When it comes to heating and cooling your home in Wilmer, AL, you’re not left with the old two-unit approach. Heat pumps have been a popular choice for decades because of their ability to both heat and cool very efficiently. Consider the following on how heat pumps work to both heat and cool your home.

Physics of Heat Transfer

Unlike a furnace, which generates heat, a heat pump works to transfer heat, both in heating and cooling modes. While in cooling mode, it transfers heat from inside your home to the air outside. To heat your home, it absorbs heat from the air outside and brings it in, even in cooler temperatures.

Controlling the refrigerant’s pressure is the key to making the whole thing work. When you want the refrigerant to absorb heat, you have to make it cold. This happens when you reduce the pressure by allowing it to expand. Then it compresses it to raise the temperature to transfer that heat to the appropriate area.

When a heat pump is in cooling mode, the low pressure happens inside and the high-pressure outside. In heating mode, that process reverses. All of this happens because of the key components in the heat pump, which are similar to an air conditioner.

Reversing Valve

The reversing valve is the one major component a heat pump has that an air conditioner doesn’t. As the name indicates, this reverses the flow of refrigerant, which manages the part of the system under high pressure.


The compressor is responsible for managing the high-pressure part of the system. It forces more refrigerant into the space following this component, raising its temperature.

It’s imperative that the system has enough refrigerant to allow the compressor to operate effectively. Besides not heating or cooling well, a system with low refrigerant could damage the compressor. This is an expensive repair and oftentimes leads to replacing the outside unit.


The refrigerant gives the system the opportunity to transfer heat. However, it’s actually the air circulating through the system that heats and cools your home.

In both the indoor and outdoor units are a set of coils through which the refrigerant runs. These coils then have air that passes over them. As that air passes, either the refrigerant or the circulating air absorbs the heat, depending on the mode.

These coils commonly collect dirt and dust and will eventually become coated impeding the effectiveness of the process. This is why routine heat pump maintenance is so critical to keeping the system working efficiently. During maintenance, your technician will clean both the indoor and outdoor coils.

Expansion Valve

The expansion valve works on the low-pressure side like the compressor works on the high-pressure side. The difference is that the valve simply restricts how much refrigerant flows through it at one time. By restricting the flow, the refrigerant expands in the coil, dropping the pressure and thereby becoming very cold.


Like any HVAC system, the thermostat is the thinking brain, signaling when to cycle on and off. The key difference with a heat pump is that the thermostat has to be specifically designed to work them.

When managing a heat pump, the thermostat must also manage the auxiliary heater. Standard thermostats may not have the capability of this added complexity, so do your research before buying a new one.

Air Handler

To circulate air, your system needs something moving the air. This is the air handler, which includes the circulating fan.

Depending on the air handler you have, this may have a single-speed or a variable-speed motor. The single-speed motor is either on or off, basically running on high all the time.

Variable-speed motors can change their speed based on the needs of the system. You typically find these motors in the most efficient system currently available.

Join the club of people who enjoy higher efficiency and lower cost heating and cooling. Call to schedule your heat pump installation consultation with the expert technicians at Air Specialty today.

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