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Topic Title: Fire Alarm Cable In Conduit
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Created On: 07 March 2013 04:55 PM
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 07 March 2013 04:55 PM
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sawdust

Posts: 3
Joined: 18 January 2003

Hello,

I was hoping for a bit of clarification (or opinions!) on a couple of fire alarm cabling issues.

1. I was in a building and noticed that they had their fire alarm cable run in white conduit held up with metal saddles.

I know that BS 5839-1 26.2.f says that "methods of cable support should be non-combustible and such that circuit integrity will not be reduced below that afforded by the cable used, and should withstand a similar temperature and duration to that of the cable, while maintaining adequate support." does the plastic conduit count as 'cable support' or simply containment?

Also note 8 reads: "this recommendation precludes the use of plastic cable clips, cable ties or trunking, where these products are the sole means of cable support." Does the addition of metal saddle give primary support to the secondary support of the conduit? HMMM.

2. When fixing FA cables to cable tray, are plastic cable ties sufficient if the tray is upright or must they be metal?

3. Is it permissible to just place them on the tray without fixing them? My sense of good practice says 'no' and I have read stories of them 'springing out' during a fire, but it's another thing I have noticed.

4. Could you repair a job where someone has secured the FA cable to inverted trunking with plastic cable ties (!) by swapping them for metal ones?

5. Can anyone tell me what BS 4678-4 is relevant to? Reference "Any non-metallic trunking used in the system should conform to BS 4678-4. "

6. If certain companies are commissioning unsafe systems, is there any framework to address this other than just not using them again?

Many thanks!
 07 March 2013 05:28 PM
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Dave69

Posts: 439
Joined: 16 July 2011

nothing wrong with plastic trunking as long as the cable is P Clipped through the trunking and into a non- cumbustible surface and the same if pvc conduit is clipped using metal sadles.

I use stainless tyraps every metre or so with plastic raps inbetween but try to avoid tyrapping where ever i can

as with any installation cable should be fixed.

if a cable has been secured with platic tyes just add a metal one in every metre

why do you say "If certain companies are commissioning unsafe systems"

If a company is commissioning a system they have to issue certs to say it complies. If they are just carrying out routine testing they probably wont bother to to check the installation work but rather just confirn that all the dectectors function, etc.
 07 March 2013 05:57 PM
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OMS

Posts: 19359
Joined: 23 March 2004

Originally posted by: sawdust

Hello,

I was hoping for a bit of clarification (or opinions!) on a couple of fire alarm cabling issues.

1. I was in a building and noticed that they had their fire alarm cable run in white conduit held up with metal saddles.


I know that BS 5839-1 26.2.f says that "methods of cable support should be non-combustible and such that circuit integrity will not be reduced below that afforded by the cable used, and should withstand a similar temperature and duration to that of the cable, while maintaining adequate support." does the plastic conduit count as 'cable support' or simply containment?

Also note 8 reads: "this recommendation precludes the use of plastic cable clips, cable ties or trunking, where these products are the sole means of cable support." Does the addition of metal saddle give primary support to the secondary support of the conduit? HMMM.

It's perfectly compliant with BS 5839 - 1


2. When fixing FA cables to cable tray, are plastic cable ties sufficient if the tray is upright or must they be metal?

They need to be sufficient to restrain the cable in fire conditions


3. Is it permissible to just place them on the tray without fixing them? My sense of good practice says 'no' and I have read stories of them 'springing out' during a fire, but it's another thing I have noticed.

Not acceptable generally (true for any cable though)


4. Could you repair a job where someone has secured the FA cable to inverted trunking with plastic cable ties (!) by swapping them for metal ones?

Yes, adding metal cored ties at sensible intervals complies.


5. Can anyone tell me what BS 4678-4 is relevant to? Reference "Any non-metallic trunking used in the system should conform to BS 4678-4. "

BS 4679 - 4:Cable trunking. Specification for cable trunking made of insulating material

It will have requirements for no fire propogation, smoke and fume emissions etc


6. If certain companies are commissioning unsafe systems, is there any framework to address this other than just not using them again?

They may have an approval body (BAFE, LPCP etc) you could go to - if they have commissioned unsafe systems there may be a legal route through contract etc - you would need to be specific.


Many thanks!


As a bit of background, the whole issue of fire related cable restraints for fire rated cables (and wider concerns for all cables) resulted from the deaths of two firefighters who became entangled in loose cables whilst wearing BA sets in a building on fire and regretably couldn't free themselves before the inevitable happened.

regards

OMS

-------------------------
Failure is always an option
 07 March 2013 07:53 PM
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dickllewellyn

Posts: 1150
Joined: 19 March 2010

OMS. Is the incident you mention the one at Shirley towers? Or was there another before that? I know that fire fighters did die at Shirley towers for that very reason, but I'd thought that fire alarm cables had needed proper support for longer.

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Regards
Richard (Dick)

"Insert words of wisdom and/or witty pun here"
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