TT and metal CU's

[davetheglitz]

Advice from my NAPIT assessor today:-

• Tails need to be clamped above the main switch terminals. Hager do a clamping kit apparently. Clamping below the board on rear entry is not deemed good enough - even with 25mm tails. Surprised as I couldn't see a 25mm tail moving in a hurry. Cable entry multigland above the main switch satisfies the clamping.
  
• If a dual RCD board is used the main switch should be a time delay 100mA RCD - as main switch to RCD cables are only single insulated. RCBOs are OK however. This backs up the OSG - but hadn't seen this reasoning before.
  
• Generally If rear entry is used the CU should be on a metal mounting plate with notches for any cables coming in - and sealed with a fireproof silicon. Not see any of this before - and didn't think this was a requirement.
  

Has anyone else had similar advice from an assessor?

 

[steptoe]

your assessor has NO idea.!

apart from maybe the 100mA TD instead of a main switch, most of the rest is ballcocks.

 

[Sharpend]

Oh dear, here we go again! Take a Reg, twist it, add a little bit and get a Reg that isn't a Reg?

next they'll require us to leave a fire extinguisher with every new board change!

so following the logic?

a rear entry board whereby the cables exit the wall should have a back plate with notches, so how do we legislate as to the size and number of notches required as every install could be different, and if this is part of the regs then why aren't these back plates provided with new boards?

and as for those tail glands they're made from that combustible material are they not, should they not be supplied with a metal shroud that slides over them?

 

[kerching]

....and a fireproof seal!...even though these boards are NOT Fire Rated...only non combustible

I fear he is blowing bubbles

none of this was mentioned by my NICEIC AE at begining of March

 

[NozSpark]

I don't understand why people don't tell their assessors that they're talking out of their carrot..

I would have no problem in telling mine what I thought of anything, if I needed to,

He keeps on picking me up for not putting circuit schedules on domestic CU's.... I told him that he'll pick me up on it again next time

 

[Sharpend]

Well if he's going to insist on paying you a visit then you may as well make it worthwhile. 

 

[Evans Electric]

So what are "Notches" ? 

I seem to remember a Reg or a Code of Practice that stated , "  Boards on  TT Systems should be made from ...........dare I utter it ?...........Plastic.

 

[davetheglitz]

Pretty much what I thought! Metal on TT is a backward step whichever way you look at it. Tempted to fit plastic in future and note as a non compliance - B and Q still selling them!

 

[apprentice87]

I was going to ask what notches are????

What regs say that the tails have to be clamped anyway?? I always thought that extra mechanical protection where they enter a metal board was what was needed. Why the courgette would you want to be clamping them above the switch?? Ohhhhhhhh, i see, because the powers that be have decided that the terminals in the switch are that **** and insecure that the cable is likely to come loose.... Well, we knew that anyway, they can take it up with the switch makers if it bothers them that much. What is happening now is a bit like if it was decided that all modern cars had to be fitted with padded front bumpers, because the brakes fitted to them were found to be no good...

john..

 

[Essex1]

A metal CU if installed properly with cable clamps and Wiska glands is perfectly fine on a TT system. 

 

[apprentice87]

Yes, but why cable clamps?? If it has been shown the the terminations are insecure, why are the makers not forced to recall them all. Car makers would be....

john..

 

[Essex1]

Yes, but why cable clamps?? If it has been shown the the terminations are insecure, why are the makers not forced to recall them all. Car makers would be....

john..

It is more to do with pulling the tails out from the CU. 

 

[Sharpend]

It is more to do with pulling the tails out from the CU. 

If that were the case then they'd insist we retrofitted the clamps? 

 

[apprentice87]

Hi Essex, I understand what you are saying, and i am not saying it is your daft idea [the clamps] or that you agree with it, but it is daft, With brute force you could pull any cable out of anywhere, i could just as easily yank them out of the cutout!!!

john..

 

[Essex1]

If that were the case then they'd insist we retrofitted the clamps? 

The thing is I actually think this should have always been done.  I am guilty of never doing it either but there has always been regulations about properly supporting cables.  

Hi Essex, I understand what you are saying, and i am not saying it is your daft idea [the clamps] or that you agree with it, but it is daft, With brute force you could pull any cable out of anywhere, i could just as easily yank them out of the cutout!!!

john..

Hi mate, I think it is sensible.  Especially in an underwater cupboard where all sorts of stuff is stored.  Unfortunately the cutout does not fall under BS7671 as you know so there is nothing we as electricians can do about that.

 

[Doc Hudson]

Hi mate, I think it is sensible.  Especially in an underwater cupboard where all sorts of stuff is stored.  Unfortunately the cutout does not fall under BS7671 as you know so there is nothing we as electricians can do about that.

An underwater cupboard?

Doc H.

 

[kerching]

Well if we are talking about underwater cupboards....i am probably the most qualified on here to enter them :slap

Especially in an underwater cupboard where all sorts of stuff is stored.  Unfortunately the c

 

[apprentice87]

I think Essex means un understair cupboard!!

john....

 

[davetheglitz]

Great for fire prevention!

 

[SLIPSHOD & SLAPDASH]

Thats in The 18th edition, all consumer units to be fitted underwater to prevent self-combustion.