Aside from the fact that they are all used in hydronic heating systems, what do the following items have in common?

Fujitsu’s Airstage VRF multi-position air-handing unit features seven models ranging from 1 to 5 ton.

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. 

An installer is asked to pipe up two larger commercial air handlers supplied by a dual boiler setup.