Electrical advice required please

[dave_87]

Hi all,

Im in the process of building a new workshop at the end of the garden. To try to keep cost to a minimum i'm planning to purchase and lay the cable myself(will get an electrician to do the connecting etc).
I'm struggling to figure out what size cable i'll need, I've been doing a lot of reading and seem to have confused myself,
Is there a formula I can use to calculate the gauge of wire required?
I'm looking to run:
Lights, Router, Bandsaw, Lathe, compressor, large ish tools.
The total cable length will be 25-30m so not sure if voltage drop will be a factor.

Thanks in advance.
Dave

 

[kevinlightfoot]

If it helps I have just completed a similar job,my electrician insisted on my installing 10 MM cable to avoid the voltage drop problem .I purchased a 50 metre drum from a firm called quickbit and the delivery was next day.I think I paid around 165 pounds for it . Installing the cable was bit of a back breaker it is very heavy and you need to bury it or if you can fix to a wall you need cleats at approximately 12 inch spacing.The remaining cable you can always sell on to recoup a few pounds if you don't need it.

 

[porker]

Rough calculator states 4mm would get 16A over 30m and 6mm <30A within 3% voltage drop. The bigger you get the more current you can draw. I would go for 10mm as above if it were me, then you have plenty of options particularly if you run a heavy machine and need some electrical heat. Also some big machines have a heavy startup current and with the protection you need could cause annoying trips on RCDs.

 

[jimmy_s]

will depend on the machinery loads, I would run a minimum of a 10mm2 SWA protected with a 45A MCB with RCBO protected ccts in the workshop. You would be better checking with your electrician and agreeing a cable spec etc before buying anything.

 

[n0legs]

Go for the biggest you can afford.
10mm will give you some sensible capacity, but bigger may be better. The cable spec massively affects what you can use now and in the future.
A larger cable running at a lower rating can easily be run at full capacity (or very near) at a later date by changing out switchgear and protection devices. Whereas uprating capacity/ability may mean digging up/removing and rep!acing a smaller cable that will be worth very little later on.
Get a spark involved sooner rather than later, there are other factors that influence cable choice.

 

[Myfordman]

Use the online calculator on the TLC website and get it right.

 

[HappyHacker]

Have a chat to your electrician first. He can tell you if there are any things you should consider in your particular circumstances. Most electricians will be happy for you to install your own cable. I agree with going for bigger than the cable calcs say to allow for future changes. The extra cost of cable will be minimal in the overall scheme of things.