Finding the correct neutral to pull in a DB

[Gurnatronics]

So, I can’t turn off the board, can’t really turn off circuits except the one I am replacing with an RCBO. It’s all singles in trunking no sheaths to trace back to find the appropriate L and CPC, and obviously, nothing is labelled and they definitely aren’t in the correct neutral terminals.

Normally I would link out L&N and bell out neutrals as I pull the neutrals out the bar but that is no good on critical live systems.

Anyone got any hacks or tricks? I don’t want to tell them it’s a no go without a shutdown

Cheers

 

[7029 dave]

clamp meter on L and N under some load, the values should match.

 

[Gurnatronics]

clamp meter on L and N under some load, the values should match.

Genius!

 

[littlespark]

It’s a no go without shutdown.

It says you’re a trainee, so you shouldn’t be poking about in a live db without supervision

And the suggestion above, clamping the L and N for load won’t help finding the cpc.

 

[Gurnatronics]

It’s a no go without shutdown.

It says you’re a trainee, so you shouldn’t be poking about in a live db without supervision

And the suggestion above, clamping the L and N for load won’t help finding the cpc.

Not a trainee I’m gold card qualified but still everyday is a school day. I need to find out how to get that tag removed

I just assume he meant clamp the L to get a reading, then clamp each N sequentially till you get a matching reading

 

[7029 dave]

Not a trainee I’m gold card qualified but still everyday is a school day. I need to find out how to get that tag removed

I just assume he meant clamp the L to get a reading, then clamp each N sequentially till you get a matching reading

You assumed correct, but as @littlespark states you wont be able to ID the cpc with a live board.

 

[littlespark]

Not a trainee I’m gold card qualified but still everyday is a school day. I need to find out how to get that tag removed

I just assume he meant clamp the L to get a reading, then clamp each N sequentially till you get a matching reading

Sorry mate. I just assumed.

You can find the L and N by comparing current, but change the current and test a couple of times…. Just in case there’s another circuit pulling exactly the same.

Still won’t help with the cpc.

This is why we have numbered terminals to match the cct numbers

 

[Gurnatronics]

Sorry mate. I just assumed.

You can find the L and N by comparing current, but change the current and test a couple of times…. Just in case there’s another circuit pulling exactly the same.

Still won’t help with the cpc.

This is why we have numbered terminals to match the cct numbers

No bother pal alls well.

Im normally an industrial install spark and everything I did in boards were in the correctly numbered terminal and cable tagged. Going into remedials now and when you gotta swap an MCB for RCBOs in and nothing is ever identified it starts doing your nut in trying to find s**t after a while, especially after a 2 hour drive and once you swapped and certified it you can go home again grrrr

 

[Deleted account]

This is why we have numbered terminals to match the cct numbers

have you ever seen a board that matched the numbered sequence. Very rare.

unless you’ve done it yourself I wouldn’t rely on that method.

 

[telectrix]

an idea is to switch that 1 MCB off. clamp each N in turn till you get 1 or more with zero current. then identify the right one by switching MCB on and finding which N jumps up.

 

[Gurnatronics]

Brilliant ideas thanks very much for the sanity checks!!

On a related note, anyone got any recommendations for a clamp meter? Im half eying up a fluke t6 or even the Megger MET1000 that I could then use for safe isolation. The open jaw clamp would work for finding the neutrals no?

 

[timhoward]

The cheapest one worth having IMHO is this one: (£40 inc vat)

https://cpc.farnell.com/multicomp-pro/mp780050/mini-leakage-current-tester/dp/IN08364?mckv=sdUObAoH2_dc|pcrid|426684131405|

That is a rebadged Tek 775 which normally costs £75+

I'm not sure I'd want my 2-pole tester to become a more sophisticated and expensive item, it gets so much abuse day in day out I don't wanting to be forking out big money to replace it!

 

[hasel5]

Working live in a DB ? Is that ok

 

[Gurnatronics]

Working live in a DB ? Is that ok

According to the EAWR regulation 14 it’s ok as long as certain precautions are taken Besides how would you ever get a ZE or PFC/PSCC without working live?

The cheapest one worth having IMHO is this one: (£40 inc vat)

https://cpc.farnell.com/multicomp-pro/mp780050/mini-leakage-current-tester/dp/IN08364?mckv=sdUObAoH2_dc|pcrid|426684131405|

That is a rebadged Tek 775 which normally costs £75+

I'm not sure I'd want my 2-pole tester to become a more sophisticated and expensive item, it gets so much abuse day in day out I don't wanting to be forking out big money to replace it!

Awesome I will check it out thanks. I just want to carry less stuff around so not having a 2 pole and multiple meters with multi batteries to keep track off would be ace, like you say though, more chance of breaking grrrr

 

[MJPD29]

Working live in a DB ? Is that ok

Unless you solely work in the domestic sector realistically it is unavoidable at times. You assess and minimise the risk according to each job.