With these heat pump basics, you will be able to make more informed HVAC decisions. The units work like a normal central air conditioning system. The main difference is that instead of taking the colder months off, the unit must work all year long.When your thermostat senses a need for cooling, the fan in the furnace or air handler comes to life. This fan blows air over a coil containing refrigerant. The outdoor unit contains a pump which is called a compressor. This compressor pumps the refrigerant to the air handler where heat from the air is transferred to the refrigerant. Then the refrigerant is returned to the outdoor unit. Here another fan pulls air over another coil and the heat is transferred to the outdoor air. This process is repeated over and over until the home is cool.To provide heat to the home a few components are added to the basic air conditioner. A reversing valve is added to change the direction of refrigerant flow. In the heating mode, this makes the refrigerant temperature higher then the indoor temperature.

Therefore, when the refrigerant flows to the indoor unit, heat is transferred to the homes' air. When it gets below freezing outside, ice can build up on the outdoor coil. This reduces the units' ability to provide the required heat. Therefore, a process is required to melt this ice.That process is called a defrost cycle. Most units use a timer, a thermostat, or a combination of the two to control this process. When the control senses the need, the outside fan is stopped and the reversing valve directs the hot refrigerant to the outdoor coil. This causes the ice to melt and the process is stopped by another thermostat in the outdoor unit.To keep from blowing cold air into the home, during this process, backup heat is provided by the furnace. If you live in an area where it regularly drops below freezing, these units may not be right for you.If you do live in these areas, you can use these units. But, it is usually a good idea to have a control installed so the unit does not run when it is freezing.

This is called an outdoor thermostat. When the outdoor temperature drops below its' setpoint, it can shut off the outdoor unit and use the furnace to provide the required heat. The latest thing on the market is called a hybrid heat system. This system combines a heat pump with a gas furnace. This control senses which type is more cost effective and switches back and forth as conditions change.through wall heat and ac units Because these units provide both heating and cooling, it is even more important that you have the proper size. top 10 hvac systemsThe wrong size unit will steal money from your pocket the whole year long. cost of ac unit per hourThat can add up in a hurry! To keep the system running in the most efficient manner, some maintenance is required.

Most dealers will provide a service contract but, with some help, you can perform the recommended maintenance. This will also make your system last longer.As with any system, things can happen to cause the unit to malfunction. Many times a simple thing can result in a big repair bill. The average repair call will be more than $100. But with our troubleshooting guide, you can diagnose the problem and repair it yourself (and keep the $100). A new heat pump system can cost thousands of dollars. There are many different models with all kinds of bells and whistles on them. Shopping for a unit can leave even a seasoned professional dazed and confused. When it's time to select a brand, wouldn't you like a helping hand through the maze? Our brand ratings pages will help you to find the right heat pump for your home and budget. We have reviews of ducted, ductless, geothermal and air to water systems. You are here » Geothermal Heat Pump Basics Geothermal Heat Pump BasicsGeothermal heat pumps take advantage of the nearly constant temperature of the Earth to heat and cool buildings.

The shallow ground, or the upper 10 feet of the Earth, maintains a temperature between 50° and 60°F (10°–16°C). This temperature is warmer than the air above it in the winter and cooler in the summer. Geothermal heat pump systems consist of three parts: the ground heat exchanger, the heat pump unit, and the air delivery system (ductwork). The heat exchanger is a system of pipes called a loop, which is buried in the shallow ground near the building. A fluid (usually water or a mixture of water and antifreeze) circulates through the pipes to absorb or relinquish heat within the ground. Heat pumps work much like refrigerators, which make a cool place (the inside of the refrigerator) cooler by transferring heat to a relatively warm place (the surrounding room), making it warmer. In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air delivery system, moving heat from the ground to the building's interior. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger, effectively moving the heat from indoors to the ground.

The heat removed from the indoor air during the summer can also be used to heat water, providing a free source of hot water. Geothermal heat pumps use much less energy than conventional heating systems, since they draw heat from the ground. They are also more efficient when cooling your home. Not only does this save energy and money, it reduces air pollution. All areas of the United States have nearly constant shallow-ground temperatures, which are suitable for geothermal heat pumps. Read how NREL helped IKEA successfully monitor the first geothermal heat pump system to be used in one of their facilities. For more information about geothermal heat pumps, visit the following resources: U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy NREL's Policymakers' Guidebook for Heating and Cooling.A heat pump is an Air Conditioning system which can also provide very efficient heating. It takes less energy to relocate heat than it does to create it.

Just as a refrigeration system removes and relocates heat from a cooler or freezer, so too does a heat pump remove heat from cold outdoor air and relocate it to within a building. A 4 way reversing valve is used to swap the functions of the evaporator and condenser in order to change from cooling to heating mode. To avoid confusion it is common practice to call heat pump coils the "indoor" and "outdoor" coil. The diagram below shows a heat pump piping layout. Click back and forth between Buttons 2 and 3 and note how the discharge from the compressor is diverted to different coils in each mode. You can also view the 2 modes showing the refrigerant states with Buttons 4 and 5. Here is another view of how the 4 Way Reversing Valve diverts flow; the pipe on the single stub side of the valve is always the discharge from the compressor. The discharge is diverted to the condenser, the middle stub is always suction going to the compressor, and the left over stub is always from the evaporator.

The switching function is accomplished by the sliding back and forth of an internal barrel which has diverting passages. The systems own high side pressure is used to ram the barrel to the desired end by a pilot duty solenoid valve. On the diagram below, click back and forth between Buttons 3 and 4 to see the barrel slide to opposite ends. Then try Buttons 5 and 6 to see the refrigerant flow being diverted. 1. 4 Way Valve2. The Liquid line always carries liquid but the direction of flow reverses in each mode. Each coil has it's own metering device with a check valve piped in parallel. When refrigerant flow meets a check valve in the blocked direction it has no choice but to divert through the TXV. When refrigerant flow meets a check valve in the allowed direction it will take the route of least resistance and go through the check valve and ignore the TXV. There are TXVs that have this check valve function built right into the valve itself. The Bi-Flow filter/drier works in a similar manner.

Inside a bi-flo drier there are check valves which ensure that refrigerant flow goes through the drier core in the same direction regardless of the liquid line flow direction. The drier core must experience flow in one direction only. Otherwise, if counter-flow was allowed debris that had been filtered out would unload and re-enter the system. The outdoor coil of a heat pump can frost up just like a freezer evaporator. The tendency to frost up increases with humidity and low ambient temperatures. There is fortunately a convenient method of defrosting the outdoor coil and that is to make the system run in the cooling mode. The outdoor coil becomes the condenser and the frost can be melted away. To keep the heat where it is wanted the outdoor fan motor is temporarily shut off. All this happens automatically and is controlled by a solid state defrost control board. Every so often it will check the temperatures of some thermistors (temperature sensitive resistors) and if a defrost is needed it will activate the defrost mode.

Otherwise it will wait for the next trial for defrost. As the defrost continues, steam will rise out of the unit. New heat pump owners should be advised to expect this. Otherwise nuisance calls may be placed by the unknowing customer. They have even been known to call the fire department thinking the unit is on fire. When the defrost is completed, the whoosh of the reversing valve can be heard, the outdoor fan restarts and a final cloud of steam is blown out by the outdoor fan. In the piping diagram above, place the unit in the defrost mode (Button 2). Note that the outdoor coil has hot gas entering it which is going to condense into a liquid as it melts the ice build up. There is no danger to the compressor because this liquid must travel through a TXV and evaporator before getting back to the compressor. However simulate the end of a defrost by putting the system back into heating mode. Note that the compressor is now directly sucking the contents from the outdoor coil (liquid) without the benefit of any TXV or evaporator to protect it.