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Proper Humidity Levels

Having proper humidity levels in your home or business is important not only for your health but also in the amount of energy your HVAC systems use to keep you comfortable. If the humidity level in your home is high in the summer you will not feel cool. If the humidity level is low in the winter you will not feel warm when the thermostat is set at an average temperature. This will result in turning the HVAC thermostat up to compensate and you will use more energy to stay warm. A properly designed and installed system will keep the proper levels of humidity in your home or business and save you money on energy used by the HVAC System. For more information on humidity and the benefits of maintaining proper levels visit High Performance HVAC's Humidifier Page.

Before You Call

Before calling a heating and air conditioning company, check the following:

Check selections on thermostat. Ensure that it is set to the desired settings.
Check power supply. This can include a circuit breaker and or/a regular looking wall switch close to the indoor unit
Check for freezing up of units. If the unit is frozen turn it off. Check the filter(s) and supply vents to make sure they are not obstructed in any way. If you find no problems leave the unit turned off and call a service company.

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Heat Pumps

Heat Pump Components

Written by Richard

High Performance Heat Pumps

Heat Pump Components

Heat Pump Component Quickpage Jump Links

Heat Pump Components

Heat Pump Controls

Heat Pump Thermostat

Heat Pump Defrost Controls

Heat Pump Reversing Valves

Heat Pump Outdoor Thermostat

Heat Pump Accummulator

Heat Pump Types Related Links

Request 3 Free Heat Pump Installation Estimates

Heat Pump Components

Heat Pumps are similar to air conditioners with a few extra components added to allow the heat pump to offer both heating and cooling. The two major differences between a heat pump and an air conditioner are the controls and the refrigeration circuit. While there are many different types of heat pumps and air conditioners the methods and means these two types of heating and cooling systems use are basically the same. An air conditioner will only cool and you will need some other type of system added to the air conditioner to provide heating while a heat pump looks like an air conditioner the heat pump can both heat and cool and it uses the same principles and methods an air conditioner uses to provide heat. A heat pump simply reverses the refrigeration process and moves the heat in a different direction. If you have read about refrigeration on High Performance HVAC then you know the process of refrigeration is simply moving heat. Refrigeration uses mechanical processes to absorb heat and move it somewhere where it is not wanted or in heat pumps in heating mode refrigeration moves heat to a place where it is wanted.

Heat Pump Components: Heat Pump Controls

Depending on the type of heat pump you have will depend on the type of heat pump controls you have. It will also depend on many other factors such as proper set up and installation of the heat pump. Some installers install the heat pump and never install an outdoor thermostat to cut the heat pump condenser off when the temperature outdoors makes the heat pump condenser useless. This is only applicable to air to air heat pumps and not geothermal or ground source heat pumps. Air to air heat pumps use the typical outdoor condenser many conventional air conditioners use. In fact, many people often mistake a heat pump for an air conditioner because airs to air heat pumps and air to air to air conditioners look the same. The difference between the heat pump and the air conditioner is the controls and refrigeration circuits are different as described above.

Heat Pump Components: Heat Pump Thermostat

heat pump thermostats, honeywell visionporheat pump thermostat, heat pump components
If you have a heat pump then you have a heat pump thermostat. The heat pump thermostat controls the heat mode through the reversing valve or the 4-way valve. The heat pump thermostat reverses the refrigeration process when the heat pump thermostat is set to heating mode. When you need a new thermostat it is important to know whether you have an air conditioner or a heat pump because there is a difference between a heat pump thermostat and an air conditioner thermostat. While some thermostat manufacturers make all-purpose thermostats all thermostats are not the same and it is very important to make sure the thermostat is the right thermostat for the application especially for heat pumps. High Performance HVAC recommends the Honeywell VisionPro thermostat (Model # RTH8500D) for heat pumps and air conditioners. It is an all-purpose thermostat that will work with both heat pumps and air conditioners. Plus it is easy to use and program if you want to program it. The Honeywell VisionPro can be programmed or used manually according to the users manual settings.

Heat Pump Components: Heat Pump Defrost Controls

Other controls for the heat pump are the defrost control board. Heat pumps typically operate below the dew point outdoors. When they run below the dew point temperature they collect frost or ice on the heat pump coils. For this reason you need a defrost control to initiate a defrost cycle from time to time. There are different methods used to initiate the defrost mode by the most popular method is to time the defrost cycle like a freezer in your kitchen defrosts. Depending on how the installation technician sets the defrost timer will depend on when your heat pump will change to defrost mode. The sequence for defrost mode is timed for both heat pump mode and defrost mode. When the defrost mode initiates the defrost control shifts the reversing valve to the air conditioning mode. This makes the condenser coils hot so the frost or ice will melt off the heat pump condenser. After the defrost time has expired the heat pump reversing valve shifts back to its heating position and the heat pump is now a heater and not an air conditioner. When the heat pump is in defrost mode you want the unit to continue providing heat but how does it do this if it shifted to air conditioning mode when the heat pump defrost control changed to the defrost mode? The defrost control board sends a signal to the indoor heat pump air handler unit (sometimes directly to the air handler unit and sometimes through the heat pump thermostat depending how the heat pump unit is wired and controlled by the heat pump manufacturers design and recommendation.) The signal the defrost control sends is to activate the heat pump back-up heat. The heat pump back-up heat engages and counters the cooling effect from the air conditioning cycle.

Heat Pump Components: The Reversing Valve or 4-Way Valve and Metering Device

heat pump reversing valve, heat pump components, heat pump troubleshooting
To separate a heat pump from an air conditioner the heat pump needs a way to reverse the process of refrigeration to move the heat in the opposite direction an air conditioner moves the heat. That is when in air conditioning mode the heat pump moves the heat outside from inside and when in heating mode the heat pump moves the heat inside from the outside. The refrigerant absorbs heat from the air and it moves the heat in the direction where it is not wanted or where it is wanted. The heat pump reversing valve accomplishes this process by reversing the refrigeration flow. The heat pump condenser has a metering device inside it so the refrigerant temperature can be dropped below the temperature of the air outdoors. When the refrigerant is colder than the temperature of the air outdoors it absorbs this heat. If the temperature outdoors is 45° F. then the refrigerant needs to be 35° F. to absorb enough heat to be effective. The heat pump metering in the heat pump condenser causes a pressure drop of the refrigerant which drops the temperature of the refrigerant. This results in the refrigerant being colder than the outdoor air temperature and allows it to absorb heat from air that is 45° F. or colder to approximately 38° F. When the outdoor air temperature is colder than 38° F. the heat pump must struggle to absorb enough heat to be effective for providing heat for indoor comfort factors. This is the tipping point or the point at which the heat pump starts falling behind in its ability to provide heating for comfort factors inside.

Heat Components: The Outdoor Thermostat

Heat Pumps should have a method to turn the condenser off when the heat pump reaches the tipping point and stops being able to produce effective heat for indoor comfort factors. Many heat pumps are installed without this method to turn it off when it reaches this tipping point of ineffectiveness. There are two methods that can easily turn the heat pump off when it reaches the tipping point described. One is to have an outdoor thermostat that will turn the heat pump condenser off when it reaches the tipping point. The other method is to use an indoor thermostat that reads the outside temperature and allow the indoor thermostat to control the heat pump condenser based on the outside temperature. The Honeywell VisionPro heat pump thermostat has this ability. Two terminals in the Honeywell VisionPro are used for remote temperature sensing. It does require running a an additional shielded wire to the remote solid state temperature sensor (thermistor) but it is far more reliable and easier to control through the thermostat than it is from an outdoor thermostat hooked up to the heat pump condenser. Plus, if it is set up properly you will be able to visually see the temperature outdoors from you thermostat. The Honeywell VisionPro has in its display a reading for outdoor air temperature if the outdoor air temperature sensor is hooked up. The real bonus to have the heat pump condenser shut down when it reaches the tipping point is that you will save energy because you do not have the run the heat pump condenser when it is not doing anything. This is why heat pumps are installed in geographical climate zones where the air temperature rarely falls below 38° F.

Heat Pump Components: The Heat Pump Accumulator

Because the heat pump operates in cold whether there is a chance the compressor can eat some liquid when it is operating in cold weather. For this reason heat pump condensers have accumulators installed in the refrigeration circuit. The accumulator collects liquid refrigerant and allows it to boil into a vapor before it enters the compressor. This prevents liquid slugging of the compressor. Liquid slugging can damage a heat pump or air conditioner compressor beyond repair. Put simply, liquid does not compress as well as vapor compresses and that is exactly what a compressor does is compress vapor. Heat Pump and air conditioner compressors are designed to compress vapor and not liquid. Heat Pump Manufacturers outfit their heat pumps with accumulators to prevent liquid slugging when the heat pump is operating in cold weather.

Heat Pump Types Related Links

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