SWA Cable question for the sparkies...

[zzr1200]

I'll soon be wiring my garage for 3ph, possibly including a socket point for a lathe with approximately a 10hp motor.

The wiring current capacity calculator I use, states that 1.5mm 4 core swa will carry the required load for 7.5Kw, but what about the start up loading for a motor, should I move up to 2.5mm or larger cable???

The cable will be clipped to the wall.

Your advice before I order the cable, please...

 

[8ob]

Cant comment on particular cable size, would say future proof it because these initial installations have a tenancy to grow

Bob

 

[zzr1200]

Cant comment on particular cable size, would say future proof it because these initial installations have a tenancy to grow

Bob

That's always a problem, but....

The distribution board is supplied by 35mm cables.

The question is related to supply from the distribution board for the lathe only...

 

[Barking Mat]

How long is the cable run?

I'd go for at least 2.5mm.

I personally run 6mm all round my workshop.

Then I can have a couple of sockets on each spur.

Difficult to use a welder and the lathe at the same time admittedly.

Belt and braces is my attitude.

 

[zzr1200]

How long is the cable run?

I'd go for at least 2.5mm.

I personally run 6mm all round my workshop.

Then I can have a couple of sockets on each spur.

Difficult to use a welder and the lathe at the same time admittedly.

Belt and braces is my attitude.

Dist board to lathe position 10m max depending on cable routing/run...

Most of my 3ph machines are possibly 4 or 5 hp max, but fancy a bigger lathe as well, I possibly have one lined up but just need to check if it's still available...

 

[Spark plug]

I gave up wiring things machine specific years ago, far too inflexible. Now I just install commando sockets as required, for your lathe the full load current works out about 18a, so I would install a 32a socket with 6mm cable.

But a 20a supply wired with 2.5mm will also do the job (depending on distance for distribution board)

 

[Barking Mat]

Where's @brightspark ?

 

[hotponyshoes]

I gave up wiring things machine specific years ago, far too inflexible. Now I just install commando sockets as required, for your lathe the full load current works out about 18a, so I would install a 32a socket with 6mm cable.

But a 20a supply wired with 2.5mm will also do the job (depending on distance for distribution board)

This is how we do it (my sparky anyway)
I put a 16a or 32a (or whatever) socket on the wall.
He wires it up to suit the socket size not what I am plugging into it.

Obviously the price of the cable is not so relevant if you are paying somebody to fit it and may be more of a consideration if you are fitting it yourself.
But if you are questioning 1.5mm vs 2.5mm that's going to be less than £10 extra on a 10m run.

 

[Matchless]

I ran 25mm 5 core to my shed, bloody sparkys always overspec everything! was 110 mtrs from the board though! 25mm five core to replace 6mm tuff cable 240v that replaced 2.5 twin and earth buried straight in the ground, what comes next!

with the 2.5 T&E I could run my mig, main problem was that my large circular saw made the florescent light drop out on start up in the winter,

 

[zzr1200]

The price of the cables not a problem but I just don't want to have to pull cable out again to upgrade it, so in effect future proofing,

 

[zzr1200]

I ran 25mm 5 core to my shed, bloody sparkys always overspec everything! was 110 mtrs from the board though! 25mm five core to replace 6mm tuff cable 240v that replaced 2.5 twin and earth buried straight in the ground, what comes next!

A set of jump leads straight off of the overhead NG power lines....400Kva............

 

[hotponyshoes]

The price of the cables not a problem but I just don't want to have to pull cable out again to upgrade it, so in effect future proofing,

For future proofing I would fit a 32a socket and the cable to match.
You can always fit an underrated breaker now making it a quick easy upgrade in the future if required.

 

[mtt.tr]

I ran 25mm 5 core to my shed, bloody sparkys always overspec everything! was 110 mtrs from the board though! 25mm five core to replace 6mm tuff cable 240v that replaced 2.5 twin and earth buried straight in the ground, what comes next!

with the 2.5 T&E I could run my mig, main problem was that my large circular saw made the florescent light drop out on start up in the winter,

Have no choice with allowable volt drop being low

 

[Alan Reynolds]

This might help. I decided to use 6mm over 25 metres for my new shed. Well over the top I think, but I can buy an offcut very cheap.

https://www.elandcables.com/cable-calculator

 

[mtt.tr]

Inrush current on startup isn't an issue assuming you have the correct mcb type.

Though selecting the correct mcb comes down to other variables.

Its almost impossible to properly advice without seeing the job.

 

[brightspark]

if your putting 30 amp sockets in you can run out in a radial to other sockets and wire in 4.0mm swa with 32 amp mcb if your just plugging your gear in and it may only be 16 amp each phase or less you would have to fit a say downrate to 16 amp triple pole mcb on the machine or whatever rating for other gear

 

[grim_d]

Go for the 2.5, be silly not to.

All my swa is 2.5 and the biggest motor is 2.2kw.

 

[Chris Snow]

I usually go for 2.5 for 16A and 4 for 32A on sensible runs.

 

[Rudi McAnichal]

..... future proof it because these initial installations have a tenancy to grow

..... and the OP is wiring a garage, so the future may include the charging of an electric vehicle.

 

[Morrisman]

I used 6mm SWA out to my little workshop, as I want to use my 180amp Mig out there, in a 16 amp socket, and a small lathe, grinders, lights, electric fan heater etc. I can’t see why you’d run anything less than 6mm actually.