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ASHP with boiler, automatic switch over

stuartf
stuartf Member, Email Confirmation Posts: 6
I am looking to have a heat pump (18k BTU) installed and maintain the gas boiler. The boiler will do domestic and the hydronics in the lowest level slab. When it gets colder would like to switch from ASHP to boiler.

The ASHP installer says it is possible but expensive and suggested using the separate thermostats so if the ASHP cannot keep up, the boiler kicks on. Not sure if that works given the remaining slab demands. Any thoughts on how to address this.

I thought I would sue the boiler when the heat pump's COP dropped below 2 or so.

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 24,727
    Slightly confused here. You want the heat pump to handle the upper level alone except when it is colder, and then kick on... what hydronic heat in the upper level? And the boiler is running anyway for your hot water and the lower level slab?

    What turns the hydronic heat for the upper level on or off? Zone valve? Zone pump? Please clarify how that level is controlled separately from the lower level slab and the domestic hot water.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England