| The seal between the furnace and the floor of the closet        The furnace is supposed to be sealed airtight between the  bottom sheet metal panel and the floor of the closet that it resides in. This  airtight seal stops the vacuum from the return air chamber from transferring to  the closet. This is to keep from pulling the flames out of the firebox and  prevent the furnace from pulling the exhaust gases right out of the vent  through the roof. The seal normally is made of latex lagging adhesive or a high  quality caulking. It gets sealed on the inside and the outside.         The actual platform with openings in it        Poorly built platforms or older platforms that are made out  of boards rather than a single sheet of plywood can separate over the years and  create cracks. These need to be filled in or covered up and sealed.         The walls meeting the platform        This is usually from sloppy craftsmanship from the drywall  company. The platform is built prior to drywall being put in. The drywall  installer set his drywall on the furnace base and did not seal the corners  properly. This can be sealed using ordinary caulking. Do not use drywall  compound as it will just crack here again.         Holes in the furnace door and lower sides        When furnaces are built they are built for multiple  positions. This means that electrical knockouts are on each side of the  furnace. If these are opened during the installation or accidental afterwards  this creates a vacuum in the furnace closet. Poorly fitting sheet metal  attached to a side entrance to the furnace can cause this as well.  No matter what kind of furnace problem you are currently experiencing we can handle it for you quickly, cleanly and inexpensively.  |