Boiler constantly fires - strange Y/S plan hybrid??

bc13 · 22 Apr 2015

My boiler is firing whether the programmer is on or off. There is no stat in the house as far as I can see. The programmer has been replaced, didn't make any difference, the heating is still constantly on.

Having looked at the controls there is a 3 port valve, which then leads into a 2 port valve on the HW side. The heating side of the 3 port Ts off, one way to downstairs but then one way to another 2 port valve on the pipe.

Pretty confused as to what's going on. Sure it's a wiring fault but the electrician won't do anything until I figure out if it's Y plan or S plan, and to me it seems a strange combination of the two. No idea what the two 2 port valves are doing on the system, they seem redundant.

Any help would be great pease!

TeaTime · 22 Apr 2015

Hopefully some of the more experienced guys on here can offer some better insight, but, for me it sounds like you have two extra 2 port valves on a Y-plan. Not sure why you would need them though if the three port is functioning correctly.

Have you got a diagram of yourfull system?

45yearsagasman · 22 Apr 2015

More info required. Cylinder type, boiler make/model, maybe a photo of the valves etc in airing cupboard. It may well be one of the valves telling the boiler to fire.

bc13 · 22 Apr 2015

The boiler is one of those little compact Pottertons, Envoy i think. Not sure on the cylinder.

FiremanT · 22 Apr 2015

BC:Are you the householder, or a plumber? If the former, them the sparks, if he is being paid, ought to help identify. He should be able to identify what is switching what.

Maybe it is a DIY install, the 3 port being operated by the programmer, the 2 port being operated by the cylinder stat. Can't imagine why, but then, I can't imagine why there is a 2 & a 3 port.

The heating on all the time is probably a stuck on micro switch on 2 port.

bc13 · 22 Apr 2015

Thanks Fireman, yes he should but I think he's in the dark as much as I am and has no idea what's going on.

I don't know if it's a DIYer but the people in the house previously lived with the heating on for 2 years and just opened the windows as a solution instead of getting it fixed.

steve32 · 22 Apr 2015

Is the hot water cylinder an unvented cylinder.

bc13 · 22 Apr 2015

Nope. Conventional set up, only differneces are a recirculating HW pump and then the suspect port valves.

45yearsagasman · 22 Apr 2015

Not going to post photos? It would save a lot of guesses.

bc13 · 22 Apr 2015

Can't i'm afraid, no longer at the house. Was just hoping someone had come across this before.

ollski · 22 Apr 2015

I'd imagine one of those zone valves has a sticky microswitch, dont need a sparky just a heating engineer with a multimeter.

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Boiler constantly fires - strange Y/S plan hybrid??

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