DIY Doctor UK DIY Forums

Hi,
I have had a new system installed and the electrician has moved before it is running properly (yea I've not paid him yet.) Anyway according to Honeywell their programmer was originally at fault, I changed it, but the problem remains. Hot water works, but 3 way valve and CH does not work independently - Programmer functions appear to work - Room Stat ‘calling for CH’ light comes on and there is a click when the dial is turned.

I can't see the wood for the trees at the moment and am stuck - can any help please

Wiring to Central Heating System.

Mains
L N E
↓ ↓ ↓
1 2 3

Programmer - Honeywell ST6400C

N L 1 2 3 4
↓ ↓ ↓ ↓ ↓
2 1 7 6 4

Boiler - Glow-worm Ultracom 30sxi

E N L R
↓ ↓ ↓ ↓
3 2 1 8

Honeywell - 3-Way Valve V4073A
G/Y Orange Grey White Blue
↓ ↓ ↓ ↓ ↓
3 8 7 5 2


Honeywell - Cylin’ Stat L641A
C 1 2
↓ ↓ ↓
6 8 7


Honeywell - Room Stat T6360B
E 1 2 3
↓ ↓ ↓ ↓
3 4 2 5



Terminal that are 'live' when controls are off and on etc.(Live =live with terminal number, ---- = not power to terminal number, X = terminal number not used);

Programmer calling for CH, Room Stat calling for CH, Boiler does not start.
Live1 ---2 ---3 Live4 Live5 Live6 Live7 ----8 X9 X10

Programmer calling for CH, Room Stat NOT calling for CH, Boiler does not start.
Live1 ---2 ---3 Live4 ----5 Live6 Live7 ----8 X9 X10

Programmer calling for HW, Cylinder Stat calling for HW, Boiler starts.
Live1 ---2 ---3 ----4 ----5 Live6 ----7 Live8 X9 X10

Programmer calling for HW, Cylinder Stat NOT calling for HW, Boiler does not start.
Live1 ---2 ---3 Live4 ----5 Live6 Live7 ----8 X9 X10

Programmer calling for CH & HW, Stats calling for CH & HW, Boiler starts.
Live1 ---2 ---3 Live4 Live5 Live6 ----7 Live8 X9 X10

Programmer NOT calling for CH & HW, Stats NOT calling for CH & HW, Boiler off
Live1 ---2 ---3 ----4 ----5 ----6 Live7 ----8 X9 X10

Programmer calling for CH & HW, Room Stat calling for CH, Cylinder Stat NOT calling for HW, Boiler does not start.
Live1 ---2 ---3 Live4 Live5 Live6 Live7 ----8 X9 X10
Sorry to be so long winded but I'm really stuck.

Thanks in advance for any help.

Wow! Reading your post, and my head started hurting.

Seems like a standard 'y' Plan to me. Have you checked the Honeywell website for the wiring diagram?



Sorry, but you have to cut and paste this address, as the URL's are disabled in this forum!

IF you can confirm that the wiring is correct first then it might be easier to diagnose.

Sounds like your three way valve is stuck on hotwater and when told isn't switching to c/h . Could be a wiring fault or your three way valve is totalled any idea how old it is?

Yea, checked the Honeywell website, then spoke to their Tech Dept. They said that the wiring was fine, but that the programmer was faulty (brand new), changed it and the room stat now works, but little else has changed.

As far as the 3-way valve is concerned - it's brand new as well !!

I'm not a happy bunny !!

Thanks for that. I undid all of the wiring and reconnected just the programmer and mains. The programmer was fine and the live I thought I was getting on the HW on / HW off was in fact induced current and not live. My next step was to check the itegrity of the wiring - fine.

Finally, the 3-way valve and I found that it was burnt out.

Replaced the head, re-connected the wiring and bob's your aunt, I have a fully running system.

Lessons;
Ask for help when you are stuck;
Do not assume something bought new is working (although having a faulty programmer and 3-way valve, bought from the same place at the same time has to be pretty bad luck.)
Beware of induced currents giving you the impression that a wire is live.

Finally thank you for your help.