What size armoured cable

Question

I'm running electrics to a garden office from which I'll run an electric heater, fridge, microwave, kettle, TV, Laptop and LED lighting.
The office is 45/50 metres from the  existing RCD.
What size armoured cable should be used?
Thanks in advance.

Kevin · Accepted Answer

16mm SWA due to distance and would also provide future-proofing

Michael · Answer

If you use Ohm's law formula p = V x  I and add your power output, you wouldn't go wrong.

for example: 3000  w Kettle + 2000 w Heater+  800 w microwave + 200 w lighting + 500 w laptop = 6,500 watts 
V = 230 
6,500 /230 = 28.3 amps; therefore, a 32 Amp breaker with 6 MM cable would be the correct size.  However, I personally always add 30 % and go up to the next size and use 10 MM SWA and make sure is 3 core.

Rob · Answer

You should run 16mm SWA at a depth of 450mm minimum. A small consumer unit in the office used to supply all the circuits;

Kieran · Answer

If you want heating 6.0mm all day long, 32 amp supply assuming upto 60m

Simon · Answer

16mm and then you’ll be future proofed. Thats a lot of load, but you’ll also be fine with 10mm

Hussain · Answer

So your total load at this new garden works out to be 28.3A

So a 32 rcbo would do

You’ll need to run SWA cable if your running the cable underground also you need your
Consider your voltage drop so if you run you main cable say 6mm2 you’ll have 1.9v for every 50m to your minimum cable size is 4mm but recommend you install 6mm2 SWA cable in an external consumer unit for the office

Aaron · Answer

I would recommend a 6mm2 SWA cable. This could be put on a 40amp breaker.

Ivan · Answer

It’s a subject to calculation of designed current but I’ll recommend 10m2 
Also an earth rod will be required for distance mentioned 
It cannot be fed from an RCD it needs to be to be on a fused isolation unit ( if you want to be certified)

John · Answer

Personally the smallest size cable i would run with the information given would be a 10mm 3core cable

James · Answer

I would go 16mm SWA due to distance run and the fact you will probably be burying it too !

David · Answer

It depends on a few factors.
Generally we would put a garage consumer unit with 3 circuits

Sockets in a ring 32a or radial 20a
Lighting 6a
Radial circuit for panel heater 16a

You take diversity into account for this
100% of highest circuit and 40% of other 2

So example 32a + 8.8a so would be looking at almost 41 amps
Then need to do the voltage drop calculation on 50metre cable to see if it's adequate within 5% 
Calculation would point to a 10mm armour cable

Nickr · Answer

Hi Richard, I would agree with others to run a 16mm cable for future proofing.
You can probably get away with size down (STC of course)
For garden offices we also like to run a data SWA too.
Consider a combined data & power cable such as:

EV-Ultra 3-Core 16mm SWA Cable with Power & Cat5e EV-ULTRA3C716CAT5SWA

other cables options are also out there

Always get a competent person to do a proper cable calc prior to ordering and installation.

Hope this helps

Nick

What size armoured cable

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