Size the heat pump with the dimensioning table
Size the heat pump against the building's heat load. The cold-weather handover point to the backup heating rod — the bivalence temperature — is set on More settings, not here.
The dimensioning table is where the attached heat pump is sized against the heat load you established.
Bivalence and the backup heater
The bivalence temperature is the outside temperature below which the heat pump hands over to the resistive backup heating rod. It defaults to −6 °C.
Lower it when the pump is sized to carry very cold days on its own, so the rod engages only in extreme conditions. Raise it when the pump is undersized and the rod will routinely cover the winter shortfall. Set the bivalence temperature on More settings under Heating Additional Settings, not on the dimensioning table, then re-run the simulation to see the annual operating cost move.
Things to know
- A lower bivalence temperature means the pump carries more of the cold-weather load itself (less resistive backup), which affects winter electricity demand — see Heat-pump demand.
- Size against the heat load from the heat-load calculation (or the indication); an under-stated heat load leads to an under-sized pump.
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