Water-to-Water Heat Pump

What Is a Water-to-Water Heat Pump?

A water-to-water heat pump, also known as a heat recovery unit, is a commercial HVAC unit that transfers heat between two fluid sources (commonly water), and it may include a reversing valve to change the roles of the heat exchanger.

Several sources may be used to supply the water, including the ground (geothermal systems), cooling towers, rivers, lakes, and even industrial process water.

How Does a Water-to-Water Heat Pump Work?

The unit uses water instead of air to move heat through a building. A water-to-water heat pump can provide cold or warm water. 

• In the cooling mode, the refrigeration circuit transfers heat from the water flowing through the “load-side” heat exchanger to the fluid flowing through the “source side” heat exchanger. This means water is used to transfer the heat outside of the building.
• In the heating mode, the reversing valve (if there is one) changes the operation of the refrigeration circuit to transfer heat from the “source-side” to the “load-side” heat exchangers.

In a water-to-water heat pump, heating is a byproduct of the cooling load and can be used to warm a different zone, making it an energy-efficient system. For example, in a building with a data center and offices, the heat from the data center could be moved through the system to warm the offices. 

Other sources of heat can include:

• Geothermal loops
• Lakes, rivers, and ponds
• Storm runoff and sewer systems
• Ambient Air
• Thermal energy storage batteries
• Exhaust air coils

The Benefits of Water-to-Water Heat Pumps

In addition to being a highly efficient means of heating and cooling, water-to-water heat pumps can

• Make the electrification of a building easy by replacing an older boiler and chiller system.
• Reduce the required mechanical space in a building compared to a chiller and a boiler.

Water-to-water technology is suited to reduce the environmental impact of schools, hotels, offices, hospitals and multi-unit residences by replacing fossil fuel boilers with high-performance heat pump technology.

Resources for Water-to-Water Heat Pumps

• Axiom™ Water-to-Water Water Source Heat Pumps
• Case study: Duke University

To learn more about water-to-water heat pumps and the transition away from boiler systems, reach out to your local Trane representative.