29
221895A
13 Fault Finding
TO TEST FOR COMPONENT OPERATION / FAILURE
Power to the appliance :- Test for 230V~ across live (brown) and earth (yellow and green), 230V~ across live and neutral (blue),
and zero potential across neutral and earth.
Thermistors :- With the power off unplug the connector and test resistance is 10k ohms at 25
°
C
Differential pressure switch :- With the power off seperate the in-line connector and test for continuity across male end. restore
the power and with demand off, open circuit, demand on closed circuit
Domestic Hot Water demand switch :- With the power off seperate in-line connector and test for continuity across male end.
Tap open, continuity between black and white cables, black and red are open circuit. With demand off there is continuity between
black and red and that black and white are open circuit.
Overheat thermostat :- With the power off unplug the connectors and test for continuity (zero resistance).
Power to the gas control valve :- With a demand on test for voltages of 24 to 50V~ across the black and white cable connectors
and 130V~ across the red and blue cable connectors.
Power to the fan :- With a demand on and the front cover removed test for 230v~ at the fan connectors.
Fan failure :- with the power off and the supply leads to the fan disconnected (pull the boots only) the resistance across the fan
coil should not be greater than 50
Ω
.
Pump :- With the power off unplug the connector from the pump. Restore the power and check that there is 230V~ between live
(red) and neutral (black) or live and the appliance earth.
Air pressure switch :- With the power off and the front cover removed pull one of the supply cables from the fan and ensure
it is electrially safe. Restore the power establish a demand, check that there is 230v~ at one of the APS cables but not at the other.
Turn the power off, refit the fan cable, restore the power and check that there is now 230V~ at both the APS connectors (Caution,
the appliance will light unless the spark leads are temporarily unplugged from the electrodes and laid where they cannot spark
and ignite the gas and are electrically safe). This indicates that the APS changes state when the fan is run.
The three way valve :- Seperate the cable connector from the motor noting its orientation and the connector numbering marked
on the motor housing. Check that with a DHW demand there is 230V~ across sockets 2 and 1 and with a CH demand there is
230V~ across sockets 2 and 3 (or ground and 1, ground and 3 respectively).
13.3 Electrical
Preliminary electrical system checks, as outlined in a Multimeter
Instruction book, are the first checks to be carried out during a
fault finding procedure.
Isolate the boiler from the electrical supply, refer to Section
11.3.
Gain access to the boiler controls by removing the outer case
front, refer to diagram 10.5.
Remove the two screws securing the controls facia, see diagram
9.1.
Hinge the control facia forward.
Remove the controls board cover by slackening the cable entry
cover screws, see diagram 10.2.
Remove the covers.
Ease the cover up and clear.
Check that all cables, multipin connectors and connectors are
secure on the board.
Test the fuse on the main control board and renew as necessary.
Fuse 1 type (2AT). If a fuse fails repeatedly or the initial fault-
finding checks described in Section 13.1 indicate a boiler fault,
check the boiler electrical circuits and follow the fault finding
procedures, see diagram 13.2, 13.3, and for clock/timer fault
finding, diagram 13.4 and 13.5.
On completion of a fault finding task that has required the
disconnection and making of electrical connections then checks,
for earth continuity, polarity and resistance to earth must be
carried out.
Before replacing any part please read points below:-
Replacement of parts must only be carried out by a competent
person.
1. Refer to Section 11.1.
2. Always isolate the boiler from the electrical supply and as
required, the gas supply, as Section 11.3.
3. On completion, make good any water loss and pressurise the
system to initial design pressure, refer to “Commissioning” in
the Installation Instructions.
Before starting refer to Section 11.1
Isolate the boiler from the electrical supply, refer to Section
11.3.