Flow/Return Reversed; Cylinder Thermistor Fault (If Fitted); External Interlock Open - Keston HEAT 2 45 Installation & Servicing

5.11 FLOW/RETURN REVERSED

Is the Pump connected the correct way?
Check that the system pipework is correct

5.12 CYLINDER THERMISTOR FAULT (IF FITTED)

Is a DHW Thermistor connected to the boiler?
Is the wiring securely connected at both the boiler and
cylinder thermistor?
Disconnect the wires to the cylinder thermistor. Check
the resistance using a suitable multimeter connected
across the thermistor's terminal pins.
At 25°C expect 9,700 - 10,300 Ω
At 60°C expect 2,400 - 2,600 Ω
At 85°C expect 1,000 - 1,100 Ω
Is the thermistor value correct?
Does the cylinder thermistor wiring between the boiler
terminal strip and the PCB have continuity and is
securely connected?

5.13 EXTERNAL INTERLOCK OPEN

Is an External Interlock connected to the boiler?
yes
Has the External Interlock operated?
no
Does the wiring from the Interlock Relay (mounted
within the boiler) to the terminal strip have continuity and
is securely connected?
Installation & Servicing
SECTION 5 - FAULT FINDING
yes
yes
yes
yes
no
Reverse Pump
no
Change menu setting for DHW Sensor
to "Switched Live"
no
Securely connect the wiring at both
the boiler and cylinder thermistor
no
Fit a new cylinder thermistor
no
Ensure the wiring has continuity and is
securely connected
yes
Replace main PCB
Ensure that a link wire is securely connected
no
across the terminals marked "External
Interlock" in the boiler terminal strip
yes
Reset the External Interlock
no
Ensure the wiring has continuity and is
securely connected
yes
Replace the Interlock Relay Kit
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