John Siegenthaler, P.E.

The heating output and coefficient of performance (COP) of any hydronic heat pump is very dependent on the water temperature leaving the heat pump’s condenser. 

Although the market for gas-fired boilers continues to track toward those that can modulate and operate with sustained flue gas condensation, conventional boilers (e.g., those not designed to operate with sustained flue gas condensation) still represent a significant portion of the market. 

As global energy planning moves away from fossil fuels and toward electricity, an increasing number of hydronic heating systems are being supplied by heat pumps. 

Heat pumps are incredibly useful devices. 

Hydronic heating professionals often promote the concept that current generation mod/con boilers can operate with AFUEs in the range of 95% and above. 

I’m sure everyone reading this column has heard the adage “a picture is worth a thousand words.”  

Whenever a hydronic system is divided into several zones, it’s worth considering a buffer tank between the heat source and distribution system. 

A zone is any area of a building for which indoor air temperature is controlled by a single thermostat (or other type of temperature controller). 

In last month’s column, I presented a “template” for a system that provides space heating, cooling and domestic water heating using a cold climate air-to-water heat pump as the primary heat source, and the sole source of chilled water for cooling. 

Most buffer tanks used in hydronic systems are piped in a “4-pipe” configuration.