Y plan heating problem low voltage

[SimonH2]

the cylinder stat has a short piece of 3 core flex which goes to the wiring centre

That's wrong, needs to be 4 core unless they've used the green/yellow as a live which is still wrong.

 

[stuartR1963]

That's wrong, needs to be 4 core unless they've used the green/yellow as a live which is still wrong.

They did they used the green/yellow for the cylinder stat 2 terminal (satisfied). Naughty but all too common practice It seems.

 

[SimonH2]

Naughty as in, not allowed by the regs. It's debatable whether oversleeving of a green/yellow core (of a multi-core cable) with another colour is allowed - I think the consensus is that it is. But apart from that, there is a requirement for there to be a CPC to the stat even if the stat doesn't need it (can't find the reg number offhand) - IIRC the only exception to that requirement is for the dangling bit of a pendant luminaire.

 

[rsgaz]

(can't find the reg number offhand)

411.3.1.1

 

[stuartR1963]

Hi all, sorry for late reply, I think I can now safely say that one of the micro switches in the valve has failed, likely the one that links the white and the orange.
Just to clear a few things up, when I was measuring the voltage, The probe was on orange and (blue) neutral then earth, I get 85-90v, however this still activated boiler. I temporary put the pump live back to the demand terminal, which has orange,blue (cylinder stat call) and boiler switch live, neither the pump or the boiler switched on at all, I waited about 10 seconds to give the valve time to move but nothing, when I measured the voltage between demand neutral and earth there wasn't any.

just thought I would give you an update
Can this be fixed without changing the valve or head?
thanks

 

[SimonH2]

Usually a microswitch can be changed - there are several standard sizes and you should be able to find a matching one. It'll probably mean some DIY & soldering.
You are looking for the same body size and actuator style (long lever, short lever, button), same contacts (changeover vs normally open - but a c/o can be used to replace either), and check that it's OK for 250V & 3A (the likely supply fuse rating).