BS 8519

Morning Chris


This is a very complicated subject. Spookily I am working on a presentation at the moment for an IET Webinar.  The target date is November 17th and in the same session another IET member is going to be doing Emergency lighting.


Every LSS installation will be different depending on the fire strategy for the building. Both the primary circuits and the secondary circuits need to be fire rated cables  and run in diverse routes through the building with fire separation. 


That is a taster for the show coming to you in the near future.

Generally, the reason for separate containment is that all and sundry messing about with non safety systems aren't likely to damage life safety cabling - although correctly you do need to consider the interaction hazard between systems.


CPC's aren't specifically a worry per se - to melt the conductor needs temperatures way beyond the fire rating of the cable - and basically a bit of copper with all the sheathing burnt off, is still an effective CPC.


There is usually no issue with BS 5839  life safety systems of differing fire resistance sharing containment - but in your example, it should raise an eyebrow as to why the fire detection and alarm is only a 30 minute system, when the refuges are a 120 minute system - one would imagine a facility needing refuge comms would also need an enhanced grade on the Part 1 system to reflect the rating on the Part 9 system.


What you shouldn't do is mix non BS 5839 systems with other systems eg, it's not appropriate to run fire and emergency lighting on the same containment (as both relevant standards advise against it for the reasons given in my first comment


Regards


OMS

Hi John, it sounds interesting. I have read both 2010 & 2020 versions along with BS 9999 and others, but I think i still have some queries that I m not able to find a clear way forward (only about details). Ideally, the respective project fire strategy/engineer should be providing the answer but unfortunately in the real world you dont always get what is required.


OMS, thanks a lot for your response. Appreciated as always.

Well I guess BS 5839 is quite clear regarding "separate" and the commentary suggests that it's to prevent damage to fire systems (or emergency lighting systems) which may be caused by all and sundry playing around with the "other systems" sharing that containment.


Sure, you see all kinds of attempts to "circumnavigate the requirements" by using a bit of space, by using a bit of a divider etc, but I would view all of those practices as "non compliant" with BS 5839 (or BS 7671).


I would have less of an issue with a properly designed (and appropriately spaced) common containment "gallery" - typically ladder brackets (M10 drop rods and unistrut) on several levels, containing (say) Main LV power trays/ladders. Voice and data baskets. BMS or other EC&I containment, local small power and lighting containment, fire alarm containment etc


I appreciate that isn't exactly how the commercial market sees things


Regards


OMS

I think the idea of seperate containment is/can be a problem.

A tray with dividers - are the divisions seperate containers? well the 2,3,4 channels might be but the overall trough isn`t.

There again completely seperate trays held by the same struts etc could be just as onerous.

Taking it further to another (silly) conclusion, a whole area/room/building is a "container".

You need to not only read the particulare reg(s) but also it`s intention of how far we mitigate risks

My understanding is that life safety supplies should be on a separate cable support system which ideally would be installed above all other services so a premature collapse of the later would not compromise/destroy the life safety circuits.


But if the spirit of the reg is that sundries of normal circuits might affect the life safety circuits then maybe a neat installation with dividers could be enough?

I suspect that this is an area where we need to read the BS very carefully. I have BS5266 - 1999 to hand, so I may be out of date, but this talks a lot about separation, then says that if such separation is not provided MICC can be used, and then says "equally acceptable would be any cable complying with BS6387 ...".

Perhaps someone can read the current versions carefully to see if this is still the situation.