A heating contractor is asked to install two identical air-to-water heat pumps to take over as the primary hydronic heat source for a large home. Each heat pump has its own internal circulator. The existing boiler will be retained as the supplemental and backup heat source. A standard multi-boiler staging controller will be used to operate the heat pumps as rotating stages 1 and 2, and the boiler as “fixed” stage 3. These heat sources will supply several zones of low-temperature thin-slab radiant floor heating.
The existing system uses a 1.5” pipe size thermostatic mixing valve to reduce the water temperature from the boiler to the floor circuits.
