Heat pumps are quickly becoming a staple among residential HVAC systems as property owners seek more efficient and environmentally friendly options. Whether you have one already or are considering whether a heat pump is right for your home, there’s some information every property owner should know. Use this guide to learn how heat pumps work, the different types of heat pumps available, the major parts, and the auxiliary heating systems available.
Heating and Cooling Using Refrigerant
To start, let’s explore how a refrigerant system can heat and cool your. Traditional heating systems produce heat by either burning fuel or using electricity. Heat pumps, on the other hand, use refrigerant to absorb heat and redistribute it elsewhere. In the summer, a heat pump will absorb heat inside and redistribute it outside. In the winter, it’ll absorb heat from somewhere outside the home and redistribute it inside. Standard heat pumps use a refrigerant that goes through a process that changes its pressure, which allows it to absorb and then expel heat.
Types of Heat Pumps
Heat pumps generally fall within two major categories: air-source heat pumps and geothermal systems. Both of those are also available in the standard central air handler configuration and ductless mini-split systems.
Air Source
The most common heat pump is the air source model that has an outdoor compressing unit, which looks similar to an air conditioner. These use the air outside as the medium through which it’ll absorb and expel heat, depending on the operational mode. These become ineffective in frigid temperatures, losing what is otherwise considered incredible efficiency.
Geothermal
Geothermal heat pumps use either the ground or a body of water as the heat transfer media rather than outside air. Ground source geothermal systems bury coils between 4 and 6 feet in the ground. Water source systems use a deep water source, such as a well, river, or even a lake. The key for water source systems is that the water is deep enough that it won’t freeze when the temperatures get cold enough.
Central vs Ductless
The standard system uses a central air handler that has a single circulating fan and indoor coil. It pushes conditioned air throughout your home through a ductwork system. The alternative is a ductless system, commonly called a mini-split system. These use smaller air handlers installed throughout your home. These are usually installed on an exterior wall, each keeping a smaller section of your home comfortable rather than trying to condition your entire home at the same time.
Heat Pump Components
A heat pump is often considered similar to an air conditioner. While some components are similar, some are unique to the heat pump.
Refrigerant
Refrigerant is the secret sauce that makes heat pumps work. As refrigerant moves through the system, it goes through high-pressure and low-pressure stages. In the low-pressure stage, the refrigerant expands and gets cold, allowing it to absorb heat from whatever medium is around the coil. The high-pressure stage compresses the refrigerant into a liquid and makes it hot, allowing it to expel the heat it absorbed during the low-pressure stage. The heat transfer principle that describes why this works is the second law of thermodynamics, which observes that thermal energy transfers heat to whatever is cold and in contact with the heat source.
Compressor
The compressor is responsible for creating the high pressure within the system. The expanded refrigerant enters the compressor, which compresses it back down into a liquid. The compressor can go bad when it’s running with too little refrigerant in the system or if there’s a problem preventing the system from expelling heat properly.
Refrigerant Coils and Lines
The refrigerant runs through a sealed system that includes refrigerant lines and two different sets of coils. There’s one set of coils outside, whether exposed to the air or buried, and another set inside your home. It’s the coils that allow the system to absorb and redistribute heat during heating and cooling cycles. The high-pressure side is known as the condensing coil, whereas the low-pressure side is called the evaporator coil.
Expansion Valve
While the compressor increases the refrigerant’s pressure, the expansion valve works on the opposite side of the system, reducing its pressure. This valve effectively restricts the amount of refrigerant that’s allowed to flow into the evaporator coil. If the coil gets too cold, the valve can allow more refrigerant to flow in, increasing the pressure and raising the temperature.
Reversing Valve
The one component that is unique to a heat pump compared to an AC unit is the reversing valve. This valve activates when the system switches between heating and cooling modes. The simple switch internally in this valve immediately changes the coils where the high and low-pressure refrigerant flows. It will also activate when the system goes into defrost mode, which pushes warm refrigerant into the outside coils to keep them from icing over.
Thermostat
Everyone knows the thermostat is what controls the temperature inside your home and whether you’re running heating or cooling. However, heat pumps that have auxiliary heaters also play the critical role of activating the auxiliary heating system at the proper time. This is why it’s critical to understand what system you have and ensure that the thermostat is capable of handling all the features you have.
Auxiliary Heating
Heat pumps are great in moderate climates. However, they can struggle to keep your home comfortable in frigid temperatures. This is why many heat pumps often have an auxiliary heating option, which is either an electric resistance heater or a dual fuel system.
Electric Resistance Heating
The most common auxiliary heating is known as electric resistance heating. This uses a series of electrical coils that get hot when current passes through them, very similar to the coil on an electric stove. These generate heat because the material in the coil has high resistance. It’s also this resistance that makes these extremely inefficient. If you have to run your auxiliary heating for more than a few hours, your energy bill may not reflect that you’re using what is otherwise a very efficient system.
Dual Fuel Systems
The alternative to electric resistance auxiliary heating is the dual fuel system. These pair either an air source or a geothermal heat pump with a gas furnace. Although a furnace has some heat loss through the exhaust, the cost of natural gas is usually considerably less than electricity. Further, furnaces use much less gas than electric resistance heaters use electricity. Although you’re still using a furnace, you’re only using it during the coldest parts of winter, so you’ll always use the most cost-effective heating method regardless of the weather outside.
Main Street Heating & Cooling has become the HVAC service provider of choice for property owners around Sandy. Our expert team provides air conditioning and heating installation, maintenance, and repair together with indoor air quality solutions and thermostat control installation and service. Call to schedule a consultation with one of our trusted heat pump experts to see which system may be the right fit for your home.
