Set Appliance State:
Mains Power Off
Set Multimeter to AC Volts 
CH Demand
DHW Selector in Minimum (-) position
CH Selector in Maximum (+) position
ON/OFF Switch in ON position
DHW Selector in Minimum (-) position
CH Selector in Maximum (+) position
ON/OFF Switch in ON position
Use Insulation Mat as required
Ensure external controls are calling
Ensure external controls are calling
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure voltage across terminal marked 3 and the terminal marked N on the controls installer interface.
If no external controls are fitted then a link should be present between terminals marked 3 and 4 on the installer interface.
If no external controls are fitted then a link should be present between terminals marked 3 and 4 on the installer interface.
Isolate as per TOPs P4
and refit as necessary