heat pump

What to Do With an Icy Heat Pump


As cold weather sets in this winter, your home’s heat pump will be working on overdrive keeping you and your family cozy and warm. When temperatures drop, it is not uncommon for your heat pump to ice up. In fact, it is perfectly normal for the unit’s coil to become covered in white frost. During certain extreme weather conditions, it may even become coated in ice.

However, it is not normal for the entire unit to be completely encased in ice, especially for an extended period of time. If your heat pump is coated in ice, it is an indication that there is something seriously wrong. To avoid serious damage to your heating equipment, the problem should be quickly resolved.

What is a Heat Pump?

In technical terms, a heat pump is a mechanical compression cycle refrigeration system. This system can be reversed to heat or cool a specified space. In this specialized system, a compressor works to circulate a refrigerant that absorbs heat from the surrounding area. The heat is then released to another area, either heating or cooling the specified space.

What is Normal?

During the cold winter months, your heat pump will naturally ice up, periodically initiating a cycle to defrost the coils. This process ensures unit continues to run efficiently.

If the coils become frozen over and blocked with ice, proper heat transfer between the refrigerant and outside air is inhibited. With excessive ice build-up damage to the fan blades can occur. Also, heavy ice can crush the outdoor coils, leading to potential refrigerant leaks.

How the Defrost Cycle Works

The unit will automatically switch to a defrost cycle to prevent the unit from developing a dangerously thick layer of ice. In defrost mode, a reversing valve is engaged that switches the system into air conditioning mode. In air conditioning mode, the outdoor evaporator becomes the condenser and the outdoor fan shuts off. Then the high pressure refrigerant circulating through the outdoor coil gets warm, causing the ice build-up to melt. Simultaneously, back-up heat powers up, offsetting cold air blowing through the vents in your home.

Different systems have different methods for engaging in defrost mode. Some use mechanical timers that work in combination with a defrost thermostat. Other systems use solid-state control modules with temperature sensors. The most sophisticated systems a Demand Defrost system. This technology makes calculations based on the temperature outside, the refrigerant temperature in the coil, and the system run time.

What Causes a Heat Pump to Ice Up?

There are several reasons a heat pump may develop excessive ice build-up. Understanding what exactly is causing your system to freeze up is essential to getting the proper service for your system.

Refrigerant Levels

Every HVAC system needs refrigerant to operate properly. Refrigerant is what transfers heat into or out of your home, depending on whether your system is set to heat or cool the space. In summer, the heat pump moves heat outside. During cold weather, the heat pump moves the heat inside keeping your living spaces comfortably warm.

If your system lacks the proper level of refrigerant, it cannot properly transport heat. A heat pump does not use up refrigerant. Instead, it circulates continuously. If your system is running low on refrigerant, it is most likely due to a leak.

If you suspect your system is low on refrigerant, it will need to be serviced by a certified technician. He or she can check for leaks, repair any that are found, and refill your system with refrigerant.

Things You Can Fix Yourself

If your heat pump is icing up, it doesn’t necessarily mean costly repairs. Sometimes ice is caused by common problems that are easily fixed by the homeowner. These situations include:

A blocked outdoor coil. If your coils are blocked by leaves, debris, or snow drifts it could disrupt air flow and cause ice to build up on the unit. Clear all blockages to ensure proper air flow.

Leaking gutters. If your home has blocked gutters, it could cause water to drip onto your heat pump. In cold weather this could produce undue ice build up. Make sure to keep your gutters free form debris to protect your unit from dripping water.

Freezing rain. Wintry mixes, sleet, and freezing rain can cause the top of unit to freeze over. Once the top freezes, it is more likely to develop an icy coating over the rest of the heat pump. This situation may not need professional attention. However, if the ice builds up on the unit, it could damage your system. You might consider turning off the system until the ice melts.

Things That Require Professional Attention

Some causes of heat pump ice build-up require a service call. If these occur, don’t hesitate to call your local HVAC professional for help. These situations include:

  • Damaged defrost timer
  • Broken defrost thermostat or sensor
  • Bad defrost relay
  • Stuck reversing valve
  • Busted outdoor fan motor
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Is A Heat Pump Right For You?

When it comes to heating your home, a forced air furnace isn’t your only option. A heat pump may actually be a better option, especially if you live in a moderate climate. First introduced in the 1940s, heat pumps are growing in popularity, and for good reason.

The Benefits of Using a Heat Pump

Quiet, safe, and efficient, heat pumps are an excellent choice for homes located in states with a more moderate climate. Here are just a few reasons to consider a heat pump to keep you cozy and comfortable all winter long.

  • Energy Efficiency. Running on good old fashioned electricity, the average heat pump is significantly more energy efficient than the average gas powered furnace.
  • Save Money on Your Annual Heating Bill. Electric rates tend to be less expensive than natural gas, at least in most areas of the United States. This means that operating a heat pump system will cost less on average than a gas fired furnace.
  • Cheaper Installation Costs. Because a forced air furnace requires an extensive ventilation system, installation can be expensive, especially in a home that isn’t already equipped with one. Installation of a heat pump system will usually cost less than the installation of a furnace in most situations.
  • Quiet Operation. In general, heat pumps do not make as much noise as a furnace. This will cause less disturbance in your daily home life, allowing you to easily enjoy activities like watching television and sleeping without being interfered by a loud heating system.
  • Safer Operation. Since heat pump systems don’t burn fuel to generate heat, there is no risk of dangerous carbon monoxide poisoning. Also, since there is no burning fuel, operating a heat pump reduces the risk of fire.
  • Heating and Cooling in One Option. A heat pump can also cool your home in the summer. By simply working in reverse, a heat pump pulls hot air from inside the house and transports in outside. This allows you to heat and cool your home using a single unit

How Heat Pumps Work

Heat pumps don’t actually generate heat. Instead, they work as a sort of heat transporter, constantly moving warm air from one place to another. Heat energy is present in all air, even air that feels cold. When the temperatures outside are frigid, a heat pump extracts even small amounts of heat and transfers it to the interior spaces of your home. When The outdoor temperatures rise, your heat pump reverses direction. Acting like an air conditioner, the heat pump transports the heat in the inside air and transports it outside.

Where Heat Pumps Work Best

There are several factors to consider when choosing between a forced air furnace and a heat pump. However, the most important factor is climate. In areas that typically experience mild winters, a heat pump will be significantly more energy efficient than a furnace.  

In areas that experience harsher winters, a heat pump could struggle to keep up. Many systems include an auxiliary heat source that kicks in when outdoor temperatures plummet. However, if temperatures remain low for extended periods, a heat pump will be far less efficient and effective than a traditional forced air furnace. Basically, the farther north you live, the more likely it is a furnace will do a better job of keeping your home warm and comfortable.

Geothermal Heat Pumps

Geothermal heat pumps can be more effective in colder climates. A geothermal heat pump draws heat from the relatively stable below-ground temperatures using a circuit of buried pipes. The major drawback to geothermal heating is the installation cost. The initial investment is expensive enough to deter most homeowners. Also, there are some locations where installation is impossible due to ground composition.

Discuss Your Options With a Professional

If you’re not sure which system is right for you, contact a qualified HVAC technician to discuss your options. An experienced professional can offer important insight into which system will work best in your climate and for your home. He or she can also help you better understand up-front investment and long-term operating costs.

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