Fault Finding; Temperature Limit Thermostat; Ignition Controller - Hamworthy Wessex Modumax 100 series Installation, Comissioning And Servicing Instructions

9.0 FAULT FINDING

The Wessex ModuMax boiler is equipped with full self-diagnostic fault indication, with faults allocated a code,
which is displayed (flashes) on the screen - refer to section 8.2.4 and 8.2.10 - Controls Operation.
The common fault codes are detailed in section 8.2.10. Fault codes not detailed in this manual should only be
investigated by an Engineer.
Should a fault code appear which cannot be reset, or a fault code repeatedly occurs,
contact Hamworthy Heating for assistance. Do not continue to operate or use the boiler
as this may cause damage to the controls.

9.1 Temperature Limit Thermostat

1. The electronic control thermostat has several safety levels built in such that a controlled shutdown should occur
before the limit thermostat is activated. Should these safety levels be overridden (say external pump overrun
failure after shutdown) the temperature limit thermostat will trip initiating a boiler shutdown, preventing the boiler
from firing. The code (111) on the controls display will flash indicating that the temperature limit thermostat has
tripped.
2. Before attempting to reset the limit thermostat the boiler must be allowed to cool to normal operating
temperature. If, after pushing the reset pushbutton and resetting the lockout (refer to section 8.2.4 - Controls
Operation), the lockout code on the display does not extinguish and the boiler does not fire up, it is possible that
the limit thermostat will not reset because the boiler is still too hot.
3. Always carry out an investigation to ascertain the reason for overheating. The most common cause of
overheating lack of water flow rate through the boiler - possibly due to external pump problem.

9.2 Ignition Controller

1. The flame is under constant supervision by the burner ignition controller. The controller monitors the flame's
ability to rectify an AC current. If the flame diminishes for whatever reason and the rectified current drops below
the controller's minimum detection current (3µA DC), the controller will de-energise the gas control valve within 1
second and commence a restart. Failure to establish and detect a flame during the light-up sequence will result in
burner shutdown and lockout within 5 seconds, requiring a manual reset to restart the ignition sequence. Refer to
section 8.2.4 - Controls Operation
2. If the boiler continues to lockout, then an investigation must be made to ascertain the cause. Refer to section
8.2.10- Controls Operation, for possible causes of lockout.
3. A false flame signal at the start and during pre-purge will cause the boiler module to restart its ignition
sequence at the end of the pre-purge period. If this occurs 3 times in succession the controls will disable
operation of the boiler module, requiring reset of the module. Refer to section 8.2.4 - Controls Operation.
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HAMWORTHY HEATING LTD WESSEX MODUMAX 100 SERIES 500001123/C