About Water-Source Heat Pumps

Water-source heat pumps

By Amy McVey

A water-source heat pump (WSHP) system operates by transferring heat between your building and a nearby body of water, such as a lake or river. There are two main methods for accomplishing this: closed loop and open loop.

In a closed-loop WSHP system, water is pumped from the building to a heat exchanger submerged in the body of water. This allows heat transfer between the building and the body of water without allowing contaminants from the body of water to come in contact with pumps or other moving parts.

In an open loop WSHP system, water is pulled from the body of water and pumped into your building, where it transfers heat to your building loop via a heat exchanger. This method removes the need for heat transfer equipment installed in the body of water. Both systems pump water through pipes submerged in a body of water at a depth where the water won’t freeze or evaporate.

Advantages of Water-Source Heat Pumps:

  • Attractive for electrification/decarbonization

  • Energy efficient

  • Provides zone heating and cooling at the highest rated levels of efficiency

  • If one unit fails entire system won’t shut down

Disadvantages of Water-Source Heat Pumps:

  • A separate dedicated outside air system is required for humidity control and ventilation

  • Retrofitting a water loop requires that new terminal devices be installed

  • Compressors are distributed throughout the facility rather than in a central location, making it harder for maintenance

Water-Source Heat Pump vs. Water-Source VRS System

Water-source heat pump systems and water-source VRF systems both use water as the heat exchange medium to transfer heat between the indoor and outdoor units. But, a water-source VRF system uses refrigerant as a heat transfer fluid. The refrigerant is circulated through the loop in order to absorb or reject heat from the water source and then circulated to the indoor units, where it's used to provide heating or cooling.

Overall, the choice between a GSHP and a ground-source VRF system will depend on factors such as the specific needs of the building, the climate, the cost of installation and maintenance, and the desired level of efficiency and control.