Choosing correct SWA cable for shed

MartyCandystripe · 4 Feb 2021

Hello,looking for some help.I am hoping to run electric to my shed.The new consumer box is 10 meters from the house and I will be running 2 heaters (2kw each),fridge freezer, a kettle and 2 LED lights.I have had 3 sparks that have gave me a quote but all have recommended different SWA sizes (4mm,6mm and 10mm).Can anyone tell me which mm would be best as I don’t want to be ripped off,thanks

RF Lighting · 4 Feb 2021

What is your earthing supply type?

Are there any extraneous conductive parts in the new shed?

How will the cable be run? Surface / buried in the ground etc.

I’ve made some assumptions in the calculation above. What makes you think the electricians who visited are trying to rip you off?

MartyCandystripe · 4 Feb 2021

Thanks for your reply, all 3 electricians said no need to bury cable it can run along the side of the house as the driveway would need to come up.Just thought it was strange that all 3 had a different opinion as to what gauge of SWA would be needed,I don’t want to be paying for 10mm when I can get away with 6mm.This table explains it better then they did thank you

Notch7 · 4 Feb 2021

4mm 2 core SWA £1.59 per metre

10mm 2 core SWA £2.82 per metre.

The cost difference is bugger all.

The difference in the electricians choice of cable is almost certainly based on how much spare capacity each feels is worth building in.

SUNRAY · 5 Feb 2021

My instant reaction is allowing for 8KW needs >32A fuse and 4mm² will be far too small.

That's a slightly unusual list of appliances, what is the planned use for the shed?

Assuming the buildings are 10m apart I've done the calcs for 20m cable @ 40A which gives 6mm². However for an outbuilding I'd always advocat erring on the side of caution and calculating @45A comes up as 10mm².

Yes 6mm² will be in the design criteria but for the extra £30 for 10mm² it's a no brainer in my opinion, it'll cost a lot more than £30 to upgrade if ever you need to.

sxturbo · 5 Feb 2021

I'm with the others, when I've done this in the past, I've calculated what I wanted, and then to future proof gone to the next size up if the cost is negligible.

bernardgreen · 5 Feb 2021

Sureitsoff? · 5 Feb 2021

go for 10mm now, much easier than having to redo it later.

securespark · 5 Feb 2021

Absolutely. Future-proof, then if you need extra capacity, there's no worrying about replacing the supply cable...

SUNRAY · 5 Feb 2021

I've known far too many times in the past, especially garages, where a cable is upgraded and sometimes after a very short time. Chances are it's probably going to cost the same as the original installation.

Otherwise the user goes through life being very careful what's running at the same time to avoid tripping the breaker.

RF Lighting · 5 Feb 2021

I’ve got a 16mm² supply to my garage

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Choosing correct SWA cable for shed

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