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DIY Forum >> Electrical Questions >> Massive cable for just 20mA
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Message started by CWatters on Nov 19th, 2015, 5:06pm

Title: Massive cable for just 20mA
Post by CWatters on Nov 19th, 2015, 5:06pm

I suspect I know the answer but...

I'm looking to use something like one of these...

https://www.tlc-direct.co.uk/Products/GLSPIKE50BK.html?source=adwords&kw=&gclid=Cj0KEQiAg7ayBRD8qqSGt-fj6uYBEiQAucjOwWLa1ad71aeMrYa0fu0PfsCVMTQJx5g3aOR-x00VDgAaAmjE8P8HAQ

.. fitted with a 5W LED to illuminate a house sign.

The route from garage to sign (8M) would be underground so I went looking for some SWA cable. I discovered that 1.5mm core seems to be the smallest (?) and that has an OD of >12mm.

The lights I've seen are typically supplied with just 3m of rubber cable which has a 7mm diameter. So the supplied gland won't take 12mm SWA  and anyway 12mm SWA would be stiff making it hard to adjust the position of the light and have it stay in position.

So it looks like it would need a length of 1.5mm SWA, an encapsulated junction box and the lamp with it's rubber cable. All seems overkill for a 20mA draw.

Alternatives?

PS I'm aware of the requirements of Part P - qualified electrician etc

Title: Re: Massive cable for just 20mA
Post by CWatters on Nov 19th, 2015, 5:09pm

I assume you aren't meant to run the rubber cable underground any significant distance?

Title: Re: Massive cable for just 20mA
Post by Lectrician on Nov 19th, 2015, 7:58pm

Extra Low voltage light (12 or 24v)?  Rubber cable in conduit.  If mains voltage, it would need to be SWA really.

Title: Re: Massive cable for just 20mA
Post by Lurch on Nov 20th, 2015, 10:13am


CWatters wrote on Nov 19th, 2015, 5:06pm:
So it looks like it would need a length of 1.5mm SWA, an encapsulated junction box and the lamp with it's rubber cable. All seems overkill for a 20mA draw.


It's not the current draw that deems the protection rating of the cable, it's the voltage.


CWatters wrote on Nov 19th, 2015, 5:06pm:
Alternatives?


12V lamp, transformer in garage, bury rubber cable wherever you want.

Title: Re: Massive cable for just 20mA
Post by CWatters on Nov 20th, 2015, 4:35pm

It wasn't so much the protection I was questioning. Just wondered why I couldn't find a smaller diameter protected cable.

Title: Re: Massive cable for just 20mA
Post by Lurch on Nov 20th, 2015, 7:23pm

Because the means of protection and the construction methods mean that even an armoured cat5e cable will still be the size of a 1.5mm² 2 core SWA when it is all done even though it only started out 6mm diameter.

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