Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Helpful Answer
  • Replies 10 replies
  • Subscribers 35 subscribers
  • Views 2428 views
  • Users 0 members are here
Options
You may also be interested in

Fire rated cables not leaving fire compartment

Gareth Rowley

Been asked a couple of questions by an installer and struggling to get a definitive answer from and standards.

First, if a landlords panelboard contains life safety circuits (in this case both primary and secondary as we have two transformers on site), do the cables between the cut-out and panelboard need to be fire rated if they are in the same fire compartment?

Second, we have a dedicated DB serving lighting in a fire fighting shaft. The DB has dual supplies via an automatic transfer switch (ATS) in a 2 hour rated enclosure. This enclosure backs onto the shaft so the lighting circuit cables will penetrate the 2 hour rated wall to serve the lighting. Do these cables need to be fire rated throughout, or just where they pass through compartments. Once in the compartment, could they just be T&E?

The reasoning for both of the above is that once in the compartment, the equipment the cables are serving will not last anywhere near as long as the cable that serves it. But after a good trawl through BS 8519 and BS 9999 and BG70, I can't find anything conclusive. 

BS 8519 would suggest that any life safety supplies need fire rated cables, so the panelboard supply would need fire rated tails. 

I would appreciate any guidance. 

Parents
  • 0

    Good afternoon Gareth

    A Safety service is defined in BS 7671 Part 2.

    You will have to reference BS 7671 general rules and especially Chapter 56. Also BS 9999 and BS 8519 will also apply.

    What does the Fire Strategy for the building say?

    You say you have a common panel for for both primary and secondary supplies to the safety services? If so that is wrong, very wrong. The primary panel and the secondary panel have to be in to separate rooms with usually a 2 hour fire separation. The supply sources have to be independent of one another such as a DNO supply and a generator. The primary and secondary supplies have to take 2 separate diverse routes through the building again usually with a 2 hour fire separation. The primary and secondary cables have to be fire resistant usually for a 2 hour rating.The cables have to have metallic supports. The primary and secondary cables should only come together at the transfer switch, the transfer switch has to be close to the particular safety service.


    This is only a summary and you need to follow the other requirements set out in the 3 references I have already mentioned and meet the fire strategy for the building.

    Hope this helps?

    JP

  • 0 in reply to John Peckham
    John Peckham said:
    You say you have a common panel for for both primary and secondary supplies to the safety services? If so that is wrong, very wrong.

    I read the OP as the DB serving normal lighting only in the firefighting shaft via two possible separate supply sources. Emergency lighting then being provided as appropriate via integral batteries. That being the case, I can’t see an issue. However, if you have a standard reference to indicate otherwise, JP, it would be helpful.

    As you say, there should be more of a holistic approach with consultation sought with the responsible person who may feel it appropriate to seek the services of his fire engineer to assist in making a determination on acceptability. 
    I don’t think I would make a call on a proposal for any work in a higher risk building without getting the nod from either BC or the FE, even if I was confident about code compliance! 

  • 0 in reply to John Peckham

    Hi John

    Thanks for the reply.

    To clarify, we have two substations on site, feeding two separate landlords panels. Each landlord panel will provide secondary supplies for the life safety systems served by the other (see Figure 3 of BG 70 as an example). 

    The Fire Strategy Report only contains the usual recommendations, e.g. service penetrations should not compromise the fire barrier. Wirings systems should not collapse prematurely in the event of a fire, cables or other electrical equipment shall not be installed in protected escape routes unless part of an essential fire safety or related safety system.......etc. 

Reply
  • 0 in reply to John Peckham

    Hi John

    Thanks for the reply.

    To clarify, we have two substations on site, feeding two separate landlords panels. Each landlord panel will provide secondary supplies for the life safety systems served by the other (see Figure 3 of BG 70 as an example). 

    The Fire Strategy Report only contains the usual recommendations, e.g. service penetrations should not compromise the fire barrier. Wirings systems should not collapse prematurely in the event of a fire, cables or other electrical equipment shall not be installed in protected escape routes unless part of an essential fire safety or related safety system.......etc. 

Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines