Set Appliance State:
Mains Power Off
Set Multimeter to DC Volts 
CH/HW switch in HW position
Ensure that the boiler is cold and ready for Pre-heat
Ensure that the boiler is cold and ready for Pre-heat
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Test for DC voltage across one of the terminals (violet) wires
on the DHW Pre-heat thermostat and the Neutral (blue) on
the mains supply connector block.
Repeat this test on the other terminal (violet) wire on the
DHW Pre-heat thermostat.
Pre-heat thermostat is the upper most of the two thermostats
situated below the diverter valve.
on the DHW Pre-heat thermostat and the Neutral (blue) on
the mains supply connector block.
Repeat this test on the other terminal (violet) wire on the
DHW Pre-heat thermostat.
Pre-heat thermostat is the upper most of the two thermostats
situated below the diverter valve.
Isolate as per TOPs P4
and refit as necessary