Sizing electrical cable for garage - is this possible?

[brightspark]

the op supply looks like a tt system using an earth rod . all circuits must be rcd protected back at source as there is no mains earth supplied

 

[wookie]

Thats the way to go but unless the workshop feed is either swa or in metallic conduit (or surface mounted along its entire length) To comply with current regs it still needs rcd protection.

Taken care of that requirement, the feed to my garage is swa that is buried for the majority of the run.

 

[brightspark]

I'd imagine your CNC machine draws too much power to give it it's own UPS ?

Since you really want to protect your CNC machine perhaps a setup similar to what I've got should do the trick.

View attachment 120532

The red group are fed from the 100A incoming switch (no RCD to trip) and the 63A MCB is the feed to my garage's consumer unit. This way the garage or the house can't trip each other out. Because the red group has no RCD I've used RCBO's to feed each of my house lighting circuits so that when a bulb blows it can only take out the lighting circuit it's on and nothing else.

The blue group of 3 MCB's are protected by a RCD, and again the green group is 4 MCB's again protected by it's own RCD.

Each group gets it's own feed straight from the 100A incoming switch. I had to buy extra copper busbars and cut them to the lengths required but I consider it worth the effort.

In my garage I have a split consumer unit again protected by separate RCD's feeding each bank of MCB's.

The only way either the house or the garage can affect each other is if I blow the DNO's fuse and if that happens I'm in the poo anyway.

providing your supply is mains earthed off supply cable you are fine with no rcd protection but tt supply u are not. best bet would be a separate db with a 80 amp double pole rcd using a time delayed 100ma trip , out to garage db then use individual rcbo /s on the final circuits

 

[knighty]

get yourself on ebay for some cheap cable... get some nice thick stuff from your main fuse box to a new one in the garage

for the CNC machine, just run a separate feed for that, from your main fuse box to a socket where the CNC machine lives, 2.5t+e will be fine for that

 

[Robotstar5]

get yourself on ebay for some cheap cable... get some nice thick stuff from your main fuse box to a new one in the garage

for the CNC machine, just run a separate feed for that, from your main fuse box to a socket where the CNC machine lives, 2.5t+e will be fine for that

Or maybe not? - cheap imported cable fire risk

 

[GW8IZR]

Or maybe not? - cheap imported cable fire risk

I like the comment in the news item, the cable was sheathed in grey plastic....

Easy to spot that then ;-)

 

[knighty]

Or maybe not? - cheap imported cable fire risk

oops sorry, should have been more clear, I meant an offcut / left over bit etc.

there's always SWA listed pretty cheap... off cuts from bit jobs, leftover bits of rolls... all the bit ssomeone can fit in the back of the van at the end of a job etc.

 

[DrDeAtH]

You might be best putting a Henley block in the meter tails and splitting the supply between the house consumer unit and a dedicated switchfuse for the garage. At least that way if there's an issue with either set of circuits you don't lose the whole lot.