Set Appliance State:
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
CH temperature selector to 0 position
DHW temperature selector to 0 position
Disconnect flame sense lead at inline connector
Attach -ve probe via crocodile to the flame sense lead attached to the electrode
Place +ve probe to earth
CH temperature selector to 0 position
DHW temperature selector to 0 position
Disconnect flame sense lead at inline connector
Attach -ve probe via crocodile to the flame sense lead attached to the electrode
Place +ve probe to earth
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Allow appliance to self check and return to standby mode.
DHW temperature selector to maximum position.
Allow fan to run and burner to ignite.
Measure voltage.
Expected voltage approximately 0.85 Volts DC.
Note:
DC voltage will only be present while the burner is alight.
DHW temperature selector to maximum position.
Allow fan to run and burner to ignite.
Measure voltage.
Expected voltage approximately 0.85 Volts DC.
Note:
DC voltage will only be present while the burner is alight.
Isolate as per TOPs P4
and refit as necessary