3 phase breaker across 2 phases?

[kris jones]

hi all,

Can anyone advise me regarding installing a triple pole mcb in a 3 phase board across phases. Simply put, if the next available ways in the board were for example 2L3,3L1,3L2 and placed my breaker here would this be acceptable?
This would normally be grey, brown, black. Hence 1 phase on 2 and 2 phases on 3. I know this will work however if the board were full and perhaps unbalanced, I would be splitting a load?
Would best practise be to use a single L1,2,3 for the breaker?

Hope this makes sense?

 

[KEV 1 N]

Im not sure if there’s any regulations prohibiting this but I feel it isn’t right and is bad practice. Would be far better to rearrange the mcbs to gain a correct 3phase position without having to go across different circuit numbers. Plus lableing the circuit would appear confusing....an isolator/accessory marked “3L123” is easier to follow than “2L3,3L1,3L2”

 

[kris jones]

Im not sure if there’s any regulations prohibiting this but I feel it isn’t right and is bad practice. Would be far better to rearrange the mcbs to gain a correct 3phase position without having to go across different circuit numbers. Plus lableing the circuit would appear confusing....an isolator/accessory marked “3L123” is easier to follow than “2L3,3L1,3L2”

thank you, a sensible and reasonable answer! thought as much!

 

[Risteard]

As stated it's poor practice. In fact other national standards (including ET101) specifically prohibit this practice.

 

[kris jones]

As stated it's poor practice. In fact other national standards (including ET101) specifically prohibit this practice.

Thank you, now we've established that, can i ask, am I right regarding the fact that because you would breach 2 phases you wouldn't be able to balance correctly?
In a over the top example, if all L1 phases were in use and the board was full (other than this breaker) and you did this, you would be potentially overloading this phase? i hope this makes sense, cant think of a better way of explaining it.

 

[Risteard]

When designing an installation (or addition or alteration) obviously you should try to balance the load across the phases as evenly as possible.

 

[davesparks]

Thank you, now we've established that, can i ask, am I right regarding the fact that because you would breach 2 phases you wouldn't be able to balance correctly?.

You wouldn't be breaching two phases, it would still be connected to the same phases and the effect on the balance of the installation woukd be the same wherever you put the breaker.

 

[westward10]

Hello Kris this is your original thread tidied up and now in the Trainee section. Your new thread which appears to be the same I have closed. Are you happy for it to stay like this?