Question regarding the installation of Non-Maintaned Emergency Lighting

[AReynolds]

Hello. I am required to produce a design for an electrical installation of a proposed Community Centre, and I am having some problems determining a workable method of connecting of the Non-Maintained Emergency Lighting, which is provided using battery packs to be incorporated into the relevant luminaires.
My problem lies in meeting one of the requirements of BS 5266-1:2016, which demands that the emergency lights monitor their circuit for an interruption of supply, with (in my particular case) the emergency batteries discharging and supplying their lights during the interruption. This is because most of the lighting circuits will be actuated by contactors, which in turn are actuated by a 230V control circuit. In addition to this, a 'Last Man Out' Switch will be provided to actuate every lighting circuit in the building, which necessitates actuating every lighting circuit through an additional set of contactors, which require input from another 230V control circuit.
As such, for most of the lighting circuits, a failure of supply from one of three circuits (Lighting supply, Operational Control Circuit and 'Last Man Out' Control Circuit) could cause the lights on a given circuit to fail. As such, there is a clear requirement for the emergency lighting batteries on most of my lighting circuits to be triggered in the event of one or more of the three circuits described failing. I do not know how to connect the emergency lighting batteries on each circuit in such a way as to make this happen.
I have considered doing away with the operational contactors and control circuit- which would result in me having to lengthen the cable runs of each lighting circuit to the point where voltage drop becomes problematic. I have also considered using programmable relays that might be deployed as a kind of 230V, 6A Three Input AND gate to facilitate the emergency light monitoring of the supply status of three circuits. However, I fear that this would be prohibitively expensive, and would increase the difficulty of maintenance.
As you can see, I am stuck for a solution, and I would appreciate the advice of anyone who knows more about Emergency Lighting and Electrical design in solving my problem.

 

[Andy-1960]

I presume that you are switching the switched input to each fitting via contactors, but you will still need to run a permanent feed to each fitting and this is what will monitor the mains failure and keep the batteries charged. The permanent feed should come from the same DB as the feed(s) to the contactors.

 

[AReynolds]

Thanks for your reply. I am indeed switching the switched input of the fittings of most of the lighting circuits through a contactor. I am aware that usually, you would simply run a permanent live back from each emergency battery to the local lighting circuit MCB. However, if the control circuit (fed from another DB) that actuates the contactor fails then the lights cannot be switched on, yet because the Lighting Circuit itself is still energised, the permanent live connected to the emergency batteries will still be live, as such the emergency batteries will not discharge- despite the fact that the contactor cannot be actuated to switch the fittings on. Basically, my problem is how to connect the batteries in such a way as to allow them to monitor a failure of both the local lighting circuit AND/OR the Control Circuit that actuates the contactor?

 

[westward10]

Fit maintained fittings or you will have to fit additional contactors for the permanent lives. Pleased to see you have spotted this the amount of installs I have seen where the emergency lighting does not operate upon failure of the control circuit.

 

[AReynolds]

Thanks for the reply. You have addressed the core of my problem. Indeed, like yourself, I have encountered a disturbing number of non-maintained emergency lighting arrangements that include this flaw. Unfortunately, I don't think that Maintained Fittings will be an option on the design, as I lack sufficient latitude to change that aspect of the design. As such, I have been considering the use of 'Volt Free'-'Normally Closed' relays, by which the permanent/battery live of each lighting circuit may be switched out in the event of a failure of the contactor control circuit. If the 'Volt Free' relay is connected to the Control Circuit live before the contactor, then it should be able to sense a failure of the Control Circuit. This is the only method I can conceive of, without resorting to laying substantially more cable. Can anyone see any flaw in this method?

 

[westward10]

I would personally try and pursue the maintained fitting route as it shouldn't affect the design with regards to light output, assuming these are bulkhead fittings then it is irrelevant what circuit/s fail. Otherwise yes you will have to incorporate additional control but you need to avoid contactors/relays which are energised 24/7.

 

[Toneyz]

I would personally try and pursue the maintained fitting route as it shouldn't affect the design with regards to light output, assuming these are bulkhead fittings then it is irrelevant what circuit/s fail. Otherwise yes you will have to incorporate additional control but you need to avoid contactors/relays which are energised 24/7.

I think that this would be the best solution thinking about it, you have lighting whichever circuit fails

 

[AReynolds]

I have discussed the issues raised here with the client, and have managed to bring them round to the maintained option. Many thanks for the assistance to those of you who answered my questions.