The heat pump basics

Posted 1/20/21

What are heat pumps?

Heat pumps are devices that are used to regulate indoor temperature and humidity throughout the year. They don’t just heat your home during the winter, they also cool …

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The heat pump basics

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What are heat pumps?

Heat pumps are devices that are used to regulate indoor temperature and humidity throughout the year. They don’t just heat your home during the winter, they also cool things down over the summer. When used properly, heat pumps have been known to control heating and cooling quite efficiently, expending minimal energy and saving users money.

How do heat pumps work?

In layman’s terms, heat pumps cool down homes in the summer by taking hot air from inside the home and pushing it outdoors; in winter, heat pumps pull heat from the outside and push it inside the home. So heat pumps never actually generate heat, they simply transfer it. Let’s consult the U.S. Department of Energy for more detail:

“A heat pump’s refrigeration system consists of a compressor and two coils made of copper tubing (one indoors and one outside), which are surrounded by aluminum fins to aid heat transfer. In heating mode, liquid refrigerant in the outside coils extracts heat from the air and evaporates into a gas. The indoor coils release heat from the refrigerant as it condenses back into a liquid. A reversing valve, near the compressor, can change the direction of the refrigerant flow for cooling as well as for defrosting the outdoor coils in winter.”

What kinds are there?

There are many heat pump options depending on factors such as the size of one’s home, climate and budget, to name a few. But Consumer Reports categorizes them into three main types: air-source, split-ductless and geothermal.

Air-source heat pumps are the most common. They have an indoor and outdoor component connected by tubing that transfers a refrigerant that picks up and gives off heat as it travels back and forth. Similarly, split-ductless heat pumps have an outdoor compressor (or condenser) and one to four indoor air handlers. The remote-controlled air handlers are typically installed high on the walls or up on the ceiling.

Geothermal heat pumps rely on the reliably moderate temperatures a few feet below the earth’s surface. A liquid solution runs through pipes buried underground and circulates through the home. Geothermal is the most expensive option to install, but they last the longest, require the least maintenance and work best in extreme climates.

Do heat pumps work when it’s cold outside?

Typical air-source heat pumps used to be appropriate for warmer climates. But according to Consumer Reports, the technology has advanced so that they work well in colder climates as well—they’re referred to as cold climate air source heat pumps. The general consensus, however, is that regular heat pumps will require a back-up heat source when the temperature drops to extreme lows, -10 to -25 degrees Fahrenheit.

How efficient are they?

According to the Department of Energy, an air-source heat pump can deliver “one-and-a-half to three times more heat energy to a home than the electrical energy it consumes,” and can save users an average of around $460 annually compared to electrical heaters. This is due in large part to the fact that heat pumps aren’t producing energy, but moving it. However, to ensure efficiency, it’s recommended that homeowners only have them installed by certified professionals, as the equipment must be properly sized and air sealing and insulation upgrades must be made to the house before the unit is sized. Once installed, the conventional wisdom is to set the heat pump’s thermostat to a comfortable temperature and leave it be all winter, but in the summer, when the heat pump acts like an air conditioner, turn it off when you leave the house.

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