Heating shuts down after 10-15 mins; Expansion Vessel?

[dazzawazza]

Hello,

I have a malfunction in the heating system of my Glowworm Swiftflow 75E.
After 10-15 of the heating being on, from cold, the boiler shuts down (incl the pump).
After 10 or so minutes it comes back on, sometimes requiring the reset button to be pressed.
The domestic hot water seems to work fine.
I've watched the pressure gauge just before shut down and the pressure increases suddenly by 1 bar before shutdown.

Any ideas?

Thanks

 

[dazzawazza]

Also, the radiators warm up slightly after a long shower or bath. I've been advised that the heating problems could be due to a faulty diverter valve, however I think this model has a twin tube heat exchanger instead?

Another idea is that the expansion vessel needs replacing. Could a faulty expansion vessel cause a sudden increase in pressure then shutdown after 10-15 mins? (The radiators aren't very hot at this stage).

Just before shutdown there is a ticking sound then as the pressure increases there is a gushing sound and banging.

Any advice please?
Cheers.

 

[dazzawazza]

After posting last night I tried the heating and it lasted a lot longer without gaining 1 bar pressure and cutting out.
By the time it did cut out , the radiators were very hot and I would have though the thermostat would have already engaged cutting the flame normally.

 

[dazzawazza]

Any ideas?
There's a definite ticking sound before the sudden rise in pressure.
This is back down to 10 minutes from cold.

Cheers