Why Is My Heat Pump Covered in Ice? A Texas Technician Answers

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Believe it or not, in winter, it’s normal for the outdoor unit of a heat pump to be covered in a light frost.

Now, this light frost shouldn’t stay on your heat pump very long; your heat pump should automatically enter a “defrost mode” to melt it.

So, if you temporarily see a light frost on your outdoor unit, there’s no need to worry.

However, if the light frost turns into ice or doesn’t go away after an hour or two, that means your heat pump likely has one of the following issues:

  • Defrost control issue
  • Low refrigerant
  • Faulty reversing valve

We’ll go into detail about each of these issues below. But first, let’s dive into why ice can form on your heat pump in the first place.

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Why ice forms on your heat pump in the first place

Your heat pump uses refrigerant, a liquid substance, to take warmth from the outdoor air and bring it inside to heat your home.

Sometimes the refrigerant can be several degrees lower than the outside air temperature. If the refrigerant temperature drops below freezing, it’s not uncommon to see frost form on your outdoor unit.

Like we mentioned in the beginning, your heat pump has a defrost function that should automatically kick in to eliminate this frost after about 90 minutes or so. The heat pump defrosts the outdoor unit by reversing the flow of refrigerant, sending the hot refrigerant that’s normally used to heat your home’s air back to the outdoor unit to melt the frost.

The defrost function works fairly quickly. If 30 minutes have passed and you still see frost or ice on your outdoor unit, you likely have one of the issues below.

Problem #1: Defrost control issue

A heat pump repair technician will usually start by checking your defrost control components.

Your heat pump has a defrost control board that regulates how often the defrost mode should turn on. Over time, parts on the board can fail, which prevents the defrost mode from starting.

Common defrost control issues include:

  • Bad defrost timer
  • Faulty thermostat
  • Broken defrost relay

A technician will have the tools to test and repair your defrost control board if that is the source of the frost problem.

Problem #2: Low refrigerant

Like we explained above, your heat pump uses refrigerant to heat your home.

If it’s dry outside and your heat pump frosts over quickly, your heat pump may be low on refrigerant.

Low refrigerant is caused by a leak somewhere in your heat pump, often in the refrigerant lines or near the compressor in the outdoor unit.

A heat pump technician will inspect your system to find the source of the leak and repair it. Then, they’ll add refrigerant according to how much was lost via the leak.

Problem #3: Faulty reversing valve

The reversing valve controls which direction the refrigerant flows in your system. In defrost mode, the reversing valve makes the refrigerant run towards the outdoor unit, so the heat from the refrigerant can melt the ice on the outdoor unit.

If your reversing valve is broken, then the defrost function won’t work, which would explain why you’re seeing frost or ice on your system for long periods of time.

The technician you hire to fix your heat pump will inspect the reversing valve and make sure it’s working properly. If the valve is broken, they can repair or replace it.

Need a heat pump repair? Call a reliable pro

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Our team of trained technicians are equipped to handle any type of heat pump repair. We can make sure your heat pump’s defrost mode is working properly, and that ice buildup isn’t interfering with your system’s normal operation.

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