Garage Supply

[GH Elec]

Hi all.

I’m a qualified electrician but haven’t had loads of experience doing domestic work so need some advice please.

The current consumer unit has no spare ways and she doesn’t want it upgraded.

I was going to install a 5 Way Henley block with 16mm tails for my new supply. I’m hearing different things on what to install. Originally I was going to put a DP Wylex Isolator in and run my 6mm 3 core SWA from that to a new Garage board, which will have an RCD and a 32a MCB and a 6a MCB.

However the wholesalers have sent me a 100 Fuse Switch. (Image attached) My friends at work have said this will be fine. But other people have told me that I need an RCD at both ends. So a Garage board with an RCD and 40a MCB at the meter end.

Also regarding the earths it’s a TNS system. The garage is only 15 metres away from the meter, can I just come off the existing MET for the garage earth. Or will a earth rod need to be installed.

Any advice will be much appreciated

 

[buzzlightyear]

So when would an install require a rod, on a TNC-S system?

unless you have metal in there like pipes or oil drill,lol.

 

[GH Elec]

use both 3rd core and armour as cpc. then you still have cpc if steel rusts.. rod only needed if TNC-S and extraneous parts in garage, unless a 10mm bonding cable is added where the cpc is below that (allowing fot the steel as 8 times less conductive than copper ).

Right ok thanks a lot for your help telectrix. So if it’s a TNC-S a rod has to be used.
[automerge]1569605518[/automerge]

your SWA needs protecting with a 40A fuse in the isolator. it does not require RCD; as long as you ensure the armour is earthed at supply end. the armour may be used as cpc for the garage sub. no rod needed.

I’ve just looked and the lowest fuse with it is 63A. Should I get a 40A fuse or will the 63 be fine

 

[telectrix]

Right ok thanks a lot for your help telectrix. So if it’s a TNC-S a rod has to be used.

not exactly. if extending TNC-S to an outbuilding with extraneous parts a 10mm bonding conductor is reqiured. the SWA may not be enough, so to save the expense of rumming in an extra boding cable, it's sometimes better to separate the earthing systems and TT the outbuilding.

 

[GH Elec]

not exactly. if extending TNC-S to an outbuilding with extraneous parts a 10mm bonding conductor is reqiured. the SWA may not be enough, so to save the expense of rumming in an extra boding cable, it's sometimes better to separate the earthing systems and TT the outbuilding.

Ok that’s good to know for future installs. Yh I can get hold of that pretty easy where I work.

 

[goasis]

I don't wish to be harsh, and I'll happily admit to having many gaps in my knowledge and experience, but I was wondering what area of electrical work you work in as you seem to have some slightly skewed ideas regarding OCPD's (or lack of) and RCD's providing additional protection.

 

[GH Elec]

I don't wish to be harsh, and I'll happily admit to having many gaps in my knowledge and experience, but I was wondering what area of electrical work you work in as you seem to have some slightly skewed ideas regarding OCPD's (or lack of) and RCD's providing additional protection.

I work on the Underground. Mostly done metal work conduit trunking tray ladder rack. Only recently out of my time. Believe it or not I have my inspection and testing qualification aswell. But just not done much of it that’s all.

 

[goasis]

I work on the Underground. Mostly done metal work conduit trunking tray ladder rack. Only recently out of my time. Believe it or not I have my inspection and testing qualification aswell. But just not done much of it that’s all.

Fair enough, I bet your tray and conduit work would put mine to shame then!! Maybe just a bit of brushing up on how and why we use fuses (over current devices) and RCD's needed then!! There's always more too learn, I feel pretty confident in some areas, much less so in others, esp compared too some on this forum!

 

[GH Elec]

Fair enough, I bet your tray and conduit work would put mine to shame then!! Maybe just a bit of brushing up on how and why we use fuses (over current devices) and RCD's needed then!! There's always more too learn, I feel pretty confident in some areas, much less so in others, esp compared too some on this forum!

Yeah it’s catch 22 though when it comes to things like this I’m not to hot on it where I’ve not done much of it. Yh I defiantly feel bit more confident about it now.

 

[Midwest]

There's the thorny issue of notification to the LBC; have you a solution to that?

 

[davesparks]

I work on the Underground. Mostly done metal work conduit trunking tray ladder rack. Only recently out of my time. Believe it or not I have my inspection and testing qualification aswell. But just not done much of it that’s all.

Presumably your training covered cable calculations for designing a circuit like this?

It's a sad reflection on the training you've been provided if they haven't managed to teach you this kind of thing in an apprenticeship.