causing it? This will rust my unit out. I have just finished off the basement area into living area. Is it possible I need a fresh air supply?