Circuit breakers and rcbos.

This is a common question, and the official answer simplified to  'don't mix brands, unless the makers tell you its OK.'

In reality of course it is more nuanced than that - there are some combinations that really cannot be mixed as the plane of the contacts is not the same, and the busbar teeth do not reach or something equally fundamental. 

Then there are others that might be mechanically compatible but might run too warm or interfere magnetically when along side another make. 

And there are a great many that will in fact be just fine  in any combination - note that on the continent in countries where there is not so much a consumer unit as a 3 phase breaker rack, it is common to mix all sorts of DIN rail items in the one box and make wire links as required to connect them. They do not have significanlty more or less accidents than we do.

The problem, from a regs point of view, is that without the makers instructions, once you stray from the approved combinations, you are adopting design responsibility for the arrangement, which is something that very few electricians  (or their insurance) are happy to do, once they realise the legal implications should there be any problem, however unlikely that is.

How problematic that really is  might be a moot point. (consumer unit makers don't actually pay up very often even when something demonstrably is their fault, like the flammable consumer units fiasco - they just lobby for  change of  rules so its not their problem) 

The safe advice in the UK at least is don't. Or at least be very careful if you have to. But if someone else has done it and it still  seems to be working, its probably OK to leave it alone but mark as an observation.

Mike.

This is a common question, and the official answer simplified to  'don't mix brands, unless the makers tell you its OK.'

In reality of course it is more nuanced than that - there are some combinations that really cannot be mixed as the plane of the contacts is not the same, and the busbar teeth do not reach or something equally fundamental. 

Then there are others that might be mechanically compatible but might run too warm or interfere magnetically when along side another make. 

And there are a great many that will in fact be just fine  in any combination - note that on the continent in countries where there is not so much a consumer unit as a 3 phase breaker rack, it is common to mix all sorts of DIN rail items in the one box and make wire links as required to connect them. They do not have significanlty more or less accidents than we do.

The problem, from a regs point of view, is that without the makers instructions, once you stray from the approved combinations, you are adopting design responsibility for the arrangement, which is something that very few electricians  (or their insurance) are happy to do, once they realise the legal implications should there be any problem, however unlikely that is.

How problematic that really is  might be a moot point. (consumer unit makers don't actually pay up very often even when something demonstrably is their fault, like the flammable consumer units fiasco - they just lobby for  change of  rules so its not their problem) 

The safe advice in the UK at least is don't. Or at least be very careful if you have to. But if someone else has done it and it still  seems to be working, its probably OK to leave it alone but mark as an observation.

Mike.