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Radial MCB size???


 
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hazey7

from United Kingdom

Joined: 09 Dec 2003
Posts: 24
Location: United Kingdom

PostPosted: Mon Jan 19, 2004 10:52 am Reply with quote

Hello Again,

Can someone give a quick answer?

3 sockets on a radial circuit from the consumer unit, ie one cable leaving the Mcb looped into each socket last socket has one cable only, (ie not a dual cabled ring main):

What size MCB 16A or 32A?
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il78

from United Kingdom

Joined: 06 Oct 2003
Posts: 701
Location: United Kingdom

PostPosted: Mon Jan 19, 2004 11:20 am Reply with quote

Depending on cable size but usually 16A MCB...
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hazey7

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PostPosted: Mon Jan 19, 2004 12:02 pm Reply with quote

2.5mm FT&E, many thanks my friend.
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securespark

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PostPosted: Fri Jan 23, 2004 8:42 am Reply with quote

Radial circuits with 16A mcb's should only feed one outlet. If you need more, then the whole circuit should be protected by a 13A fuse, so that the current drawn does not exceed 13A. Then you can have an unlimited number of outlets.

To run more than one outlet on a radial circuit you should use a 20A mcb, but bear in mind the floor area served by the sockets should not exceed 50m3
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ban-all-sheds

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PostPosted: Fri Jan 23, 2004 3:18 pm Reply with quote

Securespark - what's the thinking behind that? It seems odd that you are allowed to protect a radial cable with a 20A breaker but not with a 16A one.
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il78

from United Kingdom

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PostPosted: Fri Jan 23, 2004 4:05 pm Reply with quote

securespark wrote:
Radial circuits with 16A mcb's should only feed one outlet. If you need more, then the whole circuit should be protected by a 13A fuse, so that the current drawn does not exceed 13A. Then you can have an unlimited number of outlets.


Where did you learn that one icon_confused.gif
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securespark

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PostPosted: Fri Jan 23, 2004 11:21 pm Reply with quote

If you can get a copy of the IEE on-site guide, have a look in there.........

I don't write these b****y rules, but being a pro spark, have to stick by them or else lose certain body parts......
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securespark

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PostPosted: Fri Jan 23, 2004 11:30 pm Reply with quote

Just for those who have no access to the OSG, here is what it says about fused spurs - by the way when they say fused spurs they don't mean a connection unit with a DP switch and fuse carrier, they mean a spur off the ring that is protected by a fuse.

Quote:

The total number of fused spurs is unlimited but the number of non-fused spurs does not exceed the total number of socket outlets and items of stationary equipment connected directly in the circuit.

A non-fused spur feeds only one single or one twin socket outlet or one permanently connected equipment. Such a spur is connected to a circuit at the terminals of socket-outlets or at junction boxes or at the origin of the circuit in the distribution board.

A fused spur is connected to the circuit through a fused connection unit, the rating of the fuse in the unit not exceeding that of the cable forming the spur, and in any event, not exceeding 13A.

Unquote.

Does that make sense??

If not, don't complain to me!!!!!!!!
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ban-all-sheds

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PostPosted: Sat Jan 24, 2004 5:12 pm Reply with quote

Securespark - the original question was about a radial circuit, not a spur, and it was (paraphrased and later information included) "if I've got a radial circuit wired with 2.5mm T&E feeding 3 sockets should I have a 16A or 32A breaker?".

To which you said he could use a 20A breaker but not a 16A one. Since it struck me as very odd that the regs would ban a lower rated MCB (but not impossible, given their inconsistencies), I asked what the idea was behind this.

But you've responded with stuff about fused spurs, not radials, so not really clarifying the matter - sorry.
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ban-all-sheds

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PostPosted: Sat Jan 24, 2004 5:43 pm Reply with quote

Securespark - the original question was about a radial circuit, not a spur, and it was (paraphrased and later information included) "if I've got a radial circuit wired with 2.5mm T&E feeding 3 sockets should I have a 16A or 32A breaker?".

To which you said he could use a 20A breaker but not a 16A one. Since it struck me as very odd that the regs would ban a lower rated MCB (but not impossible, given their inconsistencies), I asked what the idea was behind this.

But you've responded with stuff about fused spurs, not radials, so not really clarifying the matter - sorry.
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securespark

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PostPosted: Sun Jan 25, 2004 2:10 am Reply with quote

b-a-s

I was respnding to il78 who said "where did you get that from" and i thought he was referring to the fused spurs bit of what I wrote.

So here follows another extract from the IEE on site guide about radials:

Quote

This table lets you know how circuits can be configured:


Circuit Rating Type T&E conductor size Max floor area

Ring 30 or 32A Any 2.5 100

Radial 30 or 32 cart or mcb 4 75

Radial 20 Any 2.5 50


Hope this clears things up a bit.
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securespark

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PostPosted: Sun Jan 25, 2004 2:12 am Reply with quote

Sorry thats a bit garbled

It looked ok when I laid it out but when it got posted all the text got pushed together


Hope you can make it out.
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yankey-sparky

from United States of America

Joined: 20 Nov 2003
Posts: 61
Location: United States of America

PostPosted: Sun Jan 25, 2004 4:08 am Reply with quote

Securespark: If you put your table in the CODE tags, it keeps the spaces you need for the formatting.
Code:
Circuit   Rating      Type       T/E conductor size    Max floor area
 
Ring      30 or 32A   Any              2.5             100
 
Radial    30 or 32    cart or mcb      4               75
 
Radial    20          Any              2.5             50
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