Where is cable sheath required?

Apr 11, 2013 11 Replies

Can the wall count as the back of the enclosure when wiring a light?



I have a bulkhead fitting whose instructions show the three unsheathed insulated conductors entering a grommet at the back of the fitting, which surprised me. I thought the sheath had to enter the enclosure, i.e. pass through the grommet.



I'm wiring the circuit in singles in conduit, so it would be handy if the space between the grommet and the light still counted as inside the enclosure. Does it?



If so, I can wire the light fitting directly through the wall. My previous plan was to run the conduit to a junction box and run multicore cable from there to the fitting through the wall.



Thanks,



Alex


The best way is to mount the bulkhead fitting on the conduit or take the conduit right up to and connected to the bulkhead fitting.

The cables will need heat resistant sleeving.

I would if I could. This bulkhead is the die-cast aluminium jobbie I posted a picture of a few weeks back [1]. It has no M20 entry, nor can I mount it on a BESA box.

It comes with two pieces of sleeving for the live conductors.

Alex

[1]
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Remind me. Were you not going to use a conduit box behind the light?

I couldn't find any way to make it stable, even if I used two. The rear is rounded and relies on the edge flat against the wall to make it stable.

Alex

It will need to be a flush conduit box positioned as accurately behind the grommet as possible, then.

Is this domestic, or do other regulations / considerations apply?

Owain

The singles would be coming straight through the brick wall, perpendicular to the fitting, so I could end the conduit itself just behind the grommet. Would this be ok, rather than sinking a conduit box into the brick? Still means the cables are outside the conduit and not quite inside the grommet for a short distance.

Generally speaking, yes the sheath should come into the enclosure. Having said that, in the circumstance you describe it would be difficult to gain access to the wires in such a way as to pose a risk. The main concern would be the effects of heat on them.

You should be able to get the conduit pretty close to that grommet, or even fettle the hole to 20mm clearance?

The conduit end will need to be bushed against sharp edges and, I think, earthed across to the luminaire.

Owain

Just noticed you need to be registered/logged in for tech info. I can email you (or anyone else) any documents you want - or just register with any company name you care to make up:-).

I've had a peek but not really sure what I'm looking for. In the mean time I've decide that trying to do it without any junction is making life difficult for myself. I'll join a length of multicore and put that through the grommet with as little sheath inside as possible.

Alex

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