Identifying single core cpc's and neutrals

[moosey86]

Just wondering if anyone has any handy tips when trying to identify single core cpc's and neutrals?

I work in a few food factories than are in constant production and switching off supplies is not an option, so identifying circuits can get pretty tricky.

Identifying neutrals is pretty simple as long as the neutral hasn't been stolen for another circuit (which I do come across a lot at one place) because clamping the live conductor and the neutral at the board should read the same amount of current being drawn (assuming it's single phase).

But cpc's are near on impossible. I'm going to get a socket and see or martindale fuse finder which would help for finding where things are fed from, but could these bits of kit be manipulated to trace back through the neutrals and cpc's? I'm guessing they can't but hoping they can!

If anyone could shed some light on any slick techniques that would help me with my problem it'd be much appreciated.

Moosey

 

[Richard Burns]

If you put a tone generator on the cpc as close as possible to the point you wish to identify then you may be able to track it to the point you need, the problem with old and extended circuits is that the cpcs could well be interlinked and the further away you are forma point the more unreliable it will be.
I am not sure if fuse finders generate a tone on the cpc (should be OK with the neutral) however I would expect that identification in a DB would be impossible still as they are all linked there.

 

[westward10]

Further complicated by steel containment if installed in such a way.

 

[telectrix]

Further complicated by steel containment if installed in such a way.

if you wanted it easy, you;d have been a plumber.

 

[moosey86]

I thought this would be the response, I've tried to think of numerous ways to identify without physically tracing. They're all the original circuits right at the bottom of the trunking and they're quite far away so it's not something that's feasible really.

I'll just identify the neutrals and then I'll just get the lad to measure voltage from phase to earth as I individually take out the cpc's.... I've got to be pretty unlucky for a fault to occur whilst doing so....unless it's my lad

It's only lighting circuits he'll live!

 

[westward10]

That really isn't the wisest of ideas in fact it is a ridiculous idea.

 

[Pete999]

I thought this would be the response, I've tried to think of numerous ways to identify without physically tracing. They're all the original circuits right at the bottom of the trunking and they're quite far away so it's not something that's feasible really.

I'll just identify the neutrals and then I'll just get the lad to measure voltage from phase to earth as I individually take out the cpc's.... I've got to be pretty unlucky for a fault to occur whilst doing so....unless it's my lad

It's only lighting circuits he'll live!

What a ridiculous suggestion

 

[Lucien Nunes]

It's technically possible. A method I have used to trace individual conductors that are paralleled up with low impedance containment was to inject a current with a split-core CT or demo transformer. Nothing needs to be disconnected and it doesn't matter how much metal is in parallel - that merely forms the return leg of the injection circuit. Assemble the transformer around one core at one end and crank up the input on a variac or labpack some known current is flowing which you can monitor with the primary current. Then pick through the options at the far end until you find a core with the same or similar current, and turn off the injection transformer to prove. If there's no parallel path you would need to run out a wander lead for your return. If there are branches then the injection current will be found in more than one place at the clamp meter end and this can help locate them.

 

[moosey86]

That really isn't the wisest of ideas in fact it is a ridiculous idea.

What a ridiculous suggestion

What about that suggestion do you find ridiculous? Are you talking on a safety point of view or a practical view?

It's technically possible. A method I have used to trace individual conductors that are paralleled up with low impedance containment was to inject a current with a split-core CT or demo transformer. Nothing needs to be disconnected and it doesn't matter how much metal is in parallel - that merely forms the return leg of the injection circuit. Assemble the transformer around one core at one end and crank up the input on a variac or labpack some known current is flowing which you can monitor with the primary current. Then pick through the options at the far end until you find a core with the same or similar current, and turn off the injection transformer to prove. If there's no parallel path you would need to run out a wander lead for your return. If there are branches then the injection current will be found in more than one place at the clamp meter end and this can help locate them.

Cheers pal I haven't read through that properly to get my head round it yet but I will do and hopefully it'll be the answer

 

[westward10]

Don't really know what to say to that, are you a qualified electrician, I have to ask.

 

[moosey86]

Don't really know what to say to that, are you a qualified electrician, I have to ask.

That is a typical hardcore forum member response, I hope you are proud of yourself for your attempt at belittling someone.

But I do know what you can say to it...you can answer my question if that's not too much bother for you?

I will answer yours....yes I am a fully qualified electrician.

 

[westward10]

I make no attempt to belittle anyone. If you feel removing the cpc and possibly the circuits mean of fault protection whilst putting the "lads" life at risk is a sensible option, fill out your risk assessment. We all make choices, some we live to regret while others suffer the consequences.

 

[moosey86]

I wouldn't say it would be putting the lads life at risk, we work near live circuits all day long it's just one of those environments.

We can make it as safe as possible when doing it and we will identify what we require in very little time resulting in a good job well done at the end of it.

Like you say though everyone has to make choices, I don't think many have died from a single phase 10A circuit that they know is about to have the cpc removed, so what you're getting at I feel is a stretch too far in my opinion.

 

[westward10]

Your last statement says a lot about your understanding of electric shock. I will leave you to it.

 

[Lucien Nunes]

Indeed - it only takes a few mA to give enough of a jolt to make someone fall off a ladder, and there might well be that much leakage if there's discharge lighting or long cable runs. Not a good idea, and if there's any contact between fittings and extraneous parts even of tens of kilohms to earth, might not reliably find the circuits anyway.

 

[moosey86]

Your last statement says a lot about your understanding of electric shock. I will leave you to it.

No I'd like you to explain yourself if that's ok?

This is meant to be a community of electricians that are there to help each other, so if you believe what you say about my understanding of electric shock then surely an explanation would be more productive than yet another belittling response.

Everyone operates at different skill levels and different knowledge and different experience in a shed load of different variations of electrical installation, control and maintanence.

If I am being utterly ridiculous then I'd rather know about it before I do put anyone's life at risk... That is not something I would be happy to do.

As it stands I still think you are going over the top but please explain to me what you believe I'm lacking in knowledge when it comes to electric shock...

 

[moosey86]

Indeed - it only takes a few mA to give enough of a jolt to make someone fall off a ladder, and there might well be that much leakage if there's discharge lighting or long cable runs. Not a good idea, and if there's any contact between fittings and extraneous parts even of tens of kilohms to earth, might not reliably find the circuits anyway.

Fair comment about falling off ladders, but we are up in a roof void and it is single core cables ran in plastic conduit. I would have suggested plugging in a klik with a flying lead with connector block at the end.

I thought maybe it won't work due to parralel paths but I figured there may be a chance it works as they are vapour proof fittings hanging from brackets.

 

[westward10]

Like I said I will leave you to it.

 

[moosey86]

Like I said I will leave you to it.

Ok top poster of the month

 

[Anthony S]

I'll just identify the neutrals and then I'll just get the lad to measure voltage from phase to earth as I individually take out the cpc's.... I've got to be pretty unlucky for a fault to occur whilst doing so....unless it's my lad

It's only lighting circuits he'll live!

Removing un-identified cpc's while an installation is energised/inservice must be one of the most pathetic things Iv'e read on this forum.

 

[moosey86]

Removing un-identified cpc's while an installation is energised/inservice must be one of the most pathetic things Iv'e read on this forum.

It's a lighting board and they will be disconnected for seconds.

 

[The Ghost]

I am sure you were really just speculating on the idea of disconnecting earths (I hope!) I am also sure you full well know the risks and regs around such a course of action. So I will not impugn your standing in the trade. I think Luciens ideas are doable, I was thinking of a small d.c. voltage (1-2v) or possibly a linesman phone at each end. Not sure how practical that is mind you. I have a cable detector that identifies up to 16 cables at a time but that is for dead circuit sadly. I do think you may find it worthwhile to flag this as a needed part of planned maintenance so when a machine is down you can test ccts for the earth in the future. As identifying correctly ccts is as important as not disconnecting the earth. As it is lighting can you not arrange for out of hours switching off? And are the circuits not placed by numbers on the board like neutral/mcb 1/cpc in 1 terminal etc?

 

[westward10]

Isolate the board, link cpc to line or neutral at end of circuit. Disconnect all cpcs in the board and assuming parallel paths don't exist you can trace the cpc by a continuity test.

 

[moosey86]

I am sure you were really just speculating on the idea of disconnecting earths (I hope!) I am also sure you full well know the risks and regs around such a course of action. So I will not impugn your standing in the trade. I think Luciens ideas are doable, I was thinking of a small d.c. voltage (1-2v) or possibly a linesman phone at each end. Not sure how practical that is mind you. I have a cable detector that identifies up to 16 cables at a time but that is for dead circuit sadly. I do think you may find it worthwhile to flag this as a needed part of planned maintenance so when a machine is down you can test ccts for the earth in the future. As identifying correctly ccts is as important as not disconnecting the earth. As it is lighting can you not arrange for out of hours switching off? And are the circuits not placed by numbers on the board like neutral/mcb 1/cpc in 1 terminal etc?

Cheers Vortigern,

I did like luciens idea, I think this is the route I will try because it is a common problem in old installations and I have wondered for a while if there was a method that was practical.

Unfortunately the factory is 24 hours all day everyday so it's something I'm going to have to deal with in some way. I've basically got a dis board mounted right next to the existing one with a temp supply and I'm installing emergency lighting and gradually swapping over the circuits to the new board one at a time. Once they're all done I will arrange a shutdown to change the existing dis board to an isolator which will feed the new one.

The existing circuits are numbered so the chances of getting the correct cpc are high. I could switch off and r1+r2 it, I just have to keep it to minimal disruption.

 

[moosey86]

Tha

Isolate the board, link cpc to line or neutral at end of circuit. Disconnect all cpcs in the board and assuming parallel paths don't exist you can trace the cpc by a continuity test.

That's very clever Westward I'm sure the customer would be over the moon.

 

[The Ghost]

That's very clever

Now now! I know it can get a little "heated" on here sometimes but stick with it and keep calm. There are some valuable insights between the thorns. If you get something a bit wrong (which I have!) and get a new backside ripped dont worry about it. Just make sure you take something of value away with you. They will calm down once they get to know you a bit

 

[moosey86]

Now now! I know it can get a little "heated" on here sometimes but stick with it and keep calm. There are some valuable insights between the thorns. If you get something a bit wrong (which I have!) and get a new backside ripped dont worry about it. Just make sure you take something of value away with you. They will calm down once they get to know you a bit

No worries, I'm not one to hold a grudge. I'm also going to get to the bottom of it somehow with one of these idea's and I'll get back to the thread with how I get on.

Sorry if I scared anyone

 

[HandySparks]

OK. How about this.
For each final circuit. Check earth continuity by wander lead or maybe by measuring Zs.
If properly earthed, introduce a small known 'leakage', line to cpc, say 5mA (47k, 2W resistor?). Get your mate to make and break the leakage load at 1 second intervals, to make it easier to spot. Put an earth leakage clamp meter on each cpc at the board and look for the one with current regularly varying by 5mA.

 

[SheffSimon]

I wouldn't say it would be putting the lads life at risk, we work near live circuits all day long it's just one of those environments.

We can make it as safe as possible when doing it and we will identify what we require in very little time resulting in a good job well done at the end of it.

Like you say though everyone has to make choices, I don't think many have died from a single phase 10A circuit that they know is about to have the cpc removed, so what you're getting at I feel is a stretch too far in my opinion.

Who benefits from you or your lad taking these risks, however small you might feel they are?

Not you I imagine, but the factory will, so why take the risk. I've worked in food and beverage factories for years. The ones I've worked in would run a mile from unsafe practices, and will arrange shutdowns on size/product changeovers etc if absolutely required.