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Overhead cable suitability for cat wire

Looked at a job for a customer and the cable supplying the shed in their garden is a pvc T&E about 5 m up spanning about 5 metres. There's some sort of catenary wire (looks like a bit of old fencing wire) and its snapped so the cable is holding the wire up. I'm going to replace it but wondered whether NYY-J cable would be considered suitable rather than SWA? it's lighter and seems to be widely considered fine for outdoor use, and is obviously quicker to joint. SWA is obviously stronger but if the cat wire does its job properly would the cable itself require mechanical protection? I cant find a reg?

  • Some people use this, but the wire rusts quite quickly.

  • NYY-J usually has solid conductors, whereas SWA usually stranded - so if its swinging about in the breeze so some extent, the extra flexibility of the stranded conductors might provide an advantage.

       - Andy.

  • 5m span is probably OK even in copper more than ~ 2.5mm2 without catenary wire.

    Cat wire is not that expensive.

    If lifespan/corrosion  is likely an issue then s/steel  wire is possible,  look at yaught/boat type places.

    Almost any cable can be used overhead, -even arctic flex or T and E is OK, but needs regular inspections- especially in location is where sunlight is strong and can embrittle plastic, but it takes several years. NYY is nice in that it has a definite UV spec, but that is not essential. 

    Like any non armoured cable, when buried in a wall it needs to follow lines of least surprise, or be protected against discovery by drills etc, much the same as T and E. When on view, no routing restrictions apply.

    Mike.

      

  • Thanks, Mike; never actually replaced an overhead before, so was just looking for a bit of reassurance. I'll use the N YY-J with a cat wire: they're not expensive and as well as supporting the cable it will stop any pressure on the ends where it enters the building, should somebody catch it with ladders/lengths of timber etc. 

  • At the risk of stating the obvious, please form the cable to make a ‘drip-loop’ so that it enters the building from outside going at least slightly up-hill, rather than heading down or level. Rain needs to be encouraged to come out, not to find a way in..

    M.

     

  • At the risk of stating the obvious

    Also remember that 521.10.202 now applies to all wiring systems … so no relying on nylon cable ties to support the cable from the catenary wire.

    I can see that the old school approach of a few turns of insulating tape followed by a couple of turns of thin wire, ends twisted together, might see a resurgence.

       - Andy.