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 AC Volts 
Use Insulation Mat as required
Gain access to main terminal block
Gain access to main terminal block
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
With no demand for heating check for mains voltage between terminal 1 (blue) and earth of the main terminal block.
Note:
Any external frost protection is also wired at these terminals, further investigation of the installed system to diagnose faulty component may be necessary.
Note:
Any external frost protection is also wired at these terminals, further investigation of the installed system to diagnose faulty component may be necessary.
Isolate as per TOPs P4
and refit as necessary