If you have a Carrier Performance 80 gas furnace, you probably live in a milder climate where a high-efficiency furnace would be an unnecessary expense, and like all furnaces, the Carrier works best if you remember to change the filter regularly. With an annual fuel-utilization efficiency rating of 80, the Performance 80 meets the minimum standards for furnace efficiency, but it doesn't earn ENERGY STAR certification. It does have a variable-speed blower, however, which is a nifty feature that can reduce energy costs and keep you comfortable in all kinds of weather.
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Performance 80 isn't a single model but a line of furnaces with various designs, and the size of the filter and the procedure for changing it depend on the model. The variations in procedure basically come down to locating the filter cover, which may be on the side of the furnace housing or on the bottom.
Get the Right-Size Filter
The size of the filter you need depends not only on the size of the furnace cabinet but also on whether the air return vent is on the side or bottom (all dimensions are in inches):
- A cabinet 17 1/2 inches wide needs a 16 x 25 x 1 filter for both side and bottom returns.
- A cabinet 21 inches wide needs a 16 x 25 x 1 filter for a side and a 20 x 25 x 1 filter for a bottom return.
- A cabinet 24 1/2 inches wide needs a 16 x 25 x 1 filter for a side and a 24 x 25 x 1 filter for a bottom return.
Note that some furnaces take two filters. If yours is one of them, you'll find this information specified in the owner's manual, which you can find on Carrier's website if you lost your paper copy.
How to Replace a Filter
Carrier recommends turning off the furnace before you change the filter to prevent the blower from switching on while the filter is removed. If you don't have an easily accessible furnace switch, you can turn off the breaker in the main panel that controls the furnace.
The next step is to locate the filter door, which is usually obvious, but you can also refer to your owner's manual if you aren't sure where it is. It may or may not have a thumbscrew, and if it doesn't, you open the door by grasping it on both sides and pulling. With the door open, grasp the filter and pull it straight out; it isn't attached to anything and is very light, so this is easy.
If the replacement filter has an arrow indicating the direction of the airflow, be sure that arrow is pointing toward the blower when you install it. Installation is just a matter of sliding it into place on the rack and closing the door on the housing.
Cleaning Washable Filters
Some filters are washable and say so on the filter frame. To clean a washable filter, always use cold water from a kitchen or bathroom sink faucet or a garden hose. If the filter is very dirty, you may also want to use a mild detergent. Always spray water in the opposite direction of where the air was coming through and be sure to let the filter dry thoroughly for a day or two before reinstalling it.