H 4 (Dry Fire Thermistor); H9/L9 (Heat Exchanger Overheat); H F (Flame Detection); H N (Phase Reversal) - IDEAL istor HE260 Installation And Servicing

104 H......4....... (DRY FIRE THERMISTOR)
Can the fault condition be reset by switching off
the mains supply to the boiler ?
Check wiring for continuity from the
PCB to the dry fire thermistor
Check resistance. The sensors can be
checked by measuring their resistance, using
a suitable multimeter connected across the
sensors' terminal pins
o
At 25 C expect
o
At 60 C expect
o
At 85 C expect
Are thermistor values correct ?
YES
Replace PCB
105 H......F........
Is there continuity between the detection
electrode terminal at the PCB and earth ?
Replace detection electrode
106 H......n........
istor system store -
Installation and Servicing
FAULT FINDING
NO
9,700-10,300 Ohms
2,400-2,600 Ohms
1,000-1,100 Ohms
NO
Replace thermistor
(FLAME DETECTION)
YES
(PHASE REVERSAL)
Check wiring to the boiler for
reversed live and neutral
H9/L9 (HEAT EXCHANGER OVERHEAT)
Is the system filled and vented and all
isolation valves open ?
Is the pump operating correctly?
Ensure flow through system.
YES NO
Check resistance using a suitable multimeter
connected across the dry fire thermistor's
terminal pins
o
At 25 C expect
o
At 60 C expect
o
At 85 C expect
Are thermistor values correct ?
YES
Inspect heat exchanger
for blockage or
damage in the
flueways. Clean or
replace as necessary
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
Check the detection electrode for
NO
continuity and visual condition.
Replace if necessary.
Fill and vent the
system and open all
isolating valves
9,700-10,300 Ohms
2,400-2,600 Ohms
1,000-1,100 Ohms
NO
Replace thermistor
o
C.
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