Set Appliance State:

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

Observation:

Ask the customer under which circumstances has/does the excessive pressure situation occur.
Is it during CH operation?
(see note)
Is it over a period of time?
(including when the appliance is not in operation)
Note.
If excessive pressure occurs during CH operation, then when system cools the pressure would been seen to decrease.