What are cracks in the base of the furnace?

There are a few different types of openings in the platform and furnace that could be identified in this way. These are, however, not an immediate threat. They must be addressed, but they are usually very minor to repair. Those issues are:

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The seal between the furnace and the floor of the closetHome Furnace repair

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 sidesCall for home furnace repair

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.


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