What is the 20° rule and why is it important for my A/C?

What is the 20° rule and why is it important for my A/C?

As summer gets into full swing and temperatures across the country rise, many people with air conditioning systems in their homes consistently set their thermostat to about 70° Fahrenheit. While this allows for a comfortable space in which to take refuge from the heat, when the outside temperature is upwards of 90°, cooling the house to 70° can be quite a challenge for the AC.

Air conditioning working overtime

Most HVAC systems have two jobs: to cool and to maintain humidity levels. The standard humidity that most HVAC systems aim for is around 45-55%. However, when the temperature outside is high and the system is working hard to cool, it has less ability to regulate humidity. The result is that the system works overtime trying to maintain conditions inside the home, using a much larger amount of energy than normal and placing strain on the system that contributes to premature wear.

Setting your thermostat

In order to avoid this, it can be a good idea follow the 20° rule. The 20° rule is a rule of thumb that states that an AC system should not be set any lower than 20° lower than the outside temperature. For example, if it is
95° outside, then the thermostat should be set 75° or higher, but no lower than that. Therefore, the maximum amount of work the AC has to do is cooling 20°. By following the 20° rule, you keep your HVAC system in prime condition by not forcing it to work harder than it comfortably can. Of course, every HVAC system is different, so the 20° rule may vary based on your location, the model of AC you have, and the size of your home.

Problems with the 20° rule

The obvious problem with the 20° rule is that if it is exceedingly hot outside, it might not be cool enough inside. For example, if it’s 100° outside, then the inside temperature would be 80°, which is a higher temperature than most people would prefer. The solution to this issue while still keeping your HVAC system healthy is to take other measures to cool down your house, for example:

• Install a ceiling fan or multiple ceiling fans
• Hang drapes or blinds to reduce the heat that comes through windows
• Install heat insulation

Applying the 20° rule in your home

By following the 20° rule, you can greatly reduce the amount of energy you use and the amount of maintenance needed on your HVAC system, therefore lowering the overall cost of your air conditioning.

Since every situation is different, the 20° rule may vary based on your location, the model of AC you have, and the size of your home. Call RC Mechanical, Redwood City’s best HVAC contractor, and our a/c installation/repair technicians will use our state-of the-art software to make sure you are getting the right-sized air conditioning system for your home. Call us today at 650-575-3915!

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