Why Isn't My HVAC System Working After a Power Outage?

HVAC systems are designed to keep your house cool during the summer months and warm during the winter — when it stops working, it can make you uncomfortably hot or cold.

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Is your HVAC not working after a power outage? Try these troubleshooting tips to get it back in business.

After a power outage, it’s likely that your AC unit or furnace won’t start working again automatically. Power surges can cause havoc on your HVAC system. Some of the issues that can leave your HVAC system not working after a power outage include tripped breakers or problems with the thermostat, heat pump or air handler.

• Tripped breakers: A power surge when your electricity came back on may have tripped a breaker. Check your circuit breaker box to see if any switches are in the off position. Try flipping the switches back to the on position. If that doesn’t work, you may need to reset your system.
• Thermostat issues: Your thermostat may have lost its settings during the power outage, and if you have a smart thermostat, it may have disconnected from your home’s Wi-Fi. Make sure your thermostat is connected to your home’s Wi-Fi, and set it to a temperature that’s hotter or colder than the temperature inside your home, depending on whether you’re heating or cooling. Setting it five to 10 degrees cooler or warmer than your home’s internal temperature can make it easier to tell if it's working.
• Problems with the heat pump: If your home has a heat pump, it may have stopped working when the power came back on. Try turning it off and on at the breaker.
• Air handler issues: Sometimes, a power surge can cause problems with the air handler. Turn off the air handler and condenser switches in your circuit breaker box, and wait for about 30 seconds before flipping the switches back to the on position.

Sometimes, these simple fixes will get your HVAC system up and running again. If your home still won’t heat up or cool down, you might need to reset your AC unit, your furnace or both.

How Do I Reset My AC Unit?

How to reset your AC unit depends on whether it has a reset button. Take a look at your air conditioner and check to see if it has a tiny, red reset button. It should be easy to find, but if you can’t locate it, read your user manual to see if your unit has one.

Units With a Reset Button

If your unit has a reset button, follow these steps to reset your AC after a power outage.

1. Turn off the power: Shut down the indoor and outdoor components of your AC unit at the breaker. Find your breaker box, and look for breakers in the off position. You’ll know which ones they are because they’ll be facing a different direction than your other breakers. If the breakers are already off, leave them alone for now.

2. Reset your unit: Press and hold the reset button for about 5 seconds.

3. Power it back up: Flip the circuit breakers back to the on position.

4. Cool your house down: Check your thermostat and make sure it’s set to “cool.” You should also ensure it’s set to a lower temperature than the temperature inside your home.

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Units Without a Reset Button

If no reset button is present, follow these steps to reset your unit.

1. Turn off your thermostat: Turning the thermostat off will prevent your ac unit from kicking in while you’re trying to reset the unit.

2. Turn off the breakers: Flip the breakers for the indoor and outdoor components of your AC unit to the off position and wait for 1 to 3 minutes before flipping the breakers back to the on position.

3. Give it some time: Your ac unit needs time to reset its internal circuit breaker. Let it sit for about 30 minutes.

4. Turn on the thermostat: Turn your thermostat back on to the “cool” position. Setting it 5 to 10 degrees cooler than the current temperature of your room makes it easier to tell if it’s working.

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How Do I Reset My Furnace?

Losing heat in the winter can leave you chilled to the bone. Follow these steps to reset your furnace and heat your house.

1. Shut down the power: Look for a power switch near your furnace. After you locate the power switch, turn it off. Don’t worry if your furnace doesn’t have a power switch. Just turn off the breakers for your furnace in your circuit breaker box.

2. Wait: After you shut off the power, either at the switch or via the breaker box, wait for about 15 seconds.

3. Turn it back on: After 15 seconds, turn the power switch back on. If you turned off your furnace at the breaker box, flip the switch back to the on position.

Keep in mind that HVAC systems are very complex. If these simple fixes and tips for resetting your system don’t work, contact an HVAC repair technician to fix your unit.