17
ELEMENT REPLACEMENT
Isolate electrical supply to boiler.
Drain down system.
Disconnect terminal connectors from high limit
thermostat
Remove thermistor from behind the retaining strap.
Disconnect electrical elements and earth wire.
Disconnect compression fitting from the top and bottom of
boiler.
Boiler unit can now be carefully removed.
Remove 8 fixing screws on top flange with and withdraw
the element assembly.
Remove bottom element positioning bracket.
Remove damaged element.
Refit in reverse order and ensure element seals are fitted.
Check for continuity through 2 terminals on each element.
IMPORTANT: Inspect all seals and change where
necessary.
FAULT FINDING
Red LED permanently illuminated indicates one of the
following faults.
High limit thermostat has operated or faulty electrical
connections
The boiler has two high limit thermostats fitted, one on the
heat exchanger and one on the tank. The high limit
thermostat on the heat exchanger is fitted to the front top
of the stainless-steel heat exchanger and secured in
position with 2 retaining clamps. The tank high limit
thermostat is fitted onto the tank on the left-hand side at
the top. 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 the red button in centre of thermostat. The
thermostat may have tripped due to one of the following:
Faulty circulation pump.
Isolation valve on system closed.
Air trapped in system.
Out of calibration limit thermostat.
Temperature settings on PCB board incorrect.
No water in system.
Thermistor
The boiler has two thermistors fitted, one on the heat
exchanger and one on the tank. The heat exchanger
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
The tank thermistor is fitted on the left hand side of the
tank at the top. 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. Check polarity.
PCB 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.
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.
Содержание AZTEC 12
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