Wire colours for central heating controls


I am planning to update my CH controls to improve efficiency (cylinder thermostat, programmeable room thermostat etc). If I connect say the cylinder thermostat with 3 (live, neutral, switched output) core cable (not TW&E) is it permissable to use the green/yellow core for the switched live return from the stat to the control block? If not how should I wire it (it's about 3 metres from the stat to the control block near the boiler)? Are there any general rules/guidelines to follow re colour coding or cable types when interconnecting all the components on a CH system? Thanks, David.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No. The reason being that the cable must have an earth in it connected to the supply earth even if there's no earth connection at the thermostat (which seems unlikely in any case). Given this, you'll be using the green/yellow core as the earth as it makes no sense to use anything else.
You can buy 4 and 5-core wire for such applications. B&Q used to sell it by the metre, but I think you have to buy a pre-cut length (or a whole drum) now. You might find it at a good electrical shop by the metre.

Not really. Stick as near to the correct colours as possible, and sleeve any live conductors with red or brown sleeving if they are some other colour.
--
Andrew Gabriel

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

have to order it in advance though
--
geoff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 01 Aug 2005 10:58:11 +0000, DavidM wrote:

Please please don't. But if you must PLEASE mark it with a red sleeve or even red tape. I have just spent an hour at a friends house working out what exactly some plumber was doing with the earth wire (NO it was not earth) on the thermostat wiring.
Dave
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

in Belgium)
--
geoff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You mean flex, rather than cable? Sleeve the entire green/yellow where exposed with red sleeving.
--
*Growing old is inevitable, growing up is optional

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.