extending from steel conduit

[moomintroll]

Hi,
I am attempting to extend my ring main to add an additional double socket. However, the cable in my house is encased in steel conduit pipe (prob 20mm). The pipe only contains the live and neutral cores (2 sets of red/black for the ring, no earth, and the whole lot is NOT encased in flex apart from the red and black core flex of course).

Are there any regs that say i cant cut into the steel conduit? Whats the best setup to extend from it? I cant seem to find any junction boxes that connect to steel conduit and have, say, 3 terminals inside.

Am i ok to just remove a section of pipe, cut 1 set of cores, and then run each end to 2 JBs, then extend from those JBs to the new socket and back?

Thanks

 

[Qedelec]

The conduit is being used as the cpc (earth). Personally I would add a cpc of 1.5mm single.

Steel conduit is a sod to get a decent circuit from when it corrodes so adding a single cable is the only alternative.

Best to check your R1+R2 value before you start, and if is within limits you can try to add an unfused spur with the cpc attached to the conduit by self tapping screw, crimped eye and serated washer.

 

[moomintroll]

Ah...thanks for that... thats solves the earth query then...

As for the remaining setup... I intend to mount the junction boxes on a joist (or similar). The cores will lead out of the pipe conduit and into the JB, do I have to seal the end of the pipe in any way to stop, say, moisture getting in? Am i ok to just wrap insulation tape around the end and around the cores up to the JB? (Its only a very short distance, 4 inches max)

I suppose ideally the JB would fit into the section of the removed conduit but as i mentioned before, i`ve not seen such a JB exist.

 

[Qedelec]

Cables must have two layers for protection and insulation.
When singles are run in conduit that affords the circuit mechanical protection. Cables that are clipped etc. have an outer sheath for protection.
Wrapping tape around singles is not regulation and you should refrain from such a practice.

 

[plugwash]

jointing steel condit properly is probablly beyond the diyer unfortunately

if you can spur from a socket using T&E this is probablly your best bet.

 

[ban-all-sheds]

I suppose ideally the JB would fit into the section of the removed conduit but as i mentioned before, i`ve not seen such a JB exist.

You'll need to also remove a section of conduit on one side of the box, and use a coupler to re-join, as you won't be able to twist the existing conduit to get it into the box.

 

[Lectrician]

The good old 'running coupler'.

Extending from steel conduit will be difficult for any DIY'er, and I the tools to do so are not sold in the DIY store! You will need a die set, and threading conduit in-situ will also prove a problem i expect.

IS this a house hold circuit, or is this in a commercial/industrial situation?? I hate seeing T+E bodged into an install, you have to ask if steel conduit was chosen for a reason...

 

[breezer]

you actually need a 20mm nipple, coupler and lockring, thing is it wont work, since how are you going to thread the conduit?

 

[Lectrician]

you actually need a 20mm nipple, coupler and lockring, thing is it wont work, since how are you going to thread the conduit?

You do indeed - sticking out of the conduit box.

You need to thread the conduit the length of a coupler plus a lock ring, and a smidge more.

Put the threaded nipple in the conduit box entry.

Thread lockring, and then coupler all the way up the conduit thread you cut.

Align conduit end to nipple.

Screw the coupler off the conduit and onto the nipple - tighten.

Screw the lockring down the conduit and tighten against the coupler.

Paint or galv spray the exposed thread on the conduit. (depending if it's enamled or galvanised conduit).

 

[breezer]

but as has been said its really not in the diy realm, and why has steel conduit been used in the first place