earthing back boxes

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dean mac

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hi does metal back boxes have to be earthed if the circuit is rcd protected thanks in advance

 

extension15

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There is no requirement as such, but reference to good practice in one of the guides...

:D

 

seajayess

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I think you have to bond them if they do not have a fixed lug that the face plate screws to ie both lugs are adjustable CJS

 

Admin1

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I'd put a flying earth on it regardless. Good practice?

 
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i dont earth the back box with a flying cpc lead, more so under 17th regs as its now required to seperate the cpc's of the ringmain, one cpc to each earth terminal so that if the connections of one fails the circuit is still protected, in which case there would be a 50% chance you wasted your time.. and as already said so long as the box has a fixed lug, as all i've ever used do, there is no requirement

 

jckent

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I'd put a flying earth on it regardless. Good practice?
Agreed-For the sake for a minute, and a few inches of cable- why would you not?

 

steptoe

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there is NO requirement anywhere to earth the back box on a flush mounted accessory.

as long as you provide an earth to any exposed conductive part(ie, the screw, earth provided via brass insert).

waste of time, Im not going to get into the reasons why I think this unless someone really wants to know.!

 

dean mac

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there is NO requirement anywhere to earth the back box on a flush mounted accessory.as long as you provide an earth to any exposed conductive part(ie, the screw, earth provided via brass insert).

waste of time, Im not going to get into the reasons why I think this unless someone really wants to know.!
so if most people do earth the back boxes do u all still supplementary bond even tho u dont have to under the 17th

 

steptoe

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so if most people do earth the back boxes do u all still supplementary bond even tho u dont have to under the 17th
NO

and

NO,

never have earthed back boxes, except under SR,

waste of time.

only supp bond where required, or on SR.

why do what your not paid to do?

good workmanship is NOT about wasting your time or doing something that has absolutely no bearing on the safety of the installation,

and I would like to read ONE reasoned arguement as to why tagging back boxes is of benefit.

 

dean mac

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NOand

NO,

never have earthed back boxes, except under SR,

waste of time.

only supp bond where required, or on SR.

why do what your not paid to do?

good workmanship is NOT about wasting your time or doing something that has absolutely no bearing on the safety of the installation,

and I would like to read ONE reasoned arguement as to why tagging back boxes is of benefit.
to be honest i agree with u
 

TTbangbang

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Good to think about these questions, my take is that the metal back box (whether for a surface-mounted or flush-mounted accessory) is an exposed conductive part and therefore is required to be earthed. The sparky has to decide whether or not the in-house earthing (adjustable lugs, earthing strap, screw eyelets) on the socket-outlet could be compromised and thus whether or not to add an earthing tail.

Whether or not there is RCD protection is not relevant, you would earth as a start and then use an RCD for additional protection in case the earth connection is/becomes ineffective.

Supplementary bonding is required under the 17th in certain conditions. See Reg. 701.415.2 e.g. in a TT system

Please would someone point out if I've spouted rubbish and :S

Blushing

Guiness Drink

 

DonkeyDong

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My personal opinion is to bond the back box to the circuit CPC via a fly lead.

There could be a situation where the cable is damaged/cut into the backbox and the CPC onto the socket is not in contact with the backbox (ie the socket front is loose or has been undone from the back box, while still live).

The backbox could be live, but not enough current could flow to trip the protective device (as it is not connected to the CPC of the circuit), but yet it would give you a nice kick!

For the sack of a few minutes I always bond them.

D.

 

steptoe

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Good to think about these questions, my take is that the metal back box (whether for a surface-mounted or flush-mounted accessory) is an exposed conductive part and therefore is required to be earthed. The sparky has to decide whether or not the in-house earthing (adjustable lugs, earthing strap, screw eyelets) on the socket-outlet could be compromised and thus whether or not to add an earthing tail.Whether or not there is RCD protection is not relevant, you would earth as a start and then use an RCD for additional protection in case the earth connection is/becomes ineffective.

Supplementary bonding is required under the 17th in certain conditions. See Reg. 701.415.2 e.g. in a TT system

Please would someone point out if I've spouted rubbish and :S

Blushing

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rubbish! if flush mounted then its not exposed or extraneous.!

if its surface mounted M/C then its part of the fitting and requires earthing.

supp bonding to 17th is similar in any domestic whether TT or TN, doesnt really matter anymore.

if its about comm/ind/agri etc then slightly different, but unless otherwise stated then I think mostly on this forum we would assume domestic.

 
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I personnally always earth metal back boxes wether they be flush or surface.

Also with the increased use of metal face plates i tend to also earth BT and TV point boxes on rewires. This way if customer then requires metal face plates, boxes are ready to take them. This is the way i do it, maybe not neccessary but old habits don't die.

Batty

 

TTbangbang

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eeek!

NICEIC say a 'metal back box for a flush-mounted socket-outlet is deemed to be an exposed conductive part (even though it may not be able to be touched).' Their highlighting. Mustn't slavishly believe everything they say I guess :D

I thought that as disconnection times cannot be met in a TT system then supplementary bonding had to be present? :(

Learning all the time Blushing

 

steptoe

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Reply to TT bangbang, I would'nt say the flush box was exposed conductive metalwork,.Wish I had thought of a barmy name now !!

Deke
'evans above, why would you want to do that now????

theres enuff loonies wantin to take over this place, I cant cope,

any more of this and Im gonna have to ring batman to come back from his holidays and help me.!

 

steptoe

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eeek!NICEIC say a 'metal back box for a flush-mounted socket-outlet is deemed to be an exposed conductive part (even though it may not be able to be touched).' Their highlighting. Mustn't slavishly believe everything they say I guess :D

I thought that as disconnection times cannot be met in a TT system then supplementary bonding had to be present? :(

Learning all the time Blushing
thats why RCDs were used, but as now we have to use 30mA to comply with 17th then TT is covered also.

could someone explain to me how a buried in the wall object is exposed?

NIC dont make the rules, in fact, sometimes they state the stoopidest things!!!

 

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