electrical supply size

[hunggaur]

ok folks what size wire should i put in as my new feed from the house to the workshop

i think 6mm is to small

i was going to go for 10mm or 16mm

is 16mm a bit over over kill

cheers

jon

 

[Racers]

Hi,

Depends on how far it is away.

Pete

 

[hunggaur]

20 meters from house 30 from fuse box

 

[twothumbs]

In days gone bye...a 30 amp cooker control was on a 6mm cable and a 45amp cooker unit fed with 10amp cable. Allowing for a voltage drop for cable length, 20m which does not seem unduly long.....think of a cable run through a large house. A 16amp a cable would serve a lot more, but then you need to think what it is your running at the same time. A lighting circuit of 6amps say, would leave a goodly amount for machines ,etc to run but how many at the same time....one at a time....machine plus dust extraction perhaps. Electricians ,and I am not one, use load diversification factors......ie you dont use full power at the same time, so a smaller suplply is installed. If the power authorities ddint use diversifiaction of loads they woudl have enormous supply problems. You could do a check on a large cooker and see what the power rating is and act as a starting point for what you are putting on the end. It all gives you a feel for what it is about. I am afraid I have forgotten where you would find the voltage drop for cable lengths but someone will know. You dont want a larger breaker unit than you need. Best wishes.

 

[Bright-Spark]

Hi Newby here! But I can offer some advice on how I would approach this

I assume that your workshop is external, so you will ideally use an armored PVC cable

You need to determine your maximum demand, select an MCB size and check your cable rating and volt drop based on these.

Using my modest single phase set up as an example the maximum demand would be my biggest machine and extractor running at once.

Lighting 4x58W lights = 1A
3.5 Kw Table Saw = 13A
3.5 Kw Chip Extractor = 13A
Air Filter = 1A

Total = 28A

This is close to 32A and as I use 16A type C MCBs for table saw and extractor I would go a size up to 45A to ensure discrimination i.e. a local fault does take out the main workshop supply.

Therefore cable rating must be > 45A
Volt drop calculated on 28A maximum demand.

A 6mm/Sq XPLE/SWA cable has a worst case current rating of 67A, installed in duct.

Single phase volt drop for the cable is 7.90 mV/A/M

So if my workshop was 30M away then the volt drop would be (7.90*28*30)/1000 = 6.6V (2.8% of 230)

You can get cable data from manufactures sites just Google AEI Cables

I would install a 3 core cable so you can use the spare core as the CPC (earth).

Your cable size should be based on the rating of the cable type you select and your maximum demand etc.. but I hope this is of some use and not too technical.

 

[Mickfb]

I am lucky, my garage is attached to the side of the house. I have got an electrician in for advice. I run a ring circuit off the consumer unit through a 40amp cooker switch. The electrician come round yesterday to check my installation and connect it up to the consumer unit. It's so much better than running everything from extension leads and so easy to isolate at the end of the day.
Mick.