Supplied By www.heating spares.co Tel. 0161 620 6677
21
FAULT FINDING
Red LED permanently illuminated
indicates one of the following faults.
High limit thermostat has operated or faulty electrical
connections
The high limit thermostat is fitted to the front top of the
copper heat exchanger and secured in position with 2
retaining clamps.
Check electrical connections on thermostat and PCB to
check thermostat has not failed using a multi meter
check continuity across terminals of thermostat.
To reset press red button in centre of thermostat.
Thermostat may have tripped due to one of the following:-
1. Faulty circulation pump
2. Isolation valve on system closed
3. Air trapped in system
4. Out of calibration limit thermostat
5. Temperature settings on PCB board incorrect
6. No water in system
Thermistor
The thermistor is fitted to the front top of the heat
exchanger and secured in position with a clamp, the
other end terminates with a white connector that plugs on
to the PCB
Check the connections on the board to make sure it is
correctly fitted; also inspect the thermistor for any broken wires.
Mains Inlet Wiring
If the mains supply to the boiler is wired incorrectly on
the inlet terminal block.
PCB Board Damage
Inspect the LED lights and the boiler temperature control
adjuster for any damage to connections to PCB
controller.
Voltage Drop
If the voltage drops below 207 volts.
Red LED flashes indicates one of the
following faults.
Poor electrical connection
Check the electrical connections to the elements and the
PCB controller, a poor controller would show up a fault.
Element Failure
To check elements for failure, disconnect each individual
element and check continuity through the element if there
is continuity between the two terminals the element is ok.
Check each element individually replacing the electrical
connectors after testing.
Element Cables
If there is a break in the element cable, this would show
up as a fault. Check all element cables and connections.
PCB Running Temperature
The PCB control unit has a built in temperature control
sensor which protects the PCB from overheating, if the
board was to overheat the sensor would detect the high
temperature and shut off the power to the board until the
board temperature has returned to normal running
temperature. The boiler will resume operation but the red
light will continue to flash to indicate a fault has occurred.
To reset the board the power must be turned off for 30
seconds then switched on again.
On the 9, 11 and 12 kW boilers a cooling fan is fitted to
the heatsink if this has failed, it would cause the PCB to
overheat.
To differentiate between a temperature or element problem,
switch off the power supply to the boiler allow the boiler
to cool down then switch the power back on, if the LED
continues to flash then check elements and connections.
Green LED
If the green LED is illuminated but the boiler is not
functioning, check that any external controls fitted are
calling for heat. If no external controls are fitted check
that link wire is in place on call terminal block (refer to
wiring diagram Fig 1)
Blown Fuse on board
If there is power to the boiler but no LED illuminated then
the fuse on the PCB may have blown. The fuse is located
above the PCB transformer (fuse type 20mm 630Ma anti
surge Bessman type S560)
The fuse may have blown due to one of the following:-
1. When multiple boilers are fitted and a larger pump is
used. If the pump is wired directly into the PCB the
fuse may need upgrading. (see page 11)
2. If the call terminal is used to supply power to ancillary
controls.
Element Jumper Connection
Fitted on 11 and 12 kw models only. If fitted to 6 and 9
kw models it will show up as a fault.
RCD UNIT TRIPS
Check that the RCD unit is correctly rated for boiler size.
If under size change.
Inspect mains terminal block wiring for short-circuiting.
Check electrical elements for earth continuity, if element
is found to be faulty fit new element.
