glowworm boiler cutting out after half an hour

[tonyguy38]

I have a glowworm economy plus 50f boiler which was installed in 1994. Theboiler will come on when required by the timer but cuts out after halfan hour to an hour. If i then go and lightly tap the boiler the boiler ignites again but then cuts out again after half an hour. Sometimes the boiler does not come on when required and just makes a slight hiss, but when i tap it it comes on. Please help!
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[tonyguy38]

I have posted the same question to glowworm and they have suggested 3 causes: air pressure switch, bad electrical connection or a sticking relay, does this ring any bells with anyone?

 

[gas4you]

Well it could be any of the 3 It could also be the gas valve sticking.

Where/what are you tapping to make it come on?

 

[tonyguy38]

Basically just the slightest tap on the outside housing of the boiler usually does the trick.

 

[gas4you]

Top, bottom? It is hard to answer this without being there to test for your self each possible component.

 

[tonyguy38]

ok see where you're coming from. there is a panel at the bottom which comes off and behind this is the housing for the control box which has an overheat button, and the thermostat control on the front of it, i usually tap around this area notat the top of the boiler.hope this helps. note i tap the cover which is still on, not the actual control box itself.

 

[gas4you]

Unfortunately all the things Glow Worm tech have mentioned are all located roughly in the same are on this boiler, so a general tap could be affecting any of them.

As it seems it is a light tap you are using I would discount the gas valve for now.

I would personally check the APS and PCB relays.

What is occurring with the boiler after half an hour? Has it been switching on and off with its boiler stat up till then?

 

[tonyguy38]

the boiler fires up intermittently about every minute or so when it is working, after half an hour this stops and all the radiators begin to get cold. i then tap the boiler and it immediatley starts up again.

 

[gas4you]

I think I would check the relays on the pcb. It would be best to leave this to an RGI because of the dangerous voltages involved.

As it is switching on/off so much I would have expected an aps to fail sooner than just after 30 mins.

Unfortunately I think it is one of those faults that you need to be there to diagnose. All we can do is offer suggestions as Glow Worm tech have done.

 

[tonyguy38]

ok,thanks for all your help and advice,much appreciated