House Wiring

[JAS21]

So we are back here again..soon for good.

Although in the ESI all my life I'm not too up on house wiring..especially in Thailand.

House is in a new complex and supposed to be well built!.

We have a 80A Supply Mitsubishi breaker. It feed to :-

Direct to Air Conditioning Units Dist Bd.

Direct to SAFE-T-CUT unit which has selection of direct/25/15/5 mA. This supplies the dist bd which has a selection of 10/16/20 and 32A MCBs

All the sockets have an earth (3-pin). The L and N positions are reversed to the UK.

I noticed that the 'electrician' wired most of the radials short. I got the company to undo every joint (they were twisted together) and to crimp instead.

I'm told that the earth rod is beneath the floor and clearly not visible.

We live off Prachachun not far from Nonthaburi Mall (Ngamwong). not sure about the spelling.

Anyone suggest a good and qualified electrician who would check earth loop impedence etc to ensure that all is ok

[Crossy]

Hi John.

Sorry I can't help with a qualified electrician in your area (if such a beast exists )

A couple of observations to bear in mind:-

We have a 80A Supply Mitsubishi breaker. It feed to :-

Direct to Air Conditioning Units Dist Bd. OK

Direct to SAFE-T-CUT unit which has selection of direct/25/15/5 mA. This supplies the dist bd which has a selection of 10/16/20 and 32A MCBs OK, but make sure the Safe-T-Cut is never run on 'direct' (no protection).

All the sockets have an earth (3-pin). The L and N positions are reversed to the UK. Correct, but please check that the ground is actually wired, it wouldn't be the first 3 pole installation with only two wires

I noticed that the 'electrician' wired most of the radials short. I got the company to undo every joint (they were twisted together) and to crimp instead. I hate this wiring technique, all to save a few metres of cable. It is perfectly possible to wire a domestic installation with ZERO joints. Any joint is a potential hotspot and fire although the crimped joints are infinitely better than the standard twist, I bet those crimps were performed with the correct crimp-tool, and protected with heatshrink tubing, not.

I'm told that the earth rod is beneath the floor and clearly not visible. How are you supposed to inspect and maintain the single most important connection in the entire installation? Does your installation have a MEN link between ground an neutral?

[Thaising]

Get a thai friend to call Metropolitan Electricity Authority office and request for house technician inspection assistance, you need to pay them some service fee. MEA call center tel : 1130 or visit www.mea.or.th

[JAS21]

Get a thai friend to call Metropolitan Electricity Authority office and request for house technician inspection assistance, you need to pay them some service fee. MEA call center tel : 1130 or visit www.mea.or.th

Thanks to both of you

I looked at the system. There are two droppers from the pole to the meter. These then feed into the roof and I guess end up at the 80 Amp Mitubishi breaker.

As before fed to Air Conditioning Unit Breakers..6 off 30A plus one spare.

Other cables to some type of earth leakage breaker and then to the Dist board. The dist bd has a 63A isolator.

1-There are twelve outgoing circuits from the dist. Bd.

2-Lighting

3-Lighting

4-Power socket

5-Power socket

6-Power socket

7-Not identified yet

8-Outside water pump

9-A spare

10-Supply for Shower heater (not connected at shower yet)

11-Supply for Shower heater (not connected at shower yet)

12- Our bathroom water heater

I have taped 10&11 off at Dist Bd 12 is just off..dont need that here!

Neutral block

Nine connections

Earth Bar

Six small cables (5 green and 1 yellow)

Plus Cable about half dia of incomer (to earth rod I believe)

Plus Slightly smaller red cable …attached to dist Bd earth screw. Earths the box.

The supply cable at the water pump has four wires…the blue is connected to the what appears to be an earth point.

The development was quite pricy..(Its called +Rich!)but I am not impressed with a lot of it..have had several water leaks due to fittings not glued etc etc

I am lost……..and I left my meter in the UK..so cant check anything.

I will get my wife to contact as suggested...But I just want to know what we have and what we should have...me to wife and wife to electricrician can loose a lot in transulation!!!!!!!!!

Maybe we should have the present earth rod replaced with one that we can actually see.

[Crossy]

I'd certainly go with the MEA inspector, but the installation should already have been inspected before it was connected to the supply (bet it was, not).

Cheapo DMMs are available all over (try Tesco or Carrefour), not wonderful but great for quick checks.

Something is not grounded, probably the two lighting circuits (not a disaster), but that still leaves one circuit with no ground connection, bet it's the water heater

In a new installation there should be a link between the ground bar and the incoming neutral (the MEN link), ask the inspector about it. If you still have the instructions for the Safe-T-Cut the wiring diagram shows it, otherwise print off the simple distribution board drawing from the website http://www.crossy.co.uk/wiring without the MEN link you are relying on the unknown quality ground to pull the Safe-T-Cut on a line-ground failure.

[JAS21]

I'd certainly go with the MEA inspector, but the installation should already have been inspected before it was connected to the supply (bet it was, not).

Cheapo DMMs are available all over (try Tesco or Carrefour), not wonderful but great for quick checks.

Something is not grounded, probably the two lighting circuits (not a disaster), but that still leaves one circuit with no ground connection, bet it's the water heater

In a new installation there should be a link between the ground bar and the incoming neutral (the MEN link), ask the inspector about it. If you still have the instructions for the Safe-T-Cut the wiring diagram shows it, otherwise print off the simple distribution board drawing from the website http://www.crossy.co.uk/wiring without the MEN link you are relying on the unknown quality ground to pull the Safe-T-Cut on a line-ground failure.

Thank you again.

I have suspecions about the testing done..I asked the then site guy about one year ago..said he did it but couldnt find figures at present..hes since gone. We have only been here a few day...

The workers have some bad practices..when they wanted to weld on my gate the disconnected at the supply meter (supply side) and joined the wires and supervision is just non. I had to stop the guy welding in sunglasses..his eyes were pretty red next day. The dumper truck has an ungarded drive belt inches from the seat..it is just unbelieveable

I have little faith in the company QA.

I only have the guarantee for the SAFE-T-CUT..not filled in and a little booklet in Thai which tells you about the guarantee.

I met the ladylast week ( young and rich) who ownes the company..it is not a small company...and has several sites at various stages...she is expecting a letter from me..I will await the test before I advise her again of a few little problems.

Is there any comback on the company if they have not tested before connection..in the UK its real bad news. They now have Part P which you have to complete a course to get qualified to do almost anything in the home. I cannot now even add a socket or even spur in th loft for a light in my own house.

I spent all my life in the ESI (generation) authorised for switching and earthing up to 400kV amounst other things)

The crimps (cable joints) were actually done with the correct tool..but no shrink wrap.

[JAS21]

I'd certainly go with the MEA inspector, but the installation should already have been inspected before it was connected to the supply (bet it was, not).

Cheapo DMMs are available all over (try Tesco or Carrefour), not wonderful but great for quick checks.

Something is not grounded, probably the two lighting circuits (not a disaster), but that still leaves one circuit with no ground connection, bet it's the water heater

In a new installation there should be a link between the ground bar and the incoming neutral (the MEN link), ask the inspector about it. If you still have the instructions for the Safe-T-Cut the wiring diagram shows it, otherwise print off the simple distribution board drawing from the website http://www.crossy.co.uk/wiring without the MEN link you are relying on the unknown quality ground to pull the Safe-T-Cut on a line-ground failure.

Thank you again.

Late extra.I find the wiring diag..it shows link from the N (before the breaker) to the consumer DB earth bar and then the connection to the earth rod. on Wed will phone elect company

I have suspecions about the testing done..I asked the then site guy about one year ago..said he did it but couldnt find figures at present..hes since gone. We have only been here a few day...

The workers have some bad practices..when they wanted to weld on my gate the disconnected at the supply meter (supply side) and joined the wires and supervision is just non. I had to stop the guy welding in sunglasses..his eyes were pretty red next day. The dumper truck has an ungarded drive belt inches from the seat..it is just unbelieveable

I have little faith in the company QA.

I only have the guarantee for the SAFE-T-CUT..not filled in and a little booklet in Thai which tells you about the guarantee.

I met the ladylast week ( young and rich) who ownes the company..it is not a small company...and has several sites at various stages...she is expecting a letter from me..I will await the test before I advise her again of a few little problems.

Is there any comback on the company if they have not tested before connection..in the UK its real bad news. They now have Part P which you have to complete a course to get qualified to do almost anything in the home. I cannot now even add a socket or even spur in th loft for a light in my own house.

I spent all my life in the ESI (generation) authorised for switching and earthing up to 400kV amounst other things)

The crimps (cable joints) were actually done with the correct tool..but no shrink wrap.

[JAS21]

Not had much success today yet..wife spoke to the SAFE-T-CUT company. He seemed not to know what a MEN link was. She told him about the drawing in the MI book. He said something about been done at the pole so not needed. We gave up.

Wife spoke to someone at MEA, no english speaker available yet..someone will call back. Thay said that in acomplex like this all will have ben agreed how to do.

l

Reading the notes on Domestic Electrical Wiring I saw a comment something like..after installing, when testing make sure that you have 220V L-E and 220V N-E. However I recall using a meter here, when the company did the cable reconnections, I got a strange reading, almost sure it was 0 volts N-E at the sockets. I'm going to get a tester later today and look again.

The step-down transformer is right outside our house. Theres the HV wires. Four terminal on top of the transf, one the star point? This is joined across the transformer to the LV side. We take our supply from that wire and one of the LV phases.

[chownah]

I could be wrong but if N-E means neutral to earth then the only way you could get 220 V between them is if the MEN link is disconnected. Isn't the MEN link a connection in the supply panel connecting the earth bar to the neutral bar? If so, then the MEN link effectively makes all of the earth wires connected to all of the neutral wires and thus make it impossible to read a voltage difference between them except, perhaps for some very small voltage indicative of the resistence in the path between the two points that the tester is touching.....but I could be wrong.

[Crossy]

Reading the notes on Domestic Electrical Wiring I saw a comment something like..after installing, when testing make sure that you have 220V L-E and 220V N-E. However I recall using a meter here, when the company did the cable reconnections, I got a strange reading, almost sure it was 0 volts N-E at the sockets. I'm going to get a tester later today and look again. You should get 220V L-N, 220V L-E and about 0V N-E. Remember L and N are the opposite way round to the UK.

[Crossy]

I could be wrong but if N-E means neutral to earth then the only way you could get 220 V between them is if the MEN link is disconnected. Isn't the MEN link a connection in the supply panel connecting the earth bar to the neutral bar? If so, then the MEN link effectively makes all of the earth wires connected to all of the neutral wires and thus make it impossible to read a voltage difference between them except, perhaps for some very small voltage indicative of the resistence in the path between the two points that the tester is touching.....but I could be wrong.

The MEN link connects the Earth bar to the INCOMING neutral (NOT the neutral bar). It is important that the link between N and E is on the SUPPLY side of any ELCB / RCCB / RCD/ GFI / Safe-T-Cut for correct operation of the protection device.

Check out the consumer unit diagrams on http://www.crossy.co.uk/wiring

[chownah]

I could be wrong but if N-E means neutral to earth then the only way you could get 220 V between them is if the MEN link is disconnected. Isn't the MEN link a connection in the supply panel connecting the earth bar to the neutral bar? If so, then the MEN link effectively makes all of the earth wires connected to all of the neutral wires and thus make it impossible to read a voltage difference between them except, perhaps for some very small voltage indicative of the resistence in the path between the two points that the tester is touching.....but I could be wrong.

The MEN link connects the Earth bar to the INCOMING neutral (NOT the neutral bar). It is important that the link between N and E is on the SUPPLY side of any ELCB / RCCB / RCD/ GFI / Safe-T-Cut for correct operation of the protection device.

Check out the consumer unit diagrams on http://www.crossy.co.uk/wiring

I went and looked and I see how you show to connect the link. Can you explain why and also is the rest of my post correct?

[Crossy]

I went and looked and I see how you show to connect the link. Can you explain why and also is the rest of my post correct?

OK Chownah, firstly, yes the rest of your post is 100% correct

This is why you connect the MEN to the supply neutral NOT the neutral bar:-

OK check out the piccy

Fig 1. Is normal operation, there is no ground current so with the MEN link in either position the Live current and Neutral current through the ELCB are both 1 Amp, no difference, no trip.

Fig 2. Now we have a fault in our appliance, a 35mA Live to Earth leak. With the MEN link connected to the neutral bar we still get the same current (1.035 Amps) through both legs of the ELCB, no difference no trip. EVEN WITH A FAULT!!

Fig 3. Same fault as in 2. With the MEN link connected to the incoming neutral we now get 1.035A in the live side of the ELCB, but we now only get 1.000A in the neutral leg, difference 0.035A (35mA) TRIP.

Whilst 2 is not inherently dangerous, it does mean that you can have a serious Live to Earth fault in the appliance without causing a trip (potential fire hazard).

NOTE. I have ignored the ground stake, its resistance is so much larger than the MEN link that it will make no difference to the operation in this case.

[chownah]

Crossy,

Thanks for the explanation. I understand that the wiring you recommend makes the main breaker/gfi combination more sensitive. I was wondering why this was recommended because in the US when I replaced my panel the MEN link was from ground bar to neutral bar...but I think this is because in the US they do not have (or did not have) main breakers that also acted as gfi.... The circuits protected with gfi have their own units...you can even buy electrical outlets that have gfi units built right in...but none of these have this super sensitve feature that you describe...I guess it isn't considered necessary in the US.

Thanks,

Chownah

[Crossy]

Crossy,

Thanks for the explanation. I understand that the wiring you recommend makes the main breaker/gfi combination more sensitive. I was wondering why this was recommended because in the US when I replaced my panel the MEN link was from ground bar to neutral bar...but I think this is because in the US they do not have (or did not have) main breakers that also acted as gfi.... The circuits protected with gfi have their own units...you can even buy electrical outlets that have gfi units built right in...but none of these have this super sensitve feature that you describe...I guess it isn't considered necessary in the US.

Thanks,

Chownah

There's nothing 'wrong' with having individual ELCB / GFI units, it's just a different, and perfectly acceptable (but possibly more expensive) way of doing it. So long as the link is on the supply side of any GFI's all will work correctly.

I suspect that having a distribution board with a combined GFI / Main breaker may be a difficult proposition with the US style bi-phase (2x110V) supply although I've never looked into it.

[SamSipEt]

On the subject of earth rods a friend recommended a seperate rod for the shower water heater positioned as closely as possible to the unit. Apparently the copper rods are not that expensive and he said that this is much safer than relying on the buildings standard earthing. Would this be true or over kill?

[chownah]

Crossy,

Thanks for the explanation. I understand that the wiring you recommend makes the main breaker/gfi combination more sensitive. I was wondering why this was recommended because in the US when I replaced my panel the MEN link was from ground bar to neutral bar...but I think this is because in the US they do not have (or did not have) main breakers that also acted as gfi.... The circuits protected with gfi have their own units...you can even buy electrical outlets that have gfi units built right in...but none of these have this super sensitve feature that you describe...I guess it isn't considered necessary in the US.

Thanks,

Chownah

There's nothing 'wrong' with having individual ELCB / GFI units, it's just a different, and perfectly acceptable (but possibly more expensive) way of doing it. So long as the link is on the supply side of any GFI's all will work correctly.

I suspect that having a distribution board with a combined GFI / Main breaker may be a difficult proposition with the US style bi-phase (2x110V) supply although I've never looked into it.

A thought that has occured to me is that with a MEN link wired in the recommended way (connecting the earth bar to the neutral at the supply side of the ELCB/Main breaker) even when you open the main breaker your wiring is still connected to the supply wiring via the MEN link. This would not be a problem if the supply side was operating properly but in the event of a problem on the supply side you could have a voltage enter your wiring system even if your main breaker was open. Have people considered installing a cutout switch on the MEN link so that you could be sure of complete isolation from the supply lines in case of an emergency or for maintenance and repair of your system?

Chownah

[chownah]

On the subject of earth rods a friend recommended a seperate rod for the shower water heater positioned as closely as possible to the unit. Apparently the copper rods are not that expensive and he said that this is much safer than relying on the buildings standard earthing. Would this be true or over kill?

I had what you described when I had an electric shower heater...I now use gas. I believe that I did this because it was the recommendation that came with the electric shower heater...but I can't remember for sure. Anyway...I believe that people here have warned against having two earth rods in that it is theoretically possible that there could be a difference in voltage between them and could thus cause an electric current to flow through someone who was touching a metal gate or something similar. I think it was also pointed out that this problem could be eliminated if a wire bonded the two earth rods together directly. I hope someone comes on and gives an explanation of this problem since I would like to hear them run through it again to help me understand it better.

Chownah

[Crossy]

A thought that has occured to me is that with a MEN link wired in the recommended way (connecting the earth bar to the neutral at the supply side of the ELCB/Main breaker) even when you open the main breaker your wiring is still connected to the supply wiring via the MEN link. This would not be a problem if the supply side was operating properly but in the event of a problem on the supply side you could have a voltage enter your wiring system even if your main breaker was open. Have people considered installing a cutout switch on the MEN link so that you could be sure of complete isolation from the supply lines in case of an emergency or for maintenance and repair of your system?

Chownah

This is one of the reasons that MEN / PME didn't catch on in the UK until recently (last 10 years or so), there is the (albeit remote) potential for voltages on the neutral.

Provided the MEN system is correctly implemented by the supply authority (MULTIPLE ground points on the neutral) it is highly unlikely that the neutral will ever get more than a few volts above ground.

The remote possibilty of neutral voltages far outweighs the increased safety from electric shock / fire provided by the MEN system.

If your incoming breaker is NOT a combined MCB / ELCB you can link to the swiched side without compromising your safety significantly BUT you are then removing one of the MULTIPLE earth points that MEN relies upon when you open your breaker.

[Crossy]

I believe that people here have warned against having two earth rods in that it is theoretically possible that there could be a difference in voltage between them and could thus cause an electric current to flow through someone who was touching a metal gate or something similar. I think it was also pointed out that this problem could be eliminated if a wire bonded the two earth rods together directly. I hope someone comes on and gives an explanation of this problem since I would like to hear them run through it again to help me understand it better.

Chownah

OK, you are correct in your assertion that if you have multiple earth rods they MUST be connected together via your earth bar in the consumer unit.

The reasoning goes something like this.

The mass of the earth is quite a high resistance. It is possible that if there is a large ground current flowing (possibly from someone elses fault) there could be a significant voltage between your ground rods. Now, of course, you need to touch both grounds together to get a shock (unlikely, but not impossible). All possibilty of shock is removed by linking the grounds via the earth bar, of course it also adds MEN protection to your water heater.

There are documented instances from the early days of electicity distribution of horses being startled by ground currents. In those days the distribution used a technique known as Single Wire Earth Return (SWER) which used the ground as one of the conductors (to save copper). Obviously in these instance ALL the load current flows through the earth and can produce significant voltages say between front and back legs, particularly if the animal is close to the grounding rod.

All in all, the risk from having multiple grounds is small, but the cost of the wire to link the rods is also small and removes all danger. as always UP2U

[JAS21]

I could be wrong but if N-E means neutral to earth then the only way you could get 220 V between them is if the MEN link is disconnected. Isn't the MEN link a connection in the supply panel connecting the earth bar to the neutral bar? If so, then the MEN link effectively makes all of the earth wires connected to all of the neutral wires and thus make it impossible to read a voltage difference between them except, perhaps for some very small voltage indicative of the resistence in the path between the two points that the tester is touching.....but I could be wrong.

The MEN link connects the Earth bar to the INCOMING neutral (NOT the neutral bar). It is important that the link between N and E is on the SUPPLY side of any ELCB / RCCB / RCD/ GFI / Safe-T-Cut for correct operation of the protection device.

Check out the consumer unit diagrams on http://www.crossy.co.uk/wiring

I have spoken to MEA via my wife ..they quited something like 3800Baht to inspect the house. Have not progressed this yet. Am holding on until I have checked what I can for myself. They couldn't guarantee to send a gy who speaks english anyway.

Yesterday I met the 'sort of boss' who sells SAFE-T-CUT at an exibition...he is arranging to send one of his guys arount to check out their equipment FOC..very kind of him.

Today my Fluke came from the UK via a friend. So I will check out what I can..each radial back to the consumer unit esrth and try and find out what is not earthed.

This is just to say I haven't let the problem drop..thanks all