Main RCCB tripping on r1+r2

[ADS]

Ha ha, I see how you read it now, Ian - it is the missing comma that caused the problem.

Anyway, he meant that the 'main RCCB' was on (closed) and the MCBs were open - except for a lighting circuit - then switched lighting circuit off to test it, using portable lamp.

Apologies if I contributed towards the mix-up.

 

[Bacon]

OMG. Please post what you mean. Missing punctuation can make something completely different. That to me reads as "Main RCCD (that is) on all circuit breakers (are) in (an) open position.....". I gather from your reply that you actually mean "Main RCCD (is) on , all (other) circuit breakers (are) in (an) open position...."See how they are COMPLETELY Different. Now which is it?

In bold,

 

[Doc Hudson]

Well the last 10 posts just show how a picture could have saved typing a thousand words! Even with a simple circuit it is so easy to misinterpret something by either mistyping or misreading.

Doc H.

 

[ianmacd]

OK so I am going to make some guesses. Please advise which are correct/incorrect.

One RCCB (possibly as a main switch) with (at least) 1 lighting circuit.

All other circuits apart from the lighting circuit were individually disconnected from the MCB and that line connected to the CPC (possibly via the ET in the CU).

The RCCB tripped on every circuit.

Please advise if thats correct.

 

[Bacon]

OK so I am going to make some guesses. Please advise which are correct/incorrect.One RCCB (possibly as a main switch)Yes main switch with (at least) 1 lighting circuit.only one lighting circuit

All other circuits apart from the lighting circuit were individually disconnected from the MCB and that line connected to the CPC (possibly via the ET in the CU)Croc clip on ET in CU then other end placed on outgoing connection on each individual circuit not disconnected,.

The RCCB tripped on every circuit. RCCB only tripped when doing R1+R2 on lighting circuit

Please advise if thats correct.

In bold

 

[Bacon]

Sort of a drawing

 

[Chr!s]

as far as I'm aware connecting onto a dead circuit with your probes is safer than connecting onto a live circuit, but I'm not going to argue because I do both and see no problem with it. I do work in live boards and I have worked with live cables. I guess I was in the wrong and will isolate DB's from now on before entering. There goes my livelyhood.Anyway back to you bacon. I beleive my below post to be correct unless anyone can tell me any different or any other ideas?

Its possible sellers, though it need not be a borrowed neutral,just a circuit energized for the current to flow to the neutral bus bar, there the current would divide, some down the neutral and some through the circuit under test shorted to earth,the cpc would be required to remain in the earth bar.

If the cpc was removed from the circuit and the link placed between cpc and line, then it will more than likely be that the cpc is either fortuitously connected to the met or not so fortuitously connected to the met. Test the disconnected cpc to met for conformation.

And for the other dabate.

http://www.hse.gov.uk/pubns/indg354.pdf

 

[ianmacd]

So you R1+R2'd a live circuit? Who ever installed that with rcbo's off an RCCB should be shot (or at least shown reg 531.2.9).

 

[Chr!s]

So you R1+R2'd a live circuit? Who ever installed that with rcbo's off an RCCB should be shot (or at least shown reg 531.2.9).

Indeed he has:red card

 

[kme]

OK.

for what its worth, I didn`t read it as a "dig" at you, ADS - just a bit of puzzlement and confusion that arose over the O/P`s ambiguous, punctuationless comment . I fully agree with you regarding Zs on a PIR - we do that almost routinely, TBH, when a shutdown is unfeasible for whatever reason.

As to Bacon`s original post - the RCCD / RCBo / MCB issue is (sort of) beside the point. The reason for the tripping, as Chris says, is down to a light being "on", and the neutral and earth bars being effectively linked by the `jumper`. It should be noted that the connection of a jumper into the MCB/ RCBo terminal is NOT good practice - besides which, you`d need to remove it for insulation testing purposes. The circuit should have been disconnected completely for testing - not just by local isolation of the MCB (unless its locked off, how do you ensure continuity of safe isolation when you leave the DB to go to the end of the circuit.

Further - if a neutral on the lighting circuit has been "borrowed", there is the possibility of a shock hazard from a "dead" circuit; or even from the inadvertent disconnection of the wrong neutral from the DB.

KME

 

[Manator]

Manator,Are you seriously suggesting that the argument that you 'needed to see what you were doing' would wash with the HSE, if your colleague was lying dead on the floor.

Not word for word, but it goes:

It is unreasonable in all the circumstances for it to be dead and

It is reasonable in all the circumstances for him to be at work on or near it while it is live

There are a multitude of alternative methods of 'lighting' a job - I'm sorry Manator, I can't agree with this.

No, what I am suggesting is that a seperated circuit which is now dead can be tested safetly even though the board is live.

The sockets provided at most DB's are for maintenance on that board, one problem that the Hse had with battery powered lighting was sudden failure at critical moments, the preferred method was a constant trusted supply. If possible it should be taken from circuits not effected by any shut down.

Admittedly there are very serious procedures to follow and a work permit should always be obtained and under no circumstances should one person be left unattended when working live.

You have also already agreed with this by saying if the main switch was on then only the busbars would be live, which is what my point was.

I would also dismiss any person I found working near live circuits without full tested and verified safe gloves. I supply inner and outer for this purpose.

 

[Chr!s]

I would also dismiss any person I found working near live circuits without full tested and verified safe gloves. I supply inner and outer for this purpose.

Those gloves are fiddly to work with, though it becomes easier when their made fingerless

 

[sellers]

This is my theory, but if you did have all circuits off when doing the test this wouldn't occur, it would only occur if at least 1 of the circuits were on.

 

[ianmacd]

Sounds like neutral was not isolated for testing. Also haven't got an answer to whether they were doing the R1+R2 test live. That'll cause an rcd to trip.

 

[Adrian]

sellers quote is spot on you would need to disconnect all lamps or remove the neutral to carry this test on a live board

sorry my reply was a bit short, i was in the middle of a quote.if you imagine you have the live from that lighting circuit and a neutral from another circuit still connected in the board. When you short r1+r2 on your isolated circuit your creating a N-E short on the circuit that is still connected through the load on the circuit you have isolated.

I hope it makes some sense.

 

[Bacon]

Sounds like neutral was not isolated for testing. Also haven't got an answer to whether they were doing the R1+R2 test live. That'll cause an rcd to trip.

Why would i do an R1+R2 on live circuit,Lighting circuit was switched off.

 

[Sidewinder]

Can anyone explain HOW to do an R1+R2 on a live circuit without "blowing" things?

 

[ADS]

A lot of controversy

I wouldn't mind knowing the reason behind the OP testing R1 + R2 in the first place.

 

[Bacon]

A lot of controversyI wouldn't mind knowing the reason behind the OP testing R1 + R2 in the first place.

So you don't do an R1+R2 when doing any PIR's ADS?

 

[Sidewinder]

TBH mate I only do them if I can't do Zs OR, if there is another issue which requires greater investigations, or, they are small installs where they are easy to do, or IF the install is a "special" one where by there are additional requirements.

In no particular order!