Heat pumps are the new stars of the heating world. These systems not only outperform other heating options on several fronts but they’re also better for the environment and help combat climate change. Heat pumps are awesome machines but complicated at the same time.
Among all the questions asked about heat pumps, one question never changes, how does a heat pump work? The technology that drives heat pumps might look mysterious to most people unless they’re an expert in physics and heating and cooling. So, in this article, we decided to demystify “how does a heat pumps work?” We’ll take a detailed look all the way down to the nuts and bolts of this technology.
What is a Heat Pump?
A heat pump is a part of the heating and cooling system installed outside your home. Unlike air conditioners and furnaces, heat pumps provide heating, cooling, and hot water with one machine. Depending on which service is used predominantly, the machine is called a heat pump, an air-conditioning unit, or a cooling/refrigeration machine.
Heat pumps are a proven technology that have been used for decades. In fact, it is likely that you interact with heat pump technology daily: refrigerators and air conditioners operate using the same principles and technology. In cooler months, a heat pump pulls heat from the cold outdoor air and transfers it indoors, and in warmer months, it pulls heat out of indoor air to cool your home.
Hope this gives you a sneak peek into how a heat pump works. Let’s dip a little deeper into how a heat pump works.
Components of Heat Pumps
Ever wondered what’s inside a heat pump system that makes it efficiently extract and transfer heat for your use? For those of you who are asking, “how does a heat pump work,” knowing and understanding the components of a heat pump will give a little idea of how it works.
- Compressor – The compressor is the heart of the system. There are basically 4 types of compressors such as scroll compressors, reciprocating compressors, screw compressors, and rotary compressors. Reciprocating compressors are the classic indestructible solution, while scroll compressors are a more modern variant that is becoming more and more popular. The compressor moves a refrigerant through two sets of copper coils, one inside your house and the other outside. It pressurizes the refrigerant as it changes into a gaseous form and back to liquid again.
- Condenser – The condenser is one of the two sets of coils containing refrigerants. The outside coils work as a condenser when the unit is provided with heat. The outside coils extract heat from the outdoor air and condenses the refrigerant into a gas. The gaseous refrigerant then travels to the indoor evaporator coils.
- Evaporator – The evaporator is a low-temperature heat exchanger where the refrigerant enters as a low-temperature liquid, absorbs heat from the heat source by evaporation at low pressure, and leaves as a low-temperature vapor.
- Air Handler – The air handler is a powerful fan and blower system. When the heat pump is in heating mode, it draws in cold air from the home, blows it across the warm evaporator coil, and blows the heated air throughout the home. In short, the air handler moves heated or cooled air from the heat pump into the duct and into your home.
- Reversing Valve – The reversing valve allows the pump to act as a heating system and as a cooling system. It reverses the flow of refrigerant through the system depending on whether it is set to the heating or cooling mode. The indoor evaporator and outside condenser switch jobs when heating the home to bring warm air inside.
- Throttle Device – A throttle device is a part of a heat pump that adjusts refrigerant flow and pressure by reducing the cross-section of the tube. When the refrigerant liquid flows out from the condenser and passes through the throttle valve, the throttle valve functions to reduce the pressure and temperature of the refrigerant.
- Heat Exchangers – Heat exchangers are integral parts of fuel cell systems for thermal management functions related to the heating of incoming gas streams, exchange of heat from various flow streams, and maintenance of the uniformity of temperature.
- Filter Driers and Bi-Flow Dryers – Filter driers and bi-flow dryers have two functions in heat pumps, 1.to catch rough particles of dirt and copper filings and, 2. to bind moisture in the system.
- Pressure Control – There are two types of pressure controllers in heat pumps, high pressure, and low-pressure controllers. High-pressure control is used as cut-outs for the compressor and low-pressure control protects the compressor from low pressure due to insufficient refrigerator, failure of primary circuit pump, etc.
The Cooling Process of Heat Pumps in Summer
During the summer, the indoor unit’s heat exchanger absorbs heat energy from the indoor room air using refrigerant as the heat transfer medium, cooling the room air. The refrigerant is then sucked back to the outdoor unit through copper pipes and the heat energy is rejected into the surrounding air outside via the outdoor unit’s heat exchanger.
The cooling process of a heat pump is like how a refrigerator works. It uses electricity to transfer heat from a cooler location to a warmer location. The fan pulls the warm air from inside your home to your outdoor unit. When the warm air passes over the outside coil the liquid refrigerant pulls that heat from the air. As the air is cooled, it is sent back into the home and circulated by the indoor fan through the ductwork.
Functions Of Heat Pumps in Winter
Most people think that heat pumps create heat, but that’s not true. The heat pump simply moves available heat from one place to another. An outdoor unit absorbs warmth from the surrounding air and transfers it into your home.
Even though it’s cold, there is still heat in the air outside. Heat pumps can collect large amounts of heat from the outside air, and pull it in. The reversing valve plays an important role in cooling the house. A heat pump in heating mode operates just like cooling mode, except that the flow of refrigerant is reversed by the aptly named reversing valve.
Heat energy is absorbed in the outdoor unit by the cool liquid refrigerant, turning it into cold gas. Pressure is then applied to the cold gas, turning it into a hot gas. The hot gas is cooled in the indoor unit by passing the air, heating the air, and condensing the gas to warm liquid. The warm liquid is relieved of pressure as it enters the outdoor unit, turning it to cool liquid and renewing the cycle.
Two Key Parts of Heat Pump System
As we talk about how heat pumps work in the summer and winter, it is also important that we understand the two key components of a heat pump. Understanding these two components will give a deeper level of understanding about how a heat pump works.
- The Vapor Compression Cycle – The vapor compression cycle is the process of transferring heat energy from place to place using the vapor compressor. The refrigerant which is colder than the heat source evaporates the heat. The evaporate heat is moved to the compressor where its temperature and pressure are increased. The refrigerant then moves to the expansion valve; drops in temperature and pressure; then returns to the evaporator.
- Defrost cycle – The defrost cycle is the process of getting the most performance out of the heat pump when it gets cold. All heat pumps undergo a “defrost cycle” to remove ice build-up on the outdoor coils. When this happens, the heat pump will temporarily stop operating for a few minutes.
Fixed Speed System VS Inverter System?
Ok, so let’s get into what ‘Fixed Speed’ and ‘Inverter Control’ means.
A fixed speed system is a system that has a single speed compressor motor that is either on or off. It works like a single speed fan heater running at its only speed that switches off when the desired temperature is reached and switches on again when the temperature drops to a set level.
The problem with the fixed speed system is it takes a lot longer to get to the desired temperature. Which often leads to a lot more power usage in comparison to inverter driven systems.
Inverter control systems use a variable speed compressor motor like a car. This system provides maximum energy efficiency as it slows down, and speeds up as needed to hold a selected comfort setting.
Another benefit of inverter control technology is it provides a more precise room temperature without the fluctuations and power wastage. This system can save unto 30% over fixed speed systems.
What Climate Do Heat Pumps Work Best in?
To be straight forward, heat pumps work in almost all types of climatic regions, be it hot or cold. But to be precise it works best in areas where the temperatures rarely drop below the freezing point. But still compared to a furnace, a heat pump can be more efficient in colder areas where the temperature reaches below freezing point.
If we talk about temperature, the idle temperature for a heat pump is 25 to 30 degrees Fahrenheit. A region with this temperature can get the most out of the heat pump.
FAQs About Heat Pumps