Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
DHW Demand
Attach "U" gauge to outlet pressure test point
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Observe fan and "U” gauge
Expected sequence of events: After approx 12 seconds fan runs
After approx 24 seconds gas valve opens gauge shows a pressure of 9.3mb
sparking occurs burner ignites and establishes (remains alight)
Click on your observation:
1. FAN RUNS BURNER IGNITES AND ESTABLISHES

2. FAN DOES NOT RUN
3. FAN RUNS SPARKING DOES NOT OCCUR

4. FAN RUNS SPARKING OCCURS BURNER DOES NOT IGNITE
5. BURNER IGNITES BUT DOES NOT ESTABLISH

6. BURNER IGNITES BUT BAFFLES OUT OR FLAME LIFTS OFF
When gauge is removed pressure test point should be tightened and checked for gas tightness.