Older boards and availability/compatibility of devices

I've noticed over the years that there are actually only about 4 or 5 variations in MCB design suggesting only a few manufacurers. The secret is finding which ones are fully interchangable so I used to have a range in my stock as it's the only way to be sure as even when a new range appears there are minor, frastrating differences.

Providing they are physically and electrically the same you are doing what is practical and safe - in my opinion!

It used to be simpler - in the past we only really worried when then assembly somehow had to be grater than the sum of its parts - e.g. putting 6kA MCBs in a plastic box and then claiming the whole lot was good for 16kA prospective fault currents - leaving individual manufacturers free to device methods of achieving that (whether it be completely relying on backup protection from an upstream fuse, or allowing the MCB to fail catastrophically but contain all the resulting fragments within its own case, or allow the MCB to explode but contain everything within the outer enclosure) - in such cases taking an MCB from one system and putting it into a different system's case may well then not have the desired result.


Things do seem to have been tightened up with the 18th - I suspect it's related to the move from the old BS EN 60439 to the new BS EN 61439 and the changes to the way things are type tested - but I don't have the details behind that.


I guess there could be some incompatibilities between different manufacturer's systems - whether it be the amount of heat an MCB generates and how resistant it is to heat from neighbouring devices or bus-bars, or rotating bits on the sides of some MCBs (intended for clip on trips or RCD modules) might get fouled by similar but different bits on other manufacturer's devices, as well as the more obvious differences in terminal size/height/type etc.


I totally agree that it results in a very wasteful system - in materials, time and money - and probably back-fires on manufacturers in the long term as people would be far more willing to try new kinds of devices (A-type RCDs, SPDs, AFDDs etc) if they could reasonably be slotted into a spare way or two of an existing system rather than necessitating a complete replacement every time. I feel sure it should be possible to come up with a much more 'compatible' system  - at least for CUs and similar 'small' DBs - with resulting environmental and economic benefits all round.


  - Andy.

@norm - thanks for the comment norm and I tend to agree !   However, what's your opinion regarding my specific question please ?

@ajj thank you too for the insight.  Same as for @norm, what is your opinion regarding my question specifically... reading your post I'm taking it that you would say it is not correct to issue an MEIWC...would that be a fair assessment  ?

Perhaps info in the attached BEAMA document may help.


F

reading your post I'm taking it that you would say it is not correct to issue an MEIWC...would that be a fair assessment  ?

By the letter of the regs, yes. Not only is there the general 'manufacturer's instructions to be taken into consideration', there's the explicit requirement of 536.4.203 - which would put you in the position of having to 'verify' that the new overall assembly complied with BS EN 61439 - if you're not able to do that, you're stuck.


Unless of course you want to go down the line of personally confirming that the arrangement 'provides at least the degree of safety as that afforded by compliance with the regulations' - but I suspect you'd be even less comfortable with that.


  - Andy.

Im presuming though that its about ensuring compliance with the standard in force at the time it was made up, not the latest (when altering things)

That sounds sensible, but if my reading of 536.4.203 is correct, I think the actual wording of the requirement is to meet the current BS EN 61439 series of standards even when putting devices into an "existing low voltage assembly" (last bit of the 1st paragraph) - so my implication including those to earlier (possibly incompatible) standards. Doesn't sound too practical does it?

   - Andy.

About 5 years ago I wanted a C type RCBO for a Volex board, and they did not seem to make them.

However, I rang them up to check and was told that, no they didn't but all their MCBs and so forth used the same internals and metalwork as the Wylex ones, only using a  cheaper printed plastic process, and that it would be fine to fit the Wylex one.

And indeed it fitted perfectly, and as far as I know it is still in service. If I'd known it would be useful, I'd have asked for it in writing.