Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
CH Demand
Disconnect leads from Differential Pressure
Switch Microswitch and make safe
ON/OFF Switch in ON Position
CH Temp Selector in Maximum position
DHW Temp Selector in Minimum position
Mode Selector Switch in Heat and Hot water position
Switch Microswitch and make safe
ON/OFF Switch in ON Position
CH Temp Selector in Maximum position
DHW Temp Selector in Minimum position
Mode Selector Switch in Heat and Hot water position
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
If required reset boiler, turn CH / DHW control to reset position.
Allow Pump to run.
Measure resistance across the exposed terminals of the Microswitch.
Allow Pump to run.
Measure resistance across the exposed terminals of the Microswitch.
Isolate as per TOPs P4
and refit as necessary