Garage Supply

GH Elec · Sep 27, 2019

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

xylophone · Sep 27, 2019

Providence or order code mix up has substituted an isolator that gives no protection to your 6mm SWA with a switch fuse which can. You will need a smaller fuse than 100A I think to protect the SWA but it sounds good IMHO.

Midwest · Sep 27, 2019

I've fitted both, similar one switch fuse to yours and the Wylex. Wylex was marginally better.

Why would an swa cable require RCD protection, and why put two RCD in series? Two fuses in series, whose guess which would go first, but if your head is 100A, suppose it would make sense to put in a lower one for your new supply to garage.

Is there any extraneous conductive parts in the garage? How are you going to manage the notification process, if you don't do domestic work?

buzzlightyear · Sep 27, 2019

if there is no room in the in ,then stick one way board and from there to new garage unit .
[automerge]1569599835[/automerge]

Sean Skino said:
can I just come off the existing MET for the garage earth.

yes ,and no earth rod.considering is a tns. read guideance note 8

Strima · Sep 27, 2019

32A for sockets in the garage? What are they growing in small quantities?

I would probably go for 40 amp BS88 at source in the switched fuse, this will give better discrimination in the event of a fault.

No need for RCD protection on the SWA. Only final circuits will need additional protection.

GH Elec · Sep 27, 2019

xylophone said:
Providence or order code mix up has substituted an isolator that gives no protection to your 6mm SWA with a switch fuse which can. You will need a smaller fuse than 100A I think to protect the SWA but it sounds good IMHO.

Yeah it has come with a 100A/80A/60A fuse. So depending on the main fuse I’ll put a lower one in to suit. Thanks xylophone
[automerge]1569603035[/automerge]

Midwest said:
I've fitted both, similar one switch fuse to yours and the Wylex. Wylex was marginally better.

Why would an swa cable require RCD protection, and why put two RCD in series? Two fuses in series, whose guess which would go first, but if your head is 100A, suppose it would make sense to put in a lower one for your new supply to garage.

Is there any extraneous conductive parts in the garage? How are you going to manage the notification process, if you don't do domestic work?

Oh so either way works. In future I think I’ll go with the Wylex DP Ioslator. The RCD is there to protect the SWA no? Yh I was going to put a lower fuse in to what’s in the head.

The garage door, which I’ll earth. Thanks Midwest
[automerge]1569603123[/automerge]

buzzlightyear said:
if there is no room in the in ,then stick one way board and from there to new garage unit .
[automerge]1569599835[/automerge]
yes ,and no earth rod.considering is a tns. read guideance note 8

Ok thanks Buzzlightyear

Midwest · Sep 27, 2019

Sean Skino said:
Yeah it has come with a 100A/80A/60A fuse. So depending on the main fuse I’ll put a lower one in to suit. Thanks xylophone
[automerge]1569603035[/automerge]

Oh so either way works. In future I think I’ll go with the Wylex DP Ioslator. The RCD is there to protect the SWA no? Yh I was going to put a lower fuse in to what’s in the head.

The garage door, which I’ll earth. Thanks Midwest

The swa doesn’t need RCD ‘protection ‘. Why do you think the garage door needs bonding (it’s not gonna be earthed)?

telectrix · Sep 27, 2019

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.

GH Elec · Sep 27, 2019

Midwest said:
The swa doesn’t need RCD ‘protection ‘. Why do you think the garage door needs bonding (it’s not gonna be earthed)?

Strima said:
32A for sockets in the garage? What are they growing in small quantities?

I would probably go for 40 amp BS88 at source in the switched fuse, this will give better discrimination in the event of a fault.

No need for RCD protection on the SWA. Only final circuits will need additional protection.
[/

Midwest said:

The swa doesn’t need RCD ‘protection ‘. Why do you think the garage door needs bonding (it’s not gonna be earthed)?

Click to expand...

Right ok. And the state of the install in the garage I’m assuming no. But until I start uncovering I won’t know.

Midwest said:
The swa doesn’t need RCD ‘protection ‘. Why do you think the garage door needs bonding (it’s not gonna be earthed)?

Right ok. And the state of the install in the garage I’m assuming no. But until I start uncovering I won’t know.

telectrix · Sep 27, 2019

you only need to bond the door if it's proven to be extraneous. i.e. resistance <0.02 Meg to MET ( using IR tester).

Midwest · Sep 27, 2019

telectrix said:
you only need to bond the door if it's proven to be extraneous. i.e. resistance <0.02 Meg to MET ( using IR tester).

Which I’ll wager it’s not.

[automerge]1569603782[/automerge]

Sean Skino said:
Right ok. And the state of the install in the garage I’m assuming no. But until I start uncovering I won’t know.

Errgh?

GH Elec · Sep 27, 2019

telectrix said:
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.

Ok thanks telectrix
[automerge]1569603867[/automerge]

Midwest said:
Which I’ll wager it’s not. ☺
[automerge]1569603782[/automerge]

Errgh?

There’s existing install there already, twin and earth supply on a washing line. Awful.
[automerge]1569603892[/automerge]

telectrix said:
you only need to bond the door if it's proven to be extraneous. i.e. resistance <0.02 Meg to MET ( using IR tester).

Ok thanks for the info telectrix
[automerge]1569604339[/automerge]

telectrix said:
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.

Although it doesn’t need an RCD in the garage. If I’ve got a garage board that’s got an RCD is it going to be detrimental putting it in?

telectrix · Sep 27, 2019

you need RCD in garage board. it will be the only one on your installation.

GH Elec · Sep 27, 2019

telectrix said:
you need RCD in garage board. it will be the only one on your installation.

Yeah ok I’m with you. Last question I promise, with the earth. I’ve got a 3 core SWA shall I just use the armouring as the earth and ditch the third core or should I use both? So when would an install require a rod, on a TNC-S system?

telectrix · Sep 27, 2019

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 ).

Garage Supply

GH Elec

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xylophone

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Midwest

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buzzlightyear

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Strima

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GH Elec

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Midwest

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telectrix

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GH Elec

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telectrix

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Midwest

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GH Elec

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telectrix

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GH Elec

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telectrix

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