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#140266 - 02/23/04 05:09 AM 27A MCB?
C-H Offline

Member

Registered: 09/17/02
Posts: 1508
Loc: Stockholm, Sweden
Question for you guys down under.

I found this page on the net:
http://www.ess.govt.nz/yellowbg/faq_i_electricity.asp


---
Q. Is a 27/25 amp MCB suitable to protect 10 amp socket outlets in final subcircuits?

A. Yes, provided that maximum voltage drop and the cable maximum current rating (when de-rated for thermal insulation) is not exceeded, a 27/25 amp MCB is permitted. The requirement for the protective device rating to not exceed twice the socket outlet rating has been deleted from the Electricity Regulations 1997.
----

A 27A MCB??? Isn't that a rather unusual size?

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#140267 - 02/23/04 08:22 AM Re: 27A MCB?
:andy: Offline
Member

Registered: 10/18/03
Posts: 272
Loc: Germany
now how does that work?
a 25A MCB for fusing a 10A Receptacle?
Now what if the Socket gets loaded with 25A due to improper Extension cords use ect?

our outlets here are 16A, and they are never fused >16A.

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#140268 - 02/23/04 05:42 PM Re: 27A MCB?
djk Offline
Member

Registered: 12/26/02
Posts: 1269
Loc: Ireland
Radial socket circuits in Ireland are either 16A or 20A.

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#140269 - 02/24/04 03:35 AM Re: 27A MCB?
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Never heard of a 25 or a 27A MCB.

Standard MCBs here these days are 6, 10, 16, 20, 32, 40A (the 6, 16, and 32 sizes used to be 5, 15, and 30A).

Radial socket arrangements recognized by the IEE may be on 20 or 32A radials, but of course BS1363 then has a fuse in the plug.

Our old BS546 5A outlets could be wired on a circuit rated up to 15A.

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#140270 - 02/24/04 10:28 AM Re: 27A MCB?
:andy: Offline
Member

Registered: 10/18/03
Posts: 272
Loc: Germany
i know about the radials and the fused plugs. But i think 10A outlet should mean that its contact are made for a 10A flow max.

25 A Breakers are common in Germany. But never heard of a 27.
usual sizes: 6 10 13 16 20 25 32 40 50 63...


[This message has been edited by :andy: (edited 02-24-2004).]

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#140271 - 02/25/04 04:22 AM Re: 27A MCB?
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
It's a valid point Andy. With the multiple adapters that were common here in BS546 days, it would have been quite easy for someone to load a 5A outlet up to 15A, although in the case of BS546 the 5A connectors would probably carry 15A without any problems anyway.

By the way, a few manufacturers here (e.g. MK) now opffer a 3A MCB as well, for separate smoke alarm circuits, bell chime transformers, etc.

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#140272 - 02/25/04 06:54 AM Re: 27A MCB?
djk Offline
Member

Registered: 12/26/02
Posts: 1269
Loc: Ireland
PaulUK:

I think Ireland had it's own slightly strange implementation of BS546. I've never seen a multiple adaptor for anything other than the 15A socket outlets.

In general there were no 5A sockets installed. The odd 2A was used high up the wall flush mounted beside a shelf for the "wireless"

They were generally wired to 16A radial circuits. Much like the European practice with schuko.

Quite difficult to overload one of those outlets though... totally over engineered.

It was quite common to find tiny appliences with a huge BS546 plug attached. or a rewirable grounded schuko.

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#140273 - 02/25/04 01:42 PM Re: 27A MCB?
:andy: Offline
Member

Registered: 10/18/03
Posts: 272
Loc: Germany
6A is not the lowest available breaker. Usual din rail breakers from ABB or Siemens are available down to 0,5A.

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#140274 - 02/26/04 04:29 AM Re: 27A MCB?
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Wow!.
I don't know what they've been smoking at the Electrical Safety Service these days!.
But, let's just get one thing straight here,
There is no way that any Electrician here would run a 10A socket-outlet on a 25A breaker, that's for sure.
Even though a circuit like this would be run in 1.5mm(16A) or 2.5mm cable(20A), the loss of the rule mentioned above, opens the whole subject up to a dangerous situation with cables being overloaded beyond their design loadings.
BTW, the 27A MCB was used for 4mm before we changed over to (ahem) International fusing sizes.
And 25A, is still only allowed for 4mm and very short runs of 2.5mm to permanently connected appliances.

[This message has been edited by Trumpy (edited 02-26-2004).]
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#140275 - 02/27/04 03:17 AM Re: 27A MCB?
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Quote:
I think Ireland had it's own slightly strange implementation of BS546. I've never seen a multiple adaptor for anything other than the 15A socket outlets.

Did you not have the adapters to allow multiple 5A BS546 plugs to be connected to a 15A outlet? They were pretty common here. as were the ones which were all 5A, i.e. a 5A 3-pin plug to a 5A 3-pin socket plus two 5A 2-pin sockets, or a multiple 5A 2-pin.

 Quote:
BTW, the 27A MCB was used for 4mm before we changed over to (ahem) International fusing sizes.

Although for radial circuits 20A is the most usual here, at least in residential work, the Regs. allow a 30A cartridge fuse or 30/32A MCB to be used for a radial circuit wired in 4 sq. mm. Rewireable 30A fuses are not permitted for such radials however.



[This message has been edited by pauluk (edited 02-27-2004).]

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