Emergency Escape Lighting

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https://cr4.globalspec.com/thread/83665/Engineering-Student

I would consider a UPS system as overkill for emergency lighting over an integral battery backup...one exception might be if your lighting system was power sensitive, then the cleaner ups power supply might be preferred...

I agree. Emergency lighting (and power) might be needed in a hospital situation, or perhaps in the storage of dangerous chemicals, but otherwise lights are easy with a battery. Have been for years.

Yes any facility that has critical infrastructure is going to have a backup generator to supply the critical circuits and emergency lighting...I used to take care of a huge hospital 10 stories, eight operating rooms, it was massive...one of my duties was starting up the generator once a month, man it was a beast, supplied the operating rooms, dialysis equipment, all the critical systems that kept people alive...It was so loud it would scare the crap out of people, great for breaking in the new guys..haha, some would run out of the room..It had a pneumatic start, it would start off slow and ramp up in speed, sounded like a jet engine, then it would kick in, shake the whole room with a thunderous roar, it was magnificent....

What the hell was it? Our radio station just had a cummins in the basement. It was loud too but jeez yours must have been a monster.

Oh I don't remember, it was 40-50 years ago now. and I was only doing that temporarily...but yeah, it was a beast...

Maybe Each room has 50% of lights on one UPS and 50% on the other UPS, covering light or UPS failure. A UPS could bypass to mains normally or to diesel supply for long term support.

The internal battery lamps usually give 3 hours light, but if you have a UPS you can have longer. However, escape lighting implies only a limited duration, round here the legal requirement is 1 hour but means you cannot use the building again following a power-cut because recharge for 1 hour reserve is 16 hours - hence usual 3 hours - also allows for loss of capacity before battery replacement.

A case where you ask what the customer means by 2 x 50%.

Lighting Level Requirements

BS EN 1838: 2013 4.2 calls for a minimum of 1 lux anywhere on the centre line of the escape route for normal risks. A uniformity ratio of 40:1 maximum to minimum must not be exceeded. This illuminance must be provided for the full duration and life of the system. 50% of the illuminance must be available within 5 seconds and the full value within 60 seconds of supply failure.

Here are the requirements according to the NECA. A lot of exceptions and rules.

https://forums.mikeholt.com/threads/emergency-light-ups-backed-vs-battery-pack.147954/

If a certain method is required in the specifications it must be followed.

The engineer that wrote the specs had his reasons for doing so.

Yes, certain applications may have more stringent requirements, hence the specification stated. It may be worth your while to check re. the availability of the UPS circuits - the ones I was involved with had those light on the emergency circuits with auto changeover to a genset, not dedicated to a UPS circuit. Unless of course you have to supply the UPS as well? Maybe they require foot traffic for extended periods and the UPS can help there. Not enough info given.

I can see little sense in using UPS for emergency lighting. You want to provide lighting at intervals along the escape route and at each change of direction. LED emergency lights do this very effectively and will illuminate the route for three hours.

Earlier emergency lighting systems used central batteries as small rechargeables , integral with the luminaire were not available. The central battery comprised wet lead acid batteries which had issues in operation and maintenance, the inadvertent generation of hydrogen gas being not the least of them, and required completely separate wiring. They disappeared very quickly when self-contained EM fittings became available.

The 2x50% configuration sounds like 2nr UPS supplying the lighting load and if one fails, half the lights go out or all the lights operate for half the time that both would supply for. This implies that the UPS is supporting the whole of the lighting installation as part of a business continuity plan rather than a means of illuminating the evacuation of the building.

If it is evacuation lighting you need, go for discrete LED emergency luminaires with a test function, supplied from the normal lighting circuits and supported by a regime of monthly and annual checks to ensure its all available when needed. A professional electrical contractor would supply such a system and it could be retrofitted to an existing installation.

Emergency escape lighting also has to let people find their way out of a smoke-filled location, so floor fitted strips of arrow lights at both sides of the exit route are used.

Smoke fills from the top, so lighting at ceiling level or high up on the walls get obscured far sooner.

Each side should be on a separate circuit.