Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Turn Hot Water Tap On
DHW temperature control to MAX
Refit combustion chamber if this has been removed
Place FGA probe in air inlet test point
(point 2 on diagram), ensure it is fitted
securely to prevent any release of flue gases
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance as necessary.
Allow boiler to complete its self check.
Allow FGA readings to stabilise and check that:
  • O₂ levels are equal or greater than 20.6%
  • CO₂ levels are less than 0.2%
    All performance testers supplied by British Gas are capable of measuring O₂.
    Please refer to performance tester instructions for information.