Why Does My Heat Pump’s AUX Heat Keep Coming On?

Why Does My Heat Pump’s AUX Heat Keep Turnin On?

The heat pump AUX heat (short for auxiliary heat) is there to give your home a quick burst of heat when you need it. Here in Arizona, that shouldn’t be especially often. If your auxiliary heat is constantly running, or if you think it’s running when it shouldn’t, here’s everything you need to know to get to the bottom of the issue.

What Is Auxiliary Heat?

AUX heat, as a feature, is most useful for homes in cooler climates than the one we have here in Phoenix. That said, it can come in handy every once in a while when temperatures dip here in Arizona. Your heat pump’s auxiliary heat helps heat up your home quickly, and it’s something like a last line of defense against the cold.

Normally heat pumps use a reverse cycle to keep your home at the ideal temperature. This is an ideal way to heat homes in hot climates because it’s extremely efficient. Unfortunately, it’s also somewhat slow. That’s where the AUX heat comes in. It creates electrical heat that works with your normal heat pump to increase the temperature more quickly.

Why Is the Auxiliary Heat Coming On?

As you might imagine, the AUX heat typically engages when your home needs to get warmer in a hurry. There are a few reasons this might happen.

You Turn the Temperature Up

If you increase the set temperature in your home by more than a few degrees, your heat pump might have a hard time catching up. That’s where the AUX heat comes in. It will engage to help get your home up to the desired temperature as quickly as possible.

For example, if you like to keep your home cool at night so you can sleep under a big blanket, you might need to turn the temperature up by several degrees first thing in the morning. Suddenly, your system recognizes that the set temperature is significantly higher than the actual temperature in the home. At this point, the AUX heat will kick on to help your home warm up.

The Weather Reaches Freezing Temperatures

When the temperature drops down to around freezing temperatures, your AUX heat might be necessary to help the heat pump keep the cold out of your home. In this kind of scenario, the auxiliary heat is working as some extra muscle because heat pumps aren’t built to handle that kind of workload. The AUX heat shouldn’t be necessary until outside temperatures dip to about 35°F or below, so you shouldn’t have this problem very often if you’re reading this from anywhere near Phoenix.

The Heat Pump Froze

Most heat pumps have sensors that can identify problems like frozen coils. If something goes wrong, the unit may go into defrost mode. Hot air from inside the home is directed to the frozen components to melt the ice. The AUX heat may engage to help keep your house warm while the other heat is being used on the system itself. Your heat pump may have a special indicator to let you know when this is happening.

This problem is a bit more common in areas with lots of snow and ice. So, again, this really shouldn’t be a concern in Maricopa County and the surrounding areas.

Your Heat Pump Is in Emergency Mode

Your heat pump probably has an emergency heat setting. If you, your roommate, or a curious child turns it on for any reason, your AUX heat will engage. Unless you turned it on for a good reason, simply turn this mode back off. Emergency heat is intended to be used for short bursts when necessary, but it’s not good to leave it on for a long time.

AUX Heat Malfunctions

If you run through the reasons above, and you can’t find a good reason your auxiliary heat is on, there’s probably some sort of problem. All of the following are signs that your AUX heat isn’t working properly:

• Aux Heat on but No Heat – If the feature is engaged, but you’re still not getting any heat, something has gone wrong. This likely means that there’s something wrong with the AUX heat feature itself because it’s not doing what it’s supposed to do. Turn the system off and call a professional to take a look.
• Heat Pump Auxiliary Heat Always On – Your AUX heat should rarely run (no matter where you live, but especially here in Arizona). If it’s constantly running, your system might be stuck in defrost mode, or it’s otherwise getting bad signals.
• Electricity Bill Excessively High – There are a number of appliances in the home that could be wasting electricity, but the HVAC system is definitely a common culprit. Even though heat pumps are designed to be incredibly efficient, they can waste a lot of energy if the AUX heat is running too much. If you can’t figure out why your bill is so high, have a professional do an inspection before you waste money too many months in a row.
• Auxiliary Heat Running During Summer – This is a big red flag. The AUX heat is only supposed to kick on when temperatures approach freezing, and summer in Phoenix never gets anywhere near cold enough for the AUX heat to be necessary.
• Changing the Thermostat Does Nothing to AUX Heat – If the auxiliary heat doesn’t cycle on and off when you change the thermostat, you’re having problems.

How to Stop Auxiliary Heat From Coming On

If you notice any of the problems above, or the temperature in your home simply becomes uncomfortable, it’s time to call the HVAC professionals. Our team at Howard Air has years of experience serving homes in Maricopa County. We take pride in our ability to respond quickly, resolve your issues, and make your home comfortable again as soon as possible. Schedule service now to get started.

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