Re BS Standards for Distribution boards and Enclosures

 using the present array of MCB's within the current Distribution boards which are some 30-40 years old in line with what the current standards BS EN 61439-3 compared to the old Standards BS EN 60439-3?

The standards for MCB (and RCCBs/RCBOs) are somewhat independent of the standard for DB that they go into - as far as I recall BS EN 60898 MCBs went into both BS EN 60439 and BS EN 61439 assemblies (although looking back 40-ish years there was an older standard BS 3871 for MCBs and many devices were stamped according to both standards during transition). All standards undergo regular revisions every so many years though - so there may be a more (to you) significant difference between two versions of the same standard (e.g. BS EN 61439-3:2024 and BS EN 61439-3:2012) as there was between one numbered standard and its differently numbered replacement (e.g. BS EN 61439-3:2012 and BS EN 60439-3:1991).

The compatibility between an enclosure and the devices within it, unfortunately, aren't a matter for standards - but are left to individual manufacturers - over time we've seen manufacturers change their range of MCBs and enclosures such that the old MCBs won't fir the new enclosures or vice versa even though everything was to the same standards as before. Mostly manufacturers only condone using their devices (and from the same range) in their DBs.

 - Andy.

AJJewsbury said:

The compatibility between an enclosure and the devices within it, unfortunately, aren't a matter for standards

Except, perhaps, for consumer units and similar distribution boards, where the 16 kA conditional short-circuit test for the UK applies.

It sort of means that, unless a manufacturer can confirm no material changes between one product range and its replacements over time, all a manufacturer could say is "not guaranteed to be compatible".

AJJewsbury said:

The compatibility between an enclosure and the devices within it, unfortunately, aren't a matter for standards

Except, perhaps, for consumer units and similar distribution boards, where the 16 kA conditional short-circuit test for the UK applies.

It sort of means that, unless a manufacturer can confirm no material changes between one product range and its replacements over time, all a manufacturer could say is "not guaranteed to be compatible".

Indeed - but I meant more generally you can't just replace an old BS EN 60898 device with a new BS EN 60898 device and expect it to fit/work/be-safe - all sort of things may differ between brands or ranges (or just over time) - not just obvious things like position of terminals and heights above DIN rails, that standards could have easily addressed but haven't - but things like heat dissipation. The 16kA is an extreme case where your using components outside of their individual specifications (e.g. 6kA MCBs for a 16kA fault situation) so you need some extra "margin" that the manufacturer has go get from somewhere, but even in less demanding situations there are lots of incompatibilities that the standard simply don't address.

   - Andy.