AJJewsbury:

Apologies for any confusion. I do intend to use brand new components from the same manufacturer. Probable Wylex in this situation.


Was just trying to understand if it is possible to connect/wire up a 4P RCCB and a 4P MCB in the same manner as a 1P RCCB and numerous MCBs? i.e. By connecting the L1 L2 L3 of the 4P RCCB to the L1 L2 L3 of the 4P MCB via a Busbar or Individual wiring of L1 L2 L3?

It's not just a matter of using components from a single manufacturer if you want to rely on their type approval - you have to assemble it according to their instructions ... which they likely don't have for anything not based on their normal layouts (but feel free to ask them of course).


In terms of wiring, in theory it is that simple  - in practice a 3-phase MCB will usually have 3 pairs of terminals and a 3-phase RCCB will have 4 pairs (to include the N) - so simple bus-bars won't usually fit... you could then go for simple bits of wire between, but then you've got the problems of fault handling etc. that the bus-bars were probably designed to avoid (especially if you're relying on the type-test for a 16kA or better fault rating or the assembly). 3-phase MCBs that also include a N would be simpler, but they're rarer beasts (especially when it comes to actually buying one rather than just perusing catalogues) and then you'd need 4-P bus-bars which can be rarer still in the UK. Not impossible, but I'd advise a fair amount of caution. Be especially careful of examples of 'continental' practice from the internet - the UK supply system has a few characteristics (in particular a relatively high protective fault current - due to our approach of supplying relatively large loads single phase) that demands a bit more consideration that is needed elsewhere where the higher impedance of lower rated 3-phase supplies is the norm.


   - Andy.

Cheers Andy.  So it's possible but not normal practice or layout?  Have you ever seen it done?  Or are RCCBs nearly always downstream?  Or a RCBO used?

AJJewsbury:

Apologies for any confusion. I do intend to use brand new components from the same manufacturer. Probable Wylex in this situation.


Was just trying to understand if it is possible to connect/wire up a 4P RCCB and a 4P MCB in the same manner as a 1P RCCB and numerous MCBs? i.e. By connecting the L1 L2 L3 of the 4P RCCB to the L1 L2 L3 of the 4P MCB via a Busbar or Individual wiring of L1 L2 L3?

It's not just a matter of using components from a single manufacturer if you want to rely on their type approval - you have to assemble it according to their instructions ... which they likely don't have for anything not based on their normal layouts (but feel free to ask them of course).


In terms of wiring, in theory it is that simple  - in practice a 3-phase MCB will usually have 3 pairs of terminals and a 3-phase RCCB will have 4 pairs (to include the N) - so simple bus-bars won't usually fit... you could then go for simple bits of wire between, but then you've got the problems of fault handling etc. that the bus-bars were probably designed to avoid (especially if you're relying on the type-test for a 16kA or better fault rating or the assembly). 3-phase MCBs that also include a N would be simpler, but they're rarer beasts (especially when it comes to actually buying one rather than just perusing catalogues) and then you'd need 4-P bus-bars which can be rarer still in the UK. Not impossible, but I'd advise a fair amount of caution. Be especially careful of examples of 'continental' practice from the internet - the UK supply system has a few characteristics (in particular a relatively high protective fault current - due to our approach of supplying relatively large loads single phase) that demands a bit more consideration that is needed elsewhere where the higher impedance of lower rated 3-phase supplies is the norm.


   - Andy.

Cheers Andy.  So it's possible but not normal practice or layout?  Have you ever seen it done?  Or are RCCBs nearly always downstream?  Or a RCBO used?