How Does a Heat Pump Work? A Phoenix Tech Answers

Heat pumps are unique systems that can both heat and cool your home.

Unlike other heating systems, heat pumps don’t actually create heat... instead, they absorb heat from the air and transfer it.

How it works:

• In the winter, a heat pump works by taking the heat from the outdoor air and moving it into your home.
• In the summer, it does the opposite and moves heat from the air inside and dumps it outside.

Below, we’ll break down the main components of a heat pump system and how those components work together to heat or cool your home.

Refrigerant lines

“Refrigerant” travels through the heat pump system inside refrigerant lines (copper coils).

Refrigerant is a special heat-transfer substance. Think of refrigerant as a sponge that absorbs heat from the surrounding air and then wrings that heat out either inside or outside of the home.

Compressor

The compressor is the “heart” of the heat pump system and pumps the refrigerant through the system.

Outdoor Unit

The outdoor unit consists of a condensing coil and a large fan. The condensing coil contains either very hot or very cold refrigerant (depending on whether the system is in cooling or heating mode). The fan helps speed up the heat transfer process.

Indoor Unit

The indoor unit (air handler) contains an evaporator coil and fan. The indoor unit works much the same way as the outdoor unit. In heat mode, the fan moves air across the coils (this time picking up the heat from the coils) and blows the now-warm air into the ducts of your home.

Reversing Valve

The reversing valve is a small valve that sits in the outside unit and reverses the flow of refrigerant. When the refrigerant flow is reversed, the heat pump switches from heating to cooling mode (and vice versa).

As mentioned above, heat pumps transfer heat from one source to another. To help explain, let's look at how a heat pump works in heating mode.

Step 1: The condensing coils of an outdoor unit contain something called refrigerant. Refrigerant lines act as a sponge, absorbing heat from the outside air.

Step 2: Once the refrigerant lines have absorbed this heat, the refrigerant is pushed towards the indoor unit.

Step 3: In the indoor unit, a fan blows air over the evaporator coil, which contains the refrigerant. The hot refrigerant inside the evaporator coil heats the air. The hot air is then pushed into your home via air ducts.

Step 4: Over time, the refrigerant loses its heat and travels back to the outdoor unit to pick up more heat to bring into your home.

Note: A heat pump uses this same process—in reverse—to cool your home. Instead of absorbing heat from the outdoor air, refrigerant absorbs heat from the air inside your home and then dumps it outside.

Now that you know the ins-and-outs of how a heat pump works, you may be wondering whether or not heat pumps are a good option for your Phoenix home.

A few pros to choosing a heat pump are:

1. You only have to install one system- Since a heat pump both heats and cools your home, you don’t have to install two separate systems for heating and cooling. This saves you money and space.
2. Low operational costs- Heat pumps generally cost less to operate than heat strips and baseboard heaters. According to Energy.gov, heat pumps can reduce your electricity use for heating by 50% compared to electric resistance heating like baseboard heaters.
3. Safe- Heat pumps are safer than combustion-based heating systems (like a furnace) because they don’t produce combustion gases.

A few cons to choosing a heat pump are:

1. Temperature limit- Heat pumps don’t work as well in cold climates, specifically below 30 degrees. Because heat pumps don’t create heat but rather absorb heat, it’s hard to extract heat when the outside temperature falls below 30 degrees. If you live somewhere that regularly reaches temperatures below 30, it’s probably best to have a backup system, like a furnace.
2. Shorter lifespan- Heat pumps have a shorter lifespan (15 years) than other systems, like furnaces (20 years).