prima 40c burner and pilot light goes off after few seconds

[sidplumb]

Greetings to all RGIs
I am a plumber by trade and not very experience with boilers, and i turn to you all for help.
In my own house i have a prima 40c. When burner lights up,after about 30 to 40 seconds i hear a click burner goes off and cuts the pilot lights off. At that point water in the systems does not get very hot. Pump carries on working,pilot light takes longer to light up and will stay on if no request is made for heating or hw.recently i hve changed the boiler stat because of the same reason but it has started up again,
I suspect the overheat stat but i like your opinion 1st

Your help will be appreciated

My thanks in advance

 

[sidplumb]

Just like to add after pressing the trip switch the burner and pilot lght goes off after few seconds

 

[twgas]

are you gas registered?

 

[penfold46]

Get the Flue checked ASAP by an RGI.

 

[sidplumb]

I am not an RGI
your advice taken and will call an RGI

appreciate your input in this matter many thanks to you all

 

[sidplumb]

Mr P a Gas Safe engineer who happened to be a friend of mine came down to day at 7pm.
he went through the usual check and then turned the boiler on burner fired up within few seconds burner and the pilot light went off.He then took the front casing of ignited the pilot light operated the boiler burner lit up,straight after a clicking sound and burner including the pilot light went off and there he said "its the OVERHEAT THERMO.
He took the inner draught assembly and flueway buffer assembly gave it a good clean as well as the burner fitted new thermo and its all working now.

He did not charged me but i have given him £90 which he refused to take but after lengthy persuasion he took it.

Now i am wondering did i paid him less cos i don't know how much is the thermo please advice cos if i have paid him less i want to pay him what the job is worth.

He just rang me and passed me a job which is complete bathroom re fit.

So all is well.

And once again thank you all I think i will do my acs next month.

regards

Sid

 

[sidplumb]

I am afraid i spoke to soon and problem still exsits
whn hw called for burner fires up 3 seconds later clicking sound from the gas valve, burner and the pilot goes off,

Mr p the gas safe engineer changed the heat thermo and 3 days earlier boiler thermo was changed. Called Mr P he is away till the weekend.

After observation i notice whn the boiler is working on HW only, heats up to a high temperature and modulate as well. but heat is not despersing pump working fine and does over run and HW in the cylinder gets very hot.
If i slide the lever on the 3 port valve in the manual position the boiler stays on and can feel heat dispersing after the pump.
but not on hw at a v.high temp it shuts off

can any one help pls

regards

sid

 

[mysteryman]

Check if your pump is running, and that there are no airlocks.

 

[sidplumb]

Pump is running and i belive no airlock. its on position 3 .
any other sugestion