4 Common Reasons Behind Heat Strips Not Coming On

Heat Strips

An efficient heating system can save you from those chilly winter nights. Heating is a part of your HVAC system, and it is imperative if you need a cozy, warm home in the winters. This system consists of various components that need regular maintenance. If not maintained adequately, some parts start to malfunction. One of those parts is the heat strips. This article talks about what they are, the most common reasons they are not coming on, and the best thing to do. Stick around to learn more.

If you want to get the best HVAC maintenance or simply do some research on your own, check out https://americanhomewater.com/ac-repair-phoenix/.

What are Heat Strips?

Heat strips provide a secondary heat source to the heat pump when the outdoor temperature gets too low. They are also called electric or auxiliary heat strips.

Basically, a heat pump functions in a way opposite to air conditioners. It captures the heat from the outside and transfers it to your home. However, when the temperatures are incredibly low, heat strips come into play.

The heat strips are located inside the air handler, and they come in different types and sizes as they have to fit the air handler that you own. Unfortunately, occasionally, you might experience certain issues with this device. 

Why Are Heat Strips Not Coming On?

Heat strips are a part of the air handler that is not on at all times. They only come on when absolutely necessary. This way, you get to save a lot of energy, and your bills are not too high.

However, on some occasions, heat strips tend to malfunction. Here are a few reasons why your auxiliary strips might not be coming on:

The Size Is Not Right

Getting the right size of heat strips for your heating system is of the utmost importance. This is one of the main issues that cause the strips to malfunction in the first place. Sizing the heat strips to match your heat pump is essential. You can find strips with capacities ranging from 3 kW to 25 kW. 

Although heat strips can provide a lot of heat for your home, they are not always necessary because:

  • There would be a lot of heat. Thus, they must be used only when temperatures are too low, and your heating system isn’t able to work effectively.
  • The bills would be too high.

This is why you do not need a heat strip with a large capacity unless your furnace requires it. For example, a 10 kW unit needs a 50 Amp breaker. This is calculated by dividing the number of kW by 240 Volts.

The Temperature Is Not Below 35-40 Degrees

Generally, heat strips are not designed to turn on unless the temperature outside is below 35 degrees. Therefore, do not panic if the temperature is low and your auxiliary strips are not coming on. Once the heat pump starts struggling to warm up your house, that is when the strips come to the rescue.

Much like air conditioners take the cool air from the outside and transfer it into your home, the heat pump will absorb the hot air and move it indoors. Once the temperature gets too low, there is no point in doing this, which is why heat strips exist in the first place.

So, before you panic and call the technicians, make sure that the temperature outside is suitable!

The Indoor Temperature Is Not 3 Degrees Colder Than That On The Thermostat

Another reason for the heat strips to come is when the temperature on the thermostat is three degrees lower than the temperature on your house!

As an example, let’s say that the temperature in your home is 59 degrees, and you decide to put it up to 54. This means that the heat strips will automatically turn on because the difference is higher than three degrees. This way, heat strips help meet the thermostat temperature faster!

Therefore, if you notice that your home is cold and the strips are not coming on, make sure to check the thermostat first. If you adjust the temperature and they still do not work, there might be a different issue, and you should call technicians to help!

Keep in mind that the rise of three degrees is an automatic setting done by the manufacturer. If you want to change that to 1 or 5, you must call in professionals. After that, the strips will be triggered at your desired temperature difference.

The Heat Pump Is Not On ‘defrost’ Mode

This one might seem a bit odd, but it is quite common for ice to build upon your heat pump outdoor unit. This is when the heat pump turns on the ‘defrost’ mode. While the pump is busy melting the ice, the heat strips are in charge of warming up your home.

However, if the heat pump can still function and does not have to go into that mode yet, there is no need for the strips to take over.

Therefore, if you notice the ice forming and the pump not switching to ‘defrost,’ do not panic. It might take some time for the system to realize that the ice needs to be melted. However, if the strips do not come on at any point, that is definitely a reason to be concerned.


Heat strips are essential components of your HVAC system. Their role is to be the secondary heat source, so your home temperature is always optimized. Whether it is hot or cold outside, they help you create an enjoyable atmosphere. 

Much like most other components, this component also experiences some issues, which can be highly inconvenient. There are several reasons why the auxiliary strips are not coming on. However, these reasons are very common, and you should not panic before checking all of them off the list. In case the problems persist, you should call technicians for help!



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