VAILLANT ECOTEC BOILER F54, F28, F29 fault codes, what does this mean? And how to fix? Gas Valve? 

Vaillant Ecotec boilers, since 2012, have a major fault with the Gas Valves.
The new modified valves are incredibly over engineered, and the stepper motor solenoids are constantly jamming or failing.
This applies to all the boilers in the range. Incl the Vaillant Ecotec 831 824 832, 6 series etc.
Vaillant appliances have had this issue ongoing for the past 8 years.
For more technical information visit:
/ vaillant (Smart Monkey)
Thanks for watching... Mark