Bosch Worcester Greenstar HIU E User Manual

Fault finding and diagnostics
6 720 808 928 (2017/06)60
9.2 Domestic hot water trouble shooting guide
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 controller.  section 6.4
▶ 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 6.4
▶ 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.  section 6.5
▶ Perform re-calibration of control valve.  section 6.4
▶ Open control valve manually using CH rotary switch on HIU control unit.  section 6.4
▶ Replace control valve if necessary
Problem Possible cause Possibly solution/check
Hot water flow rate
is too low or no flow
Domestic cold water inlet filter
blocked
▶ Ensure minimum inlet water pressure is 1.5-2 bar.
▶ Clean filter
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 safety valve has closed due to
a seized DHW control valve
▶ Check that control valve is functioning correctly.  section 6.5
▶ Perform re-calibration of control valve.  section 6.4
▶ Open control valve manually using DHW rotary switch on HIU control unit.
 section 6.4
▶ Clean valve if necessary.
▶ Replace control valve if necessary.
DHW temperature
too low or varies
excessively at the
tap
HIU Control unit incorrectly set or
faulty
▶ Ensure that the DHW temperature set-point is set correctly on the HIU controller.
 section 6.4
▶ Replace control unit if necessary.
DHW flow turbine faulty ▶ Check electrical connections to flow turbine.Replace if necessary.
Faulty DHW control valve or dirt
inside valve body causing low flow
or no flow through district supply
circuit
▶ Check that control valve is functioning correctly.  section 6.5
▶ Perform re-calibration of control valve.  section 6.4
▶ Open control valve manually using DHW rotary switch on HIU control unit.
 section 6.4
▶ Clean valve if necessary.
▶ Replace control valve if necessary.
District supply temperature too low
▶ Check that the district supply temperature is correct for the require heat output. 
figure 55, Domestic hot water performance chart
District flow rate is too low
▶ Check that the district flow rate is correct for the require heat output.  figure 55,
Domestic hot water performance chart
District supply differential pressure
is too low
▶ Check that the supply differential pressure is correct for the required heat output.
 figure 55, Domestic hot water performance chart
▶ Adjust the flow regulating valves at the heat interface unit to obtain the correct
differential pressure.
▶ Increase the supply differential pressure on the system.
Calcified plate DHW heat
exchanger
▶ Check heat exchanger.
▶ Replace heat exchanger.
Cross leaking DHW plate heat
exchanger
▶ Replace heat exchanger.
DHW temperature
too high at the tap
HIU Control unit incorrectly set or
faulty
▶ Ensure that the DHW temperature set-point is set correctly on the HIU controller.
 section 6.4
▶ Replace if necessary
Table 33 Domestic hot water trouble shooting
Problem Possible cause Possibly solution/check
Table 32 Central heating trouble shooting

Bosch Worcester Greenstar HIU E Specifications

General

Brand	Bosch
Model	Worcester Greenstar HIU E
Category	Recording Equipment
Language	English