January 24, 2019

Why Does My Heat Pump Have Ice, Frost?

Have you ever seen ice or frost on your Heat Pump in the Winter? This can often be normal to see from time to time. Your heat pump is designed to extract heat from outside and transfer it inside. As it pulls heat from outside, moisture will collect on the coils. If the exterior temperature is below freezing then frost and/ or ice will collect.

Normal Operation

Normal frost or ice at times is not a concern. At programmed intervals your unit will go into a defrost mode and will melt the frost or ice. Normally your unit can defrost at 30, 60 or even 90 minute intervals.

During defrost mode your unit will sound louder. Some units can be noticeably louder. In defrost mode, the coils will heat up to almost 60 degrees in order to melt the frost or ice.

The colder the weather the longer duration your heat pump will run. Unlike a furnace, which heats the air, your heat pump actually transfers heat. This extraction/ transfer operation requires nearly constant operation in very low temperatures. Your heat pump is designed to operate that way.

Icing Problems with your system

There are several icing problems which may indicate a problem. Some problems with over icing and not defrosting are:

• Faulty controls- There are many controls, relays and sensors utilized by your system. A failure of any of these components can cause your system to not operate properly. A sensor failure can cause your system not to defrost.
• Reversing Valve Failure- This can be a problem with the reversing valve itself or an electrical problem. Either way, it can cause your system to remain engaged in heat mode and bypass the cooling/ defrost mode.
• Refrigerant is low- Low refrigerant can cause the system to not produce enough heat to defrost the coils. If this happens, your system will also not produce heat and your will be running on your backup system.
• Exterior Fan Not Operating Properly- If the fan fails then excess ice form and the system cannot properly defrost.

These problems will necessitate a professional HVAC technician to assess the issue. Contact Air Doctor Heating and Air for a complete assessment and any necessary repairs or service.


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