Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
Gain access to PCB (use Insulation Mat as required)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure the DC voltage between Pin 14 (Green) on X25
and the earth point on the boiler chassis.
The voltage measured will vary according to the system pressure but should conform approximately to the table below.
Is the voltage measured 1 Vdc or greater ?
and the earth point on the boiler chassis.
The voltage measured will vary according to the system pressure but should conform approximately to the table below.
| System pressure | Voltage dc | 0 bar | 1.2 |
| 1 bar | 1.7 |
| 2 bar | 2.2 |
| 3 bar | 2.8 |
Is the voltage measured 1 Vdc or greater ?
Isolate as per TOPs P4
and refit as necessary