Today's board change

[uksparks]

Hi,

This morning's job, in and out in 4 and a half hours. Vast improvement. Feel free to rip it apart and tell me I'm a fool and I've made a bodge of it and don't know what I'm doing.



I did actually heat shrink the end of that line conductor and disconnect the relevant earth and neutral and shrink them the same, it was for a shower circuit thats not connect in the loft, they also got labelled accordingly.



You may say why the cable ties, I saw one of you do it the other week on here, Trev i think or GMES maybe? Looked nice.



Ok I know MCB 8 is on when it doesn't need to be, I did switch it off.

 

[uksparks]

Are you saying it will only disconnect if there's a L - E fault not N-E fault?

 

[telectrix]

no... any RCBO will disconnect on a L-E or a N-E fault, due to the current imbalance. what i am saying is that a SPSN breaks the N as well as the N.whereas a SP RCBO only breaks the L.

 

[Silly Sausage]

UKS, there's a very recent thread on this very subject, check it out...please!

 

[uksparks]

Ill be honest I've never really thought about it, I'm guessing a normal rcd or rcbo just disconnects the line then, so really one that disconnects both has to be a better option.

 

[uksparks]

UKS, there's a very recent thread on this very subject, check it out...please!

I wasn't aware there was one, I'll have a look for it, thanks.

 

[guest119]

Missing Daves point UK.
A fault wont take out half the board, just a single circuit.

Boydy

 

[Engineer54]

for my own place i'd be using SPSN RCBO's throughout, I can PM you details of where I get them from if you want

Why PM him with the details, why not post the details of these SP+N RCBO's here?? Any product or company services that is, or could be beneficial/helpful to the forum members shouldn't be of any problem at all. I take it that you have no financial or other interest in the outlet company??

 

[davesparks]

Why PM him with the details, why not post the details of these SP+N RCBO's here?? Any product or company services that is, or could be beneficial/helpful to the forum members shouldn't be of any problem at all. I take it that you have no financial or other interest in the outlet company??

Last time I tried to post details of a supplier who doesn't sponsor the forum it got deleted almost instantly by a mod.

But hey, what teh hell, i'll give it a go and see what happens.

 

[davesparks]

Missing Daves point UK.
A fault wont take out half the board, just a single circuit.

Boydy

Not missing the whole point, the N-E fault thing is part of it as well as only losing one circuit to a fault.

 

[davesparks]

Are you saying it will only disconnect if there's a L - E fault not N-E fault?

The basic problem is this:

Single pole RCBOs whicha re commonly available only disconnect the live and have a solid neutral.

So lets say a neutral to earth fault occurs on a circuit protected by said RCBO
the RCBO will detect the N-E fault
The RCBO will then disconnect the L
To the untrained eye it appears that all must be ok as whatever fault has occurred the protective device has operated so all must be safe.
Of course the N - E fault is still there and so the diverted neutral currents which could easily exceed the rating of the cable will be flowing through the fault and thus fire could start.


some people will say that this doesn't matter because fuses and MCBs don't disconnect the neutral, but this is not relevant as these devices are not designed to detect or disconnect those faults, they are designed to detect faults in the live. The issue is that you have a device which is designed to detect a fault but then reacts to that fault by disconnecting the undamaged conductor!

 

[Engineer54]

Last time I tried to post details of a supplier who doesn't sponsor the forum it got deleted almost instantly by a mod.

But hey, what teh hell, i'll give it a go and see what happens.

By all accounts this is a specialist supplier, that also only services tradesmen and companies and not the general public, so shouldn't upset any sponsoring suppliers here!!

 

[davesparks]

Well I've posted the PDF and so we'll see how long it stays here

 

[VoltzElectrical]

no... any RCBO will disconnect on a L-E or a N-E fault, due to the current imbalance. what i am saying is that a SPSN breaks the N as well as the N.whereas a SP RCBO only breaks the L.

Just like a fuse then. If they are so bad, why do they make them?

 

[Pete999]

By all accounts this is a specialist supplier, that also only services tradesmen and companies and not the general public, so shouldn't upset any sponsoring suppliers here!!

Not Electrifix by any chance? wouldn't call them a specialist supplier

 

[davesparks]

Just like a fuse then. If they are so bad, why do they make them?

Nothing like a fuse,

A fuse detects a fault in the line conductor and then disconnects the line conductor, this disconnecting the fault.

A SP RCBO detects a fault in the neutral conductor and then disconnects the line conductor, this leaving the fault connected whilst giving the uninitiated the impression that a fault has been disconnected.