Hiu Control Unit Led Indications - Bosch Worcester Greenstar HIU E Installation And Maintenance Instructions Manual

Problem Possible cause
Time taken to get Mechanical by-pass valve has dirt
hot water at the tap inside valve body
is too long
Mechanical by-pass valve is set
incorrectly, or is faulty
Faulty DHW control valve or dirt
inside valve body causing low flow
or no flow though district supply
circuit
District supply temperature too low ▶ Check that the supply temperature is correct for the required heat output.
District flow rate too low
District differential pressure is too
low
Domestic hot water circulation
pump out of operation
DHW safety valve DHW control valve stuck in open
closed position
Faulty DHW safety valve
Cross leaking DHW plate heat
exchanger
Table 33 Domestic hot water trouble shooting
9.3

HIU Control unit LED indications

Reason or Error
Outdoor temperature sensor error
CH flow temperature sensor error
CH return temperature sensor error
DHW volume flow sensor error
DHW flow temperature sensor error
Supply flow temperature sensor error
Supply return temperature sensor error
Supply flow temperature lower than CH or DHW set
points
Supply flow temperature higher than allowed (95 °C)
If a net connected HIU detects a CH module, a low loss
header must be installed and its temperature sent to the
HIU. If this temperature is not available the error
becomes true
PWM feedback signal indicates a CH control valve error
PWM feedback signal indicates a DHW control valve error
CH rotary switch position is invalid
DHW rotary switch position is invalid
Table 34
6 720 808 928 (2017/06)
Possibly solution/check
▶ Clean valve if necessary.
▶ Adjust by-pass valve.
▶ Replace if necessary.
▶ Check that the 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
▶ Replace control valve if necessary.
 figure 55, Domestic hot water performance chart
▶ Check that the flow rate is correct for the required heat output.
 figure 55, Domestic hot water performance chart
▶ Check that the 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.
▶ Check that the pump is running correctly and that there is no air in the pump.
▶ 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
▶ Replace control valve if necessary.
▶ Replace DHW safety valve.
▶ Replace DHW plate heat exchanger.
Left LED Right LED
(DHW) (CH)
No No No set point is set in case of weather compensated control
- CH function does not detect a heat demand
- Red CH and frost protection functions are disabled
- Yellow Limit return temperature functions are disabled
Red - DHW and circulation pump functions are disabled
Red - DHW and circulation pump functions are disabled
Red - By-pass, DHW and circulation pump functions are disabled
- Yellow Limit return temperature function is not working
Yellow Yellow Just error detected, HIU will keep on trying to supply heat
Red Red Control valves will be kept closed and so no function
except CH pump running can be executed
- Red CH function is disabled
- Red CH and frost protection functions are disabled
Red - By-pass, DHW and circulation pump functions are disabled
- Red flashing CH function is disabled
Red flashing - By-pass, DHW and circulation pump functions are disabled
Fault finding and diagnostics
Outcome
61