Led Displays At The Control Unit - Bosch FLOW 8000 D Installation And Maintenance Instructions Manual

Troubleshooting
Problem Possible cause
DHW temperature HIU control unit incorrectly set or
too high at the tap faulty
DHW over temperature valve not
installed (need to be installed, if the
primary flow is above 70 °C)
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
Electronic keep warm function
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 District supply temperature is correct for the required heat output,
District flow rate is too low
District supply differential pressure
is too low
DHW over DHW control valve stuck in open
temperature safety position
valve closed
Faulty DHW over temperature safety
valve
Cross leaking DHW plate heat
exchanger
Bypass temperature Wrong setting point by room
higher than 41°C controller Bypass temperature
(+ 5 K) higher than 41°C (+ 5 K)
Table 27 Domestic Hot Water trouble shooting
11.3

LED displays at the control unit

Left LED Right LED Cause
Off Off Outdoor temperature sensor error
-- Red Heating flow temperature sensor fault
-- Red If the HIU detects a heating module, a low loss
header must be installed and its temperature sent
to the HIU.
-- Red PWM signal indicates a heating control valve fault
Red -- DHW volumetric flow rate sensor fault
Red -- Supply flow temperature sensor error
Red -- PWM signal indicates a DHW control valve fault
-- Yellow Supply return temperature sensor error
Yellow Yellow Flow temperature on primary side is lower than
heating or set DHW temperatures
Red Red Flow temperature on primary side higher than
allowed (95°C)
24
Possible solution/check
▶ Ensure that the DHW temperature set-point is set correctly on the HIU room controller,
 section 7.2.
▶ Replace if necessary
▶ Install DHW over temperature valve.
▶ Clean valve if necessary.
▶ Adjust by-pass valve.
▶ Replace if necessary
▶ Adjust by-pass valve.
▶ Replace 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 DHW rotary switch on HIU control unit,  section
7.2.
▶ Clean valve if necessary.
▶ Replace control valve if necessary.
 section 13.1 "Tech data".
▶ Check that the District flow rate is correct for the required heat output,
 section 13.1 "Tech data".
▶ Check that the supply differential pressure is correct for the required heat output,
 section 13.1 "Tech data".
▶ Adjust any intalled flow regulating valves at the heat interface unit to obtain the correct
differential pressure.
▶ Increase the supply differential pressure on the system.
▶ 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.
▶ Replace control valve if necessary.
▶ Replace DHW over temperature safety valve.
▶ Replace DHW plate heat exchanger.
▶ Use the room controller and reset the temperature setting to 41°C (default value) and/
or choose "off" for the bypass function.
Conclusions
No set value has been specified for weather-compensated control. The
heating function is not detecting a heating load.
Heating and frost protection functions are disabled
Heating function is deactivated.
Heating and frost protection functions are disabled
DHW pump functions are disabled.
Bypass and DHW functions are disabled.
Bypass and DHW functions are disabled
Return temperature limit function is not working.
Fault only detected, HIU will keep on trying to supply heat.
Control valves will be kept closed and so no function except heating
pump operation can be executed.
FLOW 8000 D – 6721872703 (2024/07)