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spud1

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Hi,

Can anyone clarify for me the requirements regarding either the RCD protection of tails or glanding of tails entering a metal consumer unit in a TT system. With specific forethought to the upcoming amendment enforcing all metal consumer units.

Cheers
 
There are no specific regulations,but in order to comply with general regs then either the tails will need to have earth fault protection or measure must be taken to minimise the chance of a fault to the metal case. This would mean keeping tails sheathed all the way to the terminals....tails kept as short as possible,and most importantly an insulated bush and some form of cable clamp to prevent any movement of the tails.
 
On a TT 100ma S Type RCD protecting the tails. You would need insulated enclosure though to house the S Type RCD but then you can't use plastic on new amendment....... Very good question really, Im not sure of the answer. Someone will know on here :)
 
Will ring the NICEIC techline tomorrow and see what fob offs they can spin me. Attended a freebee Hager 'technical seminar/sales pitch' tonight through my wholesaler. The speaker couldn't give a proper answer to the question. Does anyone know of a specific double insulated/reinforced insulation grade glanding system that can accomodate tails?
 
There is mention of using wiska glands for the tails to the M/C boards , I got a phone call from Citys about some new display `M/C boards with wiska glands , Newlec , thanks but no thanks was my reply ..
 
Will ring the NICEIC techline tomorrow and see what fob offs they can spin me. Attended a freebee Hager 'technical seminar/sales pitch' tonight through my wholesaler. The speaker couldn't give a proper answer to the question. Does anyone know of a specific double insulated/reinforced insulation grade glanding system that can accomodate tails?


I can tell you exactly what the niccy will say, either an upfront S type RCD (Idn rating would depend on RA) in the tails if feeding a metal board, or use an insulated gland/bush, or use a class II certified board.

If I recall you can get a class II metal clad board with a suitably insulated cableway for the tails, some manufactures might even have conversion kits available for existing boards, Schneider maybe ?
 
I'm not sure where the bit about the new amendment is relevant. If a metal board is used on a TT now the measures I stated in post 2 apply,it will be no different under the amendment.
 
or measure must be taken to minimise the chance of a fault to the metal case. This would mean keeping tails sheathed all the way to the terminals....tails kept as short as possible,and most importantly an insulated bush and some form of cable clamp to prevent any movement of the tails.

I'm not sure where the bit about the new amendment is relevant. If a metal board is used on a TT now the measures I stated in post 2 apply,it will be no different under the amendment.

It's all well and good ensuring that the tails are kept well secure, insulated and sheathed, but what about the busbar and neutral bar?

IMHO, the only two ways to ensure adequate earth fault protection of a metal DB on a TT system are to either guarantee TN values or fit an up front s-type.

Oh, and the up front s-type will have to be housed in plastic.

This reg just makes perfect sense! LOL
 
It's all well and good ensuring that the tails are kept well secure, insulated and sheathed, but what about the busbar and neutral bar?

IMHO, the only two ways to ensure adequate earth fault protection of a metal DB on a TT system are to either guarantee TN values or fit an up front s-type.

Oh, and the up front s-type will have to be housed in plastic.

This reg just makes perfect sense! LOL

Assuming the metal DB has an RCD main switch,or was a '17th' twin RCD then the busbar(s) and neutrals would be on the RCD side and the metal case would be protected from a fault via those.
I merely stated that the requirements under the new amendment for a metal DB on a TT will be no different to those that are already in place as far as I can see.
 
Assuming the metal DB has an RCD main switch,or was a '17th' twin RCD then the busbar(s) and neutrals would be on the RCD side and the metal case would be protected from a fault via those.
I merely stated that the requirements under the new amendment for a metal DB on a TT will be no different to those that are already in place as far as I can see.

And the insulated linkage between the main switch and the two RCDs? (On a 17th edition board that is)

You're right the requirements will be no different concerning the way a metal board is protected, only that we supposedly have to fit one. Boll*cks to that, I'll be fitting plastic thanks.
 
Assuming the metal DB has an RCD main switch,or was a '17th' twin RCD then the busbar(s) and neutrals would be on the RCD side and the metal case would be protected from a fault via those.
I merely stated that the requirements under the new amendment for a metal DB on a TT will be no different to those that are already in place as far as I can see.
I know what your saying - its always been an issue where M/C CUs and TT systems are concerned, I think the point is that issue becomes all the more prevalent post June 30th 2015 when we will be forced to use M/C CUs as standard. So the manufacturers are going to have to step up and make contractors aware of the options, because at the moment all I'm getting conflicting opinions. NICEIC have just said to me that the only real option/solution is using suitable class 2 glands and reducing the likely hood of fault between the tails and the metal case using cable clamps etc.
 
NICEIC have just said to me that the only real option/solution is using suitable class 2 glands and reducing the likely hood of fault between the tails and the metal case using cable clamps etc.

And they would be very very wrong!

As I said earlier the only real option of providing earth fault protection to a metal DB on a TT system where TN Ze values cannot be guaranteed is by fitting an s-type up front.
 
And they would be very very wrong!

As I said earlier the only real option of providing earth fault protection to a metal DB on a TT system where TN Ze values cannot be guaranteed is by fitting an s-type up front.
But how do you get over the fact the RCD will have to be housed in a metal enclosure?
 
But how do you get over the fact the RCD will have to be housed in a metal enclosure?

It won't, as it would be a single RCD in an enclosure it wouldn't be a distribution board, therefore it wont be subject to the requirements of that regulation.
 
I wonder what gems they are going to come up with for say corrosive atmospheres and the like where metal enclosures are a complete No, No?? Perhaps contain the metal board within a plastic enclosure???? lol!!

The IET have been led down a path that is going to come back and bite them in the arse!!.....
 
It won't, as it would be a single RCD in an enclosure it wouldn't be a distribution board, therefore it wont be subject to the requirements of that regulation.
That's interesting I didn't know that. Bit silly though because to all intents & purposes it has all the fire risks of a DB; Tail terminations carrying the installations full load, a device which incorporates mechanical and electronic components and contacts - all capable of catastrophic failure and subsequent combustion?
 

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