Finding the source of a permanent live

[Micky d]

Hi, I am trying to replace an emergency light in a hotel but cannot isolate the permanent live. I have isolated the mains feed in from the DB but there is another PL wired in from the ceiling void. I have tried the usual isolating trips one at a time however, the board is poorly labelled and additional items have been wired all over the place. The problem is that I would normally isolate the entire board however, all of the computer systems and office is also wired on to this board so I cannot turn off the whole board.

The e/m light is the only e/m light in the room but there are over 50 individual spots in the ceiling, 20 bedrooms and a corridor full of lights (every second one is an e/m) and yes I have tried to isolate the e/m lights but this unit is still live. This PL could be coming from anywhere. As I don't fancy curly hair (whats left) can anyone advise.

cheers

 

[ashrow]

try turning off all light mcbs (very rarely you can come across a situation where light circuits have been connected wrong and are fed from 2 mcbs Due to poor installation work !)
Also in some older properties i have seen emergency lights fed from the socket circuit (i know that wrong but thats what i have found)

 

[Thefailsafe2012]

Is there no key switches anywhere?

 

[Micky d]

Hi, I have tried every key switch I can find. I have also tried every trip marked up as lighting but still live. I am inclined to sgree so far with ashrow, it could be wired from a socket. I will try and switch off one at a time of the ones that aren't linked to the essential running of the hotel. Well thats most of Monday taken care of then!! Thanks guys

 

[RogertheBodger]

Got sympathy with your situation, we've all been there, for me , 3 choices, work live, walk away, or explain the situation to the manager and tell him you need 15 mins to isolate the circuit in question, power down your office equipment at a convenient time or the job can't be done.

 

[loop3]

I take it you don't have a cable/mcb tracer. Useful in such situations. Invaluable infact.

 

[Thefailsafe2012]

Yeah they've proper stuffed you their mate! Loop3's got it right, a tracer would be a helpful tool for this!

 

[snowhead]

If YOU can't isolate the permanent live, then the E.m light can't have been routinely tested.
Have you tried asking whoever is responsible for E.M testing (assuming it's done in house) and see what switch(es) they use to do the test?

Just a thought, why did they need to get you to replace the light, it must have been tested and failed??

 

[jumpin jax]

Are you using a volt stick to test for live? If so you could just be measuring induced voltage.

 

[cobrauk]

I have isolated the mains feed in from the DB but there is another PL wired in from the ceiling void


How have you proven this as they would both be in the same terminal ? I assume you are talking about the cables in the fitting ?

Read more: http://www.electriciansforums.net/e...ding-source-permanent-live.html#ixzz2Ah7HGUuA
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[SYKRAPS]

They have maybe stolen a PL from next door so when their lights fail you EM light works lol

I would explain that the EM light should be fed from a local lighting circuit and it is clearly not as you have proven and it should be rectified, you will probably find that this is not the only one that is installed incorrectly.

You never know you may get a decent job out of it.................

Just another thought this light may be fed from the wrong side of one of the key switches

 

[egginyourface]

I went to replace emergency light fitting today. Turned all lighting circuits off but em light fitting was still live. Opened another cabinet to find a small fuse board with 2 breakers. One was labeled kitchen and the other emergency lights contactor.

Thought to myself " ooooh found it!!!"

Switched off 6 amp mcb only to find it was connected to contactor which isolated the whole installation.... Yikes

Had 20 people cussing and cursing me as they lost all there work on there computers

 

[SYKRAPS]

I went to replace emergency light fitting today. Turned all lighting circuits off but em light fitting was still live. Opened another cabinet to find a small fuse board with 2 breakers. One was labeled kitchen and the other emergency lights contactor.

Thought to myself " ooooh found it!!!"

Switched off 6 amp mcb only to find it was connected to contactor which isolated the whole installation.... Yikes

Had 20 people cussing and cursing me as they lost all there work on there computers

Ouch how did you explain that one?

 

[MarkieSparkie]

I know what my former boss would do in such circumstance, he'd say "Stop P'ing about make it safe son" meaning short the permanent live, you soon found out which circuit, breaker or fuse it's on when somebody screamed because they lost power.

 

[cobrauk]

^^^^^^^
Same here m8 lol