AAP Water Source Heat Pumps
What is a Water Source Heat Pump?
A water source heat pump is a mechanical reverse cycle device that is used to transfer heat from one medium to another. A water source heat pump extracts heat from the water when in the heating mode and rejects heat to the water when in the cooling mode. The water supply may be a recirculating closed loop or a once-thru system using water from a well, a pond or a stream. Water for closed-loop heat pumps is usually circulated at 2.25 to 3 gpm per ton of unit cooling capacity. A once-through groundwater heat pump can operate with a lower water flor, but the same range is still recommended.
The WSHP refrigeration circuit consists of a refrigerant-to-water heat exchanger, compressor, refrigerant metering device, refrigerant-to-air heat exchanger (or refrigerant-to-air coil), fan, reversing valve, and controls. Heat is transferred from one medium to the other by a hermetic refrigerant circuit.
What are the Features of this Technology?
The most common design configurations for packaged WSHP’s are horizontal units, which are positioned above a dropped ceiling: vertical units, which are usually located in basements, utility closets, or equipment rooms; and console units, which are designed for under window mounting in the conditioned space. We will discuss all the types of units in detail later in the TDP.
The feature that most distinguishes a heat pump from the typical refrigeration system is that it is reversible. This allows the unit to provide cooling in summer and heating in winter at relatively efficient level. In a WSHP unit a reversing valve switches the compressor discharge from the refrigerant-to-water heat exchanger for cooling to the refrigerant-to-air exchanger for heating.
Many of the other components required for a heat pump are the same as for a traditional air-conditioning unit. However, in the heat pump, the function of the heat exchangers can be reversed, so that they each must function as an evaporator and condenser.
Why use a Water Source Heat Pump System?
As one of the most energy efficient HVAC systems on the market, water-source heat pumps (WSHPs) are uniquely simple in design. Heat is moved through an interconnected water loop and either rejected through a cooling tower, or put to work in other areas. Each unit is an independent, packaged system, eliminating the chance of a total system failure. If one unit goes down, the other units are not affected. Usually conveniently located above the ceiling or in a closet, units can be easily accessed.
WSHPs are ideal for a wide range of building types including office buildings, apartment buildings, hotels, condominiums, schools and much more.
WSHPs are simple to service as a residential air conditioning unit, and they have a very long life. ASHRAE estimates a more than twenty-year life expectancy. That’s because WSHPs don’t have to work as hard as other systems to move heat from one place to another. For the design of an ideal heating/cooling system that offers individual zone control, recovers and utilizes excess heat for space conditioning or alternative uses, and serves multi-tenant needs simply and efficiently, water-source heat pump systems are the best choice.
If you want to learn more about the WSHP products Associated Air Products offers, check out our brand FHP.