Emergency key switch wiring

[dave19]

Hi Guys,

Can you help ? I just wanted to know how you wire a key switch and normal switch together. Is this how it should be :-

Feed from board to common on key switch
power to emergency lights comes off the load side of key switch
loop feed comes off the common side of key switch to common side of normal switch then
power to normal lights comes off load side to normal switch.


Is this it and if not is there a different way of doing it. Please explain in as simple terms as you can. Diagrams would also help ? Thanks guys.

Dave.

 

[Sintra]

That works well for stand alone fittings but for combined i would generally bring the "loop feed" from the load side of the key switch. That way the key switch operation also kills the switched supply to the fitting.

 

[Adam W]

That works well for stand alone fittings but for combined i would generally bring the "loop feed" from the load side of the key switch. That way the key switch operation also kills the switched supply to the fitting.

Depends on the use of the building/room - for internal corridors it may be better to leave some lights on. Similarly workers might not want you turning all the lights out. If you're going to be doing the emergency lighting test out of hours, Sintra's method is ideal, then you can see at a glance what lights are on.

 

[BigTom83]

Also may depend on the client /spec.

1 hospital I've worked at took the switch feed from switched side of the key switch so when you put the emg's into test it kills the power to the lights.

A different hospital I worked at had it as you suggested so the main lights still worked whilst you were testing the emg's.

Was all written in the spec.

Tom

 

[Sintra]

Yes all really site specific but the kill all method is great especially if you have to get lux levels.

 

[dave19]

So can i clarify something. If you loop feed between emergency common and switch common then what happens with both emergency and normal lights as the key switch does not turn off the power to normal lights ?

 

[Adam W]

The 'normal' lights stay on and the emergency lights go into 'emergency' mode. You need a permanent feed for an emergency light to work 'normally' even if you've got a switched feed.

 

[Guest55]

Yes all really site specific but the kill all method is great especially if you have to get lux levels.

not arguing with your comment.....

but lux levels and lighting output should be ascertained at the design stage , i cant see any reason to wire a key switch in such a way that kills all the lighting just to check that the emerg. lights are bright enough , cos if theyre not , youve gone epically wrong a long time ago
;-)
ive always done it the other way , normal lights stay on during em. light tests.

 

[Adam W]

not arguing with your comment.....

but lux levels and lighting output should be ascertained at the design stage , i cant see any reason to wire a key switch in such a way that kills all the lighting just to check that the emerg. lights are bright enough , cos if theyre not , youve gone epically wrong a long time ago
;-)
ive always done it the other way , normal lights stay on during em. light tests.

How do you know if the lux level has deteriorated then? The diffusers may have got dirty or the tubes not producing as much light as they did when they were new, or do you think that's just pie in the sky?

 

[Guest55]

How do you know if the lux level has deteriorated then? The diffusers may have got dirty or the tubes not producing as much light as they did when they were new, or do you think that's just pie in the sky?

maintenance by chance ?
christ almighty , spare us another one of your insane hypothetical scenarios.

 

[Brightspark2]

not arguing with your comment.....

but lux levels and lighting output should be ascertained at the design stage , i cant see any reason to wire a key switch in such a way that kills all the lighting just to check that the emerg. lights are bright enough , cos if theyre not , youve gone epically wrong a long time ago
;-)
ive always done it the other way , normal lights stay on during em. light tests.

I agree, testing of the emergency lights should have no effect on general lighting.

 

[accordfire]

Just to clarify, BS5266 indicates that normal lighting should remain energised while emergency lighting is activated via a suitable test switch.

That said, the method for wiring the test switch can vary depending upon whether the EL fittings are maintained, or non-maintained.

As others have pointed out, with a sustained style of fitting - e.g. where the fitting is used as a normal fitting and as an EL fitting, you'll have to deal with both permanent and switched live wiring. Both should be isolated to provide proper testing conditions.

 

[Adam W]

maintenance by chance ?
christ almighty , spare us another one of your insane hypothetical scenarios.

You're not going to know if the emergency lights aren't as bright as they were when they installed by "maintenance".
Does the idea that an infrequently used light might not be as bright 10 or 20 years after it was installed really seem that "insane" to you?

 

[Guest55]

theres no talking to you Adam , every debate ends in a --- for tat childish strop where you have to have the last word.

 

[dave19]

My problem is i'm new to this. Is it right to say that the emergency lights are just the same as tge normal lights until you switch off the key switch. What happens then as you are knocking off the power to the emergency light. Is this where thebattery kicks in and the light looks dim ?

 

[capitolltd]

Shouldn't the lights be tested at a time of low risk to allow time for the batteries to be recharge in accordance with BS5266? Why would you need the lights to then remain on?. Generally unless an indicator is wired into the circuit to indicate emergency testing, switching off all the lights is the preferred method as this reduces the risk of the lights not being re-energised after test. However, the designer will identify the risks and design accordingly.
Those electricians that undertook the old AM2, would remember the wiring of such a neon at the switch position during the exam.

 

[Adam W]

theres no talking to you Adam , every debate ends in a --- for tat childish strop where you have to have the last word.

All I said was it would be easier to test the lux level of the emergency lights if only the emergency lights were on.
Maybe I sometimes embellish my hypothetical scenarios a little, but on the whole the ideas are perfectly feasible and I don't know why you can't get your head around them.
Take this one - "light diffusers might get dirty". What is so bizarre about that? It happens all the time.

 

[Guest55]

well if you clean and lamp change the emerg lights on a regular basis you dont need to turn the lights off for the whole building just to see if light output has dropped.

its called preventative maintenance - fix the problem before the problem occurs.
its a very simple concept.
ffs.

 

[Landril]

Em lighting needs to be planned well, if u mess up the wiring it can cost u a lot of time(=money) to fix wiring issues.
It is all client based with regards to preference of how it is tested, u need to wire it with the client and regs in mind.
General rule of positions is change in level or direction too remember.Clients sometimes don't know we're em lights need to be positioned.

 

[Adam W]

well if you clean and lamp change the emerg lights on a regular basis you dont need to turn the lights off for the whole building just to see if light output has dropped.

its called preventative maintenance - fix the problem before the problem occurs.
its a very simple concept.
ffs.

I know what preventative maintenance is thank you, but no amount of cleaning the diffuser and changing the lamp every year is going to stop a luminaire becoming less efficient over time. It seems it would be far simpler just to only have the emergency lights on and walk around with a lux meter so you have an actual number to work with; when it falls below a certain level that's the time to change the fitting.