December 22, 2014

How to figure out which room air conditioner you need

By Sears PartsDirect staff
How to figure out which room air conditioner you need
How to figure out which room air conditioner you need

Buying a window air conditioner with enough power to cool the space you want cooled and then installing it correctly is essential for your comfort and conserving energy.

A room air conditioner that is too small struggles to cool the room, while a room air conditioner that is too big cools too quickly to lower the humidity. Both waste energy because they can’t work at peak efficiency.

Window air conditioners range in cooling size from 5,000 to 15,000 BTU. (One BTU is enough energy to raise the temperature of 1 pound of water by 1 degree F).

Here's the formula for computing how many BTUs to buy:

  1. Multiply the square footage of the area to cool by 20 BTUs.

  2. If more than two people regularly occupy the area to cool, add 600 BTUs for each additional person.

  3. If the room is very sunny, add 10 percent to the total. If the room is heavily shaded, subtract 10 percent from the total.

  4. If the room is the kitchen, add 4,000 BTUs.

Symptoms for window air conditioners

Choose a symptom to see related window air conditioner repairs.

Main causes: bad compressor, lack of refrigerant, bad compressor start relay, electronic control board failure
Main causes: turning the air conditioner off and the back on too quickly, dirty or restricted condenser coil, compressor failure
Main causes: dirty air filter, air conditioner is too small for the room, temperature set too cold, control failure
Main causes: clogged drain hole, air conditioner not leveled properly
Main causes: clogged condensate drain, air conditioner not leveled properly, leaky window air seals
Main causes: lack of electrical power, bad electronic control board, wiring failure, bad temperature sensor

Repair guides for window air conditioners

These step-by-step repair guides will help you safely fix what’s broken on your window air conditioner.

How to replace a window air conditioner ambient thermistor

If your window air conditioner isn’t cooling properly, it might need a new ambient thermistor. You can replace it yourself following these instructions.

Repair difficulty
Time required
 45 minutes or less
How to replace a window air conditioner user interface control board

Control buttons or lights on the user interface control board can stop working. This repair guide shows how to replace it.

Repair difficulty
Time required
 30 minutes or less
How to replace a window air conditioner electronic control board

The electronic control board is the brain of your window air conditioner. Here’s how to replace it.

Repair difficulty
Time required
 45 minutes or less

Articles and videos for window air conditioners

Use the advice and tips in these articles and videos to get the most out of your window air conditioner.

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Window air conditioner installation tips.