IDEAL HE15 Installation And Servicing page 47

73 L.......A........
Can the overheat condition be reset by pressing
the boiler reset button when the system is cold ?
Is the boiler and CH system filled with
water and all isolation valves open ?
Does the pump setting give a differential
across the boiler in excess of 25
Increase the pump setting.
Is differential now below 25
NO
Replace the system pump
74 L....8..... (FAN ERROR)
Is nominal 330 V DC present across
red and blue at the fan connector as
reset button is pressed?
NO
Check wiring harness for continuity. Is there continuity?
75 H.....1..... (FLOW THERMISTOR ERROR)
Remove the boiler flow thermistor from the CH flow
pipe and disconnect thermistor wires.
Check resistance, using a suitable multimeter
connected across the thermistors terminal pins
o
At 25 C
o
At 60 C
o
At 85 C
Are the thermistor values correct ?
Is there continuity between the
mexico HE -
Installation & Servicing
FAULT FINDING
(OVERHEAT ERROR)
YES
YES
o
C ?
YES
o
C ?
YES
OK
Is 14V DC present
YES
across yellow and pink
at the fan connector?
expect 9,700 - 10,300
expect 2,400 - 2,600
expect 1,000 - 1,100
YES
PCB and the thermistor ?
NO
NO
Fill and vent the system and open all
NO
Set CH control knob to maximum.
If the overheat trips again measure the flow temp:
Over 90
Under 90
YES
NO
YES
NO
Ohms
Ohms
Ohms
NO
YES
NO
Replace overheat thermostat
isolation valves
o
C Check control thermistor
(Refer to Frame 52) .
o
C Replace overheat 'stat
Replace fan
Replace PCB
Replace harness
Replace the thermistor
Replace PCB
Check and replace wiring as necessary
47