Correct Wiring Of Breaker Box

[topher]

I will be wiring up our new house next month and I'm planning on using a SquareD 10 way box with a RCBO 2 Pole Main breaker. I've seen several diagrams of how Thai's usually wire their breakers. One of these is the "Ground Wire PDF" that was posted some time ago on this forum, and another is the SquareD brochure.

These diagrams indicate that the Neutral should enter the box and connect to the Neutral bar. Sometimes they show it also going from there to the main breaker as well.

This doesn't make sense to me because that means the Neutral is not switched thru the breaker at all. Any voltage on the Neutral line from outside would be supplied to circuits even if the breaker was off.

Isn't it normal in western countries to run the Neutral to the breaker and from the breaker to the Neutral bar? Isn't that safer as the breaker then disconnects both incoming wires?

What would be the purpose of using a 2 Pole breaker if only 1 pole (L) is connected?

Please, if someone with proper training in this could answer. I could do it as shown in these diagrams but it seems quite wrong and I would like the safest system regardless of how locals do it.

[Crossy]

The Thai system of wiring the distribution board involves the neutral entering via the ground (not the neutral bar) bar. I too do not like it done this way.

Have a look here http://www.crossy.co...g/Consumer.html connect the MEN link (purple on the diagrams) and you have the same effect but it's easily removed for testing.

NOTE Whilst Thailand is supposed to be MEN (TN-C-S with PME) many areas are not yet wired this way and are either TT or IT, unless you KNOW that MEN is implemented simply leave out the purple link.

[topher]

Thanks Crossy.

I looked at your "simple installation" diagram and that's the way I would prefer. I am in Issan area and I'm fairly sure that this village does not have Neutral grounded at the transformer. I went and looked but it's very hard to be sure. Our meter is one of eight stuck to wood boards on a cement pole on the road in front - very minimal. Most neighbhors have no ground, no safe-t-cut, nor breakers. Just knife switch and fuse. I've seen meters catch fire and slowly melt down a couple times in 6 months being here (not my post but down a block). They don't ugrade users meters when that happens - just put the same 5(15) again.

I'll be requesting an upgrade from 5(15) meter to 15(45) from the village electric guy and will try to confirm about if the MEN link should be installed then. I am happy to follow your wiring diagram as it makes more sense to me.

Thanks!

[bankruatsteve]

Suggest you talk to your local PEA (where the electric bill is paid) vs "the village electric guy". The PEA is usually pretty good for giving you the information you need.

[topher]

Suggest you talk to your local PEA (where the electric bill is paid) vs "the village electric guy". The PEA is usually pretty good for giving you the information you need.

I shoudln't have called him that. He works for the PEA as the district manager and is the one who can arrange our meter upgrade.

[topher]

Oh, I just checked these diagrams I had again and Crossy you're right. They connect Neutral first to Ground. Then Ground to the breaker which after the switch becomes the Neutral bar.

I guess that works as long as the MEN will be installed but your diagram allows for either MEN or not (TT) and for it to be added easily later, and also it's easier to test N-E voltage.

I still I think I prefer this, though it's much the same.

Another question. Do you have an opinion as to SquareD with RCBO (QOMBGX 45 or 63A) as compared to the C.S.International breaker box with SafeTCut built in? This second one is made by the SafeTCut company but gives you a main breaker, RCBO and a bunch of breakers already in for less than the cost of the SquareD without breakers. I'd lean towards SquareD being best quality but I wonder if this other is just as good.

Edited March 14, 2012 by topher

[electau]

Neutral grounding (earthing) within an electrical installation in Thailand.

Where the neutral is required to be earthed , the main earth is connected to the main neutral bar and run to the main earth electrode. This is the method is based on the US National Electrical Code (NEC).

It is not a MEN system by definition (AS3000) or a TN-C-S (IEC). It is just a grounded neutral system.

The protective earth conductors terminate directly onto the main neutral bar. (A separate earth conductor should be run to any other distribution switchboard within the electrical installation)

This system is more difficult to test but it can be done.

The MEN system the main earth is run from the main earth bar to the electrode, and the PE conductors are connected to the earth bar. There is a link between the main neutral bar and the main earth bar. This is known as the MEN link. In is removed only for test purposes.

With the UK PME method of implimenting the TN-C-S system the N to E bond does not form part of a building electrical installation, it is made by the supply authority and is their responsibility.

Edited March 18, 2012 by electau

[electau]

It would be safe to state that over 90% of electrical installations ( in general) in Thailand do not earth the neutral, neutral earthing is only a recent development for new residential electrical installations.

You should always check with the PEA first, they will advise you.

Edited March 19, 2012 by electau

[Crossy]

This method of connection with the incoming neutral passing through the ground bar worries me on a number of fronts.

My main issue is that because the ground bar is on the uncontrolled side of the incomer there is no form of overcurrent protection provided to the ground stake.

With the Thai propensity for accidentally getting L & N reversed (something that is incredibly rare in the UK and probably Aus) there is the potential for large currents to flow down the ground stake. If it's a good one there could be many Amps in the ground wiring, if it's not a good one then all grounded equipment could potentially become lethal.

In this thread http://www.thaivisa....zero-connected/ the OP is reporting 3 AMPS flowing to his ground stake, scary.

All the documented wiring schemes I've seen both from CU manufacturers and PEA documentation show only this method of wiring the supply with no indication that TT or IT systems are used in some areas.

I expect to have an argument with my sparks as I've got my removable N - E link on the switched side of the incomer. I want to be able to completely isolate my installation from the PEA system.

[electau]

The protection is afforded by the main earth which will hold the voltage down to less than 50VAC if there is a broken neutral. Reversed polarity will not occur if the correct test procedures are carried out.

IMO earthing the neutral could be potentially hazardous because of the absence of testing.

The main earth and electrode is the most important conductor in an electrical installation.

Direct earthing is safer, ie no N to E bond. RCDs on all circuits.

Edited March 19, 2012 by electau

[Crossy]

IMO earthing the neutral could be potentially hazardous because of the absence of testing.

Direct earthing is safer, ie no N to E bond. RCDs on all circuits.

Agree 100%

I think we're both on the same page here With no N-E link a reversed supply is not immediately hazardous, add that link and reversed L-N becomes potentially lethal.

[electau]

It should be remembered that in Thailand earthing of the neutral has only been introduced recently, most Thai electrical installations use 2 pin socket outlets. It is obvious that earthing the neutral is a pointless exercise.

However, with the introduction of 3 pin socket outlets it would be logical to use an earthed neutral system.

This problem never occured in Australia with AS3000 as the MEN system is mandatory and 2 pin socket outlets were and are prohibited as they do not comply with AS3112.

However many countries still use 2 pin socket outlets including Thailand.

I can not see any Thai legislative requirement that prohibits the use of an unearthed neutral in an electrical installation.

Thailand also permits the use of RCDs to protect 2 poin socket outlets, this is from the NEC code, and the value is 5mA. Note those Safe-T-Cut units with adjustable sensitivity.

Some Thai wiring practice originates from the US National Electrical Code. And when it suits them the IEC.

The implimentation of the neutral earthing system has been poorly carried out, the PEA/MEA should be able to give a definite answer to question but they seem unable to.

[topher]

I did some walking around my village to try and see if the Neutral is grounded locally. I couldn't make out for sure at the transformer because it's hard to see the exact wiring. On the poles on my street I saw that 3 large insulated wires run with a smaller bare wire above them. I presume the bare wire is the Neutral as the feed to my meter comes from one insulated wire and the bare wire. Further down the street the bare wire runs down the post into a conduit into the ground. This seems to indicate that the Neutral has been grounded but only on some posts.

Walking along the highway into the village I can clearly see that all cement posts carrying 3 insulated and 1 bare wire all have the bare wire connected to the post rebar at top (which no doubt runs down into the ground) with a wire clamp assembly.

This all seems to indicate they have grounded the Neutral in my area. Anyone disgree?

In which case it should be ok to have the MEN link. I will try to confirm this with PEA too.

Thx.

Edited March 21, 2012 by topher

[electau]

I did some walking around my village to try and see if the Neutral is grounded locally. I couldn't make out for sure at the transformer because it's hard to see the exact wiring. On the poles on my street I saw that 3 large insulated wires run with a smaller bare wire above them. I presume the bare wire is the Neutral as the feed to my meter comes from one insulated wire and the bare wire. Further down the street the bare wire runs down the post into a conduit into the ground. This seems to indicate that the Neutral has been grounded but only on some posts.

Walking along the highway into the village I can clearly see that all cement posts carrying 3 insulated and 1 bare wire all have the bare wire connected to the post rebar at top (which no doubt runs down into the ground) with a wire clamp assembly.

This all seems to indicate they have grounded the Nuetral in my area. Anyone disgree?

Thx.

It would indicate that the distribution from this transformer is MEN the bare conductor is the neutral.

[electau]

It would appear that the neutral is earthed at intervals, ie MEN, and has been done on the cheap, using the rebar in the concrete post as an earth conductor.