Reverse Neutral/Live or has the Earth Rod Disconnected?

[Formaleins]

I posted here a couple of weeks back about measuring about 35 Volts on my Water Heater ( Panasonic 8KW) despite the breaker on the consumer unit being disconnected. Crossy helped me out somewhat to the fact it may be residual capacitance. Well, today I have been in the damn thing cleaning the filters and checking the flow valve and I can certainly tell you that it is not stray voltages or capacitance. I got such a whack from the mains that it nearly knocked me over. This was with the breaker for the shower (totally on its own - only two wires and an earth). Breaker was off.

 

I did some measurements, hopefully you can see them below. There are 4 sets, measurements in all 4 states of the switching, and then all four states measured at the Consumer unit at the output from the breaker and another set at the input to the heater - hence CU an HTR. I am about 99% sure that the polarity is reversed between L and N - However, this is for about half of the connections to the Consumer Unit, the other half seem OK. My only other worry is that the Earth into the ground strap has disconnected/ corroded, detached (buried in concrete)

 

I ran a check using the Hz. function on my meter and was getting 50 Hz. Neutral to Ground but zilch on Live to Ground. So tonight I swapped L-N and now have 50Hz on Live - Ground and Zilch on N-Ground. (which makes more sense) There is however a "Borrowed Neutral" going to some two way switches on another circuit which I reckon is causing some problems - ( I found a GREEN  Earth cable coming up and connecting to the Neutral bus, however if I pull it out of the bus it is actually at 230V, if it is connected to the Earth cable bus it trips the RCBO) Jesus, what a mess!

 

In the morning before swapping the cables and getting zapped NOTHIN tripped! The ECB on the Heater did not go, the Breaker did not go nor did the RCBO. Yet messing around on another circuit for sockets I mistakenly plugged the meter in to a plug socket still on Ohms and the RCBO went off in a flash.

 

Any ideas? Please, I do appreciate the help, I really do, but I cannot really be arsed with stupid <deleted> like how big are your cables, your cable run etc. It is just a waste of time. If you know the answer fine, but please don't just post <deleted> for the sake of it. Cheers! ( All values are Volts AC) The consumer unit measurements are after the breaker and the HTR are at the input terminals to the heater - essentially the same cable.

 

[cornishcarlos]

Single pole breaker ??

Can you post another photo, can't find the other thread...

Test 2 - breaker off but still voltage on both outlet lines !! Faulty breaker 

Live and neutral reversed and breaker reversed if that's possible ????

[BritManToo]

20 minutes ago, Formaleins said:

Any ideas?

Normal mistake is live and neutral reversed coming out of the electricity meter (or into your breaker box).

It means all your breaker switches don't work, very dangerous.

My current house was wired like that when I moved in, common mistake with Thai electricians.

 

Found it when I wired in the Shower heater in my new house, breaker off, live on the neutral ......

Went round the house with my 'glow test' screwdriver, every neutral was live with the breakers off.

I always use a 'glow test' screwdriver before I touch a bare wire.

[Formaleins]

4 minutes ago, BritManToo said:

Normal mistake is live and neutral reversed coming out of the electricity meter (or into your breaker box).

It means all your breaker switches don't work, very dangerous.

My current house was wired like that when I moved in, common mistake with Thai electricians.

 

Found it when I wired in the Shower heater in my new house, breaker off, live on the neutral ......

Went round the house with my 'glow test' screwdriver, every neutral was live with the breakers off.

I always use a 'glow test' screwdriver before I touch a bare wire.

I now try to get my wife to touch the connections first as I don't trust those "Glow" things - I have an allergy to death. I am only worried that the Earth has corroded. Not sure how to check that without a Megga!

[BritManToo]

Just now, Formaleins said:

I don't trust those "Glow" things - I have an allergy to death.

Used them all my life, I totally trust them, they've saved my life a few times.

[Formaleins]

13 minutes ago, cornishcarlos said:

Single pole breaker ??

Can you post another photo, can't find the other thread...

Test 2 - breaker off but still voltage on both outlet lines !! Faulty breaker 

Live and neutral reversed and breaker reversed if that's possible ????

Anything is possible after these idiots wired up the place - Some of my Neutrals are actually Live and the other way around. - It is all due to some Neutral they hooked up on a two way switch, but the there are no diagrams or anything to show where anything goes.

I am sure the breaker is single pole, swapped it onto the second breaker that has never been used, same result. (If I reverse he polarity half the breakers are OK, repeat and the other half go to rat <deleted>!)

[Formaleins]

1 minute ago, BritManToo said:

Used them all my life, I totally trust them, they've saved my life a few times.

Well, good luck, but I'd rather use my wife's fingers. - If she jumps you know it is live, and risk free.

[sometimewoodworker]

16 minutes ago, Formaleins said:

I now try to get my wife to touch the connections first as I don't trust those "Glow" things - I have an allergy to death. I am only worried that the Earth has corroded. Not sure how to check that without a Megga!

To avoid the problem with the “glow” things you can use one of these.

 

 

Depending on the construction of your building you can always connect The earth to the roof steel as that is almost certainly a better earth then your original earth rod assuming you’ve got a concrete reinforced steel building.

[wayned]

3 hours ago, Formaleins said:

Well, good luck, but I'd rather use my wife's fingers. - If she jumps you know it is live, and risk free.

When using wife's fingers make sure that you are wearing rubber gloves and have a suit of body amour on as you will need it when she picks herself up from the floor!

[Crossy]

I would put money on a L-N reversal somewhere, we just have to find out where.

 

Can you make some measurements to an independent ground (screwdriver stuck in the lawn).

 

Measure from your screwdriver to the incoming terminals of your main breaker as a start (care please), then to what is supposed to be your earth. Same thing at the heater, breaker on but no need to run the heater.

 

Do you have a MEN (N-E) link in the consumer unit? Post some more photos so we can see exactly what you have.

 

Whilst you're at it check the continuity (ohms) of the ground from heater to CU (main breaker off). Can you get at the ground rod, if so check continuity to it as well.

 

Also, has any work been done on your supply (new meter perhaps)?

 

 

[tjo o tjim]

13 hours ago, Formaleins said:

I now try to get my wife to touch the connections first as I don't trust those "Glow" things - I have an allergy to death. I am only worried that the Earth has corroded. Not sure how to check that without a Megga!

Repeat test 2 and measure the current for each mode.  The heating element is acting as a high resistance ground.  It is going to give you the effective ground return resistance though, not the actual ground electrode.

 

As you have alluded, you are going to need to sort out the line-neutral reversal/borrowed neutral though before you can safely fix the grounding issue.  Sounds like a mess.

[Formaleins]

Many thanks for your inputs, greatly appreciated as always!

OK, Crossy, I ran an independent Earth from outside - it was 1mm cable and 12 metres long copper, (All I had) a rod about 1.5 foot into rather dry sand / stone - L-E=230V, N-E= 0.2V and E-E 0V, and E-E resistance is 2.2KOhms.

There is no MEN on the consumer unit.

I couldn't rest thinking about these damn voltages so I reversed the L-N this morning and redid the checks, I think it now looks safe. Certainly no voltages at the shower with the breaker off. I am going to go around and use the frequency check to see if any of the sockets are reversed but I am not too worried about them as we have nothing that heavy plugged in, it was the 8000 Watt heater and 45A breaker then the 60 amp copper fuse that would need to fry that had me concerned. I am posting the table, with the second tests added. See what you reckon. Thanks for all of your help with this.

 

 

[Formaleins]

3 hours ago, tjo o tjim said:

Repeat test 2 and measure the current for each mode.  The heating element is acting as a high resistance ground.  It is going to give you the effective ground return resistance though, not the actual ground electrode.

 

As you have alluded, you are going to need to sort out the line-neutral reversal/borrowed neutral though before you can safely fix the grounding issue.  Sounds like a mess.

I could only measure live and neutral at the CU as I cannot get at the individual cables at the heater - All switched on there is 22 Amps to the heater and 27 amps total on the incoming live and neutral - (5 or so amps are all the other things running in the background) Cheers! (This is after I reversed L-N at the CU) I had to measure with a crappo Uni T clamp as my main meter will only take 20 A for a short check.

[Formaleins]

Crossy I checked the cable I used for the temporary earth and it is less than 1 Ohm end to end - and the position of the temporary ground is about 3 metres from where I think my earth rod is buried.

[Moonlover]

18 hours ago, BritManToo said:

Normal mistake is live and neutral reversed coming out of the electricity meter (or into your breaker box).

It means all your breaker switches don't work, very dangerous.

My current house was wired like that when I moved in, common mistake with Thai electricians.

 

Found it when I wired in the Shower heater in my new house, breaker off, live on the neutral ......

Went round the house with my 'glow test' screwdriver, every neutral was live with the breakers off.

I always use a 'glow test' screwdriver before I touch a bare wire.

Had the same issue with our rented place in Udon Thani and from what I gathered, every house on the moobam was the same. Changing a fluorescent circular tube was a life threatening event until I sorted it out. When I looked into it, the wiring diagram in the consumer unit was wrong!

[Crossy]

So you swapped the incoming L & N?

 

Your incoming L now really is L?

 

Since you have no MEN a L/N swap shouldn't lead to "nippy" earths,  have you been able to verify earth continuity from the heater to the CU? 

 

[Docmartin]

A few thoughts - I've seen a new build where the cabling to the GPO wall boxes was green for line (active) and neutral, and red for the earth.

At least there was an earth. Maybe.

 

Thailand doesn't run a MEN system

The MEN system is good for low earth fault loop impedance to break supply when there's an earth fault, but if the incoming neutral breaks the water pipes and steel frames are energised at line voltage, ie. you'll get a shock off a tap (via the equipotential bonds).

 

The best approach to the problem might be to treat all the wiring as suspect, isolate it, separate all the connections and start again.

But you'll need a competent sparky for that.

 

Attached - typical dodgy wiring.

Instantaneous HWS near a shower head, live terminals exposed, no mechanical protection, no double insulation, red earth wire goes out to the garden and gets buried.

Loop impedance = ???

 

 

[Crossy]

18 minutes ago, Docmartin said:

Thailand doesn't run a MEN system

 

New installations are required to be MEN, wired in the same way as the NEC by running the incoming neutral via the ground bar before it gets to the main breaker.

 

PEA document Groundwire Mk2 book-Manual.pdf

 

The important diagram from the above:-

 

[Docmartin]

Thank you for the correction.  ????

 

[Crossy]

12 minutes ago, Docmartin said:

Thank you for the correction.  ????

 

You are quite correct in detailing the issues of TN-C-S with (or without) MEN.

 

It's mitigated somewhat by having the neutral as the top wire of the 4 LV wires on the aerial distribution, hopefully it will be the last wire to get damaged.

 

[Docmartin]

Without trying to divert the thread - fyi there's been some recent incidents locally with broken incoming neutrals in domestic situations.

 

One poor little girl pulled a brass / bronze tap off an external wall due to muscle contractions (pulled the screws clean out of the plastic wall plugs or pulled the plugs out of the wall) and was brain and body-damaged as a result.

The solution would be to have a contactor in the meter that drops the supply if the neutral breaks but I'm not holding my breath.

[Crossy]

8 minutes ago, Docmartin said:

Without trying to divert the thread - fyi there's been some recent incidents locally with broken incoming neutrals in domestic situations.

 

You can make a lost-neutral detector using a regular RCD, there's a thread on the board somewhere.

 

[Docmartin]

That'd work.

[Formaleins]

2 hours ago, Moonlover said:

Had the same issue with our rented place in Udon Thani and from what I gathered, every house on the moobam was the same. Changing a fluorescent circular tube was a life threatening event until I sorted it out. When I looked into it, the wiring diagram in the consumer unit was wrong!

I wished I had wired the place myself looking back - But I had no idea how to get the nice straight lines laying the cables with those tacks and fold over aluminium retainers on the walls. I had wired a few kitchens back in the UK but it was all "Behind The Wall" so didn't need to be pretty. Looking back "Pretty" is not quite as good as having every socket wired in a different manner, borrowing Neutral connectors rather than wiring it properly and putting 2.5mm cables into a 6 KW Shower. In the past 20 years if I have learned nothing else from this place, I now know if you want to do it once and do it properly, do it yourself else be prepared to have to redo everything maybe three times until they get it right.

[Formaleins]

1 hour ago, Crossy said:

So you swapped the incoming L & N?

 

Your incoming L now really is L?

 

Since you have no MEN a L/N swap shouldn't lead to "nippy" earths,  have you been able to verify earth continuity from the heater to the CU? 

 

Yes, continuity from the heater is fine, I re did the cables with new 8mm and there is no issue there. I think it is looking OK for the heater, now just got to go through all the other garbage. (The heater was the worry as it is the big deadly one with the high load and water into the mix)

[Formaleins]

41 minutes ago, Docmartin said:

Without trying to divert the thread - fyi there's been some recent incidents locally with broken incoming neutrals in domestic situations.

 

One poor little girl pulled a brass / bronze tap off an external wall due to muscle contractions (pulled the screws clean out of the plastic wall plugs or pulled the plugs out of the wall) and was brain and body-damaged as a result.

The solution would be to have a contactor in the meter that drops the supply if the neutral breaks but I'm not holding my breath.

Hear you loud and clear! Over the years there has been probably thousands of needless deaths here in Thailand just because of stupidity and bad practice. I moan about the "Nanny State" now in the UK, but at least some of the things they force people to do actually saves lives. Things are getting better though, there are a lot more regulations here than when I was building my place. Sadly it always seems that a backhander can get round anything. (and the worse thing is they actually applaude it and think these people are Smart "Geng Loi"

[Moonlover]

16 minutes ago, Formaleins said:

I wished I had wired the place myself looking back - But I had no idea how to get the nice straight lines laying the cables with those tacks and fold over aluminium retainers on the walls. I had wired a few kitchens back in the UK but it was all "Behind The Wall" so didn't need to be pretty. Looking back "Pretty" is not quite as good as having every socket wired in a different manner, borrowing Neutral connectors rather than wiring it properly and putting 2.5mm cables into a 6 KW Shower. In the past 20 years if I have learned nothing else from this place, I now know if you want to do it once and do it properly, do it yourself else be prepared to have to redo everything maybe three times until they get it right.

Scary isn't it. We have a renovation ongoing right now, including new bathroom. I'll be watching sparky like a hawk.

[Docmartin]

25 minutes ago, Formaleins said:

 I moan about the "Nanny State" ....

Yes - electrical fascism is appropriate.

Unskilled people just can't be trusted with lethal energy.

I train electricians to be high voltage operators and am sometimes astonished by some of the things they say.

Procedures and standards are there for a reason.  

[Formaleins]

2 hours ago, Crossy said:

 

New installations are required to be MEN, wired in the same way as the NEC by running the incoming neutral via the ground bar before it gets to the main breaker.

 

PEA document Groundwire Mk2 book-Manual.pdf

 

The important diagram from the above:-

 

In this situation, having the incoming Neutral bonded to the Earth rail, what would be likely to cause the RCBO to trip......no don't say it "A borrowed Neutral?"

[Crossy]

10 hours ago, Formaleins said:

In this situation, having the incoming Neutral bonded to the Earth rail, what would be likely to cause the RCBO to trip......no don't say it "A borrowed Neutral?"

 

Actually, if the borrow stays on the controlled side of the RCBO it wouldn't. The fun starts when someone wants to retro-fit RCBOs, too often the local chap gives up as none of the beasts will stay engaged because of the habit of picking up any old neutral when making additions.

 

Even in our nicely wired condo all the aircons were wired L-E (it was TNS wired so it worked just fine), only noticed when I wanted to install an RCBO main switch.

 

Arggh!