48
mexico HE
-
Installation & Servicing
Fault Finding
F
AUL
T FINDING F
AUL
T FINDING F
AUL
T FINDING F
AUL
T FINDING F
AUL
T FINDING
77 h......F........ (FLAME DETECTION - shORT CIRCUIT ERROR)
Replace flame detection electrode
Is there continuity between the 2 terminal pins ?
Replace PCB.
NO
78 h.....4...... (DRy FIRE ThERMIsTOR ERROR)
Check wiring for continuity from the PCB
to the dry fire thermistor
Can the fault condition be reset by switching off
the mains supply to the boiler ?
Is the system filled and vented and all isolation
valves open ?
Is the pump operating correctly? Ensure flow
through system.
NO
Check resistance, using a suitable multimeter
connected across the dry fire thermistor terminal
pins.
At 25
o
C expect 9,700 - 10,300 Ohms
At 60
o
C expect 2,400 - 2,600 Ohms
At 85
o
C expect 1,000 - 1,100
Ohms
Are dry fire thermistor values correct ?
Replace PCB
Replace dry fire
thermistor
Fill and vent the
system and open all
isolating valves
yES
Check resistance, using a suitable multimeter
connected across the flue thermistor terminal pins.
At 25
o
C expect 9,700 - 10,300
Ohms
At 60
o
C expect 2,400 - 2,600 Ohms
At 85
o
C expect 1,000 - 1,100
Ohms
Are thermistor values correct ?
Inspect heat
exchanger for
blockage or damage
in the flueways.
Clean or replace as
necessary
Replace thermistor
NO
79 h......n........ (phAsE REVERsAL ERROR)
yES
NO
yES
NO
Remove flame detection electrode terminal from PCB.
h9/L9 (FLUE gAs OVERhEAT)
yES
Check wiring to the boiler for
reversed live and neutral
Note.
With V9 Primary Control PCB, overheat LA/HA or
H9/L9 when reset will display 3 horizontal lines and will
not attempt to re-fire until the temperature in the heat
exchanger drops below 50
o
C.
Summary of Contents for he15
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