Cable Selection for an External Sub Building

[papafett]

Hi all,

I'm currently doing a load of landscape gardening and while I've got all the earth up I want to run an armoured SWA cable to an external building. Someone already put something in as a spur from main room ring mail in the house - not ideal and the wall switch for it gets hot under load so I want to run a cable from this all the way to the main fuseboard and have an electrician terminate it properly.

So I estimate the cable run from the external building to the fuseboard in the house will be 30 metres, allow for a HUGE margin for error. Assuming this, I want to be able to allow for 18Kw draw from this building (electric shower plus usual extras). Can someone confirm what I would need for a 240VAC, 18Kw draw over 30 metres? I've tried finding online calculators but not luck!

if it turns out to be a ridiculous gauge of cable (and so cost), I'll ditch the shower and allow for a 8Kw draw instead.

Also, I'm assuming I can just bury armoured cable in some plastic ducting, lay some 'electric cable hazard' tape above it and that's legit?

Thanks everyone for any and all help!

Bob

 

[Pete999]

Hi all,

I'm currently doing a load of landscape gardening and while I've got all the earth up I want to run an armoured SWA cable to an external building. Someone already put something in as a spur from main room ring mail in the house - not ideal and the wall switch for it gets hot under load so I want to run a cable from this all the way to the main fuseboard and have an electrician terminate it properly.

So I estimate the cable run from the external building to the fuseboard in the house will be 30 metres, allow for a HUGE margin for error. Assuming this, I want to be able to allow for 18Kw draw from this building (electric shower plus usual extras). Can someone confirm what I would need for a 240VAC, 18Kw draw over 30 metres? I've tried finding online calculators but not luck!

if it turns out to be a ridiculous gauge of cable (and so cost), I'll ditch the shower and allow for a 8Kw draw instead.

Also, I'm assuming I can just bury armoured cable in some plastic ducting, lay some 'electric cable hazard' tape above it and that's legit?

Thanks everyone for any and all help!

Bob

Not just a case of throwing in some SWA, all sorts of other considerations to take into account.
What extras will there be?

 

[Bobster]

Have an electrician come and specify the cable needed, at Pete stated there are a number of variables that will influence a suitable cable size being selected.

The electrician will probably let you save some cost by laying the cable for him. They will also advise you on suitable burial methods.

 

[papafett]

Thanks Guys! Time is my problem. I suppose I could simply bury the ducting and warning tape, leaving a pull cord in it ready for the armoured cable, etc. at a later date

If you could let me know the key other factors that would be great so I can have everything ready for the sparky when he comes!

 

[Pete999]

Bonding requirements, voltage drop, diversity to name a few, your Electrician would be able to work out what's required, if he is any good.

 

[papafett]

Thanks again - really appreciate it! If you ever need any advice about I.T. or websites let me know!

 

[Spoon]

If you are putting some ducting down you might as well put a small ducting down as well for things like alarm wire, Ethernet, phone cable, if they are needed.

 

[papafett]

Thanks Spoon - already on it! I'm running some for a few CAT6 cables, getting some gel-filled direct burial brought over from the U.S. (seems really hard to get it in the UK).

 

[Spoon]

Thanks Spoon - already on it! I'm running some for a few CAT6 cables, getting some gel-filled direct burial brought over from the U.S. (seems really hard to get it in the UK).

But if you are using ducting to put the CAT6 in aren't you going a bit over the top with the gel-filled direct burial able? Or are you only using ducting for the power cable?

 

[ruston]

Do yourself a favour too, don't put to many bends in the ducting if you can help it,especially if it is of small diameter.

 

[Paul.M]

Thread moved to DIY section.

 

[papafett]

Quite possibly but I want the ducting in place in case I decide to pull more cable or fibre in the future, plus - if the worst happens and my ducting gets flooded, my CAT6 will be a bit more resilient!

To be honest, for exterior cabling I only ever use gel-filled (habit I got in to doing cabling in the Caribbean for years!).