25mm SWA alternative?

[speccy]

We are having our CU upgraded and some cables rerouted one feed is to a small 6pitch caravan site. Currently fed by 16mm twin and earth through the house to an outside point.
The sparky has suggested we run 25mm SWA to this point instead just to keep resistance down over the length (30metre run). Is there not an alternative as it means currently running about 20metres of SWA through the house to the outside feed and then 10metres external to the junction. Seems alot of money and overkill?

He also mentioned the cable will stick out the wall exiting? Surely you drill the exit at an angle so the cable can exit the wall pointing already in the right direction and not perpendicular etc.

Thoughts appreciated!

 

[SUNRAY]

We are having our CU upgraded and some cables rerouted one feed is to a small 6pitch caravan site. Currently fed by 16mm twin and earth through the house to an outside point.
The sparky has suggested we run 25mm SWA to this point instead just to keep resistance down over the length (30metre run). Is there not an alternative as it means currently running about 20metres of SWA through the house to the outside feed and then 10metres external to the junction. Seems alot of money and overkill?

He also mentioned the cable will stick out the wall exiting? Surely you drill the exit at an angle so the cable can exit the wall pointing already in the right direction and not perpendicular etc.

Thoughts appreciated!

If the existing T&E is suitable for the installation, run a second 16mm² T&E and parallel feed it, that'll be 32mm² for cheaper and easier and probably neater than a SWA.

 

[Adam_151]

What size supply is the feed to the caravan park? 30m is not that far, and you'd be limited to 63A off a domestic CU anyway so a can't see that you'd need bigger than 16mm, Its not ideal feeding something like this off a domestic CU anyway, where does the supply actually originate from? Whats the earthing arrangement.

I think pictures of the existing arrangement would be useful

 

[ericmark]

Theory since caravans have lights volt drop should be limited to 3%, but in practice as long as above 207 volt not really a problem. In the main caravans have battery back up, so lights are 12 volt, the biggest problem with caravans is the earthing arrangement and power requirement, the BS 7671:2008 says 16 amp per outlet, OK some diversity, but most CU's can only support a 45 amp MCB, the old loadmaster had 70 amp, but over that looking at moulded breakers.

I only have the 2008 copy of BS 7671 to hand, section 708 electrical installations in caravan / camping parks and similar locations is three pages long. In it there is a
"NOTE: In the UK the ESQCR prohibit the use of a TN-C-S system for the supply to a caravan or similar construction." and "708.553.1.10 The current rating of socket-outlets shall be not less than 16 A. Socket-outlets of higher current ratings shall be provided where greater demands are envisaged."

I think the rules are now even tighter, however each edition of BS 7671 has the date at which new designs must comply, changing the supply cable is making it into a new design, so doing anything like that could be opening a can of worms.

 

[SUNRAY]

What size supply is the feed to the caravan park? 30m is not that far, and you'd be limited to 63A off a domestic CU anyway so a can't see that you'd need bigger than 16mm, Its not ideal feeding something like this off a domestic CU anyway, where does the supply actually originate from? Whats the earthing arrangement.

I think pictures of the existing arrangement would be useful

Applying any derating factors gives no suitable T&E for 63A & 30m (TLC on line calculator)

 

[Ragnar_AT]

25 mm2 Hi-Tuf (NYY) possibly? It’s still more unwieldy than T&E but a lot less than SWA.