Set Appliance State:

Mains Power Off
Ensure no demands
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Monitor the boiler display after mains power is turned on.
How long does solid red lockout take to occur?
Note:
Use ON/OFF switch to repeat test if necessary.
If solid red occurs after a significantly different time or does not reoccur click HERE to use full diagnostic model.