Control system not working, HW but no CH

[dbleman]

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 through a connection box.

Mains
L N E
to; to; to;
1 2 3

Programmer - Honeywell ST6400C

N L 1 2 3 4
to; to; to; X to; to;
2 1 7 X 6 4

Boiler - Glow-worm Ultracom 30sxi

E N L R
to; to; to; to;
3 2 1 8

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


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


Honeywell - Room Stat T6360B
E 1 2 3
to; to; to; to;
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 and hope all of this makes scense, but I'm really stuck.

Thanks in advance for any help.

 

[njk]

Hi,

You have wired it correctly. It seems that the 3-way valve is not working properly. When the hot water is not calling for heat there is no direct live to the boiler. The 3-way valve should recognise this and connect internally the live to the orange (pos. This is not happening, hence the blame appears to be the 3-way valve.

good luck

 

[dbleman]

Thanks

I got all of the controls from screwfix. When I replaced the programmer I realised that the first one they had given me was not as new as I thought(the sticker over the display was missing and the user booklet was missing). Now I'm wondering whether I've been given some returns !!

Any thanks for your help. I'll let you know if it works.

 

[bones001]

what you have said is that when you have heating only on you have 240 at hw off which is correct but you also have 240 at hw on which you shouldn't have

 

[dbleman]

Sorry you've lost me which connection is the HW off and on.

 

[MANDATE]

I'll just add my tuppence worth.
Valve operates over two sections.
With both HW and CH called for room stat supplies power to white wire of valve. This moves valve, but only to mid point. This gives both HW and CH until one side has been satisfied. Check white wire and neutral If this is not happening.
Valve will only move from mid position onwards if the grey wire is live. For this to be live HW must be switched off, or if it is on then it must be satisfied. there are two feeds, one from HW OFF terminal and one from cylinder stat (satisfied terminal)
If valve does move to CH position there should then be power output from the orange wire. If there isn't then micro switch at fault.
First thing is to establish is the wiring, then to listen if valve is moving as it should.
There are some aspects that may mislead you. When CH is turned off and HW was already off, the programmer cuts the supply to room stat and the white wire which connects to orange wire and boiler stops, but the motor stays energised so it does not drop back to HW position as may be thought.
When HW and CH are selected it is only till one side is satisfied, this would usually be the HW because radiators are losing the heat quicker.
So valve moves to CH side but if micro switch faulty it can not light boiler.
If HW is called for either alone or with CH, boiler receives power from cylinder stat and not the orange. However the wires are linked so orange will be live in some situations, but its not coming from the valve.
On the programmer the CH switch is one way (make or break)
The HW switch is two way HW ON and HW OFF, wires are used from both these but not at the same time, so I agree with 'bones001'

 

[dbleman]

Thanks

I'll check it all out.

 

[bones001]

number 1 from the programmer to number 7 on the terminal strip is HW OFF

3 from the programmer to 6 to the strip is HW ON

4 from the programmer to 4 on the strip is CH ON

What I would do if I were you is take out all other wires and just leave these ones in from the programmer (leave the mains in). turn CH on only and you should have live at 1 and 4, if there is live at 3 also then there is a problem with the programmer

 

[dbleman]

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 bones001, MANDATE and njk (and diynot.com).