Second CU in garage

[turningtim]

Hi All

I want to tidy up the garage wiring and add a few more bits, Im thinking that a second CU would be the easiest with separate sockets\isolators for individual equipment (compressor, pillar drill, lathe etc) Im looking at 16a radial for the compressor (3hp motor) with 16a 230v Blue, round 3 pole plug\socket and standard 30a ring main for the rest (all 1/2 or 1/3 hp motors) or hand tools plus lights on 6a radial.

Should the seconday CU be fed from an MCB off the primary CU or direct from the isolator, or the incommer?

and what size cable to use to link both CUs -we're talking appox 15m.

(its all certifiable (arent we all!) I'm just doing the labour and prep work to trim the bills down)

 

[ricicle]

Who is going to be certifying the work ? As it is their name on the certificate they will need to decide what size cable and how the mains is configured, along with any remedial works at the existing installation if required.

 

[EdwardCurrent]

Hello,

As Ricicle has 'said' it is better that you talk with the person signing off the work. It would be a mistake/shame to install it as advised by others, only to have your electrician turn up and tell you that he was going to do the work in another way.
There is no harm in you doing the 'donkey work', just ask the elec what you can do (position of equip, cable sizes etc etc). If he knows that you are doing some of the work, did he expect you to know what to do without you talking/writing it down with him ????

Ed.

 

[turningtim]

Point taken, I've got the floors etc up for the plumbing and adding insulation replacing the broken boards from the original heating system etc, and wanted to get ahead of the game and not have to get the whole lot back up again. and for my own interst really!

 

[EdwardCurrent]

At least you enquired, thats better than throwing in whatever you thought would 'do'. Give the electrician a call, he will prob be supplying the cable, and can advise you how and where he wants it run etc. I would leave all your work exposed so that he can check it afterwards too.
Keep that darn insulation well away from your cable runs !!!!!!!!


Ed

 

[turningtim]

thanks All

Sparky's been over and is happy with chasing, cable routes etc and sorted all the rest, but to day been on with the lights.

All the switches are in slim (18mm??) back boxes, these are bolted and clamped to metal conduit running to the ceilings. Its all earthed via the back box but no grommets -don't see how there could be given the clamps. Even the black enamel has been scraped off and I get a zero ohms reading of a digital multimeter between earth and back box or conduit.

Is that ok or should i break out the plaster trim the conduit, replace the boxes and add grommets? Sparks is on holiday this week and I'd like to press on but not going to hassle the guy while he's on leave