TEMPRA 30
37
8. FAULT FINDING
Before beginning any fault fi nding ensure that gas, water and electricity are available.
WARNING
: DO NOT link any terminals on block X10 or X11 as this will damage the PCB beyond repair.
8.01 Operating Sequence
With the power established the boiler is in its stand-by mode i. e. power on but no demand. The operational
sequence for C.H. and D.H.W. are as follows:
Central Heating Mode
External Call for Heat:
The temperature regulator, built in or remote clock and room thermostat, if fi tted, must
all call for heat. This will cause the pump to run.
Internal Call for Heat:
C.H. fl ow temperature sensor, 88°C high limit all calling for heat. If both external and
internal calls for heat are present the PMF03 PCB will energise.
In demand the fan will go to high speed causing the air pressure switch to operate. If the overheat (100°C) stat is
closed circuit the ignition will operate and the gas valve will be energised.
The burner will light at ignition burner pressure, automatically range rating itself up to the heating load, then
modulating down when the boiler reaches the desired fl ow temperature. When the central heating is satisfi ed the
burner will go off and the fan stops i.e. stand-by mode.
Note -
If the boiler thermostat is set to maximum than the burner pressure will go to maximum effectively
bypassing the auto range rating facility
8.02 Limit thermostats
T/Stat Location Function Nominal Circuit Wiring
Operating Colours
Temperature
C.H. Limit
Top RHS Shuts downmain 88°C Low voltage Blue
of Heat burner if boiler DC Brown
Exchanger thermostat fails
Frost
Incorporated Fires the boiler 7°C - 14°C Low voltage Red
in C.H. and runs pump to DC Red
Sensor maintain minimum
water temperature
Overheat
Top LHS Protect boiler by 100°C 240V AC Brown
of Heat stopping ignition Blue
Exchanger and cuts power
to gas valve
8.03 PMF03F PCB
The PMFO3 PCB has fi vediagnostic lights, each light corresponds to a particular function and will light in turn as
the boiler goes though its sequence of operations.
In order, the four lights indicate:
1
Boiler On Indicate
2
Boiler Shut down warning
4
Central heating standby (Flashing Light)
Central Heating circuit ON (Permanent Light)
5
Insuffi cient pressure in Central Heating System (Flashing Light)
Electric power supply ON (Permanent Light)
Note:
Always check for suffi cient gas supply (20mbar inlet working pressure for NG and 37mbar for LPG).
Minimum of 22 mm diameter pipework on C.H. fl ow and return with adequate by-pass. A correctly installed
fl ue system and a 3 amp fuse.
When operating the C.H. the following lights should be on: 4, 5 and fl ame on light.
