Amendment 2 BS7671 again

[cliffed]

Just watched a video by J Ward covering parts 1,2 & 3, any thoughts on the consumer unit, this being a Type Tested Assembly, where if non compatible Mcb’s are used it does not comply & does not remain a Consumer Type Tested Assembly.
No mention of what it becomes though, so what happens next, there’s thousands of Consumer Units out there with other brands of Mcb used in the CU.
The statement:An assembly of one or more protective devices, Proven during the TypeTest of the assembly as suitable for such use.

 

[Simon47]

It is still a consumer unit. If it has mixed-brand parts then it is not a type-tested CU.

Actually, as it's no longer type tested, it's no longer a CU according to the definition in BS7671 : "Consumer unit (...). A particular type of distribution board intended for operation by ordinary persons, comprising a type-tested coordinated assembly for ..."
With mixed devices, it then becomes a distribution board : "Distribution board. An assembly containing switching or protective devices (e.g. fuses, circuit-breakers, residual current operated devices) associated with one or more outgoing circuits fed from one or more incoming circuits, together with terminals for the neutral and circuit protective conductors. ..."

I'm sure I remember there being some restrictions on the types of distribution board allowed for operation by "ordinary persons", which I vaguely recall mandated a "CU" for domestic environments. But I can't find that now.

 

[pc1966]

Visually it may seem fine but how can you be certain it is safe for continued use.

Well strictly speaking you can never know if anything is safe for continued use, unless you can see in to the future (in which case you are probably better off playing the lottery than being a spark). The best you can do is apply engineering judgment to what you are able to inspect and test.

Adding in mixed-brands of course adds to the uncertainty which I guess is why the BPG#4 has such specific notes on it.

Just to be clear on the matter I don't think mixing stuff is a good idea, but if it has been done for whatever reason it is not automatically a reason to fail something.

 

[pc1966]

Actually, as it's no longer type tested, it's no longer a CU according to the definition in BS7671 : "Consumer unit (...). A particular type of distribution board intended for operation by ordinary persons, comprising a type-tested coordinated assembly for ..."

That is a good point to raise.

I am pretty sure there is more to the "domestic CU" aspect than just the type-testing (e.g. type of isolation switch, etc), but however it is done it is always the person who mixed thing's responsibility for safe operation as it no longer has that guarantee.

But then it is also the responsibility of the installer of a type-tested CU that it is safe with correct design of circuit protection, quality of workmanship, etc.

 

[cliffed]

That is a good point to raise.

I am pretty sure there is more to the "domestic CU" aspect than just the type-testing (e.g. type of isolation switch, etc), but however it is done it is always the person who mixed thing's responsibility for safe operation as it no longer has that guarantee.

But then it is also the responsibility of the installer of a type-tested CU that it is safe with correct design of circuit protection, quality of workmanship, etc.

That’s exactly how the Video described it, it’s not a Consumer Unit when non compatible Mcb’s are used, but didn’t actually say what it then becomes, maybe a Distribution Board….

 

[Lister1987]

Most common thing that comes to my head is adaptable box with din rail mounted connectors

 

[Simon47]

Something else to consider ...
What about a situation where one brand really is the same article as another but with different screen printing ?

 

[Lister1987]

Something else to consider ...
What about a situation where one brand really is the same article as another but with different screen printing ?

Depends on your due diligence and how covered you want your arse as I'd want concrete certainty that the badge is the only difference before I start mixing switchgear

 

[westward10]

Something else to consider ...
What about a situation where one brand really is the same article as another but with different screen printing ?

I would only use the scenario with Schneider for replacements in Merlin Gerin or Square D boards where the manufacturer confirms compatibility.

 

[LastManOnline]

I would only use with scenario with Schneider for replacements in Merlin Gerin or Square D boards where the manufacturer confirms compatibility.

Are there documented cases of the dangers that using different makes pose?.

I ask as I have not had personal experience of this issue. From what I,ve read so far the 2 areas of concern appear to be....

1) possibility of overheating due to incompatible buzzbars
2) the electronics and magnetism of different mcb types interfering with operation of each other

I still can,t figure out how both issues can,t be addressed by physical distancing of the different types in the same CU.Over here we use a 2 row D.B. Having one make on the top row and another on the bottom row has never led to any issues in my experience.
The situation I describe would be unusual ( and unprofessional in my view).
But occasionally circumstances require it.

 

[nicebutdim]

Aside from other considerations, few domestic DBs in the UK have more than one row.