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Posted By Topic: NS joint

Jan 16 2018 07:51

After joining NS cable with crimps and layers of heavy heatshrink, would sleaving the joint it with HD conduit restore the integrity of protection?

Jan 16 2018 10:28

That would depend on the installation conditions.
One of the reasons we're allowed to bury (most) N/S direct , or to have it more accessible than other cable types; is the construction - with active(s) in centre surrounded by N. A joint doesn't replicate that. But if the joint is given additional protection, such as would be acceptable for a TPS in similar situation, then in my view that's good enough.

Jan 16 2018 11:16

Thanks AlecK. My thinking the same. All sections of cable must be compliant but they don't have to achieve compliance by a common method.

Jan 16 2018 20:25

in a ceiling, underground??? why not use a proper cable joining kit?

Jan 16 2018 21:07

From experience of having NS joints fail from ingress of moisture in the ground (no matter how well the Raychem has sealed), I've gone to a Raychem epoxy resin joint kit. In Christchurch the water table comes up quite high in areas and quite often cables are dripping wet. Even earth rods corrode badly.

Jan 17 2018 12:03

Original question was aimed at category A buried direct.

Are there small joining kits available that preserve continuity of the neutral screen?

The epoxy filled ones I've seen simply encase the crimp joints. Without the screen they'd require additional protection I would think. Still worth considering for moisture exclusion.

Jan 17 2018 12:38

To maintain the screen effect, would need a conductive enclosure / cage around the joint, connected to N, and insulated.
Easier to add some additional mechanical protection.

Jan 18 2018 08:57

You can get a tinned mesh kind of like a finger trap that you can slide over the joins to maintain the N/S protection 360degrees around the cable after the joint is made though it isn't the same thickness as N/S copper.

When doing a join like this I join all the conductors including the neutral with crimps and heat shrink the crimps, then slide the mesh over the whole join, this is held in place by circular springs and then heat shrink over the rest of the join.