Neutral Grounding

[4.real]

I noticed 'Crossy' has referred to 'neutral grounding'.

Could somebody explain what this is please?

Thanks in advance for any response.4.Real

[Crossy]

First of all go here http://www.arca53.dsl.pipex.com/index_files/elect4.htm to understand the difference between TT, TNS and TNC-S distribution systems.

Multiple Earth Neutral (MEN) sometimes called Protective Multiple Earthing (PME) is TNC-S with the addition of extra ground points along the length of the neutral (literally a metal stake in the ground at every 3rd pole or so), in the UK that would be it, but in Thailand we also add our own ground stake at each home.

All mains class 1 appliances (appliances that are not double insulated) must have the protective earth connected. This will normally be connected to the case if it is conductive and the mains transformer if present. Technically neutral and earth in a power outlet should be the same but the earth conductor is only ever used as a failsafe against electrocution in cases of neutral failure or when the active shorting to a metal case etc.

It is VERY IMPORTANT to understand that adding a N-E link where MEN / PME is not implemented could lead to a hazardous situation. It's not immediately dangerous (you're not going to die), but loss of the neutral between you and the transformer could lead to potentially lethal touch voltages on all your grounded appliances. If you're not sure leave out the N-E link so your system is TT.

Use of an RCD (ELCB, Safe-T-Cut) is extremely wise, and is mandatory if you have a TT system.

[Pacificperson]

Crossy, When a house has a earth rod connected to the main distribution panel and a single E-N inside the panel, is it normal practice not to have any other E-N connections within the wiring? Why? I also remember that one should not separately ground sub-panels in out buildings to a second rod because of lightening strikes.

[Crossy]

There must be only one N-E link,and that must be where the supply enters the property (usually in the distribution panel).

The main reason is that any other N-E links will cause problems with RCDs (mainly that they won't stay in or if they do they could trip randomly).

Outbuildings would be on a sub-main and have their own TT supply and RCD, you would not normally link N-E in these buildings.

[4.real]

Thanks,Crossy.

Does that mean that with my 2 pin wiring [positive/negative] I should have a lead from my square D box to an earth rod?

I have put in an earth lead from my shower ,A/C and computer connected to a copper coated grounding rod

[Pacificperson]

Crossy, Thanks a lot.

[InterestedObserver]

Thanks,Crossy.

Does that mean that with my 2 pin wiring [positive/negative] I should have a lead from my square D box to an earth rod?

I have put in an earth lead from my shower ,A/C and computer connected to a copper coated grounding rod

The earth lead or grounding conductor for equipment safety grounding would involve a third pin at your sockets. It would also require three pin plugs. Earthing at the Square D box is determined largely by system configuration and your use of RCDs.

[4.real]

I have never had a 2-pin system before so I am unaware of how any [if any] earthing is done for some minimal protection.

With just the 2 leads [positive and negative] is there any form of earthing?

I have noticed a 6 mm cable that comes from somewhere in my square D box and appears to go to a grounding rod by the side of my shower room.

[InterestedObserver]

I have never had a 2-pin system before so I am unaware of how any [if any] earthing is done for some minimal protection.

With just the 2 leads [positive and negative] is there any form of earthing?

I have noticed a 6 mm cable that comes from somewhere in my square D box and appears to go to a grounding rod by the side of my shower room.

A "2-pin system" has no protective earth (PE) conductor, usually green or green-yellow in color, for personal safety protection. Houses in Thailand are usually wired with two-prong sockets without ground.

Edited February 25, 2011 by InterestedObserver

[Crossy]

I have never had a 2-pin system before so I am unaware of how any [if any] earthing is done for some minimal protection.

With just the 2 leads [positive and negative] is there any form of earthing?

I have noticed a 6 mm cable that comes from somewhere in my square D box and appears to go to a grounding rod by the side of my shower room.

Have a look here http://www.crossy.co.uk/wiring/2pin.html

[4.real]

Thanks Crossy.

I will have to have my wiring renewed .Hopefully he can run an earth cable to the sockets that I cannot run an earth wire to

[tight angles to replace existing wiring.

Firstly I will replace my main switch in the Square D with an RCD.

I have already run a separate earth from Comp.shower and A/C.

[David006]

There must be only one N-E link,and that must be where the supply enters the property (usually in the distribution panel).

The main reason is that any other N-E links will cause problems with RCDs (mainly that they won't stay in or if they do they could trip randomly).

now and again

Outbuildings would be on a sub-main and have their own TT supply and RCD, you would not normally link N-E in these buildings.

interesting re RCD Crossy..maybe why our domestic panel RCD trips now and again...we have a little pump shelter with RCD fed before the house with ground rod ...rcd there never trips..I always thought it was the flaky supply somehow getting unbalanced....or a flaky RCD ( no rheostat)

It's not a biggy just a little inconvenient....always know it's not an outage as the water still pumps and have trained wifey to switch back on..Thanks for the info..

david

[rmacdon61]

I have never had a 2-pin system before so I am unaware of how any [if any] earthing is done for some minimal protection.

With just the 2 leads [positive and negative] is there any form of earthing?

I have noticed a 6 mm cable that comes from somewhere in my square D box and appears to go to a grounding rod by the side of my shower room.

Have a look here http://www.crossy.co...iring/2pin.html

Thank you for that site. Answers questions, but raises more

I am new to Thailand but have a passing understanding of house wiring from having wired 2 homes I built in Canada.

Typical saying is "I know enough to be dangerous"

I have looked around at building supply stores here in Chiang Rai, looking at electrical supplies. I plan on building new here.

Questions: Is 14/3 available in Thailand?

I did find copper rods but no panels for a grounded system? (typical 100amp/200amp things)

GFI breakers for thai voltage?

Surge protectors (in panel), have seen lightning strikes!!!!

Little off topic, but I have 220 volt equipment (60 C) I am considering importing, large table saw, band saw, planer etc. Forget it, sell it and buy here?

Thanks for any info

Bob

[ELCata]

How is everyone testing the fault loop impedance or electrode resistance? Or is everyone just winging it?

I'd suggest a 100mA RCBO at the main DB as a fail-safe, along with the usual 30mA ones for power circuits. I'd be interested to know how the Thai distribution system works. Is the TN-C-S system common, with the N connected to the earthed star point of the local transformer? Obviously the TT system would be the weapon of choice in the 'moobahn', which would be about 99% of LOS.

Wouldn't it be better to earth any small external buildings via the secondary DB, if TN-C-S is used at the primary DB, rather than rely on TT?

[Crossy]

How is everyone testing the fault loop impedance or electrode resistance? Or is everyone just winging it?

I'd suggest a 100mA RCBO at the main DB as a fail-safe, along with the usual 30mA ones for power circuits. I'd be interested to know how the Thai distribution system works. Is the TN-C-S system common, with the N connected to the earthed star point of the local transformer? Obviously the TT system would be the weapon of choice in the 'moobahn', which would be about 99% of LOS.

Wouldn't it be better to earth any small external buildings via the secondary DB, if TN-C-S is used at the primary DB, rather than rely on TT?

I'm using my old 16th Edition installation tester, but I suspect 99.999999% of everyone else is winging it and relying on the RCD to open on a L-E fault.

Agree with the 100mA RCBO as a belt-and-braces approach.

Theoretically Thailand is TN-C-S with MEN / PME via local earth stakes at the DB. That said, TT is widespread on older installations, IT has been seen quite commonly too (relying on the domestic stakes to keep neutral near deck), to broaden the confusion some villages are 3-phase 3-wire with 220V between phases.

In the UK exporting a TN-C-S ground to an outbuilding is prohibited, the issue is that there is a possibility of significant voltage between the local ground (water pipe, building metalwork) and the TN-C-S exported ground, potential for a dangerous cross-body shock.

[Crossy]

Questions: Is 14/3 available in Thailand?

I did find copper rods but no panels for a grounded system? (typical 100amp/200amp things)

GFI breakers for thai voltage?

Surge protectors (in panel), have seen lightning strikes!!!!

Little off topic, but I have 220 volt equipment (60 C) I am considering importing, large table saw, band saw, planer etc. Forget it, sell it and buy here?

Wire sizes here use the Metric system and quote the Cross Sectional Area(CSA) of the conductors in mm², you can find the current ratings of the various sizes here http://www.crossy.co.uk/wiring/Circuit%20types.html

Plenty of Western style dizzy boards here with an integral earth bar, have a look at offerings from Schneider / Square D.

All GFIs here are 220V, but we call them RCDs, ELCBs or Safe-T-Cut.

Try a forum search for MOVs, there are a few threads on surge arrestors.

Your 60Hz motors will run slow on 50Hz and may overheat. Solutions:-

1. Suck it and see, with the limited duty-cycle these things tend to see things will very likely work just fine.
   
2. Replace the motors when you arrive with 50Hz versions.
   
3. Shell out on an electronic 60Hz drive.
   

[ELCata]

I'm using my old 16th Edition installation tester, but I suspect 99.999999% of everyone else is winging it and relying on the RCD to open on a L-E fault.

Agree with the 100mA RCBO as a belt-and-braces approach.

Theoretically Thailand is TN-C-S with MEN / PME via local earth stakes at the DB. That said, TT is widespread on older installations, IT has been seen quite commonly too (relying on the domestic stakes to keep neutral near deck), to broaden the confusion some villages are 3-phase 3-wire with 220V between phases.

In the UK exporting a TN-C-S ground to an outbuilding is prohibited, the issue is that there is a possibility of significant voltage between the local ground (water pipe, building metalwork) and the TN-C-S exported ground, potential for a dangerous cross-body shock.

Your 16th Ed tester will serve you well. Which model do you have? Have you seen the price of the 'Part P' 17th Ed testers now.

I'm confused about your '3-phase 3-wire with 220V between phases' comment. Do you mean TP&N (standard in the UK) or 2P&N? Obviously the voltage between phases is zero.

Also in the UK, it is acceptable for outbuildings to use the earth from a 2nd DB as the return path. I'm not talking about heavy commercial bordering on industrial, but a simple domestic outbuilding (not for agricultural purposes for instance). The voltage differential problem can be solved in the usual way by equipotential bonding AFAIK.

Edit: BTW, if you're in the Bangkok / Pattaya area next month. I can bring over the 17th Ed regs, along with 16th Ed GN3, if you're interested in taking them off my hands?

Edited February 27, 2011 by ELCata

[Crossy]

I have a well used but serviceable Robin KTS 1630 which was an eBay purchase after I ditched all my test gear before coming here, 'never going to need that again', wrong!!

I was over-simplifying the TN-C-S export issue, we are not a technical board here so care is required not to cause information overload. It's all about extraneous conductive parts, lots of discussion on the IET forums http://www.theiet.org/forums/forum/categories.cfm?catid=205&entercat=y (you can read if you're not a member).

The village connections are 3-phase 3-wire with a delta connected Tx. 220V ph-ph supposed to have DP breakers etc etc. I'm not 100% certain the Tx is delta, could be star with the star-point grounded but not connected to the LV distribution system. Philippines is mostly like this I believe a hang over from US influence (it's still 60Hz).

[ELCata]

OK point taken about the technicality & thanks for the link. What I was worried about is the 0.12 Ze needed for a TN-C-S system. In the UK this is the distributors responsibility so I assume the same applies in LOS? TT as I'm sure you know is a whole different ball game. Without peeking at GN3 I believe 6666 ohms is allowed for a 30mA RCD, but in practice much less.

I have a friend who is building a house in the village ATM & has been picking my brains. He was having trouble differentiating the incomers. I suggested sticking a megger on them to show + / - 240 polarity. Do you have a better suggestion?

Nice to have a chat with someone who knows their onions for a change.:jap:

[Crossy]

Welcome to the world of Thai electrics where the sensible is ignored and the downright dangerous is the norm. I'm sure your input here will be most valuable (and possibly even welcome ).

To differentiate the incomers (L & N), stick a big screwdriver in the ground and measure Volts AC between it and each incoming wire, use a DMM not an analogue meter, 220V = L, OV or thereabouts = N If you have an earth stake you can use it instead of the screwdriver, but ensure you disconnect everything else from the stake. If you get odd readings you can bet that the installation is IT, assume the lower voltage is neutral for want of a better idea but do NOT connect a N - E link.

Thai regs for domestic installations are largely non-existant, I've never seen anything mention Ze (or any other parameter we would routinely check in the UK). You're lucky if your sparks has a meter, the chap who looks after my step-sons restaurant has a couple of old screwdrivers and a pair of industrial scissors (I won't go near it, I'd want to rip the lot out).

The general consensus of the sparkies that occupy this board is that in the absence of anything else the Aussie regs are a best-fit for local conditions. That said, it's important to take a pragmatic approach to your installation, just because something does not comply with your local home regs does not mean it's hazardous. Wire a home in Oz to UK regs and it would fail inspection (and probably vice-versa).