Central Heating- wiring new, relocated, components

[Dean Heighington]

I need some help rewiring a couple of components which form part of my domestic heating system. They are the programmer (which has been relocated but not renewed) and the roomstat/rheostat/thermostat (which has also been relocated AND replaced with a more modern device).

By way of explanation... recent home improvements to my 1930's 3-bed semi have included blocking off half of the 'original' galley style kitchen, which was straight ahead of you when entering the front door. The new kitchen is now located behind this in the left half of a rear extension and also occupies what used to be the back of the garage. The rear left-hand corner of the house was removed and supported by steels, to 'open-up' the new kitchen. The door that used to lead into the old kitchen remains, but is now the entrance to a downstairs shower/basin/wc.

Previously, the CH & HW programmer and the Roomstat used to be mounted on the same wall as the doorway by which one entered, on the left hand side. (On the other side of this wall is/was the understair cupboard and is where these two components were electrically connected.

Also involved in the renovations, was converting the first 2/3rds of the garage into a kids' den and a doorway is to be knocked through from the hallway (left of the front door) into the garage.

As a result, I decided it would be practical to relocate the Roomstat/rheostat/thermostat to the hallway (on the right just before the doorway into the downstairs shower room) and the Programmer to the den (on your left after passing through the doorway from the hall) as this is where my boiler is located (in the 'old' garage).

The cables have all been run to their new, appropriate, locations: The

2.5mm T&E and the 1.0mm flex (3-core & Earth) that went to the Programmer and Roomstat are now in the garage by the boiler; and I have run a new 2.5mm 3-core & Earth (new colour coding) from that same position to the new roomstat location.

My system consists of the following...

1. GARAGE: Potterton boiler and Froststat (+ existing, but relocated LANDIS & GYR programmer: RWB200)

1. HALLWAY: Relocated and NEW Roomstat: TowerStat RS

2. 2ND BEDROOM AIRING CUPBOARD: HW Cylinder, immersion heater, pump and 2 x 2-port motorised valves.

I made a note of the wiring before disconnecting the Roomstat and Programmer and intended to rewire accordingly. However, having purchased the new Roomstat and by speaking with my local electrical retailer, it appears that the new stat needs to be wired differently to the old and from my scribbles, his opinion is that the original wiring was a bit of mess anyway and would be worth starting from scratch!

Trouble is, I don't have the original wiring diagram for the existing programmer or the boiler and am not that familiar with how these circuits are wired up... if I new what did what and where it went, I'm confident I could not only wire it correctly, but could tidy everything up at the same time!

Can anyone help shed any light? Perhaps supply me with a standard wiring diagram that I could follow, or suggest ways to proceed. If it proves too complex, I will call in a sparks, but I'm interested to find out for myself... I know I could probably achieve this by tracing each wire to its destination but that would take me more time than I have right now.

I can supply more details if necessary, but this really is a 'standard' system and I'm sure that those of you with the knowledge and experience can visualise exactly what I have here. Its not the original system and was put in before I bought the house (between 9 and 13 years ago, I reckon).

Any help would be great.

cheers, Dean.

[Set Square]

Although you don't specifically mention a cylinder stat, I assume that there

*is* one - and that what you have is a standard S-Plan arrangement. Having 2 x 2-port motorised valves is consistent with this.

If you wire it according to the S-Plan diagram in

you should be ok.

The principle of operation of an S-Plan system is that the CH motorised valve opens whenever the CH is on at the programmer, and the room stat is calling for heat. Similarly, the HW motorised valve opens whenever the HW is on at the programmer and the cylinder stat is calling for heat.

The clever bit is that each of the motorised valves has an independent (i.e isolated from the motor feed) pair of contacts which close when the valve is fully open. One side of the contacts (both valves in parallel) is supplied with a permanently live feed, and the other side (again in parallel) is connected to the boiler and pump. So the boiler and pump run whenever either (or both) circuits are calling for heat - and shut down when both demands are satisfied.

[Dean Heighington]

I hope your ng client will flag up this reply, as its been some time since you posted the above.

Thank you for your response and sorry about the delay, but I've not had the time to follow up my thread!

You are quite right, my system does include a cylinder stat and I forgot to mention this. I also have no doubt that, as you assume, my system is an S-plan arrangement... my house is a typical 1930's, 3-bed semi and I can't imagine that the heating system would be anything specialised.

Thanks for the link you posted, after sending this, that's my next stop and I'm determined to understand the set up and not just follow the dots according to an existing set of instructions.

Some time ago, I replaced the head of one of the motorised valves and I do distinctly remember discovering a constant LIVE even though the valve was not being called. Your post has now informed me why that was (is).

Please keep an eye on this thread as a will probably be back with more questions, if you don't mind that is?

thanks again,

dean.

[Set Square]

Feel free to ask. I'll try to produce a sensible response!

[deano]

Cheers... much appreciated. On first glance of the diagrams at the link you supplied, I notice that a 10-way junction box or wiring centre has been employed in the circuit... I know this is now a common practice and makes things much clearer when servicing the system at a later date, but mine doesn't use one of these... just connector blocks behind the controller for wires that go to the stat! Would it be worth putting one of these in and rewiring the whole system? In the long run, it might be more practical than deciphering the diagram to not include the use of a jb!

What's your opinion?

Dean.

Set Square wrote:

[Set Square]

There's no easy answer to that one. It depends to some extent on how much effort would be required to re-wire it. If all the cables come together in one place and are long enough to connect into a junction box rather than barrier strips, it would probably make it easier for you - and others - to understand in future. If it means a lot of taking up floorboads and installing new cables, I wouldn't bother. What I *would* do is draw my own diagram of how everything is physically connected and maybe label the individual wires with the terminal number to which they would be connected in a junction box, if I had one - IYSWIM.

[deano]

Hi again....

Hmmnnn... your ng ident "Set Square" suggests a connection with the graphical world, to which (as a graphic designer) I am a fully-paid-up member! As opposed to the carpentry/metalwork/DIY world, which would, instead, be more closely associated with a "Try Square"! Am I right in my observations?

Don't be afraid to say MYOB... I was just wondering if your are an Artworker or Draughtsman or such like!

I've been away for this week on a short family break to the south coast... hence another delayed response. My last post was sent just before jumping in the car and heading off. I had all good intentions of using the laptop to follow my ng threads, before realising what a sad holiday activity that would be to embark upon. So, sorry again, I hope you still get this, now I have returned and followed it up!

Reading your reply, I appreciate your weighing up of the pro's and con's, associated with starting from scratch and rewiring the circuit. I, long ago, decorated the upstairs rooms in my house and did all the work necessary to avoid future disturbance of the floors in each room. So, no, I don't want to go there!

Therefore, as you suggest, it would be much more practical for me to trace the route of each wire (although I doubt they will correspond with the colour coding indicated at the URL you supplied) to it's source and label as applicable!

This is where I can see myself with a couple of wires that will leave me stymied... a bit like a bag of MFI flatpack fittings tends to leave one!

I'll be back, no doubt. Thanks again

Dean.

[Set Square]

No, my professional career was almost entirely in IT and telecoms - but I'm now retired.

I invented the handle "Set Square" in an attempt to convey the fact that I aim at accuracy in my DIY work - using appropriate tools like spirit levels and set squares (maybe it should be try squares!) to ensure that things which should be horizontal or vertical *are* so, and likewise for things which should be perpendicular to each other.

Good luck with tracing your CH wiring. As you say, the colours probably won't correspond with the Honeywell diagram - but if you can identify both ends of each multi-core cable, you should be able to draw your own diagram showing what's connected to what.