Troubleshooting
Greenstar – 6721852556 (2022/11)
24
Table 26 Central Heating trouble shooting
11.2
Domestic Hot Water trouble shooting guide
Room controller incorrectly set or
faulty
▶ Check that room controller is set correctly and is calling for heat.
▶ Replace room controller if necessary.
Faulty Central Heating control valve
or dirt inside valve body causing low
flow or no flow through District
supply circuit
▶ Check that control valve is functioning correctly,
▶ Perform re-calibration of control valve,
▶ Open control valve manually using CH rotary switch on HIU control unitcontrol unit,
section 7.2.
▶ Clean valve if necessary.
▶ Replace control valve if necessary.
District supply temperature too low ▶ Check that the district supply temperature is correct for the required heat output.
District flow rate is too low
▶ Check that the district flow rate is correct for the required heat output.
District supply differential pressure
is too low
▶ Check that the supply differential pressure is correct for the required heat output.
▶ Adjust any installed flow regulating valves at the heat interface unit to obtain the correct
differential pressure.
▶ Increase the supply differential pressure on the system.
Central Heating flow
temperature too low
HIU control unit incorrectly set or
faulty
▶ Adjust HIU control unit,
section 7.2.
▶ Replace if necessary.
Room controller incorrectly set or
faulty
▶ Adjust room controller.
▶ Replace if necessary.
Outdoor sensor positioned
incorrectly
▶ Position outdoor sensor correctly.
District supply temperature too low ▶ Check that the District supply temperature is correct for the required heat output.
District flow rate is too low
▶ Check that the District flow rate is correct for the required heat output.
District supply differential pressure
is too low
▶ Check that the supply differential pressure is correct for the required heat output.
▶ Adjust any installed flow regulating valves at the heat interface unit to obtain the correct
differential pressure.
▶ Increase the supply differential pressure on the system.
Central Heating flow
temperature too
high
HIU control unit incorrectly set or
faulty
▶ Adjust HIU control unit. Ensure that the flow temperature set-point is set correctly on
the HIU room controller,
section 7.2.
▶ Replace if necessary.
Room controller incorrectly set or
faulty
▶ Adjust room controller. Ensure that the flow temperature set-point is set correctly on
the HIU controller,
section 7.2.
▶ Replace if necessary.
Central heating flow sensor out of
position or faulty
▶ Ensure sensor is in correct position.
▶ Replace sensor
Faulty central heating control valve
or dirt inside valve body causing
valve to seize.
▶ Check that control valve is functioning correctly,
▶ Perform re-calibration of control valve,
▶ Open control valve manually using CH rotary switch on HIU control unit,
section 7.2.
▶ Clean valve if necessary.
▶ Replace control valve if necessary
Problem
Possible cause
Possibly solution/check
No hot water output
from HIU
Potable cold water inlet strainer
blocked
▶ Ensure minimum inlet water pressure is 1.5-2 bar.
▶ Clean strainer.
Inlet water pressure too low
▶ Increase domestic cold water supply pressure into HIU by consulting the water supply
company.
▶ Clean plate heat exchanger if there are signs of calcification.
DHW over temperature safety valve
has closed due to a seized DHW
control valve
▶ Check that control valve is functioning correctly,
▶ Perform re-calibration of control valve,
▶ Open control valve manually using DHW rotary switch on HIU control unit,
section 7.2.
▶ Clean valve if necessary.
▶ Replace control valve if necessary.
Hot Water flow
temperature too low
HIU control unit incorrectly set or
faulty
▶ Ensure that the DHW temperature set-point is set correctly on the HIU controller,
section 7.2.
▶ Replace control unit if necessary.
DHW flow turbine faulty
▶ Check electrical connections to flow turbine.
▶ Replace if necessary
Problem
Possible cause
Possibly solution/check
