Identifying single core cpc's and neutrals

[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.