D
Deleted member 9648
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?
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 ?
Think I saw a hager DB somewhere which was a metal clad with a main switch witha built in clamp to sit the tails into. Can't imagine they'd be that cheap tho
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
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Deleted member 9648
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.
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.
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?
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.
E
Engineer54
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!!.....
The IET have been led down a path that is going to come back and bite them in the arse!!.....
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?
Exactly my point lol! The regulation is a joke, hence why I'm still happy to install plastic.
This does only apply to domestic DBs remember. I can't think off the top of my head where you might have a corrosive environment within a dwelling?
You can use plastic consumer units so long as its in a fireproof cupboard which eliminates the problem
P
Plonker 3
How about installing it correctly and doing away with all this nonsense?
Yes you are right although I'm not sure how feasible it will be install a fireproof cupboard every time you encounter a CU change + TT system...
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Plonker 3
Well for this new reg to be there, it must be because they are not being fitted correctly by everyone isnt it!
T
trev
CU fires are caused by 2 things. Defective materials and poor workmanship. If a metal clad CU is installed poorly then there's still plenty of plastic in there that will melt/burn/give off toxic fumes.
This utter nonsense is the powers that be trying to escape from the fact that what went around is now coming around.
D
davesparks
But it would be similar switchgear, or whatever the slightly vague description is.
S
Silly Sausage
It's in the BEAMA statement, non-combustible CUs are being introduced to prevent the spread of fire caused by poorly made terminations!!!!!!
The mind boggles.
Yup, hence the pointlessness of all this 'fire resistant' malarkey.
I wish, not quite though.
The reg, extends to all similar equipment, thus a KMF, a REC2 etc.
However, they don't HAVE to be steel, they just need to meet 61439-3 & shall...
(i) have their enclosure manufactured from non-combustible material,
S
Silly Sausage
And it says this where?
It only mentions distribution boards.
The intent of the regulation may extend as you say, the wording however is all that matters for compliance purposes.
If the wording truly reflected the intent, then on a TT without TN Ze values, you'd be damned if you did and damned if you didn't.
As I keep saying, the departures section of an EIC is there for good reason!
Plastic all the way for me. I don't care what the regs say, you won't find me connecting tails into unprotected metal boards in domestic TT systems.
And it says this where?
It only mentions distribution boards.
The intent of the regulation may extend as you say, the wording however is all that matters for compliance purposes.
If the wording truly reflected the intent, then on a TT without TN Ze values, you'd be damned if you did and damned if you didn't.
As I keep saying, the departures section of an EIC is there for good reason!
Plastic all the way for me. I don't care what the regs say, you won't find me connecting tails into metal boards unprotected in domestic TT systems.
In the BYB:
421.1.201 Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall:
- (i) have their enclosure manufactured from non-combustible material, or
- (ii) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.
NOTE 2: The implementation date for this regulation is the 1st January 2016, but does not preclude compliance with the regulation prior to that date.
BTW, direct copy from the electronic version of the BYB a few seconds ago.
You know the scope of 61439-3
I realise that there are other 61439-* standards, and you could argue that some of them apply.
Also some similar switchgear will be made to alternative -* numbers, there in lies another failing of the reg.
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trev
The thing that boils my wee is, once again, the assumption that somehow electricity used in a domestic environment is somehow more dangerous than that used in a commercial setting.
How many shops have you seen with plastic CUs?
A crap termination is a crap termination. It doesn't matter if the CU is made of bloody asbestos, you cannot make a silk purse out of a pig's ear. There's still going to be combustible material in there that can and will get hot and burn.
How many shops have you seen with plastic CUs?
A crap termination is a crap termination. It doesn't matter if the CU is made of bloody asbestos, you cannot make a silk purse out of a pig's ear. There's still going to be combustible material in there that can and will get hot and burn.
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Silly Sausage
Archy, how about rock, preferably igneous. It will melt at high enough temperatures but I don't think a house fire would generate anything high enough.
There may be weight issues for the fixings if granite CUs existed but at least they could be made to look pretty
Aye, that would look nice matching my Brazillian green granite kithen worktops.
I could locate it above the hob.
It is all to do with rescue / escape times in domestic premises, CU's under the stairs etc.
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