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Have you ever found your L-N service conductors reversed?


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After reading this forum and living in Thailand a few years, I have heard several stories that L-N service conductors or feeders are reversed somewhere between the PEA drops and the CU -- therefore creating a serious safety hazard.  I thought it would never happen to me because I have the knowledge, tools, and safety-conscious mindset to find and fix issues like this before someone gets hurt or something catches on fire.  Nevertheless, I got a big surprise yesterday when I touched the stainless steel shower valve.  Found L-N reversed at the meter.

 

How many other members in this forum have had to deal with this?  I'm interested to learn from other experiences about what was the first indication that you noticed a problem? How did you resolve the L-N reversal?  Did you experience an electric shock or indirect injury, such as falling down, as a result?

 

My L-N is installed correctly now, and I'm still alive to share stories.

 

I have to go now, but i will share my story and some questions in the comments later today.

Edited by captainjackS
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Enough members have found L - N reversal for it to be worrying, including one on a TNC-S service who noticed the kitchen floor over his (buried of course) ground rod was getting warm!

 

It usually happens after a meter swap or some other work involving disconnection at the meter or the incoming side of the main breaker.

 

Definitely not something you want!

 

 

 

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2 minutes ago, peterfranks said:

How you check if it is reversed?

 

If you have a neon screwdriver (or one of the non-contact live-wire detectors) it should light up on the screw connection to your MCBs and not on the neutral bus bar.

 

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41 minutes ago, captainjackS said:

How many other members in this forum have had to deal with this?  I'm interested to learn from other experiences about what was the first indication that you noticed a problem? How did you resolve the L-N reversal?  Did you experience an electric shock or indirect injury, such as falling down, as a result?

Me, in my new house ........... discovered the day I moved in when I was fitting an electric shower heater. Touched all the wires with my test screwdriver before fitting, screwdriver lit up even with the shower fuse off.

Moobaan electrician was round the next day to change the wires at the meter.

The misses noticed him checking out the meters in the whole street after.

 

Test screwdriver costs 20bht, never touch a wire with anything else before starting work.

 

Off topic,

They also didn't screw the lid onto the septic tank, I had to show them that it needed to be secured, they claimed they never knew it had to be drilled and screwed down ...... and they had just built 250 houses like that.

Edited by BritManToo
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40 minutes ago, captainjackS said:

I have heard several stories that L-N service conductors or feeders are reversed somewhere between the PEA drops and the CU -- therefore creating a serious safety hazard

Why is it a serious safety hazard?

One shouldn't touch L or N. In some 1st worlds countries, the plugs don't even have a difference between N and L.

Earth should obviously be used, and it shouldn't be confused with N - which unfortunately is another "Thai" issue, much more serious.

jung-ren-aflow-ww-af581ww-a1520ww-socket

 

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5 minutes ago, OneMoreFarang said:

Why is it a serious safety hazard?

1. Because there are no fuses in the neutral wiring, effectively your house wiring is no longer fused. Turn off an individual circuit breaker to work on a socket and still fry.

 

2. Because the neutral side is connected to your earth rod, so you have incoming live on your ground all around your house. Step in a puddle in your garden and burn! (not to mention all the units heating your garden will use) 

Edited by BritManToo
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15 minutes ago, BritManToo said:

Me, in my new house ........... discovered the day I moved in when I was fitting an electric shower heater. Touched all the wires with my test screwdriver before fitting, screwdriver lit up even with the shower fuse off.

Even if L and N is wrongly connected that shouldn't happen. 

Any metal which you can touch should be connected to earth. 

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Posted (edited)

My story:

PEA is doing a major upgrade in the area that includes replacement of old power poles on which the meters are installed.  New poles have been up for a while.   Time comes to relocate all the meters onto the new poles.  My wires were marked on both ends by a PEA electrician who installed the wires. (brown tape on L, no marking on N).  Looks like the meter guys cut the wires shorter (and lost the tape markings) to fit the new pole install location.

After getting a shock from the shower handle, I went out to look at the meter and wires.  No tape markings.  Measured 230V from N-E in the CU using multimeter. 

Since it is a long holiday weekend, I didn't bother calling PEA. 

I have a 2-pol disconnect between the meter and CU, so i was able to safely switch off, swap the wires on the non-live side of the switch.  Stick new tape markings on all the wires.

About the shock - 24 hours later I can still feel some tingle in my hand like something happened, but no loss of mobility so I will probably be fine in  few days.

 

 

Edited by captainjackS
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1 minute ago, captainjackS said:

I have a 2-pol disconnect between the meter and CU, so i was able to safely switch off, swap the wires on the non-live side of the switch.  Stick new tape markings on all the wires.

About the shock - 24 hours later I can still feel some tingle in my hand like something happened, but no loss of mobility so I will probably be fine in  few days.

Is your earth rod connected before or after the 2 pole disconnect?

You really don't want the incoming live connected to your earth rod.

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Posted (edited)
14 minutes ago, BritManToo said:

Is your earth rod connected before or after the 2 pole disconnect?

You really don't want the incoming live connected to your earth rod.

2 pol disconnect is "floating". No N-E bond.  The only N-E bond is in the house in the CU.  Nobody wants L to Earth, but thats what happens when 230V is connected to the wire marked "N" which is bonded to Earth in the CU.

Edited by captainjackS
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2 hours ago, OneMoreFarang said:

Use something like this, available online.

IMG_20220812_144807.thumb.jpg.3af5414e3cce772fe35d71770f74cd4a.jpg

No that will just tell you if that one socket is wired correctly, it will not tell you if the whole house input is incorrect which is the topic.

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4 hours ago, OneMoreFarang said:

That's why they invented RCBOs.

 

And just how does that solve the problem?

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1 hour ago, Crossy said:

 

And just how does that solve the problem?

It doesn’t, the difficulty is that those who don’t know all the wonderful ways that faults can do nasty things to you, sometimes terminally bad ones, think that because some circuits can “not kill” you when badly installed sometimes it is an excuse to allow bad practice. 
 

Just because you haven’t managed to trip over faulty wiring doesn’t make it safe.

 

There are reasons for wiring codes, many designed to prevent Darwin Awards.
 

Thailand is supremely lucky that the vast majority of EV chargers have been installed with some reasonably competent instructions. This is likely to change and there will be some idiots who will claim that being electrocuted or frying the local youngsters was accidental rather than incompetent criminal cretins. 

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9 hours ago, OneMoreFarang said:

Why is it a serious safety hazard?

One shouldn't touch L or N. In some 1st worlds countries, the plugs don't even have a difference between N and L.

Earth should obviously be used, and it shouldn't be confused with N - which unfortunately is another "Thai" issue, much more serious.

I have to apologize for any confusion/misunderstanding.

 

When I initially read the first post, I thought this is about one or several power outlets with incorrect connected N and L. I wrote it shouldn't matter and I am pretty sure if this would be just about the power outlets then it really wouldn't matter. But please correct me if I am wrong.

 

For the whole electrical installation in a house the N and L should obviously be connected correctly.

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Posted (edited)
10 hours ago, OneMoreFarang said:

 

@OneMoreFarang sometimes vocabulary can inconsistent too.  In the OP subject, I wrote "service conductors". i don't what they are called outside the US. (the wires between the power company equipment and my first means of disconnect)

Edited by captainjackS
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2 hours ago, captainjackS said:

@OneMoreFarang sometimes vocabulary can inconsistent too.  In the OP subject, I wrote "service conductors". i don't what they are called outside the US. (the wires between the power company equipment and my first means of disconnect)

Thanks. Somehow I thought you have those things (from any possible power plug) in your mind ...

Power-plug-type-F.jpg

 

But now I know you had these cables, "service conductors", on your mind.

ECM_0820_Fig1.5f3d8cd47f682.png?auto=for

 

 

 

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11 hours ago, OneMoreFarang said:

But please correct me if I am wrong.

think about power outlets using 3 prong plugs, there are many

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The neon test pen is a valuable piece of gear even in todays environment with all of the test gear us leckys have to hand.

Remarkedly though, with all the required test gear calibration certificates, never had the test pen queried.

Then again a whopping great test certificate wrapped around a test pen would make it unreadable.

Word of warning though.

I have seen el-cheapo units that were dodgy, wherein the internal high value resistor was low, very low and enough to give a decent boot.

I tend to use more costly devices and test any new ones on a megger, just in case.

 

Non contact testers can be iffy in that they can detect adjoining cabling being active which will induce false readings and so not really trustworthy.

They can also be rather orintation dependant to give a signal.

As a result I don't use them anymore.

Edited by bluejets
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