Question about emergency lighting switches

[Adam Funk]

All the corridors and some of the rooms in my office building have emergency lights with what I think is the usual switch arrangement: a two-hole grid plate with a normal switch for the main lights beside a key-operated switch for the emergency light.

I recently saw someone going through the building testing the lights and I noticed that each keyed switch cuts the power to the emergency lights (so the little green charging indicator goes off and the emergency light comes on) but also cuts the power to the main light (I watched and the tester was not flipping the "normal" switch).

So I'm just curious why the test switches cut off the main lights --- is it just to make it more immediately obvious that the emergency ones are working?

[Colin Bignell]

Probably because it is the failure of the main lighting circuit that triggers the emergency lights to come on.

[John Rumm]

Emergency lights come in two forms - non maintained, and maintained. The difference is that the maintained ones can be switched on with a switch, or by disconnecting the power. The non maintained ones don't have the switch option, so the only way to turn them on manually is to cut the power. The cheapest and most commonly used are the non maintained ones.

So the key switch just needs to simulate failure of power to the circuit. You also don't need extra wiring for a separate switch to the lamp. That will test the lights - including their batteries and inverters etc. The side effect will be to cut power to the normal switched lights as well.

[alan_m]

And in many (not all) units on sale the only difference is the provision for a link on a connector. Many unit sold as non maintained can be wired in three ways. i) Off whilst mains is being supplied and on via a battery when the mains fails. ii) Permanently on whilst mains is being supplied and on via the battery when the mains fails. iii) On/off via wall switch whilst mains is being supplied and on via the battery when the mains fails.

I have two units purchased as non-maintained. One that has a three terminal connector for the permanent mains and cannot easily be converted without possibly getting to the circuit board. The other has an additional terminal for switched live which can either be linked internally to the permanent live or alternatively linked via a switch.

[alan_m]

I wonder what testing regime they had? When one of my emergency lights came to the end of it life a quick couple of minutes check wouldn't have identified it. With mains removed the light came on but for only around

10/15 minutes and not the 3 hours when new. The old unit had a fluorescent tube and I elected to replace it with a LED version rather than just replacing the battery.

Note: the availability of fluorescent light products is likely to be somewhat limited now, or a bit later this year.

or

[Tim Lamb]

In message [e-mail]>, alan_m [e-mail]> writes snip

I have a flock of part used 5' and some 6' tubes if anyone has a need:-)

[Adam Funk]

That makes sense, thanks.

[Adam Funk]

The testing I saw very quick, probably less than a minute for each keyed switch. Maybe they do longer tests then the building is mostly unoccupied, but I don't know.

[Colin Bignell]

The regime in my factories was to check that the emergency lights came on when the mains failed as part of the factory's monthly planned maintenance, with a four hour test as part of a less frequent planned maintenance. I think that was the annual one, when lamps were being cleaned or replaced and production was stopped for other annual maintenance.

When one of my emergency lights

[Animal]

Does thst mean no more halogen headlamp bulbs? Can LEDs be retrofitted into halogen designs & give suitable beam pattern?

[Rob Morley]

Why would legislation on mercury vapour lamps affect halogen lamps?

[Animal]

I assume it covers both for the same reason, poor energy efficiency. Halogens aren't significantly toxic afaik.