metal Cu earth straps

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binky

binky

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Whilst fitting a board yesterday I was considering the need for the earth strap included for the front cover. Given that we earth metal back boxes via the cover screws, and I don't think I've ever seen earth straps on 3 phase boards, and that the metal front is secured by metal screws to the metal back back panel (which cuts through any paint), then the question is 'are these straps actually needed?'.

 
Depends which manufacturer you ask!

I've fitted mainly Hager boards since Amd3 but someone gave me an MCG board to fit the other week. There was an earth strap on it which threw me a bit, I was wondering if this was excessive or if the Hager ones should have one.

Not sure who else does/doesn't supply earth straps, but I bet those that do just do it because 'why not'. I see no need for one. Never ever fitted one on 3 phase boards, type A boards, ordinary metalclad or any other consumer unit/distribution board assembly so not sure why we need to suddenly do it now.

 
Afaik there is no requirement to earth back boxes with a lead if one of the fixing lugs is fixed, never come across earth straps to CU covers but  a lot of street furniture has bonds to the door. A metal roadside cabinet I fitted recently had a door bond, most metal street lighting columns I've worked on have a bond to the door too, though I suspect this is because they are covered by different regs, not BS7671.

 
phil d said:
a lot of street furniture has bonds to the door. A metal roadside cabinet I fitted recently had a door bond, most metal street lighting columns I've worked on have a bond to the door too, though I suspect this is because they are covered by different regs, not BS7671.
Click to expand...


I think that's also because there isn't usually good metal to metal contact. We do the same with panels and enclosures. Doors/sides etc are always bonded, and the same with data cabinets.

 
phil d said:
Afaik there is no requirement to earth back boxes with a lead if one of the fixing lugs is fixed, never come across earth straps to CU covers but  a lot of street furniture has bonds to the door. A metal roadside cabinet I fitted recently had a door bond, most metal street lighting columns I've worked on have a bond to the door too, though I suspect this is because they are covered by different regs, not BS7671.
Click to expand...


street lighting is covered by 7671

Geoff1946 said:
Who earths back boxes via cover screws?
Click to expand...




pretty much everyone...

 
  • Ah, OK. I honestly believed the back boxes were supposed to be independently earthed via the terminal provided. I've always done this on my wiring, though I'm not a practicing electrician.
 
control gear supply a fly lead too, with threaded studs [welded/pressed] on unit and front cover.

MK dont,

BG do as well,

fitting some boards for a builder atm, he seems to appear with a different make of board for every flat,  :shakehead

 
I mostly fit Control Gear and find the earth strap fiking annoying, which is why I'm asking the question.

AFAIK it has 2 fixed lugs ergo the strap is unnecessary.

 
Last edited by a moderator:
binky said:
I mostly fit Control Gear and find the earth strap fiking annoying, which is why I'm asking the question.
Click to expand...
I feel the same  TBH  . I also fit Control Gear but  I think the earth leads are OTT .  Your typical Sarel universal cabinet will have an earth jumper onto the hinged door , sme hinges are plastic etc makes sense but a consumer unit , as said , is screwed to the main enclosure .

And what a pain in the aristotle  when you take  the front off and it dangles there in your way .

Trouble is we are told if we don't follow manufacturer's instructions we will be carted off to the electrician's prison.

A colleague got  3 years for not painting a runner thread , came out a broken man .  Another guy in solitary, a lifer , sent down for a borrowed neutral in 1969. 

 
Last edited by a moderator:
binky said:
AFAIK it has 2 fixed lugs ergo the strap is unnecessary.
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I would agree but it is going against manufacturers instructions so it's a bit of grey area. I'd have no issues with it being left off, but I wouldn't recommend any else did IYSWIM.

 
binky said:
I mostly fit Control Gear and find the earth strap fiking annoying, which is why I'm asking the question.

AFAIK it has 2 fixed lugs ergo the strap is unnecessary.
Click to expand...


One positive thought about these straps is that it stops you dropping the front cover .....

I fit CG CU's and also fit them.....

 
If it's supplied then I will fit it.I cannot see the need for it though.

i look upon it as an "anti litigation device".....some bewigged member of our Ambulance chasing industry would not be able to say my installation caused an entire tower block to collapse because I missed an Earth bond link

"has your Llama suffered a miscarriage?.....Has your Pangolin lost its scales?...has your tumble drier burst into flames due to a 💩 Design flaw that is not being rectified?

then contact us.......then WE will fight your case so that YOU get the compensation that YOU deserve.  Thousands of homes are missing 75mm of green and yellow wire and this may well,be the cause of your angst"

.....and you think it will,never happen?....There are firms out there suing the people that got you your compo in the first place if you think you deserved more!

the country is Barrymored 

 
Andy™ said:
or you dont see it, remove cover and then pull the CU off the wall whilst trying to walk away with the cover
Click to expand...


Like I do all the time with alarm panels, TBF some of them have the strap, some don't. Again I have never seen the point, some just have a spade connector which isn't a major issue, some have a full on ring crimp and nuts/washers so ends up dangling in the way scratching paintwork. Maybe it's more for EMI than electrical safety?

 
Lurch said:
Like I do all the time with alarm panels, TBF some of them have the strap, some don't. Again I have never seen the point, some just have a spade connector which isn't a major issue, some have a full on ring crimp and nuts/washers so ends up dangling in the way scratching paintwork. Maybe it's more for EMI than electrical safety?
Click to expand...


That may well be the case. I’ve never fitted alarm panels but I have fitted many free standing industrial monitoring units. One for level control I get so fed up with the front panel bonding jumper getting in the way I cut it off. Chaos followed, the touch pad mounted on the front panel relied on the grounding jumper. Lesson learnt.

 
Lurch said:
Like I do all the time with alarm panels, TBF some of them have the strap, some don't. Again I have never seen the point, some just have a spade connector which isn't a major issue, some have a full on ring crimp and nuts/washers so ends up dangling in the way scratching paintwork. Maybe it's more for EMI than electrical safety?
Click to expand...


may well be EMI. at least texecoms are only a spade connector and not bolted / screwed

 
Wasn't it NIC that issued the missive about not bonding metal back boxes if they have a fixed lug?

I think it was about 15 years ago.

I still bond them with a flying lead.

Otherwise they are not bonded once the screws are removed.

As far as I'm aware NIC don't write the regs, they are not a regulatory body.

Around that time I was wiring a wooden prefabricated building.

It was massive, half of the first floor consisted of 12 x 3bedroom flats.

I had a visit from the Zurich insurance inspector once a week.

NIC came round once a fortnight to inspect my work.

Zurich insurance bloke was happy as larry with the fire barriers and firewalling etc.

NIC bloke told me I'd got it all wrong, in fact l was completely incompetent and needed instruction and it would go in his report.

Enter Zurich bloke and l explained the situation.

One very short discussion later after NIC bloke was told in no uncertain terms that if l followed his advice Zurich would not insure the building

and Zurich bloke was putting NIC bloke in His report.

He was supposed to be there to inspect and offer advice if he found anything worth mentionng

Not to inflict his opinion on others.

He took the NIC blokes name and made a phone call.

For the rest of the job I never saw that NIC bloke again.

 

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