Diagram from the bticino manual attached.

Am I understanding this correctly ?

It looks like the L for the RCD protected side comes from the MCB in slot 10, which is getting its L feed from the built-in busbar. Then the MCBs on the protected side are getting their L feed from the RCD via an add-in tooth like busbar which connects at the bottom of the RCDs in 13-16. It means the L feed to the circuits comes out the top of the MCB's 13-16.

If this is correct then I have a few questions :

- how is the L running through the built in busbar stopped from entering the MCB's 10-16 ?

- it looks like I need 2 types of MCB's for the protected and non-protected sides ?

- should the MCB in slot 10 be the same A as the RCD ?

- is slot 9 usable or is that were some-kind of disconnect of the L is hapenning across the built-in busbar ?

Thanks for any help.

God that's unclear, and I know how it works

Have a look here http://www.crossy.co...g/Consumer.html scroll down for the split load diagram.

Yes, it does look like you need different MCBs for the protected side, built in busbar does not connect to the protected MCBs. It looks like the split in the neutral bar is between 11 and 12.

Have you bought this unit? You would be better off getting a CU with DIN mount MCBs and modifying it to be split load.

Crossy, your link is where I got my understanding from... your L feeds are coming in at the top. That's why I'm a bit confused...

Remember that the RCD's compare L current with N current and if they are different, it trips. What that means is that all loads connected to an RCD through an MCB must have dedicated neutrals to that RCD. If you have an ohm meter, you might want to check how those bars are connected and isolated as that might help. I looked at some of these types of boxes and decided to go with RCBOs to help keep things simple and to help in isolation of problems.

Actually what you surmise in the OP is pretty well correct. To be honest it looks like a bodge.

I think slot 9 is just a regular but unused slot so you can add an unprotected MCB.

If you dont know how it should be done should you be messing with electricity, from a sparky

If you dont know how it should be done should you be messing with electricity, from a sparky

Generally true.

BUT

Have you seen a split service CU built quite like the OP shows? Totally different MCB types on the protected and unprotected sides.

The other issue, as I'm sure you know, is finding a domestic sparks who actually knows what he's doing. Thai commercial electricians are very good, but they're all earning big (ish) bucks on major projects or O&G, they won't go near domestic as there's no money in it. The chaps doing domestic tend to own 2 screwdrivers (+ & -) a pair of industrial scissors and a roll of tape.

Crossy, can you recommend a CU that can be wired up split-load as you show in your link ? I had a look round the local sparks shops but couldn't find one that will hold 14 MCB's + an RCD. Thanks.

Have a look at the Haco HD-M17 looks like it holds 17 units plus a main switch or the HD-S224 which has two rows of 12, ABB also do some fairly big units with DIN rail fixings.

The load centre appears to be a US pattern (NEMA) with plug in protective devices. Yes it is a split unit as nonprotected (MCB only) and protected (RCD with MCBs).

I note that there is no earth (ground) bar.

This might explain the neutral earthing that is implimented in Thailand in that it may originate from the USA. (NEMA).

I think the earth is top right and the split neutral bar on the left. MCBs 1-10 are,as you say, plug in types. 10 provides the supply to the RCD. The RCD and MCBs on the protected side are DIN types and an adaptor is used to seat these in the CU and disconnect them from the live supplied through the clip-in system. Well, thats what my latest understanding is...