Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
Turn Hot Water Tap On
CH temperature selector to 0 position
DHW temperature selector to 0 position
DHW temperature selector to 0 position
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Reset lockout as necessary.
Test 1:
DHW temperature selector to maximum position. Allow fan to run.
Measure voltage across the connections on gas valve 1 (grey leads, solenoid farthest to the right). Expected voltage approximately 26 volts DC DHW temperature selector to 0 position.
Test 2: Reset lockout as necessary. DHW temperature selector to maximum position. Allow fan to run.
Measure voltage across the connections on gas valve 2 (grey leads, middle solenoid). Expected voltage approximately 26 volts DC
Note: Voltage will only be present for approximately 5 seconds after the fan has started to run and appliance will go to lockout as burner will not ignite.
Test 1:
DHW temperature selector to maximum position. Allow fan to run.
Measure voltage across the connections on gas valve 1 (grey leads, solenoid farthest to the right). Expected voltage approximately 26 volts DC DHW temperature selector to 0 position.
Test 2: Reset lockout as necessary. DHW temperature selector to maximum position. Allow fan to run.
Measure voltage across the connections on gas valve 2 (grey leads, middle solenoid). Expected voltage approximately 26 volts DC
Note: Voltage will only be present for approximately 5 seconds after the fan has started to run and appliance will go to lockout as burner will not ignite.
Isolate as per TOPs P4
and refit as necessary