Some Carrier models may require two filters. Consult your owner's manual for specific procedures for your model. "The Homeowner's Handbook to Energy Efficiency" suggests vacuuming or wiping down the filter cabinet during filter replacement to pick up any loose dust and debris.
Do not operate your furnace without a filter.
Replace the filter on your Carrier Performance 80 furnace at least twice a year, according to the manufacturer. Periodically installing a new disposable filter will prevent undue stress on the furnace; not to mention it will also keep your energy bills tame. Use the same type and size filter as the old one; compare them side by side when you pull the old one out just to be sure. Filter replacement on the Carrier 80 is simple.
Turn the electrical supply switch on the furnace to the "Off" position.
Open the filter cabinet door. There may either be a knob that you turn counterclockwise or a screw that you twist out with a screwdriver to release the door.
Grab the old filter with your hands and gently tug it out of the cabinet. Place it in a trash bag.
Install the new filter by simply pushing it into the housing where the old one was and close the cabinet door.
Turn the electrical supply switch to the "On" position to start your furnace again.
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Dave Baker is an editor and writer based in New York. He has more than a dozen years of experience in the media industry, including work for "The Nation" magazine, the "New York Times" and the "Times-Picayune" of New Orleans, where he shared two staff Pulitzer Prizes after Hurricane Katrina.