Set Appliance State:

Mains Power Off
Turn Hot Water Tap On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Observe the burner while the
appliance operates for hot water.
Does the burner remain lit throughout
(i.e. hot/cold is due to modulation)
or does the burner cut out completely?