Wire sizing

[ronan]

I am going to finally wire my shed properly , i am going to run a cable from the house fuseboard to a fuseboard in the shed, i asked someone years ago what size this cable should be and was told 6mm squared, i will be running the usual lights and 220v sockets and in addition my 5hp lathe , 3hp compressor and a 1hp pillar drill ,i hope to add a bridgeport milling machine in the future.
Does this size of cable sound correct ? The distances between the fuseboards is 22meters.

 

[troppo]

The laws are different here (got to get a licenced sparkie for anything like this) but i would work out your maximum draw at any one time eg lights, music and the most powerful tool you have. Work out how much current you will be drawing at any one time and then excede that by maybe 20% just to be on the safe side. After you`ve worked that out a couple of beers with a sparkie will get you every detail you could need. In other words those with the proper training are the best to ask.

 

[Ed.]

x2 what "troppo " said, Although I would go for the next size up,10mm as a minimum, not that you would probably need it at this stage, and if you can afford to do it, get 3 phase as it is even better. It's for those little extra's that most likely will turn up in the future that you hadn't planned for yet. The cost of that cable is going to be relatively inexpensive compared to the total job cost and it's easier to do it now then later. Bigger and more is always better!

To give you an example, I built my 12mt x 6mt shed which is only about 10mts away from the main switchboard and put in 10mm cable (2 core and earth). I was thinking about 3 phase but thought,... nah! not going to happen, thinking this 60amp cable is more than I need, put the conduit under ground encased in concrete as it ran under the carport, called in a sparky and he wired up the switchboard and the sub-main in the garage.

All good... but 6 months later a nice MIG welder turned up and you guessed it... 3 phase. Damn. The conduit I used wasn't big enough to pull the 3 phase cable through. Had to dig another trench, more concrete and another larger switchboard, another visit from the sparky.

Funny thing is, when we built our house I was thinking about putting in 3 phase but didn't think I would ever use it so only got single phase put in. It would have been significantly cheaper at that stage.

If I ever get another house built, is is going to have 3 phase from the start. A largish 3 phase lathe has also been added to the garage now. 3 phase gear is much cheaper to buy than single phase. So the moral of the story is "listen to your inner voice". Plan for the future, you never know what goodies or toys will turn up when you least expect them. Especially if you are into metal working as I see you are.

 

[ronan]

Our electricity supply board will not as a matter of policy install three phase power into houses, oh but that they would , working in engineering i have seen some lovely useable three phase machinery dumped in the scrap yards because it had been replaced with newer kit. Most of it could have been bought for the price of a couple of pints .

 

[Ed.]

Our electricity supply board will not as a matter of policy install three phase power into houses, oh but that they would , working in engineering i have seen some lovely useable three phase machinery dumped in the scrap yards because it had been replaced with newer kit. Most of it could have been bought for the price of a couple of pints .

Well that's bad. What if you wanted to install 3 phase reverse cycle airconditioning into your house, would they knock you back on it then?

Oh well, then back to my original suggestion... 10mm at a minimum.

Over here where I am in Queensland Australia, if you tell them it's for a 3 phase aircon they don't even charge you to connect to the house from the street. You only pay for what ever it costs to run it down from your house connection on the roof ie; the sparky, the cable to the first meter and all the subsequent circuit breakers, RCD, switches, ect. They even provide the polyphase meter for free.

By the way the 3 phase aircon never did eventuate but my 3 phase welder and lathe did. .

 

[ronan]

Well that's bad. What if you wanted to install 3 phase reverse cycle airconditioning into your house, would they knock you back on it then?

Oh well, then back to my original suggestion... 10mm at a minimum.

Over here where I am in Queensland Australia, if you tell them it's for a 3 phase aircon they don't even charge you to connect to the house from the street. You only pay for what ever it costs to run it down from your house connection on the roof ie; the sparky, the cable to the first meter and all the subsequent circuit breakers, RCD, switches, ect. They even provide the polyphase meter for free.

By the way the 3 phase aircon never did eventuate but my 3 phase welder and lathe did. .

Air conditioning , in ireland , i had to wear my old barbour bike jacket the other day going out as it was so cold and wet , and its the height of our summer over here.
Nope nothing over here is easy and i presume its the same in the uk , the health and safety nazis shake their heads at absolutely everything.
What is the heaviest single phase cable available ? i might as well fit it , its only about 25 metres i need.

 

[graffian]

You could say you have a three phase water heater/shower.
I wired to my raj with 10mm.

 

[Ed.]

Air conditioning , in ireland , i had to wear my old barbour bike jacket the other day going out as it was so cold and wet , and its the height of our summer over here.
Nope nothing over here is easy and i presume its the same in the uk , the health and safety nazis shake their heads at absolutely everything.
What is the heaviest single phase cable available ? i might as well fit it , its only about 25 metres i need.

Oops, I forgot about your weather, as for the cable you can get whatever size you want, ie: 10mm, 16mm, 32mm. The bigger the cable the more $ it will cost. I got most of mine from an auction and the rest was used cable from a metal salvage yard where they were getting ready to strip the insulation off for the copper. So long as the cable isn't damaged it should be fine.

There are a few other points to consider before you get the cable. As I said before you will need to talk to your sparky first. He will have to find out what size wire is going into to your house switchboard first, eg: if it is 4mm then there wouldn't be any point in putting in heavier cable bigger than 6mm as your shed is only 25mts away (unless you get those cables upgraded as well.) If it is 10mm going into your house then I think 10mm (60amp) should be ample, which I think will do about 13200Watts or 17HP,

When working out a cable size the sparky will have to work out what your house load is and then add the anticipated additional shed load to it. Just my 2 cents worth hope it helps. .