my Vaillant thermocompact combi will not light. fault no f.28?
I switched off boiler to flush out a cold radiator. Refilled system till pressure was ok,bled the system ok,switched boiler back on and after a minute or so fault no 28 is displayed.
In the manual this indicates no gas, bit all other gas appliances ok.Have tried resetting as stated in manual to no avail
to fix this fault, underneath or around the boiler case somewhere, there is a little valve connected to pipe( in my boiler there is just one valve), open that valve carefully while keeping an eye on the Bar Gauge i said earlier. opening the valve MUST increase the pressure and push the gauge to the green area. when the guage hand reached somewhere betwwen 1 and 2, close the valve again and fire up the boiler... it should fix the problem....
Hadi
December 2010
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