IDEAL icos system HE15 Installation And Servicing page 56

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81 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
Set CH control knob to maximum.
If the overheat trips again measure the flow temp:
o
Over 90 C Check control thermistor
(Refer to Frame 83) .
o
Under 90 C Replace overheat 'stat
82 L....8..... (FAN ERROR)
Is nominal 330 V DC present across
red and blue at the fan connector as
reset button is pressed?
NO
83 H.....1.....
Remove the boiler control thermistor from
either the CH flow/return pipe and disconnect
Check resistance, using a suitable multimeter
connected across the thermistor terminal pins.
o
At 25 C expect
o
At 60 C expect
o
At 85 C expect
Are the thermistor values correct ?
56
FAULT FINDING
(OVERHEAT ERROR)
YES
YES
o
C ?
NO
YES
Check wiring harness for
continuity. Is there continuity?
(CONTROL THERMISTOR ERROR)
thermistor wires.
9,700 - 10,300
2,400 - 2,600
1,000 - 1,100
YES
Is there continuity between the
PCB and the thermistor?
NO
NO
Fill and vent the system and open all
YES
Check that the pump is rotating freely.
Replace the system pump
Note.
With V9 Primary Control PCB, overheat LA/HA or H9/L9 when
reset will display 3 horizontal lines and will not attempt to refire
until the temperature in the heat exchanger drops below 50
Is 14V DC present
across yellow and pink
at the fan connector?
NO
YES
NO
Ohms
Ohms
Ohms
NO
YES
NO
Replace overheat thermostat
isolation valves
Is differential now below 25
NO
YES
Replace fan
Replace PCB
Replace harness
Replace the thermistor
Replace PCB
Check and replace wiring as necessary
icos system -
Installation and Servicing
o
C ?
YES
OK
o
C.