58
Fault Finding
Fault Finding Fault Finding Fault Finding Fault Finding Fault Finding
Keston Combi - Installation and Servicing
76
OVERHEAT LOCKOUT - 1 FILL SYSTEM TO 1.0 BAR - 2 BLEED RADIATORS -
3 CHECK RADIATOR VALVES OPEN - 4 RESET BOILER - 5 CONTACT INSTALLER
Is the Boiler and CH System lled with water and all
isolation and radiator valves open?
YES
Fill and vent the system and open all
isolation valves, then reset boiler
Is the Flow/Return Differential across the Boiler in
excess of 30°C?
NO
Check that the Pump is rotating freely. Is
the Differential now below 20°C?
YES
NO
Replace the Pump,
then reset boiler
NO
OK, now
reset boiler
YES
RESET PROCEDURE - To reset boiler, turn mode knob to reset
position and immediately turn knob back to required setting.
Check the Return Thermistor (Refer to Frame 49)
Check resistance using a suitable multimeter
connected across the thermistor’s 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
77
IGNITION LOCKOUT / FLUE OVERHEAT - 1 CHECK OTHER GAS APPLIANCES WORK
- 2 RESET BOILER - 3 CONTACT INSTALLER
If the boiler is reset does the boiler ignite
for a short time and then extinguish?
YES
YES
Is the Gas Pressure available at
the Boiler Inlet (>18 mbar)?
Check the detection electrode and
associated harness for: continuity,
visual condition and position (Refer to
Frame 52). Check if the condensate
pipe is blocked. Replace as necessary
NO
Check gas supply and
rectify fault
NO
YES
Is approx 215Vdc supply available
at the Gas Valve? (* See note)
YES
Check spark generator and associated
harness for: continuity and visual
condition. (Refer to Frame 53) Are
these functioning correctly?
Check ignition electrode and associated
harness for: continuity, visual condition
and position. (Refer to Frame 51) Are
these functioning correctly?
Check siphon and condensate drain
pipe work for blockage and rectify if
necessary. Boiler now working OK?
Check wiring connection
from gas valve to PCB for
continuity. If the wiring is
OK then replace the PCB
NO
Replace Spark
Generator and harness
as necessary
NO
Replace Ignition Electrode and
associated harness as necessary
NO
Check if burner is damaged
Unplug gas valve. Is resistance
between outside pins 4KΩ (±2)?
YES
Replace Gas Valve
NO
YES
RESET PROCEDURE - To reset
boiler, turn mode knob to reset
position and immediately turn
knob back to required setting.
NO
Check ue for obstruction
Check wiring to thermostat
Check ue temperature always
remains below 90ºC
YES
Clear obstruction
YES
Ensure wiring correctly
connected
YES
YES
Replace Thermostat
Replace heat exchanger
* Note: due to the wave form of
the rectied voltage, the reading
will vary depending on the type
of meter used to measure the
value. In general terms a reading
greater than 150V indicates that
the correct voltage is supplied to
the gas valve.
Replace burner
NO
NO
NO
NO
(54 pages)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Comments to this Manuals