Replacement Of Failed Components; Hot Surface Ignitor And Flame Probe Assembly; Flow/Return Sensor; Temperature Limiter - Hamworthy Wessex ModuMax mk3 WM97/97H Installation, Commissioning And Servicing Instructions

in place the gap between the ends of the baffle and the
end plates must be sealed with silicon sealant. Remove
the existing heat exchanger to casing sealing gasket
and fit the new gasket previously hung on the lifting eye.
Clean mating surfaces of the heat exchanger tube
header castings and cover plates. Re-assemble the
heat exchanger assembly using new gaskets.
Ensure that the cover plates are re-fitted in the
correct orientation. Evenly torque the bolts and
nuts to 7kg m.
Refit heat exchanger ensuring correct rotational
orientation, so that the water connection nipples and
safety valve pipe pass through the holes in the rear of
the casing, fastening in place with the 6 M10 nuts. Refit
the water connection and safety valve pipe sealing
plates, renewing all gaskets and o-rings. Reconnect the
system pipework and check for soundness.
Ensure that the cover plates are re-fitted in the correct
orientation. Evenly torque the bolts and nuts to 7kg m.
Re-fit the burner assembly. Test all gas joints broken
or disturbed for soundness before firing.
Refer to Section 8 Commissioning The Boiler, for
correct procedures.

11.0 REPLACEMENT OF FAILED COMPONENTS

There are a number of components listed below which
can be replaced simply and quickly by following the
given procedure. In each case the operation of each
replaced component must be checked by carrying out
the appropriate part of the commissioning procedure.
See Section 8: COMMISSIONING & TESTING.
Note:- Isolate all electrical supplies to the boiler
module before removing the front cover and
commencing any
exchange procedure.
removed, turn off the gas supply at the service
valve.
11.1 Hot Surface Igniter and Flame Probe Assembly
Part Nos. 563801019 & 533805021
Note:- The igniter and flame probe ceramics are
very fragile.
Unplug the igniter from the harness, remove the single
socket cap head screw securing the igniter to the burner
flange and withdraw the igniter. When fitting the
replacement carefully feed the igniter through the
mounting hole and secure with the socket cap head
screw.
Flame Probe - The only maintenance which can be
carried out is to clean the wire of any deposits with an
abrasive paper, taking care not to damage the
electrode. A typical flame current is 10µA, (high fire)
with the lockout threshold at 3µA,
Disconnect the flame probe lead & earth lead, remove
the single socket cap head screw securing the probe to
HAMWORTHY HEATING LTD
servicing or component
With the front cover
Wessex ModuMax mk3 Boilers
the burner flange and withdraw the probe. When fitting
the replacement carefully feed the probe through the
mounting hole taking care not to damage the ceramic.
Note:- Do not remove both securing screws at the
same time as the separate flange and Mica sight glass
will become detached.
Ensure the positions of the igniter and probe are as
recommended in Figure 10.2.
11.2 Flow / Return sensor
Part No. 533901431
The two identical sensors are located in pockets on the
flow and return pipes at the rear of the boiler. To remove
the sensor, unplug the sensor from the harness, loosen
the M3 screw securing the sensor in the pocket and
withdraw the sensor.
Upon replacement ensure that the sensor is fully
engaged and secured into the pocket.
11.3 Temperature Limiter (Limit Stat)
Part No. 531040016
To replace the limiter, remove the boiler front cover
to expose the control panel assembly. Remove the
electrical connections from the limiter body noting
the position of the coloured cables. Unclip and
remove the thermostat bulb from the pocket in the
front of the heat exchanger. Undo the 2 fixing
screws in the front of the control panel and remove
the unit.
Check the operation of the replacement device by
carefully applying a heat source to the bulb. The
temperature of the replacement limit stat is factory
set and will not require adjustment.
Fit the replacement limiter in reverse order ensuring
that the electrical connections are in the correct
positions.

11.4 Gas Valve

Part No. 533903044 (97, 116 & 147)
Part No. 533903036(196 & 254)
Note:- Some gas valve components can be replaced
without completely removing the whole assembly from
the boiler. However, Hamworthy Heating strongly
recommend that a complete new gas valve is fitted to
ensure safe, reliable operation of the boiler. Please
refer to Hamworthy Heating Technical Department
before attempting to remove components from the gas
valve.
Ensure that the boiler module electrical power and gas
supplies are isolated. Unfasten the gas valve plug
securing screws and disconnect the plug by pulling
firmly away from the valve. Unfasten the low gas
pressure switch plug and remove the low gas pressure
switch from the gas valve (97/116/147 only) by
removing the securing screw.
Remove the 4 M5 cap head screws securing the gas
valve to the gas inlet flange, allow the flange to hang
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