Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Ensure there is no demand for either CH or DHW
Set Multimeter to DC Volts 
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure the voltage between pins 8 (Black) and 9 (Red) of plug X22 and compare the reading to the table below.
Does the voltage reading correspond to the system pressure?
| Pressure (Bar) | DC Volts | 0.7 - 0.9 | 1.4 - 1.7 |
| 1.0 - 1.2 | 1.8 - 2.1 |
| 1.3 - 1.5 | 2.2 - 2.5 |
Does the voltage reading correspond to the system pressure?
Isolate as per TOPs P4
and refit as necessary