Heat Pumps | HVAC Heating and Cooling
Heat Pump Systems There are different types of Heat Pumps in use in both the commercial HVAC heat pump markets and the residential HVAC heat pump markets. The two main types of heat pumps are the air source heat pumps and the water source heat pumps (or geothermal heat pumps). Within the water source heat pump types there are several sub-categories. Mechanically and electrical speaking, heat pumps all work the same way but use different methods of moving the heat from one place to another. Regardless of the type of heat pump it is, heat pumps are based on the theory of heat pumps that says heat can be moved from a warmer place to cooler place. Air source heat pumps are popular in southern regions where the temperatures in the winter are considered to be mild while water to air heat pumps can be used in any climate as long as there is a moderate (temperature) and reliable water source to move the heat from one place to another.
Heat Pump Systems & Air Conditioning Systems Differences
To the untrained eye air source heat pumps and water source heat pumps can easily be mistaken for the typical air conditioning systems. Both systems provide cooling for the structure or dwelling but only a heat pump system can provide heating using the refrigeration process. Both air conditioning and heat pump systems are similar in that they have similar components like a condenser coil and an evaporator coil, compressor and refrigeration lines to move the heat and refrigerant, and electrical controls in the condenser and air handler.
Heat Pumps components differ from air conditioners in specific areas:
Unlike air conditioning systems, heat pump systems have a reversing valve in the condensing unit to reverse the flow of refrigerant and thereby the direction at which the heat is moved from one place to another. The reversing valve works off of an electrical control which requires a heat pump thermostat to energize the reversing valve. The heat pump reversing valve switches positions depending on the thermostat setting (manually by the end user) and this setting determines whether the heat pump unit is going to provide heating or air conditioning. Therefore, heat pumps have different control wiring than air conditioners.
Heat Pump Systems have an extra metering device inside of them. Typically, the type of metering device is either a fixed orifice type or a thermostatic expansion valve (TXV) type. This metering device is located near the heat pump condenser coil and meters the refrigerant into the condenser when in the heating mode. When the heat pump unit is in the cooling mode there is a bypass for the refrigerant to bypass this metering device.
A heat pump system has different HVAC electrical controls than air conditioning systems. As stated in number one, a heat pump needs a heat pump thermostat to control the system so the user can manually select between the heating and cooling modes. The heat pump thermostat controls the reversing valve on air source heat pump systems and also controls whether the back up heat is going to energize as necessary. The colder the temperatures drop outside the less heat the air source heat pump can absorb. When the temperature outside drops below a certain threshold the air source heat pump cannot keep up with providing the necessary heat to the dwelling to satisfy demand. When the temperature indoors drops below 3 degrees Fahrenheit on a heat pump system the thermostat energizes the secondary heat which can be either electric, gas, or oil. The most common heat pump back up heat is electric heat because gas or oil back up heat is more expensive to install but in the long run more efficient and cost effective than electric heating back-up.
Another area in which an air source heat pump system differs from a regular air conditioning system is that the air source heat pump needs defrost controls. There are different methods for control the defrost cycle but the most common is timed method for heat pump systems. Every hour or hour and a half the unit automatically defrosts itself without any user input. A person standing near the outside heat pump unit will hear a loud whooshing sound and think the heat pump unit is broken. Another sign that a heat pump system is in defrost is to observe steam rising from the heat pump condensing unit. People commonly mistake this steam as smoke and an electrical component burning. Typically, when this is observed, the heat pump unit is only defrosting itself so that it can provide the heat necessary to maintain comfortable temperatures inside the dwelling and there is no reason for panic. After all, if it was an electrical component and the system was installed correctly fuses and breakers should eliminate any possibility of the heat pump having an electrical fire.
Heat Pump & Air Conditioner Advice
Regardless of the type of heat pump or air conditioner systems you have it is important to have either type of HVAC system checked out by a professional on a regular heat pump or air conditioner maintenance schedule. This keeps the heat pump or air conditioner in tip top shape so it will provide reliable and efficient heating and cooling for you year round.
Additional Information about Heat Pumps can be found here.