It's a hager fuseboard with hager 6ka rcbos in guys

goldenboy1818 said:

It's a hager fuseboard with hager 6ka rcbos in guys

Domestic Consumer Units made for the UK market should meet annex ZB of BS 61439-3, which has extended tests with 16 kA fault currents to permit 6 kA or 10 kA protective devices to be used with fault currents up to 16 kA. The reason for this, is that it's taken that fault currents in domestic premises can be up to 16 kA for 100 A single-phase supplies.

If you have any doubt about this, you should check with the technical helpline of the manufacturer in question.

As others have said, though, it's important to only use protective devices endorsed by the manufacturer in UK consumer units, because of these enhanced 16 kA fault current tests.

this makes me wonder why they mark them as 6KA at all? no manufacturer would approve of their MCB in another’s enclosure , or does the consumer unit itself play a part in containment of the fault current?

this makes me wonder why they mark them as 6KA at all?

The can go in things other than consumer units - where their individual breaking capacity is relevant -  e.g in distribution boards, or caravan hook-ups or equipment (e.g. larger UPSs) or just a random modular enclosures; or may be fed by something of a higher rating than a BS 88-3 fuse. Yes, one option the CU manufacturer has is to use the enclosure to contain arc products if the MCB can't, to achieve the 16kA rating (but there are other options too).

   - Andy.

Newfutile said:

this makes me wonder why they mark them as 6KA at all?

The range may well be used in other applications than the domestic CU, but fundamentally unfortunately the breaker standard requires the marking.

I would interpret the marking as 'Usually suitable for 6 kA, but if installed (in accordance with manufacturer's instructions) in a DBO (consumer unit) that it has been tested in to the UK national annex, and protected by an upstream BS 88-3 or BS 1361 fuse up to 100 A, it is suitable for 16 kA.'

If we take the PFC to be 8 kA at the DB, and let us suppose that the sparks failed to protect the cable e.g. with a grommet and it has chafed so that a 8 kA fault occurs and the RCBO survives, what then? Must the RCBO be replaced? I would suggest that it should because its rating has been exceeded. (A 10 kA RCBO could remain in service.) So there is a reason for marking the RCBO even when supplied as part of a populated DB.

Frankly, the whole scenario seems most unlikely.

this makes me wonder why they mark them as 6KA at all?

Also the same MCBs will be sold across CENELEC land - only the UK has this conditional 16kA rating. That's down to our peculiar supply system - if you want a 22kW supply in the rest of Europe you'd usually get 3-phase 32A on much thinner supply conductors, and consequently lower fault currents.

   - Andy.

Newfutile said:

this makes me wonder why they mark them as 6KA at all?

The breaker isn't capable of breaking 16kA.  The fully assembled consumer unit is capable of surviving 16kA for long enough for the service fuse to blow.  But it's the service fuse that breaks the current in the end, not the 6kA-rated breaker.

Indeed, basically the are saying that the  breaker will not be damaged by the maximum energy that a 100 BS1361 or BS88-1 fuse might let through while breaking a fault current of up to 16kA PSSC, and also for faults of 6kA or less, it will do the disconnection itself safely, at least once, without relying on any upstream device to actually interrupt the fault current.

Despite statements to the contrary, this has very little to do with makers boxes, use of bus bar versus cable or anything else about the breaker really, and  has far more to do with the let-through energy limiting properties of the typical UK service fuse.

Mike.

Indeed, basically the are saying that the  breaker will not be damaged by the maximum energy that a 100 BS1361 or BS88-1 fuse might let through while breaking a fault current of up to 16kA PSSC, and also for faults of 6kA or less, it will do the disconnection itself safely, at least once, without relying on any upstream device to actually interrupt the fault current.

Despite statements to the contrary, this has very little to do with makers boxes, use of bus bar versus cable or anything else about the breaker really, and  has far more to do with the let-through energy limiting properties of the typical UK service fuse.

Mike.

mapj1 said:

has far more to do with the let-through energy limiting properties of the typical UK service fuse.

... and the bit about "has to be in the correct manufacturer's box it's been tested in" of course relating to the way the product has been tested (or, in the case it's in another box, not tested) for the UK-specific market conditions.

Arguably we should also be looking at the upstream fuse and the compliance or not of its installation with the test assumptions with the same or more perhaps scrutiny - however this is usually the DNOs and therefore considered to be off limits.

Mike.