Idiots

[sometime]

The local (Najomtien) electricity company went around yesterday before 7am removing all the electric meters from all properties in the area and just taped the wires together, oh good free electric.

At 4pm they arrived back and put the meters back in place, I never gave it another thought until just after the sun went down then I noticed a slight glow in the lights although they were turned off.

Yes the Idiots had got the wires the wrong way round so everything negative in my house is now live, and I can almost guarantee I won’t be the only one, let’s hope no one gets a nasty shock, I’m waiting for them to arrive, I could just change the wires over in the consumer units x 3 but I will wait.

[slapout]

They were in a hurry to get to the local roadside bar for happy hour prior to clocking out. Dont you see?

[Crossy]

Arghhhh!!

This is not an uncommon situation apparently.

Beware, if your house is wired MEN (as it should be here) ALL your grounded metalwork could be live!! Avoid touching anything (or pull the main breaker) until it's been rectified.

[Beardog]

A suggestion .....We had the same thing done in our house. Hook up in the later afternoon & when it starts turning dark the can see the screwed up to fix the problem . ours was wired in the attic wrong & the dweebs had to grovel upstairs with a flashlite to rectify the problem. Most of these clowns don't use any type of meters to check if the wires are hooked up in phase.

[how241]

Yes, you have to be real careful about the "ground" situation or lack of in Thailand. Many don't feel that it is so important.

[sometime]

Arghhhh!!

This is not an uncommon situation apparently.

Beware, if your house is wired MEN (as it should be here) ALL your grounded metalwork could be live!! Avoid touching anything (or pull the main breaker) until it's been rectified.

Thanks Crossy I just put a meter from the NEG that is now live to the stainless steel sink and it's reading 215 volts, shit!!!!

[lopburi3]

That is a normal reading from a hot (live) to ground. So your sink is well grounded it seems.

[Crossy]

That is a normal reading from a hot (live) to ground. So your sink is well grounded it seems.

Yup.

To be sure measure between an independent ground (a big screwdriver in the lawn will do) and all your metalwork.

Check to live first to verify your screwdriver is providing a ground.

[david96]

If you have an effective and complying earthing system, MEN, the touch voltage will be over 50VAC and you have a potentially hazardous situation.

Polarity testing must be carried out before initial conection to supply.

People have been killed or severely injured in situations similiar to this.

[david96]

This is where the direct or TT earthing system has an advantage, if the polarity of supply is reversed a hazardous situation is not created.

Most Thai electrical installations do not use the MEN system.

[Crossy]

This is where the direct or TT earthing system has an advantage, if the polarity of supply is reversed a hazardous situation is not created.

Most Thai electrical installations do not use the MEN system.

Exactly david, this is my biggest worry about having MEN in Thailand. All is fine, then some tit reverses the supply at the meter (like happened to our OP) and all grounded metalwork heads in the direction of line potential.

This is not the first report of L N reversal being caused by idiots

[sometime]

This is where the direct or TT earthing system has an advantage, if the polarity of supply is reversed a hazardous situation is not created.

Most Thai electrical installations do not use the MEN system.

Exactly david, this is my biggest worry about having MEN in Thailand. All is fine, then some tit reverses the supply at the meter (like happened to our OP) and all grounded metalwork heads in the direction of line potential.

This is not the first report of L N reversal being caused by idiots

They duly arrived today to reverse the wires, so all is Ok, wouldn’t you think that they would have checked all the other properties to see if any other mistakes have been made “or is that me being an IDIOT”

[bankruatsteve]

So, Thailand has polarity in the AC supply??? Amazing. I wonder how they do that?

[Crossy]

So, Thailand has polarity in the AC supply??? Amazing. I wonder how they do that?

In common with most 3 phase 4-wire systems yes, neutral is grounded at the transformer so the supply is polarised, one wire bites the other doesn't.

Our OP is mistakenly calling N Negative instead of Neutral, it does not make his situation any less hazardous.

[bankruatsteve]

OK - I was a bit cheeky about the "negative" references. Anyway... single phase (which most of us have) also has neutral.

The thing is, I just can't imagine the situation as described. If the system was grounded and the wires crossed at the meter, something would have fried (probably the supply cable effectively connecting the hot feed to ground). If the system was totally ungrounded, then it wouldn't have made any difference.

Or, what's an explanation?

[Crossy]

OK - I was a bit cheeky about the "negative" references. Anyway... single phase (which most of us have) also has neutral.

The thing is, I just can't imagine the situation as described. If the system was grounded and the wires crossed at the meter, something would have fried (probably the supply cable effectively connecting the hot feed to ground). If the system was totally ungrounded, then it wouldn't have made any difference.

Or, what's an explanation?

Remember that the MEN link is in the distribution board linking ground to the incoming N. Reversing L and N at the meter then puts 220V on N. This in turn puts 220V on G.

The resistance to ground (via the ground stake) is likely in excess of 200 Ohms (IEE regs allow 800 in a TT system) so a current of a few amps will flow down the ground wire pulling it and anything connected to it towards L potential, how high it gets depends upon the ground resistance, but it will certainly get high enough to bite.

In the OPs case it seems he did not have MEN so the only side-effect was his fluorescents glowing when off.

[bankruatsteve]

OK - I was a bit cheeky about the "negative" references. Anyway... single phase (which most of us have) also has neutral.

The thing is, I just can't imagine the situation as described. If the system was grounded and the wires crossed at the meter, something would have fried (probably the supply cable effectively connecting the hot feed to ground). If the system was totally ungrounded, then it wouldn't have made any difference.

Or, what's an explanation?

Remember that the MEN link is in the distribution board linking ground to the incoming N. Reversing L and N at the meter then puts 220V on N. This in turn puts 220V on G.

The resistance to ground (via the ground stake) is likely in excess of 200 Ohms (IEE regs allow 800 in a TT system) so a current of a few amps will flow down the ground wire pulling it and anything connected to it towards L potential, how high it gets depends upon the ground resistance, but it will certainly get high enough to bite.

In the OPs case it seems he did not have MEN so the only side-effect was his fluorescents glowing when off.

Huh? I think connecting L to ground no matter how you do it will heat something up (as in short curcuit). And I hope you're not saying that reversing the "polarity" on a light makes a twit of difference.

[Crossy]

Huh? I think connecting L to ground no matter how you do it will heat something up (as in short curcuit). And I hope you're not saying that reversing the "polarity" on a light makes a twit of difference.

You are assuming that ground has no, or a very low resistance, this is simply not true. If you connect L to your ground stake (not the Ground in your outlets which may be MEN linked) only a few amps will flow, the ground will get hot but the MCB is unlikely to open.

A common problem in Thailand is fluorescents that glow even when off. The usual cause is a switched neutral (rather than live). The OPs L N swap at the meter caused all his lights to become switched neutral, it was the glow when off that alerted him to the problem.

[bankruatsteve]

Huh? I think connecting L to ground no matter how you do it will heat something up (as in short curcuit). And I hope you're not saying that reversing the "polarity" on a light makes a twit of difference.

You are assuming that ground has no, or a very low resistance, this is simply not true. If you connect L to your ground stake (not the Ground in your outlets which may be MEN linked) only a few amps will flow, the ground will get hot but the MCB is unlikely to open.

A common problem in Thailand is fluorescents that glow even when off. The usual cause is a switched neutral (rather than live). The OPs L N swap at the meter caused all his lights to become switched neutral, it was the glow when off that alerted him to the problem.

Well, I'm pretty darn sure that a copper rod (which is what should be used as a ground stake) has effectively 0 ohms resistance and I'm also pretty darn sure that reversing neutral and hot on any type of light will make absolutely no difference. If they glowed it must have been from sun spots, microwaves, or UFO. Cheers.

[Crossy]

Well, I'm pretty darn sure that a copper rod (which is what should be used as a ground stake) has effectively 0 ohms resistance and I'm also pretty darn sure that reversing neutral and hot on any type of light will make absolutely no difference. If they glowed it must have been from sun spots, microwaves, or UFO. Cheers.

Of course the rod has a low resistance

It's the connection between that rod and the mass of the earth along with the resistance of the earth back to the ground mat at the transformer that forms the ground resistance. After all we don't make wires out of rock.

And, as I noted, switching the neutral rather than the live will often result in fluorescents glowing dimly when 'off'. Whether, and how brightly they glow depends upon the cable run length, its route and its parasitic capacitance to ground.

[powderpuff]

Happened to me too when I ugraded my meter to 30/100 amps. Bloody dolts.

[tjo o tjim]

Of course the rod has a low resistance

It's the connection between that rod and the mass of the earth along with the resistance of the earth back to the ground mat at the transformer that forms the ground resistance. After all we don't make wires out of rock.

And, as I noted, switching the neutral rather than the live will often result in fluorescents glowing dimly when 'off'. Whether, and how brightly they glow depends upon the cable run length, its route and its parasitic capacitance to ground.

But with MEN, won't the return path be distributed-- you will also get the MEN link at your neighbor's place, putting both houses at risk?

[CDNinKS]

Sorry guys, I'm confused.

Crossy, you state that MEN is the proper way to wire a house here in LOS, which I see your point. However, unless I misinterpret these posts, it seems that NOT wiring it MEN would alleviate the problems of reversed L and N. What am I missing?

[sometime]

OK - I was a bit cheeky about the "negative" references. Anyway... single phase (which most of us have) also has neutral.

The thing is, I just can't imagine the situation as described. If the system was grounded and the wires crossed at the meter, something would have fried (probably the supply cable effectively connecting the hot feed to ground). If the system was totally ungrounded, then it wouldn't have made any difference.

Or, what's an explanation?

Remember that the MEN link is in the distribution board linking ground to the incoming N. Reversing L and N at the meter then puts 220V on N. This in turn puts 220V on G.

The resistance to ground (via the ground stake) is likely in excess of 200 Ohms (IEE regs allow 800 in a TT system) so a current of a few amps will flow down the ground wire pulling it and anything connected to it towards L potential, how high it gets depends upon the ground resistance, but it will certainly get high enough to bite.

In the OPs case it seems he did not have MEN so the only side-effect was his fluorescents glowing when off.

Hi Crossy

Could you briefly explain what if house is wired MEN actually means?

[sometime]

Sorry guys, I'm confused.

Crossy, you state that MEN is the proper way to wire a house here in LOS, which I see your point. However, unless I misinterpret these posts, it seems that NOT wiring it MEN would alleviate the problems of reversed L and N. What am I missing?

Don’t forget by Reversing N&L if you intend to work on a particular circuit you can’t just throw the breaker for that circuit because it will still be live

[CDNinKS]

Could you briefly explain what if house is wired MEN actually means?

The MEN (Multiple Earthed Neutral) system of earthing is an arrangement that uses the network neutral conductor as the conductive path for installation earth fault currents.

MEN explained

Edited February 21, 2010 by CDNinKS

[sometime]

Could you briefly explain what if house is wired MEN actually means?

The MEN (Multiple Earthed Neutral) system of earthing is an arrangement that uses the network neutral conductor as the conductive path for installation earth fault currents.

MEN explained

Thanks, as you can see from photo I don't have MEN

And seeing that in this area we get frequent lightning strikes to the ground I don’t think I with alter what I have

Edited February 21, 2010 by sometime

[david96]

If you do not implement the MEN link your earthing system will be direct or TT.

You must have RCD protection on all final subcircuits as the fault loop impedance will be insufficient for auto disconnection in the event of an earth fault by an overcurrent protective device.

Auto disconnection must occur if the touch voltage exceeds 50VAC.

With an MEN system the current flowing in the electrode and ground is negligible and can be ignored.

Main earth restance not to exceed 0.5 ohms ( from earth bar to earth electrode).

Electrode 12mm 1.2M copperclad steel minimum for MEN installations, 1.8M for TT installations.

Earth fault impedance low and high earth fault currents for a MEN system.

Earth fault impedance high and low earth fault currents for a TT system.

Touch voltage only occurs under earth fault conditions.

If you have problems with lightning instal surge protection on the main switchboard an protect with a 32A MCB

Edited February 22, 2010 by david96

[Crossy]

Sometime.

I'll echo what david said, you REALLY need to install some form of RCD if you only have a TT installation, a quick and easy solution would be a whole house Safe-T-Cut installed in front of your distribution board.

I also see a couple of grey wires going to MCBs, naughty, naughty

[CDNinKS]

Thanks Crossy, I have since found and bookmarked your Thailand Wiring Page.......invaluable info there for sure.

I built 2 houses in Canada and I'm sure they were not MEN, but I could be wrong on that as by code (at the time) the only circuits that need GFI (ground fault interrupter) protection were ones in the bathroom and any outdoor plugs. I had heard that the code was going to be changed to also require GFI in the kitchen as well.

I do know that the Ground rod was galvanized steel and not copper cladded, does that mean it was TT?

I also was wondering why in sometimes picture there were neutral (gray) wires on the hot side of the breaker???

We are having a house built as we speak in Hua Hin and I'm afraid I don't have a lot of confidence in the electrician, if I can even use that term in this instance. When I told them that the system must be earthed with 3 prong receptacles in the wall, he gave me a blank stare. The building contractor seemed to understand and there was a flurry of thai and then the electrician nodded his head........

I have heard of too many horror stories here in LOS, but the funniest one was the guy who found that the electrician had grounded his system to a water pipe......the pipe was plastic

You can bet your bottom dollar I will be checking very closely what is and is not hooked up.

Thanks for the info that to identify if the line is MEN to check if some of the poles have a copper earth bar.