Heat pumps are often thought of as being a device which help keeps your home warm during the cooler months, but what is often overlooked is the fact that heat pumps are also one of the most energy-efficient ways to cool your home during the warmer months as well.
Definition of a heat pump
A heat pump is a mechanical system that moves available heat from one area to another. Since heat flows naturally from a higher temperature to a lower temperature in an effort to reach thermal equilibrium, heat pumps use very little energy to push or “pump” warmer air around. During the winter months, a heat pump provides warm air by removing heat out of the air or ground and transferring it into your home. During the summer, the heat from your home is transferred outdoors leaving cooler air behind. Moving heat from place to place instead of generating heat, as a furnace or central air conditioning unit would do, uses significantly less energy providing huge cost savings over other types of HVAC systems.
Brief history of the heat pump
In the 1940s, Robert C. Webber, an American inventor, noticed that the outlet pipe of his freezer became very hot when he lowered its temperature. He soon realized the potential applications for the heat which was being discarded. Running pipes from his freezer to his boilers, Webber captured this displaced heat to provide his family with hot water. Next, he piped hot water into coils and used a fan to blow over the coils sending warm air into his home. Soon after, Webber figured out how get heat from underground and use to warm the air thereby inventing the first ground-source (geo-thermal) heat pump in the late 1940s. Soon after, electrical and gas heat pumps were developed.
It hasn’t been until the past 10-15 years, however, that heat pumps have gained significantly in popularity due to their eco-friendly manner of operation, their ability to both heat and cool, and their cost-savings energy efficiency. Additionally, advancements in heat pump technology are improving their performance even further. Newer, high-efficiency models utilize the heat that is wasted heat when the system is in cooling mode to heat water at two to three more efficiency than an electric water heater would.
Understanding your heat pump
Heat pumps operate via the principle of heat transference. When in heating mode, a heat pump extracts heat from the outside air and moves it into your home. While in cooling mode, the heat pump removes heat from the air inside your home to the outside leaving cooler air behind. Only a small amount of energy in the form of electricity or gas is required to transfer the heat from indoors to outdoors or vice versa.
When the air outside is too cold for extracting heat, the system’s “backup heat” will come on using an alternate form of heat, usually heated coils knows as “strip heat” or “aux heat” to warm the air inside. This backup heat, however, is powered by electricity or gas which consumes a lot more energy to run.
How does a heat pump work?
Heat pumps provide heating and cooling to your home by moving heat around and by employing a reversing valve, which changes the directional flow of the refrigerant depending on whether cooling or heating is required. Heat pumps are similar to split central air conditioning systems in that they have both an indoor and outdoor unit. They also share some of the same major components, which are:
- Compressor:The compressor compresses and circulates the refrigerant which absorbs and releases heat as it travels between the indoor and outdoor units.
- Condenser & Evaporator Coils: The condenser and evaporator coils work with the compressor to heat or cool the air, depending on which mode the heat pump is in.
- Air Handler:The air handler blows the warmed or cooled air into the ducts of the home to distribute the cooled or warmed air.
- Heat Strips:Heat strips are an electric heating element used for auxiliary (back-up) heat when the weather outside is too cold for heat extraction and an additional heat source is needed.
- Reversing Valves:Unique to heat pumps, reversing valves change the directional flow of the refrigerant to either heat or cool the interior of your home.
Unlike central air conditioning systems, though, heat pumps are much more efficient at heating your home in the winter because it removes heat from outside air and pumps it indoors, whereas a central AC system must use a great deal more energy in the form of gas or electricity to create heat in your home and raising the amount of your utility bill.
How does a heat pump cool?
Heat pumps can cool your home just as effectively as energy efficient air conditioners can. Warm air is pulled out of your home by a fan while refrigerant is pumped from the exterior condenser coil to the evaporator coil indoors absorbing the heat from the air. The air handler then pushes the cooled air through the ducts into various rooms of your home. This cycle starts again and continues on a repeating loop until the desired interior temperature is reached.
Can a heat pump dehumidify?
Heat pumps are great dehumidifiers due to their typically larger condenser coils which work better at treating and eliminating moisture from the air than regular air conditioners. After the liquid refrigerant is evaporated and turned into a gas, it is then compressed by the condenser unit and turned back into a liquid, releasing heat into the surrounding air as it does so. As the heat cools, the moisture in the air is removed by the condenser coil thereby lowering the humidity levels. Reduced humidity in the air will immediately make you feel a few degrees cooler than it actually is, providing additional energy and money saving benefits.
Advantages/disadvantages of a heat pump
There are a lot of advantages of having a heat pump in your home, not the least of which you can use it all year round as it provides both heating and cooling. Also, as the primary function of a heat pump is to transfer heat from one place to another, it’s a very economical and efficient way to make your living space comfortable.
There are some disadvantages to heat pumps, though. For example, they are not as effective in extremely cold climates where the temperature falls below freezing on a regular basis. There is more heat to transfer from one place to another in more moderate climates than in very cold climates, so if the auxiliary or backup heating system comes on frequently, then it’s not really operating as an energy-efficient system. Also, in colder climates there is still heat available in the outside air which can be pumped indoors, but the heat pump will need to work a lot harder to extract it.
Another possible disadvantage is that the heat produced by a heat pump isn’t quite as hot and intense as the heat produced by gas furnaces or electric HVAC systems. However, as heat pumps move heat around, heated air is more evenly distributed throughout your home with fewer “cold spots” that homes with traditional heating systems can often have.
The biggest advantage to using a heat pump, though, is that is the heat in the outside air, which is free(!), for heating and cooling making it much more efficient than other systems that use inefficient sources of energy such as oil or electricity. Though the upfront costs of purchasing and installing a heat pump may be higher than traditional HVAC systems, the payoff will be more than worth it as you’ll see reduced energy use and lower utility bills over the heat pump’s life span.
Types of heat pumps
There are three types of heat pump systems: air source, which is the most popular, geo-thermal, and absorption. The difference between them is where they get their heat source from.
- Air-source heat pump: The air-source heat pump uses fans to transfer heat from the air outside to inside your home and vice versa. Since heat is being moved around instead of generated, relatively little energy is consumed in operating this type of system. Compared to electric or gas-operated heating systems, an air-source heat pump can reduce your utility bill by as much as 50% over these other systems.
- Geothermal heat pump: Also known as a ground-source or water-source heat pump, the geothermal heat pump transfers heat from underground or a nearby water source. The earth is an excellent source of heat as it absorbs a large amount of solar energy, allowing it to maintain a moderate temperature just below the surface all year round. Geothermal heat pumps use refrigerant or water in pipes submerged underground to absorb the earth’s heat where it is extracted and then sent as warm air into your home. Very efficient, long-lasting, and environmentally friendly, geothermal heat pumps can provide heating and cooling for your home while reducing your utility bill by up to 65%.
- Absorption heat pump: The absorption heat pump is an air-source heat pump that uses a variety of heat sources, such as natural gas, solar energy, geothermal energy, etc.) instead of electricity to operate the compression cycle for heating or cooling your home. Also, an environmentally-friendly ammonia plus water solution is used to generate heat instead of an ozone-destroying refrigerant.
Clear list of steps to operate the heat pump
Since heat pumps don’t generate heat from scratch, but instead use available natural sources of heat and move it around, there are some factors users should keep in mind when operating their heat pump system.
- Don’t set the temperature too high in the winter or too low in the summer. Heat pumps generate a more continuous moderate temperature to eventual reach the desired warm or cool temperature rather than higher- or lower-temperature blasts of air. Therefore, the air coming into the home may not seem warm enough, or cool enough, at first, but heat pumps run in longer cycles to achieve the desired temperature.
- If you want to raise the temperature in your home, do so gradually by adjusting the thermostat only 1-2 degrees higher at a time. Doing so will keep your system from employing the auxiliary heat which uses more energy and could affect your utility bill.
- Don’t do setbacks with your heat pump. Traditional HVAC users have been taught to “setback” their air conditioner and heater to a much lower or higher temperature when they are out of the house to save on their electric bill. However, doing this with a heat pump system may not only trigger the back-up heat to kick on, but it may also take the system several hours to reach your home’s ideal temperature. It’s best to just set your ideal temperature and then walk away to reap the most benefit in cost savings and comfort from your heat pump.
Also, it goes without saying that just with any HVAC system, proper maintenance is important to maintain efficient operation of your heat pump. Make sure to clean or replace filters on a regular basis (usually monthly), make sure there is no debris, vegetation, or clutter around the exterior unit, check ducts, coils, and registers regularly and clean when needed, and check for refrigerant leaks.
How much does a heat pump cost?
The typical range for installing a new heat pump is between $4,000 and $7,000, depending on the type of heat pump you purchase and the size of your home. Geothermal heat pumps are generally more expensive to install since there are component that require being placed underground. As a heat pump can provide both heating and cooling, it eliminates the need for a furnace and an air conditioner. Though upfront costs may be high, heat pump systems can significantly reduce your energy consumption and keep more money in your pocket making it a worthwhile investment for your home and your budget.
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