20
Heating Only Hybrids
A heating only hybrid system is a combination of a fossil fuel boiler and a heat pump.
In a hybrid system the heat pump only provides heating and cannot heat the domestic hot water. The boiler and heat pump will never operate at the same
time.
Operation
As the domestic hot water is only heated by the boiler, the old/existing boiler can still be used.
• The heating system is controlled via a thermostat / time clock, the run signal is sent to the heating controls to operate the boiler.
• Whilst the heat pump is running, it will be constantly adjusting the water temperature to suit the ambient temperatures and conditions. This is
the weather compensation of the unit.
• There will need to be a changeover temperature (heat pump to boiler), for example 3°C.
• When/if the ambient temperature falls below the programmed set point, a run signal is sent to the boiler to activate, the boiler symbol will show
and the operation of the heat pump will stop.
• When the outside temperature rises back above 5°C, the boiler will stop and the heat pump will take over.
• In this setup, the RHI will be calculated and paid dependant on the heat provided by the heat pump only, this will require a heat meter.
HP 2
HP 1
Heat
Exchanger,
Buffer Tank or
Low Loss
Header
Combi
Boiler
Combi Boiler
must be set to
run at below
65°C
