HAMWORTHY HEATING LTD
WESSEX-HE 200 BOILER
500001008/K
13
12.0 FAULT FINDING
The controller fitted to the Wessex-HE 200 boiler
incorporates a rotating coloured disc fixed to the cam
timer which provides information with regard to the
position that has been achieved at any point in the
sequence. This disc with the relevant sequence
information is shown in Figure No. 7 and in general
the fault can be located by observing the position at
which the disc stopped rotating and the functions
controlled to that point.
BOILER SEQUENCE CONTROLLER, OPERATION
AND FAULT FINDING
12.1 Summary of Safety Features
1. Flame failure when running results in burner
shutdown and lockout within 1 second.
2. Failure to establish and detect a flame during the
light-up sequence results in burner shutdown and
lockout within 2 - 5 seconds from the initial release of
fuel.
3. Air supply failure at any time, results in burner
shutdown and immediate lockout.
4. The differential pressure proving switch, is
checked in both the "no air" and "air supply proved"
positions.
5. Restoration of the power supply after an
interruption, results in a full light-up sequence to
safely restart the burner. Power failure after a
lockout, will not interfere with this condition when the
supply has been restored.
6. False flame signals at the start point and during
pre-purge result in burner shutdown and lockout.
7. The light-up sequence can only commence
providing the cam switches and relay contacts within
the control box are at their correct relative positions,
and continuity of the lockout relay circuit is proved.
12.2 Fault Finding - See Figure No. 7.
1. Fan will not start.
Coloured programme indicator
stopped in white sector.
a) Check electrical supply is switched on.
b) Check that thermostat circuit is "calling for heat"
and time switch circuit (if fitted) is made. A 230-Volt
supply on the Programmer Terminal No.1 will
determine this.
c) Check that the remote stop/start circuit loop across
terminals C5 and C6 is made. Check Fascia mounted
switch is in the ‘ON’ position.
2. Burner will not start.
Synchronous motor runs,
coloured programme indicator rotates but burner
does not start.
Check differential pressure proving switch is in
correct state i.e. “no air” position.
3. Fan starts but the boiler goes to lockout.
Programme indicator stopped on red line in blue
sector.
a) Check differential pressure proving switch.
b) Check that a load, e.g. pilot gas valve is connected
to terminal C.
c) Check continuity of pilot gas valve coil winding.
d) Check for flame simulation or false flame signal.
4. Fan starts but the boiler goes to lockout.
Coloured programme indicator stopped in blue sector.
a) Check for combustion air supply failure.
b) Check for flame simulation, if necessary, change
control box.
c) Check for continuity of pilot gas valve coil circuit.
5. Burner starts, flame established but control
box goes to lockout.
Coloured programme indicator
stopped at end of first yellow sector/start of red sector
or in red sector.
a) Check that flame detection probe is in contact with
the flame.
b) Check that flame probe insulator is not cracked. A
cracked insulator will be sufficient to give rise to an
AC current leakage.
c) Check that flame probe is not in contact with other
metallic parts of the burner.
d) Check gas supply turned on.
6. Burner starts, flame established but control
box goes to lockout.
Coloured programme indicator
stopped at end of 2nd yellow/start of green sector.
This is an indication that the main flame has not been
established or detected and lockout has resulted
immediately the interrupted pilot has been switched
off.
7. Burner starts, flame established but control
box goes to lockout.
Coloured programme indicator
stopped in green sector.
Check that when main gas valve is energised, a
change in combustion or flame characteristics has not
