Y plan wiring conundrum.

[Gr fto reborn]

You know those jobs you wish you never got involved in. I'm in one.
An old friend had a whole new set of controls and a 3 port installed. All Honeywell parts. His gloworm boiler has only ever reached 52 degrees and won't get any hotter. I'm called in. So I get to the bottom of the boiler issue dip switches had been moved. Boiler now works correctly when a switch live is put to it. I then find the boiler is firing on its own when the programmer is off on HW and heating. The cylinder stat was overdoing it somehow even though I went through all the wiring and its all as the Honeywell y plan diagram. I changed the cylinder stat even though it was brand new and presto it all worked and shut off when it should.
i then get a call saying the heating won't come on. So I popped in and cylinder stat is satisfied, programmer is on constant for heating and HW room stat is whacked up but no switch live is getting to the boiler. I turned the HW off on the programmer and the switch live was made and the boiler fired on heating. Turn on the HW and it killed it. So I then turned the cylinder stat up fully and the boiler fired. I then turned the cylinder stat back so it was satisfied. And it kills the switch live again. I tested power was getting to the white cable on the 3 port and there is 240v. I keep thinking there is a problem with the three port but its new. it moves over and fires the heating when the programmer has the HW off but with the HW on and a satisfied cylinder stat no switch live is there. I'm confused. Any help is appreciated.

thanks
greg

 

[lame plumber]

you got the same as me an my s plan im seeing on tuesday, and mine is were the cyl stat is firing up the pump and rayburn boiler even when i have removed the programmer off its wall plate! so its all down to a wiring issue. So come tuesday all out and go for a rewire to ensure its right, only way fwd imho

 

[R1CKY]

You need power to the white AND grey for heating to work by itself. Check that the satisfied terminal from the cylinder stat is connected to the grey on the 3 port.

 

[BLOD]

As Ricky says - sounds like the grey wire n the valve isn't getting power when the cyl stat is satisfied

 

[sonray ltd]

I'm confused. Any help is appreciated.

Sounds like your not getting 230v off the cyl stat satisfied on the grey.
But your getting 230v off the hw off on programmer to grey.

 

[lame plumber]

so whats my issue guys, programmer off wall plate and cyl stat can fire up the boiler and pump!

 

[sonray ltd]

so whats my issue guys, programmer off wall plate and cyl stat can fire up the boiler and pump!

Is the valve open or closed ?
Can be the m.switch stuck on the hw valve.

 

[R1CKY]

Sounds like you've got a permanent live wired to the cylinder stat somewhere Lame. The cylinder stat on an S-Plan should only have power going to it when HW is selected on the timer. Trace the wiring from the stat to the wiring centre and check where the power is coming from. The only things that should have permanent lives in a conventional S-Plan are the timer and the grey wires to the zone valves. If the boiler has pump over run, that needs a permanent live too, but I doubt a Rayburn will have one.

 

[lame plumber]

valve to cyl opens and closes perfectly, micro switch working a treat cyl stat working on/off fine, but all indepentdant of the proogrammer. new tenant had £200 bill for 28 days supply last month, they arent happy, which isnt surprising as the boiler is constantly short cycling. seems to me that who ever wired it all in was clueless, theres a programmable room stat for 4 rooms worth of underfloor heating in a cupboard in the kitchen hanging next to the underfloor flow and return! plus some other examples of how not to wire in a fused spur etc etc. So tues me and my sparks are having a morning rewiring it all in properly.

 

[sonray ltd]

Sounds like it's live to cyl stat is taken from elsewhere but the programmer.

 

[lame plumber]

its certainly got a live fm somewhere but not where Id have taken it fm, being as the whole wiring setup is a snakes wedding, Im going to have it all out and start again, agree with all you have stated and having played with it on fri, opted to start fm scratch and do it as per the book and slightly more professionally than the original installer. Farmer thats used it for 8 years never noticed his pump ran most of the night in his bedroom as he was deaf!, didnt seem to notice extortionate gas bill either

 

[Gr fto reborn]

The satisfies terminal on the cylinder is connected to the grey on the 3 port but I see where your coming from. Thanks guys ill have a looksie

 

[ambrosia]

so glad i'm not you Gr fto reborn, thats a stressful sounding post