Sparkingchip said:

In the video there is a SPD in the new consumer unit, but it’s not OEM from the consumer unit manufacturer, which doesn’t help the argument in favour of fitting an additional consumer unit because the existing has “obsolete” devices.

Yes, I did make a passing comment about that above, but without checking compatibility, all I can say is that I observed a different manufacturer ... in the case we were looking at in the YouTube video, if the SPD was not deemed compatible with the new CU then I agree, one of the arguments put forward is also true of the new CU.

whjohnson said:

The thing with that old chestnut is that in reality it is just pure protectionism. All such kit has to be made to BS60898 for example, and that should be good enough.

Here we are talking about a type-tested assembly of products to a particular standard.

A manufacturer carries out the (very expensive) type tests with a range of equipment (from their own product ranges).

Are you suggesting that they either:

(a) ought also to test other manufacturers' equipment?; or

(b) that the product standards for protection, control, SPD, etc., devices, are deficient in not specifying appropriate limits for ALL physical parameters (including mechanical), AND the type-tested assembly standard somehow cover tests assuming worst-case conditions of the product standards?

I think there are a number of issues with (b), that stifle innovation, but I'm sure the relevant BSI committees responsible for those standards would welcome input and ideas to improve standardization.

The SPD is one of the SY products which Wylex have approved for use with their kit (others have followed since). Hager not so much. At the time of initial introduction during one of the ELEX shows, the Hager stand was next to the SY stand, and with SY wanging out their SPDs for around £30 ea and Hager hawking their own branded device priced at around £300-odd, there was no love lost between the two exhibitors. We must not lose sight of the fact that SPDs comprise of jellybean components at fractions of a dollar each. There is nothing clever about SPDs,

That we should have standards is not in question. The problem to me is that standards suffer from mission creep and tend to over-arch into areas which should not be of their concern. There is a lot of money made from creating 'standards' which in reality are introduced to enable profits to be enhanced rather then the product quality.

I reckon the 'standards' system could be very much simplified. One thing is form factor. The footprint for a mcb/rcbo should be standardized to enable fit inter compatibility across what are essentially simple enameled metal boxes with a small strip of copper connecting the internals together. It is no more complicated than that, nor should it need to be.

All these distractions about grouping devices from different brands is just a smokescreen for protectionism.

We used to knock up our own enclosures from sheet steel, then add some DIN rail and fit whatever was in the stores at the time, and we never experienced any problems nor detrimental effects as a consequence of doing so. Sometimes, and more often than not, a Rittal box was simply unavailable in time.

I believe that b) would indeed provide an ideal solution, otherwise the manufacturers are just duplicating effort. What is the point in Maker A testing the mcbs in his range which come from the same factory as those from Maker B who has already done the testing?

How much science actually goes into designing a simple steel box to contain it? All they have to do is ensure that holes and brackets are drilled/affixed in the correct locations and that the correct gauge of steel sheet is employed for the application. I'll bet more study goes into the type of paint and finish than anything else,

We are not designing a spacecraft here, but merely a steel box, some fixing holes and brackets, and a durable paint finish.

As for stifling innovation, I'm pretty certain that the BSI committees are aready doing that all by themselves.

Not having access to BS EN 61437 I can only speculate on the requirements, but I imagine it might include: tests of the assembly being subjected to 4kV; that nothing overheats when full of MCBs with currents near their max rating while at a high ambient temperature; that when a breaker trips and extinguishes the arc, any expelled hot arc gases don't damage anything; and for annexe ZB, testing with a 15kA fault (with an upstream BS88 fuse) and making sure the whole box doesn't explode.

So I think there's a bit more to it than bashing out a metal box and adding a DIN rail.

I wonder if the DNO would be happy with them fitting 3 henley blocks in the meter box, taking up space which is not theirs to take, when they could have been sited in the garage

That depends upon how specific the BS is. It would be a queer business if one could only use MK plugs in MK sockets. However, the two types of Wylex MCB are certainly not interchangeable - the busbar won't fit.

I agree - in many way's it's not intuitively obvious that a complete CU - as distinct from each component module - needs to be type tested. We don't insist on manufacturer agreement for mixing different brands of accessory & cable, or cable & cable clips or sockets and back boxes, or as you say plugs & sockets. In many ways it shouldn't be beyond the wit of man to produce standards for each component in such a way that any reasonable combination should be safe and satisfactory.

On the other hand, in the UK especially, we have a problem with using components outside of their individual specifications (e.g. 6kA MCBs on a 16kA PFC system) - so I can see some argument for 'whatever results from it going bang remains inside the box' approach. However in probably the majority of cases, that 's not required (I very few domestics have a PFC of over 6kA in practice, whatever the DNO might write).

It's interesting to see pictures of common CUs from other countries - many French ones for example seem to dispense with bus-bars altogether, using off-cuts of wire to daisy-chain MCBs together (so no problem with differing terminal heights) and a complete mix of brands (including the enclosure itself). Their laws of physics can't be that different from ours (even if the PFC is likely to be lower). Irish ones have a DP MCB incomer - so the same current goes through three thermal elements rather than one, yet we worry about the heat generated by one extra 16A MCB for a PV system.

   - Andy.

The thing that is odd, is that in the UK an MCB stops working when you take it out of the makers enclosure.

By all means test an assembly with many breakers in the box mounted on the maker's bus bar.

But the whole question could be resolved, I suggest, with one other cheese cloth test, where the MCB  is not in box,  but with wired leads that are long and thin, so they do not significantly cool the device. If the cloth catches fire when the the MCB breaks the maximum fault, then it cannot safely be  used in an unknown containment, as the case alone has not retained the highest temperature arc products.  All MCBs fire hot gas out (a hole in the back somewhere, never the front or sides) during such an event, but the internal arc traps should catch the hot metal that might ignite something.

Any device meeting this test is OK for any kind of containment from the perspective of ignition. The only other aspect is self heating or neighbour heating, and this is only a question of knowing the voltage drop on load or dissipation, and max permissible temperature. Both could be on the data sheet.

When used on a rigid bus bar, is it beyond the wit of man to mandate the offset from the DIN rail reference plane to the tooth, and say that if that condition is not met then only a flexible link may be used.

Mike.

mapj1 said:

The thing that is odd, is that in the UK an MCB stops working when you take it out of the makers enclosure.

Well, there is the UK National Annex for 16 kA requirement, which comes out of ENA ER P23 ... but the value is not new, and not based around the latest version ... it's been in place for a very very long time, and we have been cautioned about changing breakers, and the conditional fault rating of the assembly, since we moved over to BS EN 60439.

I think really you'll find that's one of the key issues behind it. Many many years later, we're still sucking through our teeth at it.