reusing earth wire in a 5-core cable

[Geronimo W. Christ Esq]

All,

I'm currently installing the electrical bits of a Y-plan setup, which includes a new time clock, cylinder/room stats, motorized valve, and obviously the connections to the pump and boiler. The control electrics are all Honeywell parts.

The time clock connection needs a total of five conductors - neutral, live, hw on, hw off, ch on. However, I've found it impossible to find cable with more than five cores, so have wrapped some insulating tape around the earth wire (which was already insulated green/yellow). None of the components have metal parts (the spur switch I've added is metal, and is earthed off the house earth) and the cable is just fixed to the wall with cable clips, so there's no likelihood of drilling through by mistake (unless you really are a total chump). Am I breaking any rules here (common sense or otherwise) ?

Regards

GWC

[Andy Wade]

Yes you are: (a) there's a general requirement in BS 7671 to run a circuit protective conductor (earth) to all wiring points, and (b) the colour green/yellow is reserved exclusively for protective conductors and application of tape or even sleeving is not acceptable.

This is what you need

[Bob Eager]

purpose. I got some from the local plumber's merchant.

[Owain]

YES.

Even if things are double insulated, ALL cables need an earth conductor running to all termination points.

Also G&Y must NOT be used for any purpose other than electrical earth.

Use two 3-core + earth cables.

Owain

[Geronimo W. Christ Esq]

I thought so.

Oh, I didn't know about that. Great, thanks.

[Geronimo W. Christ Esq]

It's surprising how hard to find the stuff is. The sheds only have the five core (and are dastardly expensive).. toolstation, screwfix etc don't do it at all, and googling for it, nobody seems to have heard of it.

I've just ordered a wodge off it from TLC, so hopefully it'll show up soon.

[Andy Wade]

Google for "YY cable" or "YY control cable" and you'll get lots of hits. RS do it up to 18-core 2.5 mm^2.

BTW you'll need to mark the neutral core with blue sleeving and all the lives with brown to comply with BS 7671.

[John Rumm]

Nothing stopping you using more than one cable either...

[Bob Eager]

>

I ordered it from TLC, for collection at branch. I eventually got an email saying it was out of stock.

I surmised that a plumber's merchant would have it, since plumbers use it! I was right..and the place is only half a mile away as well!

[Matt]

You only really need the 7 cores for S plans. If it's a Y plan installation then 6 cores are enough for the run up to the cylinder thermostat and mid position valve (and also the run from the boiler terminal box to the timer and thermostat if you are not using a 3 terminal room thermostat)

Toolstation have for quite a while now stocked 6 core flex with multi-coloured cores rather than just 6 blacks and a green/yellow in the TLC offering. What's more the cable is less than one third the price of TLC.

Core colours are brown blue red black white green/yellow

£26.96 for 50 metres of 0.75mm^2

[Bob Mannix]

I would use twin and earth for live and neutral and a separate 3 core and earth for the others.

[Geronimo W. Christ Esq]

>> Mt TLC was out of stocl when I wanted some a few weeks ago for just this

TLC wrote this morning to say it was dispatched, so looks like they have it again.

Makes sense, but the plumber's merchants here are quite some distance away ;)

Cheers

GWC

[Geronimo W. Christ Esq]

D'oh, toolstation's search is crap. This cable was not listed under with the rest of the electrical cable and does not come up when you search for "6 core cable" (you get some alarm cable instead). Damn.

50m would be way too much for my needs anyway.

[Ian_m]

My last system used 2 x 5 core taped together with insulation tape which in the heat of back boiler all oozed off in the most stickiest mess ever. Current house has cable ties holding the two wires together.

[Geronimo W. Christ Esq]

Yeah, it's not nice stuff when it oozes.

My 6-core + earth cable from TLC showed up today (pretty damn quick!) and I replaced the dodgy wiring with it instead, with a spot of brown tape marking the live wires. Much better.