Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Attach temperature probes as indicated by the red arrows
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow burner to ignite and CH to operate and reach a reasonable
operating temperature, approximately 55°C.
Measure the temperature differential across the primary heat exchanger.
Expect a differential of approximately 20°C or less.
Note:
1. Initial temperature differential may be greater than 20°C when system is heated from cold, but should start to reduce as the return temperature rises.
2. To reduce the time for the test the heating load can be
reduced by turning off some radiators.