Vaillant Turbo max 824 /2e fault code f 22

[mew]

I have a valiant turbo Max boiler which keeps locking out with fault code f22 which is(low water or no water in the system)i have had a valiant engineer around to fix the problem but he reckons it's a system fault he said it needs a inhibitor adding to the system as the was non added when the system was installed the engineer that fitted this system at the time said it didn't require it the system is about four years old, I have flushed the system with a cleaning agent and added a inhibitor and bled the system but after about four days the problem reappears, I suspect it might be the PCB as there is new part number for the PCB it looks like they have replaced the board, I would appreciate any help or advice on the subject, mike

[G.W. Walker]

There is a newer PCB for that boiler -- I had to get one to fix an odd diverter valve problem. No idea what else they changed on that board, though.

[Ed Sirett]

I had this on the only model that failed out of the box. It was due to duff NTC(s) which were replaced under warranty.

So provided the pump is going and there is water in the system and the auto air vent is working correctly then try new NTCs.