Fault finding and diagnosis
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Greenstar 4000 – 6 720 891 162 (2020/09)
System gassing
WARNING
If you suspect the heating system is gassing, you must exercise
caution when carrying out testing or remedial work as the gasses
produced can be flammable.
Do not vent air from radiators whilst the central heating is switched
on. Allow 30mins after venting the radiators before using the
central heating or hot water.
▶ Whilst venting radiators, do not allow the pressure on the boiler to
drop below the point at which it is normally set.
▶ If the system is to be drained, the boiler must be electrically isolated.
CAUTION
If system pressure is repeatedly increasing, even when the
appliance is not operating, you should first check that the filling link
is fully closed and confirm that it is not passing. If radiators are also
not heating to the top of the panels and repeatedly need venting, the
heating system may be suffering from gassing. This is an indication
that corrosion is taking place and requires the system being cleaned
and treated to BS7593:2019.
▶ This should be confirmed by taking water samples to check pH levels
and turbidity.
▶ Failure to properly maintain the heating system may result in damage
to the system and appliance, and may affect the boiler warranty.
