Detached garage wiring - a little guidance please.

[shrunkenmaster]

(Please note - I'm in my 2nd year of the 2357 course. I will not be attempting any work on my own.)

I'll soon be moving to a new house with an external double garage that has power to it already for a couple of sockets and lights. I will need to rewire as I'm planning to use the space to house several arcade video games, along with a small workshop.

The games draw approximately 4-4.5A each and I'll need to allow for 18 of them. I'll only be using basic power tools in the workshop, no welders or the like. Only other load would be basic fluorescent lighting.

Obviously the total demand would be quite high when all the games are powered up (this will be the case a lot of the time), so I was thinking about taking the meter tails, into an isolator switch, then into a henley block which would feed the house CU and the external CU in the garage. I understand the tails from the henley block should not be more than 3 metres, so was wondering the best way of accomplishing this?

I haven't been able to assess how the garage is connected to the CU yet, although I'm assuming it's buried somewhere as there's nothing overhead!

The house is using a TN-S system.

 

[monkeyelectric]

A switchfuse dear fellow

 

[shrunkenmaster]

A switchfuse dear fellow

Care to expand on the subject my good man?

 

[monkeyelectric]

Here you go 60 Amp Switchfuse SP & N Insulated - Ex Fuse, there are others available that are smaller and obviously different size fuses to suit
These are better http://www.qvsdirect.com/Excel-80A-Fused-Double-Pole-Main-Switch-pr-22561.html

 

[Mork]

Your about to increase your load by 72 amps, youll probably require an extra phase, do your calcs.

 

[shrunkenmaster]

Here you go 60 Amp Switchfuse SP & N Insulated - Ex Fuse, there are others available that are smaller and obviously different size fuses to suit
These are better Excel 80A Fused Double Pole Main Switch - QVS Electrical Supplies | Electrical Wholesaler

So, going from the henley block to switch fuse, to SWA, out to the garage CU? Would the external cable run not need additional protection?

 

[shrunkenmaster]

Your about to increase your load by 72 amps, youll probably require an extra phase, do your calcs.

Thanks, I was thinking that the additional load might be pushing things along with the house circuits! Will be having a look at calcs next, just thought I'd ask to see if I was missing anything else.

 

[Des 56]

Would the external cable run not need additional protection?

Its Swa so its wearing it

 

[shrunkenmaster]

Would the external cable run not need additional protection?
Its Swa so its wearing it

I was thinking non-mechanical protection, or am I just having a stupid Sunday?

 

[telectrix]

SWA buried 18" deep will not require RCD protection. sand below and above to prevent sharp stone damaging it. don't forget the warning tape. or you could duct it. that load for the machines seems a bit on the high side. double check that. you might get away with 10mm SWA.

 

[shrunkenmaster]

that load for the machines seems a bit on the high side. double check that. you might get away with 10mm SWA.

Thanks - I'm erring on the side of caution with the loads. Basically each machine has a monitor rated at 1A, plus a PC-based system at 3A. I'm pretty sure the computers don't pull that much though.

 

[telectrix]

think you could have problems with earth leakage tripping any RCD you fit.

 

[shrunkenmaster]

think you could have problems with earth leakage tripping any RCD you fit.

What's the solution to that then? Was thinking of 3 separate power circuits in the garage - 6 machines on each, with the third jointly used for the workshop, which would not be operational at the same time as all the games.

 

[monkeyelectric]

So, going from the henley block to switch fuse, to SWA, out to the garage CU? Would the external cable run not need additional protection?

Everyones already answered it but swa is already wearing its suit of armour so doesn't need any additional protection

 

[monkeyelectric]

What's the solution to that then? Was thinking of 3 separate power circuits in the garage - 6 machines on each, with the third jointly used for the workshop, which would not be operational at the same time as all the games.

Rcbo's and a seperate 4mm earth in a ring around the sockets