Ideal Heating LOGIC+ SYSTEM S18 - L4 or F4 - Control; no Flow Thermistor Fault; F5 or L5 - Return Thermistor Fault; F6 - Outside Sensor Fault

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FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING FAULT FINDING
Installation and Servicing
SECTION 4 - FAULT FINDING
4.8 ‘L4’ OR ‘F4’ - CONTROL / NO FLOW THERMISTOR FAULT
4.9 ‘F5 OR L5’ - RETURN THERMISTOR FAULT
Remove the Control/No Flow Thermistor from the
Heat Exchanger and disconnect the wires.
Check the resistance using a suitable multimeter
connected across the thermistors terminal pins.
At 25
o
C expect 9,700 - 10,300 Ohms
At 60
o
C expect 2,400 - 2,600 Ohms
At 85
o
C expect 1,000 - 1,100 Ohms
Is the Thermistor value correct?
Remove the Return Thermistor from the CH Return
Pipe and disconnect the wires.
Check the resistance using a suitable multimeter
connected across the thermistors terminal pins.
At 25
o
C expect 9,700 - 10,300 Ohms
At 60
o
C expect 2,400 - 2,600 Ohms
At 85
o
C expect 1,000 - 1,100 Ohms
Is the Thermistor value correct?
YES
YES
NO
NO
Replace PCB
Replace PCB
Fit a new Thermistor
Fit a new Thermistor
Is there continuity between the PCB and Thermistor?
Is there continuity between the PCB and Thermistor?
NO
NO
YES
YES
Check and replace wiring as
necessary
Check and replace wiring as
necessary
4.10 ‘F6’ - OUTSIDE SENSOR FAULT
Disconnect the wires to the outside sensor.
Check the resistance using a suitable multimeter
connected across the Outside Sensors terminal pins.
At 0
o
C expect 31,000 - 35,000 Ohms
At 15
o
C expect 15,000 - 16,500 Ohms
At 30
o
C expect 7,700 - 8,500 Ohms
Is the Outside Sensor value correct?
Replace PCB
Fit a new Outside Sensor
Is the wiring securely connected between the
incoming terminal block boiler connection of
the Outside Sensor and the PCB?
NO
YES
Securely connect the wiring at
the Terminal Block and the PCB
Is the wiring securely connected at both the boiler and
Outside Sensor?
YES
YES NO
NO
Securely connect the wiring at both the
boiler and Outside Sensor