Emergency durations

Hi all
As a supplier to the wholesalers of luminaires I am getting reports that some of our products, which are emergency pack equipped, are not lasting the full 3 hours on discharge. Presently we are checking discharge rates, battery capacity, etc. Some manage 2 1/2 hours; some just a minute or two short of 180 minutes, but I suppose even a minute under 3 hours is a failure to BS5266.

What do you guys tend to find when testing for duration? Is it a particularly pedantic sparky that insists on 3 hours? Is there some leeway? Does it vary from place to place both with how rigidly the end users insist on 3 hours and does everyone test for this or do a lot just fit and then providing they light when power is removed see them fit for purpose - even if they only lasted 30 minutes?
Your very valuable experience and tales would be appreciated!
Lightingman.

 

Thanks Caddy, but I think I am right in thinking that the duration has nothing to do with how long it takes to empty a building but more how long to restore the power after an event. As with most buildings you could, as you say, empty it in a few minutes but take advantage of the three hours to let people get back in seeing their way with the emergency lighting but giving you (the restoring electrician or DNO) a couple of hours or so to identify the fault and restore power. I have read that you can get away with one hour only in places where the people would know the layout of the building and are familiar with the exits, 3 hours is needed for either sleeping accommodation or places where the occupants wouldn't be expected to know their way around, such as cinemas, restaurants etc.
When you guys come to test these things do you hang about for the three hours observing all lamps last that long? Or is there a bit of play in it?!

 

Thanks all for your comments.
Caddy; I wonder how many power outages take longer than 3 hours to remedy? Not many I guess, wouldn't most be simply a trip gone either at the board or the substation in which case most institutions would surely have a maintenance guy on site who would soon rectify or the DNO would put right rapidly. Power cuts I have experienced have been pretty short but I suppose it depends on areas and circumstances. Not many would be caused by board fires would they? As for waiting till the batteries are charged fully before reoccupying: I agree in principle and I think it does say this in the standard but this would be 24 hours...how often would that be allowed to happen? When you say "expect them to be working a few minutes before their duration" I guess you meant "after" their duration?
Tomorrows task for me is to closely study BS5266 as I have a copy and we pay to be members of BSI so I might be giving them a call too.

It's interesting what you say **; would your customer be prepared to wait a year till the next test for you to rectify any under 3 hours? You are right about batteries; they do deteriorate and some quite rapidly. Li-ion are used more and more now due to the low power needed (circa 3W for one lux) with LED's...so small size but power effecient.

Have you guys thought about how you are going to do the 4 year battery replacements when most battteries are now Li-ion, or NiMH, and not lead acid anymore, a lot in sealed packs as well? I suppose like everything else it will be a new fitting each time...more for the recyclers! (but more business for yours truly!)

 

Thanks Lectrician, I have booked onto an ICEL course soon so hopefully will be an expert after that!....but.....3 hours to evacuate a building?? Who on earth came up with thinking it might take that long??!!

 

Hi Lectrician,
I cant thiok the emergency services would be relying on the lux levels of emergency lighting in a smoke filled building, wouldnt they use their own? Maybe you meant the occupants which I can understand and that would be why the standard recommends certain heights for them and where they are put.

I have been studying BS5266 today (Yes, pretty boring!) and it made me realise.....why do the premises have to be evacuated? Except in a fire of course when the fire alarm would go off but the power may well stay on. I think everyone, me included, seems to think in a power cut then the building has to be evacuated...why, if its safe to stay with a well designed emergency lighting set up? Could be enough natural light as well.

In the standard it does state that the 3 hours is for premises that could take time to shut machinery down etc but also states that the 3 hours allows people back in and to carry on without waiting for the batteries to recharge. Its obvious when you think about it, unless you have a building where no one could do anything without power why would you evacuate? I have worked in many factories and we didnt go outside every time we got a power cut, we carried on and if it was dark outside hoped that the power would come back before the batteries flattened.
As I said earlier I have a days training with ICEL soon so if anyone is interested I will report back the official stance!