Hi, please could I ask for help with the following...

We are in Bangkok under the M.E.A.

We have a house with an old consumer unit (square d attached pic no1) that needs replacing.

The meter is a 30/100a, is across the road with a cable run of no more than 15m from meter to main breaker, and uses a thw-a aluminium 50mm sq cable to feed the consumer unit.

We think we have an earth, but cannot actually observe the rod in ground, just the cable going to ground and can follow it to the earthing busbar, its about 10mm sq.

We have what appears to be a m.e.n system with a shortcable running from the earth to neutral.

Im looking at a haco or bticino consumer unit, with a 100a main breaker.

We will have 3 x ac's (9000btu x 2, 15-18,000 btu x1)

3 x hotwater heater ( 2x 4500w 1x 6000w multipoint)

1x washing machine, 1x mid size fridge

3 floors of lights and main sockets

Ive seen many diagrams (see attached no.2) of various consumer units where the main tail neutral goes into the ground bar first, before the main breaker, but in my current old setup (as pictured) both the live and neutral goto the main breaker first, and the m.e.n link is installed.

The first (of many) small issues is the incoming tails just about fit through the wall and into consumer unit with no additional space for movement or to move them freely as I will be needed to renew the CU, not least considering its a 50mm sq cable.

I currently have no rcd protection or rcbo.

I was thinking of 2 choices;

1) just using main breaker >mcbs >and then rcbo's for shower heaters, outside lights.

2) main breaker > rcbo's than split with 1 rcd > mcbs

Does anyone kindly have any ideas or opinions that might help me understand what we need to do, or any corrections to what i have stated or understand to be the case...?

Thank you in advance.

Sorry forgot to add pics

The position of the N-E link for MEN to keep with Thai regs is incoming neutral going via the earth bar to the main breaker.

That said, I would use the same arrangement as is used in your current board when you replace it.

Note that if you have an RCBO main breaker then a N-E link placed after that breaker will cause unpredictable trips in your future life.

I would use RCBO's for "risky" circuits - Water heaters, bathroom outlets, outdoor stuff and leave the rest as MCB only.

Since you have a permanent meter (around 4 Baht per unit) there's no requirment for any further inspections so it's up2u and your sparks.

You really need to test that earth is actually an earth.

1 hour ago, Crossy said:

The position of the N-E link for MEN to keep with Thai regs is incoming neutral going via the earth bar to the main breaker.

That said, I would use the same arrangement as is used in your current board when you replace it.

Note that if you have an RCBO main breaker then a N-E link placed after that breaker will cause unpredictable trips in your future life.

I would use RCBO's for "risky" circuits - Water heaters, bathroom outlets, outdoor stuff and leave the rest as MCB only.

Since you have a permanent meter (around 4 Baht per unit) there's no requirment for any further inspections so it's up2u and your sparks.

You really need to test that earth is actually an earth.

Thats great, i really appreciate your timely response. Thank you.

I was thinking about getting a multimeter (fluke or klein tools), so i will definitely test the earth. What is the desired range for resistance in this setup please?

What exactly is the difference between mains neutral to earth busbar first, as per regs, or as in my case, both mains to breaker with a link between earth bar and neutral please?

Im not planning on using an rcbo main breaker, but singular rcbo's after the 100a main breaker. I think if im right, that i would need a CU case with a 2nd neutral bar, so as to keep them separate or downstream of the ne link, as you mention.

One more question if I may?

I would like to fit a 100a modular isolation switch(cut off) between the meter and the CU because those chunky main tails barely make it through the wall.

My thoughts were i could use a 100a cut off in place of the old CU case to change from the thw-a 50mm sq aluminium cable on one end to THW 35mm sq copper tails to the CU, giving me more length on the tails into the new CU, with the ability to work on the CU without asking the MEA to disconnect everytime this was needed.

Do you think this would work?

If so, do you know of any such devices, other than the chang lever style 100a crab arm switches because i generally cant find anything other than this or cheaper chinese switches like the The TOMZN TOG100 (often designated as TOBIZ-100 or TOB1Z-100) is a high-capacity DIN-rail miniature circuit breaker (MCB) or isolator cut-off switch. It safely isolates circuits.

Many thanks again.

You definitely need a multimeter, but you are not going to test your earth with a regular one.

Ideally, you should find your rod and verify it's connection to the earth bar.

You need a ground test meter https://www.lazada.co.th/products/pdp-i16085615823-s126732837020.html

You may find a used "16th or 17th Edition" Installation Tester on EBAY UK, that's where I got my old Robin unit, still works fine just out of calibration now.

<Danger Area>

You really shouldn't do this!!

Failing that a small (say 15W) incandescent lamp connected to your isolated rod lead (pull it from the earth bar) and carefully dabbed onto the live, lamp lights, decent earth, certainly good enough to trip an RCD, no light, start looking!

</Danger Area>

Electrically, there's no difference between the N going via the earth bar and N-E being linked in the CU (Aus uses this way).

A 2-pole cutout is a useful addition, maybe get a 100A main-switch from the UK like we did?

https://www.tlc-direct.co.uk/Products/BGSW100.html

There are all sorts of local things that could be used including purpose made isolators in nice boxes, with a nice price.

1 hour ago, Crossy said:

You definitely need a multimeter, but you are not going to test your earth with a regular one.

Ideally, you should find your rod and verify it's connection to the earth bar.

You need a ground test meter https://www.lazada.co.th/products/pdp-i16085615823-s126732837020.html

You may find a used "16th or 17th Edition" Installation Tester on EBAY UK, that's where I got my old Robin unit, still works fine just out of calibration now.

<Danger Area>

You really shouldn't do this!!

Failing that a small (say 15W) incandescent lamp connected to your isolated rod lead (pull it from the earth bar) and carefully dabbed onto the live, lamp lights, decent earth, certainly good enough to trip an RCD, no light, start looking!

</Danger Area>

Electrically, there's no difference between the N going via the earth bar and N-E being linked in the CU (Aus uses this way).

A 2-pole cutout is a useful addition, maybe get a 100A main-switch from the UK like we did?

https://www.tlc-direct.co.uk/Products/BGSW100.html

There are all sorts of local things that could be used including purpose made isolators in nice boxes, with a nice price.

Again this is great invaluable advice. Thank you kindly.

Regarding the earth.

What seems to be the earth, as in, its a thick cable connected to the earth busbar and trails away to the ground is completely buried. So far about 30cm under ground but looks like it has a redbull bottle sitting as a hat to the rod maybe to protect the connection, so i have to do a bit more digging.

Failing that and the danger test, i brought a 5/8th copper plated steel rod 3m long, would it just be better to install my own right next to it and just swap over the cable?

Regarding the isolation switch. Sorry for my psudeo understanding...

Funnily enough i was looking on screwfix and did see these, i had 2 concerns, one being that they most only take upto 25mm sq tails and the other was that i thought it should be a manual switch, possibly with a lock so that its not easily switched back on.

I had read that an mcb switch was sometimes not ideal because its too easily switched back on, but also because it can sometimes be an issue with the main breaker in the CU for offering no discrimination between the 2.

I can actually get a bticino 100a main breaker mcb that will take 50mmsq mains here, are you confident to say this would be fine, or should i go with a dedicated isolator switch.

Thanks again.