Are Hager MTN MCBs backwards compatible with Hager MT MCBs? EVSE consumer unit upgrades.

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.

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.