Worcester 28I switches off after a couple of minutes

[swintondude]

Good Evening All,

I am having a problem with my Worcester 28I. I shall explain.
I have a kitchen sink, bathroom sink and bath all connected to my combi. I also have 4 rads connected. I replaced the fan approx 2 years ago. My problem is this:-

If I turn on the hot water taps on any of the sinks (kitchen, bathroom and bath) then the combi switches itself off after 3 minutes (the flames ignite normally and the water temperature is as it should be) This same thing happens with the heating, if I switch it on then it fires up and after 3 minutes, it switches itself off.

If I wait a while ot even power off/on the combi then it will work again, ONLY for about 3 minutes though.

I have tried to do some research into this but am getting all kinds of suggestions ranging from replacing the gas valve, to changing the board, to thermistor fault or air pressure switch fault. I am hoping that someone has come across this before and can tell me how they resolved the problem.

 

[clf-gas]

Simples, check the pump

 

[bengasman]

If this is the old model, non condensing, it is a biflow which would make the hex my first suspect. I doubt it is the thermistor as it is unlikely to give exactly the same fault on ch and dwh. Could be any of the other suggestions, hard to say without being in front of the boiler, and you can add aps and venturi to the list.