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.

You are caught in the manufactures instructions / specifications 'dilemma / predicament / quandary'.

They should be interchangeable (high level specifications on a part level basis). However, they will have been tested by individual manufactures on a complete consumer unit basis, as an integrated assembly, with possibly some manufacturers warnings about what can be put next to what, and positions within the box, etc. which could affect things like thermal characteristics.

If you mix and match you are taking on the risks of incompatibility...

To be avoided. I do not think that the wholesaler did not stock it is an acceptable excuse - look elsewhere.

However, if the original is no longer available and the choice is between repairing the installation or a new DB, it may be acceptable. As Mike says, it does need to fit properly. DIN rails may be standardized, but busbars are not.

Budget also comes into it. For me, the real question is, "Would I do it in my own home?"

Have to order from UK as I live in Guernsey so new board it is if it carries on .

What brand of board is it? Any ideas as to how old it is? What BS EN number is on the mcbs? Some earlier stuff is fine when used with a so-called 'other brands'. Take Wylex for example, Earlier Wylex stuff was exactly the same as Volex - both made by Electrium who own the Wylex, Volex and Crabtree brands.

Another example is the earlier MK, Square D and Merlin Gerin mcbs, all had the same moulded case and were identical in all dimensions. A cynic might be forgiven for thinking thst they all came form the same factory.............

I'm going to go out on a limb here and say that the electromagnetic and thermal arguments are spurious and without foundation. This is more about protecting market share and profit.

In these days of design to repair, and green conservation and reuse of materials, one might suspect why the manufacturers have not been brought to heel when it comes to componant interchangability for their products. After all, they are all made to the BS standard.

I'm going to go out on a limb here and say that the electromagnetic and thermal arguments are spurious and without foundation. This is more about protecting market share and profit.

 You might think that, you might very well think that... And you may well be right !! But we cannot easily prove it.

The problem is the makers are not prepared to test and give their approval to anything other than their own stuff.

As I noted, in other parts of the world mix and match is common and not usually a great issue in practice - but they do tend to leave more gaps between things.

The other imaginary spectre sometimes incorrectly raised as a blocker  is the 'conditional' 16kA rating of a 6kA consumer unit protected by a 100 company fuse. There is nothing conditional or UK specific or breaker brand specific about it. The fact is that it is the physics of the 100A fuse that limits the energy available to damage any stuff downstream once the PSSC is high enough to have to think about it, which is a small subset of real installations anyway.

Mike.

Not sure that Guernsey has the same regulatory regime anyway,  a great many UK rules are not transcribed, after all the whole place is plugged into Jersey, and their electrons are generated in France ! More seriously I know it is 13A sockets, but I'd be surprised if there was anything like part P.

mapj1 said:

Not sure that Guernsey has the same regulatory regime anyway,  a great many UK rules are not transcribed, after all the whole place is plugged into Jersey, and their electrons are generated in France !

Same here, Mike!

France usually sends us electrons (which it can do 'cos it is d.c.), but very occasionally, we send them back. https://bmrs.elexon.co.uk/interconnector-flows

Chris Pearson said:

France usually sends us electrons (which it can do 'cos it is d.c.),

Interestingly, if it's 50Hz AC, then the electrons never leave their host atoms (assuming all conduction electrons are doing a shimmy), which was a surprise to me when I did the calculation. 

I'd wondered how far the fusing coulombs of current (Cu) travelled each half cycle, relative to the Cu crystal lattice size (i.e. atomic width). The AC <-> DC transition frequency is very low by that mechanism (does the conduction electron move to the adjacent atom)

Gewiss