Thai Electrics... Yet Again

[carlmeek]

We own a 2 year old house built in Bangkok as part of a large village. Shortly after moving in, we paid a local guy to upgrade the consumer unit in order to install five air-conditioning units. He advised us how to do this, and installed a Safe-T-Cut RCBO as part of that install. It all looked very professional, so we were happy with the job.

I’d like to install a second electric shower, and after reading many horror stories, i thought i’d investigate the electrics setup to see just how dangerous it all is.

My background - an avid DIY enthusiast in the UK, and i've wired up two new home extensions which were later certified as compliant by an electrician, so i know what i’m doing within the realms of the UK… but this is a bit different!

Attached is a photo of the setup. It took me a while to figure it out, and got more and more horrified as I did!

My observations:

- Earth and Neutral are blended into one! The main cabinet casing, and the outer casing of the Consumer Unit are all connected to Neutral.

- Almost all sockets around the house are 2 pin, so no earth fed to these boxes. There are only 2 green earth feeds, one to the shower, and one somewhere else (no idea where)

- The “neutral bar” of the main cabinet seems to have two feeds in. It’s not isolated from the cabinet, so the main cabinet is therefore neutral. I wonder if one feed is an earth - who knows, they are all black.

- The large 5 breakers in the middle bypass the Safe-T-Cut and feed the 5 A/C units. Whereas the main consumer unit feeds everything else, including electric showers which also have ELCB's built in (which i presume are pointless).

- In other words - There is no earth whatsoever.

- The neutral lines are split - half going to the proper neutral bus in the consumer unit, and half going to what should be the earth bus. Looks like half are the ones in the consumer unit, and half the breakers that are separate from it.

- Supply cables to the house circuits are gray/white and no earth anywhere. Except there are two green cables in there, connected to Neutral.

- Colours appear to be white or green for neutral, grey or blue for live. black for everything that requires a fat wire, with red insultating tape denoting live.

In order to investigate further i decided to remove the consumer unit and look behind it. What i found....

- Lots of "connections" - twisted together wires with insulating tape around. These are extending the previously short wires to a bit longer so they can meet the consumer unit in it's new location. Three are the big black wires, all unlabelled - one live, one neutral (heading upward) and an earth (heading downward). Neutral and earth both connected to the earth bar in the cabinet.

- I disconnected both earth and neutral, after it was switched off at the big switch. I was getting small shocks whilst touching it, and mild sparking when tapping both earth and neutral back onto the bar. It turns out there's a light on the front of the cabinet (a green indicator) that's been connected in on the supply side of the main switch, so is causing current to travel into the neutral line even when isolated.

- So I moved the indicator to the safe side of the switch and stopped getting shocks.

- I then disconnected earth and neutral in turn, and tested to see how it behaved. I found that either being connected "worked" - so current was flowing from live to both neutral and earth lines. I'm Guessing that this is OK - live flows to earth.. but it wasn't quite what i expected. I've never tested this back home in the UK!

- I rewired it to split earth and neutral, using a new connection block to feed neutrals to the A/C bypassing the Safe-T-Cut.

- I replaced twisted together wires with proper block connectors and crimps.

- I turned the safe-t-cut down to 5ma instead of 30ma as it was set before.

- Final problem, and one I cannot think to resolve, is that the neutrals seem to be cross-connected. I disconnected them all, and connected one-at-a-time, testing each circuit. There are 6 breakers, i labelled A-F, and then tried to match neutrals to the breakers. I ended up labelling the neutrals "A&C", "A&C", "B,D,E","B,D,E" and "F". because connecting either of the A&C cables made both A&C breakers live. Same for B&D&E except there are only two cables here making live 3 circuits. Baffling, but i'm guessing there are no proper rings, and things are just connected any-old-how.

- It's all working fine, but then it was before... but hopefully it's slightly less deadly now.

It appears to me, and as i've read before, this guy (and presumably many others) simply don't understand earth at all. The fact that the outer cabinets, and all earth wires, were simply neutral sounds scary to me.

So i think i've done some good, but it's still not perfect. I'm shocked that it can be botched so badly, but then with so many deaths on the roads, who cares about electrics? It would be amusing if it were not so sad and tragic.

TIA,

-C

[bankruatsteve]

I can hardly wait to see what Crossy has to say about this. In the mean time, I suggest that you quit playing.

[Crossy]

Read this http://en.wikipedia.org/wiki/Earthing_system#Comparison_of_Earthing_systems

You are interested in TNC-S and MEN as that's how Thai systems should be connected (yes, N and E are linked). The UK uses a similar system, usually called PME, the N-E link is in the service head so you don't see it.

You should have a rod somewhere, if that's missing you've taken what was a reasonably safe installation and made it hazardous! If you do have a rod you are now TT with an RCBO so it's not too bad.

The fact that the RCBO stays in on 5mA is a positive indication (does it trip when you press the test button?).

Download this document (yes it's in Thai but there are pictures) http://www.crossy.co.uk/Handy%20Files/groundwire.pdf

[carlmeek]

What i've done is really take the installation back to the way the village installed it - as evidenced by looking at next door's board. It was the after market electrician who linked N&E in the board. Without evidence of seeing next door I would not have made any changes.

Yes, it trips when tested. There is a cable that all evidence suggests is an earth rod, but i cannot find the rod itself. It's been on 5ma all evening, no issues so far. The evidence that it's an earth rod is the fact two fat black cables come into the property overhead, and both are found coming down a trunk from above into the CU, whereas a third cable of the same gauge heads downward. Also, when L is connected, and either the overhead N or this cable is connected the house electrics apparently "works" - i.e. lights come on. I did not load it up any higher than that, I didn't want to push my luck. When I tried this, i had not yet removed the CU and could not see where the black cables went - but once removed it all became clearer.

The one final thing i'm going to resolve tomorrow is to buy some more proper connector blocks and fully remove any "twisted" joins where the guy literally just twisted wires with plyers and taped.

I'll have a read of that rather large document when it finally finishes downloading...

-C

[Crossy]

Good

There is little doubt that it's not actually correct anyway but there's lots of space so we can get it fixed reasonably easily.

The Thai way of implementing MEN is to feed the incoming neutral via the ground bar (that's the big copper bar in your box) and then to the incoming side of your RCBO, your ground rods should be on this bar too.

Where is your incoming supply in the box?

The earth bar in the CU should also be linked to the same place (this is where I think things are going to go wrong), that CU isn't right now you have an RCBO.

Neutral from the RCBO should go to the neutral bar in the CU.

It should be reasonably easy to get it all set up and safe.

Do post a photo of it as it is now.

If you still have the instructions for the Safe-T-Cut have a look there too.

Sorry about the size of the document, it's a scan of a PEA document (scanned by PEA) and I've not managed to reduce its size without losing what little detail there is.

==================================================

To get you started I would do the following:-

Move all the neutrals (white) wires on to the 'proper' neutral bus in the CU, bet they're too short, buy more crimps.

Remove those green 'earth' wires from the CU neutral, put them on the earth bus.

The fat wire currently on the CU earth bus should go to the big copper earth bus in the box if it doesn't already.

That should get you at least in the correct ball park.

[carlmeek]

The photo doesn't make much sense, as everything's black and following the same paths.... it's attached, but i'll write it out here also.

INCOMING.....

-Two fat black cables from the overhead feed ---> These feed to a big switch (top left)

-One fat black cable going downward, presumed to earth rod. ---> This feeds to the big earth bar in the cabinet.

BIG SWITCH.....

-It feeds direct to the RCBO (both live and neutral)

-It also feeds Live direct to 5x Breakers for 5x A/C units

-It also feeds Neutral to a connection block with 5x neutrals for 5x A/C units.

RCBO SAFE-T-CUT

-It feeds both live and neutral to the consumer unit

CONSUMER UNIT

-Feeds 5x circuits

-Also feeds the electric shower

-Will also feed another electric shower

EARTH BAR (top left)

-Fed from the downward heading cable

-Feeds to an earthing point inside the cabinet

-Feeds to an earthing point inside the consumer unit, as well as the earthing bus in the CU

-This Feeds to two green cables, one unknown, one the shower unit.

So -> As well as the obvious re-jigging, the biggest thing is that there is no longer a link between neutral and the earthing bar. This existed after the guy installed the Safe-T-Cut, but does not exist on other properties in the village. Unfortunately no manual for the RCBO exists here any more.

[Crossy]

That looks much better now, despite my earlier statements you now have a decent TT system (pictures are worth many words). Assuming that cable does go to a rod somewhere (or the building steel, Google "Ufer ground") you're in a pretty safe situation The fact that your lights worked with just the 'rod' connected suggests it's a half-decent ground wherever it goes.

I would consider returning it to MEN (N-E linked as shown in the PEA book) but not before doing a little investigation. One way to check that you have MEN in the village is to look at your power poles, a MEN system will have the neutral (usually the top wire) earthed at every 3rd pole or so.

If you don't spot this multiple grounding don't link N-E, if you do see neutral grounding making it MEN is safer, particularly in the event that your RCBO fails (they do).

Well done old bean

[noikrit]

Crossy The Man !!! .... Well Said !!

[carlmeek]

We have definitely gone deep outside of my experience here, MEN and PEA is a bit tougher than wiring a ring main

I've taken a look at the poles and we have three wires running high, transformers below and 5 wires running below those. Neater than many tangles seen locally that's for sure.

I can't spot any obvious groundings of the top conductor, I counted 3 or 4 poles all looking the same.

This has certainly been educational, at the start I assumed N-E link was a stupid mistake, but turns out it's more complex than that

Thanks for the comments so far, I wonder what I should do now, whether to leave it as is (as was pre RCBO effectively) or relink the N-E.

[Pib]

I live in a large moobaan in western Bangkok and it's a TT system setup. The only place I see grounding on the soi lines is at the "transformer poles/transformers" where I see one or two grounding wires running down the two transformer platform support poles to ground....there is no grounding to ground at any of the other poles running along the sois. My mother-in-law's village out in the province is the same way. Maybe you have the same setup....take a closer look at the poles which have transformers.

[Crossy]

Thanks for the comments so far, I wonder what I should do now, whether to leave it as is (as was pre RCBO effectively) or relink the N-E.

If you can't see any obvious grounding of the LV Neutral (that would be the top wire of the four lower ones, it's usually a bare conductor, not sure why you have 5 LV wires) and considering your investigation of the other homes in the area showed no N-E link I would leave it as it is now, as a TT with a front end RCBO.

The problem here is that many of the guys who install these RCBOs (Safe_T_Cut) blindly follow the instructions regarding the neutral routing without understanding what they are doing. This often results in two N-E links (the second being the original in the CU). This actually defeats the operation of the RCBO lulling the home-owner into a false sense of security he thinks he's safe because of the new RCBO, in fact although he is indeed safer, he's not as safe as he could be.

[jackflash]

> not sure why you have 5 LV wires

Three phases, Neutral and Street Lights = 5

[Crossy]

> not sure why you have 5 LV wires

Three phases, Neutral and Street Lights = 5

Could well be, we don't have the luxury of street lighting