Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
CH Demand
Gain access to PCB (use Insulation Mat as required)
Ensure all external controls are calling
Ensure all external controls are calling
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Measure the AC voltage between the terminal marked RT at the connector for the incoming 240v external controls and a suitable earth.
Expect mains voltage.
Note:
If the appliance is fitted with 240v external controls the link present between the two terminals for 24v controls (white section of connector X100) should have been removed.
Expect mains voltage.
Note:
If the appliance is fitted with 240v external controls the link present between the two terminals for 24v controls (white section of connector X100) should have been removed.
 pcb in situ.gif)
 connector x1.gif)
Isolate as per TOPs P4
and refit as necessary