Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Disconnect EBUS wiring from connector X100 and make safe
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

With the EBUS external controls disconnected does
the boiler respond to a CH demand?
Note:
Ensure the wire link fitted between the 24 volt external
connections is left in place.