emergency lighting

[jon b]

if the emergency lights fail there 3 hour test do you have to retest for a futher 3 hours and if the batteries have been replaced do you have to return to carry out a 3 hour test

[Galeon]

This is a bone of contention with me , manufacturers used to make 1 hour and  3 hour fittings , obviously you need only 1 hour duration unless there is a sleeping risk , however it seems in their wisdom they dropped manufacture of the 1 hour fitting ,possible for ease sale of one fitting batteries getting better , however you by default have to discharge the fitting to its designed rating and not the risk.
What you don't know is how good your new fitting is , it could have been sitting on the shelf for 12 month , so check the product label , in the real world it should last the annual discharge at full duration.

[AnthonyB]

Not saying this is right or wrong but in practice when a fitting fails the 3hr test it's batteries (or often the whole unit) are replaced, flick tested and that's it - it is subject to monthlies until the next annual test comes up.

Disruption & expense means a full retest isn't done except when it really has to be.

[ChrisH]

Hi

I work for a major UK lighting manufacturer and have particular responsibility for emergency lighting.  

Three points:

1. Re: jon B's first question. Any replacement of a failed emergency luminaire or replacement of a battery should be subject to a full 3 hour test, after allowing sufficient time for the batteries to fully charge - typically 24 hours.

BS5266-1:2005 12:1 & Appendix C refer to commissioning tests that should be carried out on a new or modified installation which include a duration test. Our policy is that the installion instructions included with all emergency luminaires state that a full duration test must be carried out as part of the commissioning process.

2. Re Galeon's point on the choice between 1 hour and 3 hour duration.  
There are a number of factors at work here:
a) 3 hour duration is specified on most projects, so that's what we supply.
b) Whilst 1 hour duration meets the minimum standard, it does raise a potential problem. Consider this scenario: A power cut occurs and the emergency lighting comes on. After 1 hour, the batteries are effectively flat, so when the power comes back on, the building has no emergency lighting coverage, because the batteries will take at least 8 hours to fully charge. The RP has to make a decision - does he allow people to occupy the building knowing there is no emergency lighting coverage? If 3 hour batteries are used, there is a greater safety margin. If the power comes back on after 2 hours, there is still 1 hours capacity left in the cells, so the RP doesn't have to make the decision unless the power is off for 3 hours.
c) It might sound bizarre, but it's down to economies of scale.  3 hour cells (typically 4.5mAh) are actually cheaper than the smaller cells (1.5 mAh) used in 1 hour battery packs.

3. Rechargeable cells self-discharge over time when stored.  If the fitting has been on the shelf for some months, the cells will be really really flat, and the initial 24 hour charge period may not be enough to get them to full capacity. So, if they fail the first duration test, it may be worth giving them another 24 hours to charge and then another test. I have found this works, and thereafter the cells function to specification.

[Galeon]

Chris ,
I get the point but surely a back up generator is the way forward , as I said sleeping risk for the 3 hours , most consultants specify 3 hours and they haven't even thought of the risk. It is not an answer to keep encourage persons to stay in a risk , why do you need 3 hours to evacuate safely a standard scenario ?

[Dragonmaster]

Chris ,
I get the point but surely a back up generator is the way forward , as I said sleeping risk for the 3 hours , most consultants specify 3 hours and they haven't even thought of the risk. It is not an answer to keep encourage persons to stay in a risk , why do you need 3 hours to evacuate safely a standard scenario ?

There is a difference between emergency lighting and escape lighting. The latter, required for escape, should provide the minimum of 1 hr, however emrgency lighting can be used to re-occupy the building, whether there has been a fire or not e.g. in the event of a power cut when people still need to move about safely.