Boiler Lock-Out

[garrytheskate]

Saunier Duval SB30e
I have had this problem for over a year with a competent CH man visiting 6 times and not being able to sort the problem.
Just to explain that when the system calls for heat or HW the boiler starts up then after a few seconds goes to lock-out. Previously with the pump on the fastest speed if I pressed the reset button the boiler would fire up and run, no problem.
What I did today is select the slowest speed on the pump. The boiler starts up as before and goes to lock-out. If I press the reset button it will run for a few seconds and go to lock-out every time.
Items replaced so far - PCB, Gas Valve, igniters, thermister, boiler cut out.
Anybody got any ideas
Regards

 

[Agile]

I have had this problem for over a year with a competent CH man visiting 6 times and not being able to sort the problem.

Items replaced so far - PCB, Gas Valve, igniters, thermister, boiler cut out.

Anybody got any ideas

Regards

My idea is that he cannot be competent if he is unable to diagnose the problem in a common boiler.

Changing all those parts indicates to me that he is a parts changer with no inkling of how to actually diagnose boiler faults.

Tony