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Manual 2100-520
Page 4 of 7
2. The compressor, which is a sealed pump that moves the refrigerant through the system.
3. The
water coil where the heat that was absorbed from the indoor space is discharged to the
circulating water supply. A pump is required somewhere in the system to move the water through
the heat pump water coil.
HEAT PUMP (HEATING MODE)
The system operates in reverse cycle, meaning that it acquires and moves heat from the water
supply flowing through the water to refrigerant coil, and transfers it indoors to be rejected into the
circulating air stream.
Most water-to-air heat pumps will also be equipped with some amount of electric heat to supplement
the heating capacity of the compressor system on an as needed basis. This operation is entirely
automatic and is controlled by the indoor thermostat.
Because of the design of water-to-air heat pumps and the water temperatures involved, no defrost
system is required as in air-to-air heat pumps.
WATER SUPPLY SYSTEMS
Depending upon type and application of the water-to-air heat pump, the water-side of the system
could be one of the following:
1. Individual closed loop buried in a trench or vertical bore hole(s).
2. Individual loop submerged in a pond.
3. Water supplied from a well and discharged into pond, stream, ditch or another well.
4. Water supplied from a boiler/tower system, typically only in larger multi-unit installations.
A properly sized heat pump cannot cool a structure off rapidly, and instead will pull down the temperature
slowly. It also will remove a certain amount of moisture (humidity) from the circulating air stream in the
process. It may take several hours to pull down a hot, moist building or structure on initial start up, or
anytime the system has been turned off for a long period of time. It is generally best to set the
thermostat at a comfortable temperature and let it control the system as needed, rather than turning it on
and off.
Moisture (humidity) removal with a conventional air conditioner (cooling) unit, or heat pump when operating
in the cooling mode, is not directly controlled and is a by-product of the unit operating to control temperature
in response to the temperature (thermostat) control device. Over-sized equipment can easily control
temperature but will have short run-times, thus reducing its ability to remove moisture from the circulating
air stream. There are also many additional influences that can affect humidity levels within the conditioned
space such as laundry appliances, cooking, showers, exhaust fans, and any other items that can generate
moisture or affect its removal from the space. Therefore, while operation of the air conditioning or heat
pump system in the cooling mode will remove some amount of moisture as it reduces the air temperature,
precise humidity regulation in the conditioned space cannot be assured and additional equipment such as
a dedicated dehumidifier may be required.