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View Full Version : filter on gravity furnace



John Arnold
04-28-2007, 11:24 AM
I don't think I've ever see anyone put a filter on an old gravity furnace. I would think even a clean filter would restrict air flow too much. Plus, it's holding up that door that slides down over the return side.
I'm not sure of the reason for those sliding doors that drop down - are they there to adjust the volume of return air, or are they safety covers that are supposed to drop down in the event of a fire?
I'm just curious, really. I wrote the whole thing up as obsolete, inefficient and unsafe. There's a gas water heater just on the other side of the furnace.