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Mr T

Emergency Lighting wiring set up

Question

Mr T

Hi

Pls can you help with the following emergency lighting query

The set up consists of a key switch, a neon and a 1 way switch

t&e mains ran to the supply side of the key switch and a 3 core ran to provide the Emergency Live on the load side , the N and a switched live for the 1 way switch

Links to Neon L&N taken from the load side of the key so that when the key is operated the Neon goes out (simulates a mains fail)

link from L on the supply side of the key taken to Common on the switch ( so that the lights stay on and only the emergencies go off )

thats my understanding , however 2 little things that bug me which I know will be very simple once explained...

1. the link from the supply side of the key to Common on the switch - what is the purpose of this link ? Im thinking its so when you switch of the lights from the 1 way switch it also switches of the emergency is this right ? however im thinking it wouldnt switch them as the link is taken to the supply side hence leaving the bottom side ( load untouched) this is where im getting confused about the purpose of the link , I thought of it being to provide a permanent live however the supply side of the key is fed from the mains...

any help would be greatly appreciated

thanks

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spinlondon

Not certain why you have the extra one way switch.

There are two ways these key switches are normally wired.

One so that all power is cut, simulating a power failure.

This would leave only the emergency lights lit, and you would be able to check light levels and determine whether any lamps or batteries have failed.

The other is where just the permenant live to the emergency lights is cut.

This will switch on the emergency lights, whilst leaving the normal lights on.

This makes it difficult to ascertain whether light levels are adequate, and whether lamps or batteries have failed.

The only thing I can suggest, is that you operate the one way switch.

Then the key switch followed by the one way switch, and note what happens.

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sellers

Thought I'd draw a quick diagram to help clear things up.

Is this how you mean?

emlight.jpg

If so, you have 2 options when wiring in this way. You either take the supply to the 1 way switch from the switched or unswitched side of the key switch.

This is the way I would wire it, so when switching the keyswitch it switches off all normal lighting and activates the EM lighting. You can however take the 1 way feed from the unswitched side and then when switching all lights remain on and emergency lights switch over to thier battery.

It is difficult to see whats what with the second option and you would have to take the neutral out of the DP switch and connect it though.

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Mr T
Thought I'd draw a quick diagram to help clear things up.

Is this how you mean?

emlight.jpg

If so, you have 2 options when wiring in this way. You either take the supply to the 1 way switch from the switched or unswitched side of the key switch.

This is the way I would wire it, so when switching the keyswitch it switches off all normal lighting and activates the EM lighting. You can however take the 1 way feed from the unswitched side and then when switching all lights remain on and emergency lights switch over to thier battery.

It is difficult to see whats what with the second option and you would have to take the neutral out of the DP switch and connect it though.

thanks , yes the lights are wired so that when you key the switch all other lights remain on , it is in a school so I guess they wantg it this way so when testing the kids are plunged into darkness...

good point about the Neutral..id wired the Neutral into the load side of the key so when I tested today it was knocking the lights off ( losing a neutral at the gregg fitting)

the live link from the supply side of the key to the 1 way switch .. what is the purpose of this link.. this is the 1 thing that bugs me... it is to simply provide a common for the 1 way switch ?

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Mr T
Not certain why you have the extra one way switch.

There are two ways these key switches are normally wired.

One so that all power is cut, simulating a power failure.

This would leave only the emergency lights lit, and you would be able to check light levels and determine whether any lamps or batteries have failed.

The other is where just the permenant live to the emergency lights is cut.

This will switch on the emergency lights, whilst leaving the normal lights on.

This makes it difficult to ascertain whether light levels are adequate, and whether lamps or batteries have failed.

The only thing I can suggest, is that you operate the one way switch.

Then the key switch followed by the one way switch, and note what happens.

the key switch/ emergency light is in the classroom along with the normal lights so this is why we have the 1 way switch

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sellers

the link is to provide a live for the switch, so you can operate the lights under normal conditions.

I take it the lights you have are something like a 600x600 fitting with 4 tubes, 1 tube being the emergency

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Andy™

It is difficult to see whats what with the second option and you would have to take the neutral out of the DP switch and connect it though.

reminds me of a job a few years ago. in the spec that all switching must be DP. it was pointed out that it wouldnt work, but we were still told to wire it that way. then ended up going back and connecting neutrals... at the time, the 'electrical engineer' couldnt understand why the lights were fully out on test, and not partly lit

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Mr T
the link is to provide a live for the switch, so you can operate the lights under normal conditions.

I take it the lights you have are something like a 600x600 fitting with 4 tubes, 1 tube being the emergency

thanks

yes 600x600 only 2 T5 tubes , 1 being for the emergency

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Evans Electric

The point of the neon ,in my experience, is to be lit when the key has been operated for testing, to make sure they are not left in the test position.

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