The reading on the pressure gauge might not be accurate
I would drain all water from the boiler and see if needle on pressure gauge DROPS
If needle still shows pressure in boiler after draining all water then the pressure gauge is defective hence F22 fault
There are other causes of F22 but I would try this first
Q
August 2015
You must have missed this when you did a search to try and help yourself before asking us: http://www.vaillantservice.co.uk/Vaillant_Fault_Codes.html
F.22 Dry fire, low water in system/Overheat
See this, which may also be useful: http://www.justanswer.com/uk-plumbing/7jyg6-vaillant-turbomax-plus-828e-pressure-1-5.html
XXX
August 2015
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