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Topic Title: FP200 cable protected by 20A mcb
Topic Summary: which table?
Created On: 16 June 2011 10:01 PM
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 16 June 2011 10:01 PM
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aargeitakis

Posts: 139
Joined: 14 July 2005

Hi everyone,
I had a circuit today wired with FP200 cable and feed a fire alarm panel. Cable is 1.5mm, it is buried in the wall and protected by 20A mcb. I think 20A mcb is ok but which table am I looking for in the regs?
Thanks Paul.
 16 June 2011 10:35 PM
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Avatar for kj scott.
kj scott

Posts: 2144
Joined: 02 April 2006

Manufacturers.

-------------------------
http://www.niceic.biz
 16 June 2011 10:45 PM
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ant1uk

Posts: 2376
Joined: 22 June 2010

Have a look here at the bottom of the page.

Does your panel require 4.5kw?
 16 June 2011 10:56 PM
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aargeitakis

Posts: 139
Joined: 14 July 2005

thanks for your replies.
I did a pir today. I didn't check what kw the panel required. I try to find if 20A MCB is overated for 1.5mm or if its ok.It was a nice and neat installation without any defects.
 16 June 2011 11:00 PM
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Maxpower

Posts: 349
Joined: 15 February 2008

When installing FP 1.5mm to a panel I usually use a 6A MCB, fused down to a red switched fused spur with a 3A 1362 fuse in. Most of them consume mere milliamps. I also tend to put in a DP keyswitch near the panel for tamperproof DP isolation.
 16 June 2011 11:04 PM
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aargeitakis

Posts: 139
Joined: 14 July 2005

It is a 3-core and instead of a fused spur there was a 2-pole isolator with key(similar with the emergency lights key test switch). I cound see this switch to survive if 20A pass through.
 16 June 2011 11:09 PM
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ant1uk

Posts: 2376
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I would say it is over rated for the cable and probably the panel as well. can you not find out any data for the panel?
 16 June 2011 11:19 PM
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daveparry1

Posts: 5891
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I can't imagine any fire alarm panel would need to be on a 20 amp supply, more like 6 amp I would think?

Dave.
 16 June 2011 11:30 PM
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aargeitakis

Posts: 139
Joined: 14 July 2005

It is hard to go back but i will try. It is an empty shop but is hard to get the keys. I am not familiar with fire alarm panels but I never see on before on 20A. If there is a need for 20A supply I was expected to wired with 2.5mm and a different type of isolator than the keyswitch which i dont think is rated up to 20A
 16 June 2011 11:36 PM
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ant1uk

Posts: 2376
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I was hinting in my first reply that 20A wasn't required for a fire alarm panel. It is only a circuit board with something like 24 volts going to the out going circuits.
 17 June 2011 10:26 AM
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Avatar for OMS.
OMS

Posts: 18935
Joined: 23 March 2004

Get a grip chaps - clearly we have a situation where the MCB is not offering overload protection to the fixed panel load (internal panel fuses will deal with this).

So the MCB is simply providing earth fault and short circuit protection - it's extremely unlikley that the fault levels will such that a 1.5mm2 FP200 will be overwhelmed by the energy let through of a 20A MCB.

Essentially it's a safety circuit - you don't want your protection to be too close do you ?

Regards

OMS

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Failure is always an option
 17 June 2011 11:50 AM
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aligarjon

Posts: 2738
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i suspect inside the panel immediately after the line connection you will have a fuse protecting the board as well anyway, but as OMS said, its a fixed load .

Gary

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Specialised Subject. The Bleedin Obvious. John Cleese
 17 June 2011 02:24 PM
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Gavins

Posts: 4
Joined: 17 June 2011

For reference, from Prysmian's data sheets the current carrying capacity of 1.5mm, 3c FP200, enclosed is 16.5A.
 17 June 2011 06:50 PM
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aargeitakis

Posts: 139
Joined: 14 July 2005

Thanks for your replies everyone
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