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Topic Title: Temporary supply
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Created On: 01 October 2012 06:59 PM
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 01 October 2012 06:59 PM
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goldenboy1818

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Hi all, wondered what was the current situation for domestic temporary supply's and earthing, for like rewires/ refurbs etc etc, thankyou for any replys
 01 October 2012 08:51 PM
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slittle

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I'd install a small board (we've got a couple pre-made) with a two way RCD protected mains and a couple of double sockets on.

and I'd TT the board as you can not be certain of anything else


Stu
 01 October 2012 09:11 PM
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DOUGIE1000

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Let's not be daft, were experianced tradesmen, we have a small bit of wood with 2ft of flex with flex stripped back leaving 6inches of exposed L+N and albout 18 inches of gy. Our flex runs to a robbed garage board with 16amp mcb and supplying a 2x 2gang socket, most of time these skts only used for 110 tranny (other trades as we mainly use battery power) and lots of battery chargers.

Our flex is connected either into load side of meter or hengly blocks if present. Ready for you to shout at me haha

-------------------------
Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!
 01 October 2012 09:26 PM
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slittle

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Dougie,

My original answer was the way I'd want to see it done.



In practice, two foot cut off extension lead, choc blocked to tails.

Earth, who needs it, most cordless chargers are class two and the site kettle is probably plastic.


Stu
 01 October 2012 09:26 PM
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primo

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Exactly! I currently have a couple of temp boards on the go. One is a 6 way Wylex (RCD main switch) with the obligatory 2 DSO on a piece of ply, but, I've upgraded the flex to a henly block with 16mm tails...it's so good that I'm considering just leaving it there as the final product!

Kept it as TN-S as far as earthing goes.
 01 October 2012 09:29 PM
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DOUGIE1000

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I'm lying............... I don't connect it into the load side of the meter :-)

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Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!
 01 October 2012 09:56 PM
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sparkingchip

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I have sent you a picture to your works email Stu to see if mine passes.

Andy
 01 October 2012 11:02 PM
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peteTLM

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Im constructing at the moment a 2 way garage board made up with some 10mm SY flex, with the end made off with heatshrink leaving a couple of inches of line and neutral made double insulated with heatshrink, and 18 inches of earth with a lug and a bootlace ferrule to cover most scenarios.
On the garage board are 2 panel board commando sockets for 2 adapted extension leads to plug into.

-------------------------
----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 02 October 2012 07:19 PM
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OldSparky

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Originally posted by: peteTLM

Im constructing at the moment a 2 way garage board made up with some 10mm SY flex, with the end made off with heatshrink leaving a couple of inches of line and neutral made double insulated with heatshrink, and 18 inches of earth with a lug and a bootlace ferrule to cover most scenarios.

On the garage board are 2 panel board commando sockets for 2 adapted extension leads to plug into.



wow thats some temp board
 02 October 2012 08:48 PM
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weirdbeard

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Originally posted by: slittle




and I'd TT the board as you can not be certain of anything else




Why? what is there not to be certain about?
 02 October 2012 09:09 PM
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slittle

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If it's PME, i'd be concerned about the possible lack of bonding

Stu
 02 October 2012 09:16 PM
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weirdbeard

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Would you not be concerned about the lack of bonding in a TT situation - BS7671 that i can see doesn't seem to give any leeway regarding the type earthing system?
 02 October 2012 09:28 PM
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slittle

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Yes, but it's not as much of a problem when things go a bit wrong. Remember my outside tap post



Stu
 02 October 2012 09:41 PM
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weirdbeard

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Originally posted by: slittle

Yes, but it's not as much of a problem when things go a bit wrong. Remember my outside tap post




Not exactly, though I do recall seeing a dno document(a link from this site to a central networks doc) saying that if it's not possible to bond extraneous conductive part then they will only supply a TT system - I'm just not sure how this stands with signing off a TT installation to BS7671 if there are extraneous conductive parts that arent bonded? ie, the dno doc says it's ok if it's TT'd if there isn't bonding to XCP's, but BS7671 doesn't seem allow for such an issue, they have to be bonded regardless whether its a temporary installation or permanent.
 02 October 2012 09:46 PM
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slittle

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Trouble is when the bonding disappears because on a refurb the plumber decided to cut out a section of pipe.

I seem to remember 7671 says that a "construction site" must be TT but i'm away from my books tonight so can't find the wording. I guess it's down to how you define a site, but I reckon the man in the grey wig would look at a refurb job as a construction site.


Stu
 02 October 2012 09:59 PM
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AJJewsbury

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I seem to remember 7671 says that a "construction site" must be TT

Almost - 704.411.3.1 prohibits PME unless all extraneous-conductive-parts are reliably bonded to the MET (hence TN-S, PNB etc would be acceptable too).

The trouble with construction sites it that it's expected that other trades will be introducing exposed-conductive-parts during the lifetime of the (temporary) installation.

- Andy.
 02 October 2012 10:02 PM
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UKPN

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---the topic is regarding temporary supplies.

its a question of practicalities, PME wouldnt be given because it
would be impossible to do the bonding.

the same as with a half built property with perhaps a couple of inches
of water main. it is not practical to string bits of earth wire across the room to such water pipe.

much the same as buildings close to stuarts heart--farm buildings.

so the DNO allow an RCCD and earth rod.

Regards.
 02 October 2012 10:12 PM
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weirdbeard

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Originally posted by: UKPN



much the same as buildings close to stuarts heart--farm buildings.



so the DNO allow an RCCD and earth rod.




Hi ukpn, are you saying then that if a farm building such as a barn has embedded steel uprights
(ie likely to be extraneous conductive parts according to BS7671) linked with wooden cross beams, and a non metallic roof covering the extraneous conductive parts don't need to be bonded? I was under the impression that a connection by the DNO would be refused if the installation wasn't compliant with BS7671?
 02 October 2012 10:12 PM
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slittle

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Off topic but sort of related to your post UKPN,

We're on a duck farm at the moment, The first building has a PME incomer in it, now how that got connected I'll never know.

You can guess what I'm doing with our new building.


Stu
 02 October 2012 11:42 PM
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weirdbeard

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Originally posted by: slittle

Off topic but sort of related to your post UKPN,



We're on a duck farm at the moment, The first building has a PME incomer in it, now how that got connected I'll never know.



You can guess what I'm doing with our new building.





Stu


Ducking the regs?
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