Fault Finding - Saunier Duval THEMA F 23 E Installation And Servicing Instructions

FAULT FINDING

Prior to fault finding, check :
Inlet gas pressure = 20 mbar
Electrical supply = 240 V - 50 Hz
Central heating system is pressurised at 1 - 1,5 bar.
Overheat thermostat on RHS of heat exchanger has
not tripped reset if necessary.
Carry out electrical system checks i.e. earth continu-
ity, resistance to earth, short circuit and polarity with
a suitable meter.
Note : these must be repeated after any servicing or
fault finding. Ensure that all external controls are cor-
rectly wired and calling for heat.
The fault finding charts will enable the majority of faults
to be diagnosed. To use the charts effectively, it is
necessary to determine exactly which aspects of the
boiler are working correctly and which are not.
Turn ch temp. control to
max. does burner fire ?
NO
Does pump run ?
YES
Does fan run ?
YES
Is short selector lever on
front of reversing valve in
right hand position ?
YES
Does burner fire when
a hot tap is opened ?
External controls
(if fitted)
Short out external controls
connection on top of
reversing valve. Does
burner fire ?
NO
Remove leaos from boiler
thermistor. Check its
resistance according to
thermistor value table.
is thermistor ok ?
YES
Replace main pcb
CHART 1
26
NO CENTRAL HEATING
NO
Refer to chart n 3
NO
Refer to chart n 4
NO
Refer to chart n 2
YES
YES
YES Rectify wiring
operation faults on
external controls
NO
Replace thermistor
For example:
If the domestic hot water works but the heating
doesn't, refer to chart No. 1.
If heating works correctly but the hot water doesn't,
refer to chart No. 2.
IMPORTANT: Always adopt a logical, step by step pro-
cedure starting at the beginning of the appropriate
fault finding chart.
WARNING. Always isolate the boiler from the electri-
cal supply before carrying out any electrical replace-
ment work.
Always check for gas soundness after any service
work.
Internal control
(clock)
Is there
continuity across
terminals 3 and 4
of clock ?
NO
Is clock calling for
heat ?
YES
Replace clock
YES
Is wiring between
clock and pcb
connection cn7 ok ?
YES
Replace
main pcb