Does a Heat Pump Condenser Need to Be Outdoors?

The reason why we have central air conditioning and heating in our homes is to maintain the temperature at comfortable levels. We control the temperature by regulating the amount of heat flow in and out of the home. You can accomplish this with a heat pump unit.

How the Heating System Works

A heat pump system has essentially two main parts, a heat pump condenser, and an evaporator. The basic principle of how heat is moved in and out of the home is described below. The evaporator absorbs the excess heat in the home. This heat is transferred to a liquid, called the refrigerant, contained in the evaporator. When the refrigerant absorbs the heat, it warms up and changes state into a gas. This gas carries the heat energy to the next part of the system called the condenser. The condenser absorbs the heat from the gas and releases it to the environment outside. Because the gas has lost the heat energy, it reverts to a liquid state. The liquid refrigerant is now recirculated back to the evaporator by the pump. Through this cycle, heat is transferred from the home. The combination of the condenser and the pump is what is called a heat pump condenser unit.

How the Condenser Works

The purpose of the condenser is to transfer heat from the refrigerant, and for this reason, it is called a heat exchanger. When the gas loses heat the process of condensation, or changing state from a gas to a liquid, occurs. Note that the recirculation of the refrigerant requires pressure to move it through the ducts. The pump provides this pressure.

Types of Condensers

Condensers are categorized into three broad categories based on how they are cooled.
  • Air-cooled condenser

These operate with the use of a fan which forces air through the cooling coils of the condenser.
  • Liquid cooled condensers

These operate by running coolant through the cooling fins of the condenser. Note that the coolant is separate from the refrigerant.
  • Evaporative condensers

These aspirate the heat naturally by transferring it directly from the cooling fins to the environment.

Condenser Efficiency

Liquid cooled condensers are the most efficient followed by air-cooled condensers and lastly evaporative condensers.

Does a Heat Pump Condenser Need to be Placed Outside?

Air conditioner unitFor heat exchange to occur, the air surrounding the condenser needs to be at a lower temperature than the refrigerant. Therefore, liquid cooled condensers and the air-cooled condensers do not have to be placed outside simply because they are forcefully cooled. Even if they are indoors, their cooling mechanism forces them to be at a lower temperature than the surrounding air.

For the evaporative condenser, the situation is different. This type of condenser will not operate efficiently because its temperature will be very close to that of the surrounding air. During the summer, when the temperature differential between the home and the outside air is very close, an evaporative condenser's cooling is not as efficient.

Purchasing a Heat Pump Unit

The cooling requirements of your home which dictate the size of the heat pump unit your need are determined by the square footage of your home. Below is a brief discussion on how to buy a heat pump.


Heat pumps are appropriate for climates with moderate temperature swings and therefore moderate heating and cooling needs. A heat pump is not a sufficient heat source for areas that experience cold winters. Areas with extreme temperature swings would require a central heating system in addition to a heat pump unit.

Energy Efficiency of a Heat Pump

The energy efficiency of a heat pump is measured by SEER. For areas in the Northeast, Midwest, Mountain States and Pacific Northwest, the federal minimum is 13 SEER. For the rest of the country, the minimum is 14 SEER. When you search for heat pumps for sale online, the SEER value is part of the product description. If you live in a hotter climate, you should select a heat pump with a SEER higher than 14 and lower then 14 SEER for colder climates.

Selecting the Size of a Heat Pump

As a rule of thumb, you should look for one ton of heat pump size for every 650 square feet of home space. The tonnage of the heat pump is also part of the product description. For example, a 1200 square foot home would require a 2-ton unit.

Hire a Professional

You should always engage the services of a professional to ensure your home is energy efficient and to install your heat pump system.
December 21, 2018
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