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Discuss 3 zone S plan plus with UFH problem in the Central Heating Systems area at ElectriciansForums.net

V

v.elec

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Hello.

I have wired an S plan plus system. 1 zone for DHW, 1 zone for CH and 1 zone for UFH (underfloor heating).


3 channel programmer, 3 motorised valves, cylinder stat, room stat for UFH, no stat for CH & 2 pumps.

Honeywell motorised valves, Horstmann 3 channel programmer, Grundfos pumps and Potterton system boiler


Here is the problem guys.


Switch the central heating on and everything is fine. HW and UFH - it all works. HOWEVER, HW and UFH only work if heating is ON. A.k.a, they are not independently controlled.

Three orange switched live from valves all going into same terminal together to switch on boiler and pump.

Room Stat signals MV via brown wire which turns on underfloor heating

Cylinder stat signals MV via brown wire which turns on hot water.

Programmer has direct switched live to MV brown wire, a.k.a, no room stat.

I think it may be the wiring centre, but I can't think of what mix up of wiring would cause Zone 2 and Zone 3 to only work when Zone 1 is.


Hope you can help. Thanks.
 
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M

Megavolt

  • Thread Starter Thread Starter
  • #2
Hello.

I have wired an S plan plus system. 1 zone for DHW, 1 zone for CH and 1 zone for UFH (underfloor heating).


3 channel programmer, 3 motorised valves, cylinder stat, room stat for UFH, no stat for CH & 2 pumps.

Honeywell motorised valves, Horstmann 3 channel programmer, Grundfos pumps and Potterton system boiler


Here is the problem guys.


Switch the central heating on and everything is fine. HW and UFH - it all works. HOWEVER, HW and UFH only work if heating is ON. A.k.a, they are not independently controlled.

Three orange switched live from valves all going into same terminal together to switch on boiler and pump.

Room Stat signals MV via brown wire which turns on underfloor heating

Cylinder stat signals MV via brown wire which turns on hot water.

Programmer has direct switched live to MV brown wire, a.k.a, no room stat.

I think it may be the wiring centre, but I can't think of what mix up of wiring would cause Zone 2 and Zone 3 to only work when Zone 1 is.


Hope you can help. Thanks.

Sounds like these not a permanent power supply to the grey wire on both the HW and UFH zone valves to me I would check that first.
 
V

v.elec

  • Thread Starter Thread Starter
  • #3
Sounds like these not a permanent power supply to the grey wire on both the HW and UFH zone valves to me I would check that first.

Ok Elrick, I will check that next week. Thanks.

Would that be the reason because the orange wire from the ONLY heating valve is turning on the boiler? Therefore, the HW + UFH can operate without it's grey wire? Just I'm sure I connected them into perm live terminal on 12 way block. I will defo check next week.
 
M

Megavolt

  • Thread Starter Thread Starter
  • #4
Yes as the brown on the zone valve opens the valve allowing the water pass though the valve and the grey is a permanent supply to a micro switch that makes when the valve opens sending power to the boiler via the orange
 
M

mountainman

  • Thread Starter Thread Starter
  • #5
Get a heating engineer in who knows about 'S' plan zoning, wiring and diagnostics.
Where are you? If your local to me I'll help you out for a modest fee.
 

Amp David

-
Mentor
Arms
Just download a diagram mate and spend a bit of time checking a double checking. Balls to the heating engineer idea!:rockon2:
 
M

mountainman

  • Thread Starter Thread Starter
  • #7
Just download a diagram mate and spend a bit of time checking a double checking. Balls to the heating engineer idea!:rockon2:
Those that can, do. Those who can't, become sparks who can't figure out a basic 'S' plan wiring system.
Shameful IMO.
 
V

v.elec

  • Thread Starter Thread Starter
  • #9
Hundreds of miles away.

I am an electrician. I have wired a few S plan and Y plan before. This was already wired however, but incorrectly and unsafe with no enclosures or containment, so I disconnected it all and had to trace and ring out wiring. It was like the guy before only used what he had, bits of single wire going into boiler and connector block taped up...etc. One of the wires which is grey is not actually grey, it was blue but sleeved grey with 2no 3 core HOFR flex in parallel.

It is easier to wire from scratch, compared to fixing someone else mess and making it work.
 
M

mountainman

  • Thread Starter Thread Starter
  • #10
I agree that it's easier to rewire from scratch but a custard doesn't want to pay for non-essential rewiring work when a simple diagnostic job is all that's needed.
 
M

mountainman

  • Thread Starter Thread Starter
  • #12
Ps
I've wired many hundreds of Y, S, Multizone and three wire 'Guaranteed Warmth' systems over the years, particularly when I was installing the heating systems too.
They are all pretty simple once you understand the circuit diagram.
 

Amp David

-
Mentor
Arms
Think there's only one of us around here with needs that are 'special', He joined in Jan of this year:iamwithstupid:
 

topquark

-
Mentor
Arms
Think there's only one of us around here with needs that are 'special', He joined in Jan of this year:iamwithstupid:
I looked it up in the "Urban Dictionary", never heard of it before.
 
V

v.elec

  • Thread Starter Thread Starter
  • #17
Ps
I've wired many hundreds of Y, S, Multizone and three wire 'Guaranteed Warmth' systems over the years, particularly when I was installing the heating systems too.
They are all pretty simple once you understand the circuit diagram.

Yeah, they are. But I ain't paying you to fix it. Went early this morning, it's fixed now. Thanks Elrick.
 
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