Heat Pump Types – From Geothermal Heat Pumps to Air Source Heat Pump Systems
There are different types of heat pumps available on the market today. A heat pump is an air conditioning unit that cools when the temperature is hot and provides heating when the temperature is cold. There are many different types of these heat pump systems available. There is the geothermal heat pump which can either utilize a series of closed loop water pipes buried in the ground or other methods of heat exchange to remove or absorb heat for heating and cooling. There are air source heat pumps and these can be configured differently. One type of air source heating will utilize electric heating for backup heating while another may use a gas furnace for back up heating. These types of systems can also be split systems or package units and nearly all share a similar heat pump sequence of operation. A description of the various types of systems and how they work is below in this article on heat pumps types. These systems utilize similar heat pump components but differ in how the heat pump works.
Heat Pump Heating
A heat pump is a large refrigerator which moves heat from one place to another. When the temperature is hot and it is in air conditioning mode it moves the heat from the inside to the outside. When the temperature is cold it absorbs heat from the outside and moves it to the inside. Yes, there is heat in air which is 40° Fahrenheit and the heat pump absorbs this heat and moves it here it can be used for comfort. All air conditioners and heat pumps utilize the process of refrigeration to move heat from place to another. The classic definition of refrigeration is a mechanical process that moves heat from a place where it is not wanted or needed to a place where it doesn’t matter. An air conditioner moves heat in one direction, from the inside to the outside, while a heat pump moves heat in both directions depending on the heat pump thermostat setting.
Geothermal Heat Pumps
Geothermal heat pumps utilize the natural heat of the earth to produce heat and there are different types of geothermal systems available. Depending on where you live, whether you are located in a Northern or the Southern region will depend on the temperature of the earth but the temperature of the earth is warmer than the air is outside in the wintertime and cooler than the air is outside in the summer. The geothermal system takes advantage of this stable temperature of the earth to exchange heat in both directions. Because of these stable temperatures, the geothermal system is much more efficient that and air source system. The difference is installation cost between the two. A geothermal system can cost thousands of dollars more to install than an air source heat pump but the geothermal system is much cheaper to operate and will generally give you a pay back for the extra installation costs within five years. Geothermal systems also have a longer life expectancy than air source heat pumps. There are also some geothermal systems which provide hot water for domestic use so the advantages of having a geothermal systems are greater than having an air source heat pump.
Many geothermal systems use an open loop well system for a geothermal heat pump system. There two wells drilled and one well is used to dump the water from the condenser and the other well is a feeder well to feed the geothermal heat pump system. This system uses a pump to pump the water to the dump well and from the feeder well. Certain conditions must be met for this system to work properly and reliably. Check with you local geothermal HVAC contractor to see if this is the right system for you.
Horizontal closed loop geothermal systems have piping buried in the ground from 4 to 6 feet in depth in trenches which are dug somewhere near the home or business where the geothermal heat pump is installed. When the geothermal unit turns on, a pump is also turned on and circulates the water through the piping buried under the ground. The heat exchange process takes place between the piping and the ground where the pipes are buried.
The vertical closed loop geothermal system is used for areas where land is limited like in a big city for a building or home that has a little plot. Holes are drilled into the earth more than 100 feet (the depth depends on the size of system and how deep the holes need to be for proper heat exchange) and piping is fed into the holes. The pipes are connected at the bottom with a U-bend. The same thing happens as with the horizontal geothermal system so when the geothermal unit kicks on a pump also turns on and pumps water through the piping in the earth for heat exchange.
The closed loop pond or lake system utilizes a pond or lake which meets certain criteria for use in a geothermal loop system. Obviously, the piping must be installed deep enough in the lake or pond to prevent freezing of the pipes. This system is cheaper to install than other methods for geothermal systems described above but it is important that the pond or lake meet the criteria for geothermal heat pump use. Check with your local geothermal HVAC contractor to see if the lake or pond meets the criteria. You must also consider local codes and regulations but the geothermal HVAC contractor will be knowledgeable to all these regulations.
Some commercial systems use a geothermal heat pump but instead of using the earth they use a water tower for heat removal in the summer and a boiler to heat the water for winter use. Depending on how the system is controlled will depend on the energy savings realized from this type of system. Typically the water temperature is maintained between 70 and 80 degrees using the water tower or the boiler depending on the season.
Heat Pump Types – Air Source Heat Pump System Types
Air source heat pumps rely on the temperature of the air outside for proper heat exchange. Since the temperature of the air outside can vary greatly these systems are less efficient than geothermal heat pumps. Air source heat pumps systems also need a defrost cycle and back up heat because when the temperature outside falls below 38 degrees Fahrenheit the system loses its ability to absorb heat. In this case, backup heat is needed and the majority of air source heat pumps utilize electric heating for backup heating while some of the other air source heat pump systems utilize gas or oil for backup heating. The gas or oil backup heating systems are more efficient than the electric backup heating but the installation costs are higher. These air source systems are available in both a package unit where all the components are in one package or in a split system here the air handler is inside and the condenser is outside.
A specific list will include all of the following types of heat pumps:
- Geothermal Systems as described above
- Air Source Systems which will include the following
- Split System Heat Pumps where the condenser is remote to the air handling unit
- Package Unit heat pumps where the air handler and the condenser are integral
- Mini-split Ductless Systems
- Portable Terminal Heat Pumps are system one would see in a hotel
- Window unit heat pumps