Wiring help please

[skins_uk]

I'm trying to figure out how to wire in our new thermostat but I cannot find any wiring diagrams specific to our system, even though I'm sure it's a fairly standard setup.

System details:
Vented system, tank in loft, boiler in utility and HWC in airing cupboard
The hot water from the boiler flows into the airing cupboard, through the pump and splits to:

• the hot water cylinder via a 1-way thermostatic valve (only twin + earth leading from it)
• the central heating system via a 2-port, motorised valve (4-core + earth leading from it)

There's a junction box in the airing cupboard linking a 5-core cable to the junction box next to the boiler (with no earth (the earth is pinched from the immersion fused spur)).

I hope I've explained this with enough detail. I can post pictures if required and would be grateful of any help to sort the wiring out.

I can only find diagrams with either a 2-way cylinder stat or 2 motorised valves or a 3-way valve. It's a Nest room stat I'm hoping to install BTW.

Thanks

 

[Mike Jackson]

Pictures please. It's very dodgy nicking an earth from another circuit means there is a cable with no protective conductor and a short to earth on the other circuit could liven up the cylinder or controls.

 

[lame plumber]

sounds like an old system if your using a mechanical valve on the cyl, which has a simple feed back to the wiring centre. What you need to have done first is change the cyl valve for a motorised valve and set it all up as an s plan then consider putting your upgrade to a nest on

 

[stevetheplumber]

with the two wire valve you wont be able to get heat and hot water timed seperately as you only have one micro switch to fire the boiler you would have to fire the boiler from hw on terminal on the time clock and run the supply to the two wire valve through the cylinder stat
then the heat on terminal on the programmer would be wired to activate the 2 port valve via the roomstat you wouldnt use the microswitch at all
not very efficent i would change the 2 wire valve

 

[skins_uk]

Thanks for your replies. It looks like I'm restricted posting pictures/url's but cutting & pasting the URL below into your browser may work.

s3.photobucket.com/user/thorman/library/Heating%20system

I know that earth continuity is important but I didn't wire this system in. The house is 30 years' old so maybe something was added and they had to "borrow" the earth from the linking cable. It's not easy to re-run a cable.

Can you give an example of a replacement thermostat valve please? We'll want to install a pressurised system in the not too distant future so don't want to spend much money on it.

Thanks

 

[AWheating]

If possible reuse the 5core from the boiler to junction box in cylinder cupboard and connect up an s plan with wireless programable room stat.

 

[stevetheplumber]

Ignore what i said previously that two wire valve isnt what i thought ,the two wires are switch lives to fire the boiler you can wire it as an s plan but the two wires from that drayton replace the grey and orange from a normal two port valve the grey will go to hot water on at the programmer via the cylinder stat and the orange will go to boiler or pump and boiler

 

[skins_uk]

Is there a relevant wiring diagram for my setup then? I just want to check it's wired-up correctly.

 

[skins_uk]

It seems to me like it would be a better idea to house the control box of the Nest sysrem in the airing cupboard instead of by the boiler. Are there any issues doing this? It should mean I can run the earth cable as an earth.

 

[skins_uk]

I think I've nearly sussed it now. Found out that the Nest is CH only so will need to install a timer switch for the HW. I've made a wiring diagram below for my system. Please can someone check it to make sure it'll work OK?

i3.photobucket.com/albums/y67/thorman/Heating%20system/Wiringdiagram_zps3d0a2288.png~original

 

[stevetheplumber]

page doesnt exist

 

[skins_uk]

page doesnt exist

Sorry but I can't post links properly - it keeps saying I'm restricted.

It seems to work if you copy and paste the whole URL into your browser. It misses the "i3." off the link.

Thanks

 

[learnplum]

Hi what is a one way thermostatic valve please?

 

[learnplum]

Hi I think the poster is confused.
The one way thermostatic valve he refers to, is the cylinder stat?
I think he has C plan in situ?:tounge_smile:

 

[Ermintrude]

Don't fit nest it's pish [emoji37]

 

[learnplum]

Wot do you mean?:tounge_smile:

 

[learnplum]

Nest stat is over-engineered?
Quite good though?:tounge_smile:

 

[dancinplumba]

Hi what is a one way thermostatic valve please?

A valve that allows water to flow through it one way only

 

[learnplum]

Hi dancin, is it a cylinder stat then?:blush5:

 

[dancinplumba]

Hi dancin, is it a cylinder stat then?:blush5:

Sort of, it fits on heating pipe to cylinder and closes when cylinder at right temperature bit like a TRV on a radiator

 

[learnplum]

Thanks Dancin, my head is cavin in,Thanks all,:tounge_smile:

 

[dancinplumba]

The thanks button is in the bottom left hand corner 😉

 

[skins_uk]

Hi I think the poster is confused.
The one way thermostatic valve he refers to, is the cylinder stat?
I think he has C plan in situ?:tounge_smile:

I thought a cylinder stat IS a thermostatic valve. Happy to be corrected though. The one-way part I was referring to is a bit like light switches - I only have two cables (+ earth) coming from the stat, not 3 - so my translation is it's a one-way switch, not a two-way like most stats.

Am I right in saying that when the cylinder stat valve is open the two wires coming from it have a closed circuit, and when the valve is closed the circuit breaks thus switching the pump + boiler off (if the CH isn't on)?

I just need to know if my wiring diagram will work or not.

 

[learnplum]

Hi can you look in the junction in the cupboard, and see what the brown cable of the valve connects to?
For example, does it connect to one side of the cylinder stat?:tounge_smile: