Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
Selector switch to hot water
DHW temperature selector to maximum
Set flow rate at hot tap to approx 4l/min
DHW temperature selector to maximum
Set flow rate at hot tap to approx 4l/min
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Allow burner to ignite and water to heat for approximately 30 seconds.
Measure the voltage across the grey wire (-ve probe) and black wire (+ve probe) at the connectors on the gas valve.
Turn down the DHW temperature selector to low and observe the multimeter.
The voltage should change as the temperature demand is met. The voltage should vary between 9.5 V DC to 2.5 V DC.
Note:
The voltage is unlikely to be stable and may modulate down and back up in an attempt to maintain temperature of the hot water.
Measure the voltage across the grey wire (-ve probe) and black wire (+ve probe) at the connectors on the gas valve.
Turn down the DHW temperature selector to low and observe the multimeter.
The voltage should change as the temperature demand is met. The voltage should vary between 9.5 V DC to 2.5 V DC.
Note:
The voltage is unlikely to be stable and may modulate down and back up in an attempt to maintain temperature of the hot water.
