Domestic Hot Water Trouble Shooting Guide - Worcester Greenstar HIU Installation And Maintenance Instructions Manual

Troubleshooting
Problem Possible cause
Room controller incorrectly set or
faulty
Faulty Central Heating control valve
or dirt inside valve body causing low
flow or no flow through District
supply circuit
District supply temperature too low ▶ Check that the district supply temperature is correct for the required heat output.
District flow rate is too low
District supply differential pressure
is too low
Central Heating flow HIU control unit incorrectly set or
temperature too low faulty
Room controller incorrectly set or
faulty
Outdoor sensor positioned
incorrectly
District supply temperature too low ▶ Check that the District supply temperature is correct for the required heat output.
District flow rate is too low
District supply differential pressure
is too low
Central Heating flow HIU control unit incorrectly set or
temperature too faulty
high
Room controller incorrectly set or
faulty
Central heating flow sensor out of
position or faulty
Faulty central heating control valve
or dirt inside valve body causing
valve to seize.
Table 26 Central Heating trouble shooting
11.2

Domestic Hot Water trouble shooting guide

Problem Possible cause
No hot water output Potable cold water inlet strainer
from HIU blocked
Inlet water pressure too low
DHW over temperature safety valve
has closed due to a seized DHW
control valve
Hot Water flow HIU control unit incorrectly set or
temperature too low faulty
DHW flow turbine faulty
24
Possibly solution/check
▶ Check that room controller is set correctly and is calling for heat.
▶ Replace room controller if necessary.
▶ Check that control valve is functioning correctly,  section 7.3.
▶ Perform re-calibration of control valve,  section 7.2.
▶ 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.
▶ Check that the district flow rate is correct for the required heat output.
▶ 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.
▶ Adjust HIU control unit,  section 7.2.
▶ Replace if necessary.
▶ Adjust room controller.
▶ Replace if necessary.
▶ Position outdoor sensor correctly.
▶ Check that the District flow rate is correct for the required heat output.
▶ 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.
▶ 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.
▶ Adjust room controller. Ensure that the flow temperature set-point is set correctly on
the HIU controller,  section 7.2.
▶ Replace if necessary.
▶ Ensure sensor is in correct position.
▶ Replace sensor
▶ Check that control valve is functioning correctly,  section 7.3.
▶ Perform re-calibration of control valve,  section 7.2.
▶ Open control valve manually using CH rotary switch on HIU control unit,  section 7.2.
▶ Clean valve if necessary.
▶ Replace control valve if necessary
Possibly solution/check
▶ Ensure minimum inlet water pressure is 1.5-2 bar.
▶ Clean strainer.
▶ Increase domestic cold water supply pressure into HIU by consulting the water supply
company.
▶ Clean plate heat exchanger if there are signs of calcification.
▶ Check that control valve is functioning correctly,  section 7.3.
▶ Perform re-calibration of control valve,  section 7.2.
▶ Open control valve manually using DHW rotary switch on HIU control unit,
 section 7.2.
▶ Clean valve if necessary.
▶ Replace control valve if necessary.
▶ Ensure that the DHW temperature set-point is set correctly on the HIU controller,
 section 7.2.
▶ Replace control unit if necessary.
▶ Check electrical connections to flow turbine.
▶ Replace if necessary
Greenstar – 6721852556 (2022/11)