Grounding: Earth And Zero Connected

[Crossy]

Getting a rod down to 5 ohms will be difficult and not really necessary with an RCD. Anything < 300 ohms will be achievable and will work just fine. Anyway, few people have the correct kit to actually measure the ground resistance.

I would be tempted to leave the N-E link off at least for now and rely on the RCD and local ground rod.

[dhrobertson]

Totally agree! However, nuisance tripping may be an issue.....

[electau]

If your polarity test was correct and you still have 3 amps flowing in the main earth conductor you may have a high resistance in the incoming neutral. TN-C-S System.

TT system you may have a fault on a final subcircuit and it is connected to an MCB, the protective device will not trip in this case. An RCD will.

[electau]

The purpose of the main earth and electrode is to hold the touch voltage down to less than 50VAC if the incoming neutral is broken. It does not normally carry current when the neutral is bonded to the earth with a TN-C-S system.

[mistitikimikis]

With such a high current flowing to ground from the neutral, I think there is a problem with the system ground at the transformer star point. Neutral is generally bonded to ground at the transformer and then every third pole in Thailand. Get local PEA to check this.

TN-C-S is strongly recommended as it is very difficult to get god enough ground performance from local ground rods. Link should be not less than 50% size of the feeders and should be made at the origin of the supply only (at your main load panel). Local ground rods should also be installed. Add rods until you get a resistance to earth of less than 5 ohms.

ELCB/RCD/RCBO protection is required for all types of water heater in Thailand. You may want to consider adding a main ELCB (Safe-T-Cut or similar) to protect the entire installation.

That's why I combine the question with the frequent dips / cuts after down-poors.

"Neutral is generally bonded to ground at the transformer and then every third pole in Thailand." I don't even trust their third poles anymore knowing the culture of all these providers and / or their staff!

I want to extend the number of rods and connected already the iron floor-mats of about 50 square mtrs. from the the house-extention during the construction. The high potential at my zero can be caused by a far better grounding-installation than my neighbours............. i.e. their "failures" are flowing to my installation.

I never forget that I saw once in the house I rented a couple of years ago that I saw a earth-rod outside wired to the breaker-cupboard. But................ from there absolutely NOTHING to contacts, i.e. there was not any earth-contact in the house!

As I said before I trust here not any instant water-heater either their installation: have seen enough "earth-connections", even in hotels............ (for example earth-wires of not more than 0.75 / 1 square mm.). Plus the fact of their power-load is heavy and their water-flow lousy. For more security and a really full (hot)water flow I installed an electric storage tank ("boiler").

The main-breaker will be 40 Amps. (the previous "electrician" wanted to install 100 Amps.........................) and the ELCB not more than 40 mAmps. However, indeed, I'm not sure if there shall be no tripping-problems now. I can remember that in older days, when just in use, the kitchen and its utensils was excluded in the ELCB because of the easy-tripping.

[mistitikimikis]

Getting a rod down to 5 ohms will be difficult and not really necessary with an RCD. Anything < 300 ohms will be achievable and will work just fine. Anyway, few people have the correct kit to actually measure the ground resistance.

I would be tempted to leave the N-E link off at least for now and rely on the RCD and local ground rod.

"few people have the correct kit to actually measure the ground resistance."

Yes, I definite separate earth and zero in the next few days! I can only rely on myself and my imported stuff which is definite not Chinese / local. In the mean time let's wait for the provider and his excuses he is able to invent...............

Anyway, we are here in BKK and not somewhere in the far North-East

[mistitikimikis]

A thought, since the N-E link is in the CU and therefore on the consumer side of the meter are those 3 Amps going to cause the meter to spin?

Once I checked that and didn't notice something. I think to get the meter registering I think you need at least the phase if not included with the zero.

I stick for the time being to the conclusion that I'm functioning as a guest for neigbouring houses concerning their "safety". Why am I measuring (now 4 Amp.), but Friday-evening all of a sudden 10 A.??? (Unfortunately it was too late to check at that time the tension)

[mistitikimikis]

The purpose of the main earth and electrode is to hold the touch voltage down to less than 50VAC if the incoming neutral is broken. It does not normally carry current when the neutral is bonded to the earth with a TN-C-S system.

True enough!

[mistitikimikis]

If your polarity test was correct and you still have 3 amps flowing in the main earth conductor you may have a high resistance in the incoming neutral. TN-C-S System.

TT system you may have a fault on a final subcircuit and it is connected to an MCB, the protective device will not trip in this case. An RCD will.

"high resistance in the incoming neutral" That was what somebody somewhere-else was already suggesting many months ago: the 0-supply wire could be insufficient!

No, a breaker shall never react at that and the use of a RCD I can forget forever as long as this problem hasn't been solved!

[mistitikimikis]

As I have to go now and to sort something out with another local highly sophisticated provider TRUE I put my problem on hold for a moment.

During my recent philosophy I thought it's better to keep zero and phase connected with a proper earth because when I divide the mess I'm only relying on the RCD and I don't know (yet) if that one is working properly now. At least I diverse the zero-@#$% to the earth. And when I'm starting redoing the breakers I think I make a short-cut switch zero to earth for the time being until I'm sure about the RCD. Otherwise I have to start (re)wiring again. I know VERY amateuristic but OK.

[electau]

A high resistance on the incoming neutral could be at the meter, or at the connection to the network conductors. It may be a burnt or corroded connection. TN-C-S

One does not have to check the resistance of the ground (soil) all that is required is that the electrode is driven to an depth of at least 1.2/1.8M.

Do your lights dim when load is applied? This can indicate a faulty neutral.

You should check each circuit for correct polarity and insulation to earth, have you got 30mA RCD protection on all circuits?

　

　

　

　

　

　

Edited March 27, 2012 by electau

[mistitikimikis]

Thanks! I will start asap to (re)do the breakers and their (house)distribution.

Anyway, the failure is showing 100% outside without any connection to the house.

Dimming lights I cannot notice (anymore) as they only sell now the cost saving "long lasting (???)" lamps and when they dim, indeed they dim due to electricity-supply failures during a down-poor. (the tension dives than to about 160 Volts....). Normally I cannot notice.

Like everywhere with the big Thai providers one cannot get a proper "service". We went to their office Ramintra/Minburi and there they are only to collect money, the girl at the counter didn't look even up from her keyboard, gave a general telephone-number, instructed us to phone which resulted in waiting, waiting, waiting at the phone-answering robot, the whole holy day.

I'm afraid that whenever a "technician" can be contacted there will be a usual @#$%-excuse and/or turning the failure at me. They never admit their mistakes and/or want to spend "unnecessary" money : TIT.

Yesterday I noticed a current-increase to 8 Amp. but was just too late to check the tension.

Indeed, I'm afraid when I install the ELCB it will trip every time and cannot be used and when there is an accident it will be in the news and afterwards

[Crossy]

Indeed, I'm afraid when I install the ELCB it will trip every time and cannot be used and when there is an accident it will be in the news and afterwards

Provided that any link between N and E is on the PEA side of the ELCB then it will work properly to protect your installation.

[mistitikimikis]

Indeed, I'm afraid when I install the ELCB it will trip every time and cannot be used and when there is an accident it will be in the news and afterwards

Provided that any link between N and E is on the PEA side of the ELCB then it will work properly to protect your installation.

Wait a minute (ok, in Thai it means a bit more). I'm completely separating the two wires passing the garden from the main-supply to the breakers to prove easier that's not me. I can only check the meter for spinning again. Unfortunately I cannot prove my theory (measure) near the meter as there is no earth coming down the pole at all.

When you hear an ambulance going to Symphaet-hospital you can be sure that's this time my PEA by being upset and/or making a mistake..................

[mistitikimikis]

In the mean time I discovered that the electrician messed with the wires coming from the mains leading to the house as he used two cables with an outside diam. of 16 mm. (which isn't necessary in my opinion and even thicker than the wires coming from the electricity-pole...........) and the "same" wires entering the house are 16 mm. (phase) and........... 12 mm. (zero), so he made a connection under the soil with cello-tape for sure. I don't know if there is some resistance due too that connection.

Can you give me your meaning about your recommended (inside) diam. The length is about 17 mtrs. In Spain we had the rules that the supply in between the meter-road cupboard and the house had to be 6 sqmm. diam. which is sufficient enough I think.

[Crossy]

The cable from the meter to the house should be a minimum of 10mm² if you have a 15/45 meter, 6mm² would be ok on a 5/15 meter. If you have a long run a larger cable will be needed to minimise volt drop.

Hmmm, if you have an underground 'Thai style' connection this could be the cause of your issues (high resistance neutral). Time to get the digging kit out.

[mistitikimikis]

The cable from the meter to the house should be a minimum of 10mm² if you have a 15/45 meter, 6mm² would be ok on a 5/15 meter. If you have a long run a larger cable will be needed to minimise volt drop.

Hmmm, if you have an underground 'Thai style' connection this could be the cause of your issues (high resistance neutral). Time to get the digging kit out.

Surprise!

I better spend a bit of money and go tomorrow to a supplier (which will NOT be Home"Pro" for sure ) to buy new cable according to your advice, install it and see what is happening.

To-morrow i'll continue my job:

http://www.antoni-uni-photography.com/THAILAND/TECHNICAL-STUFF/Various/16175222_p7gJ73#!i=1768556708&k=FmdqhPn&lb=1&s=A

http://www.antoni-uni-photography.com/THAILAND/TECHNICAL-STUFF/Various/16175222_p7gJ73#!i=1768556966&k=4txqzkq&lb=1&s=A

Keeps avoiding me to visit lower-Sukhumvit

http://www.antoni-uni-photography.com/THAILAND/Bangkok-strolls/Bangkok-Sukhumvit-Nana/10520844_nXzvVF#!i=1766533467&k=Ws5hDPD

[mistitikimikis]

"Hmmm, if you have an underground 'Thai style' connection this could be the cause of your issues (high resistance neutral). Time to get the digging kit out"

I don't think the problem is there but throwing a whole new cable without is worth as my intention is to split zero and earth and I can rely on my electricity-provider . Anyway, the "Thai style" connection under the clay was more than one month inundated by sewer-polluted flood-water.................... I'm very curious about how it looks now!

[dhrobertson]

15(45) kWh meter is desiged to supply 15A continuous, 45A maximum.

Ampacity for underground cables in non metallic duct is 36A for 6mm2 and 50A for 10mm2. I noted your 40A breaker so 10mm2 is fine unless the distance requires a larger size to avoid excessive volt drop(These relate to the cross sectional area of the copper conductor).

Cable type should be NYY!!!

The underground joint may well be the root cause of your problem! Photos please!

The ground conductor should not be less than 50% of the size of the main feeders. In your case 6mm2 should be fine. I usually use an array of ground rods each 3m long and burried to 0.5m.

I do recommend TN-C-S system and use this all the time here. The link should be made using 6mm2 in your case. How far away are you from the transformer? Have a look at the poles inbetween. Can you see any ground conductors from neutral to ground?

The problem with using a TT system with no link and a single main RCD is nuisance tripping. To provide protection against fatal shock in general requires an RCD rated at 30mA. However, certain types of equipment have significanjt leakage currents. Switching power supplies found in computers for example may have leakage currents of 5mA or so. Also ovens, electric hobs etc may have small leakage currents. So the risk of nuisance tripping is quite high.

One solution if you don't fancy TN-C-S is to use TT with a main RCD rated at say 300mA. This would result in touch voltages not exceeding 50V even if the ground rod impedance is as high as 166 ohms (very poor) while avoiding nuisance tripping. You could then protect individual circuits with 30mA RCBOs mounted in your load panel to protect circuits supplying water heaters and socket outlets.

[mistitikimikis]

"15(45) kWh meter is designed to supply 15A continuous, 45A maximum."

In fact that was in Europe same same that's why a maximum main-breaker of 40 Amps (slow). Believe it or not the first "electrician" started with a main-breaker of 100 Amp.............. I kicked him out.

"burried to 0.5m" which I wanted to do already to avoid corrosion, here they "hide" the whole lot. Might be I look for some thick grease as protection.

"How far away are you from the transformer" about 300 meters from a sub-transformer. And they grounded every third pole, but.............................

There is a TN-C-S; again, I'll separate zero and earth. The tripping I can experience afterwards.

Next week I'll try again to let the electricity-provider change my house-connection to another phase in their distribution but I'm afraid they will fail and ignore my demand.

To get the material here (in BKK) is another question, hopeless knowledge, interest, service even in the outlets where they are supplying the installers. And not to forget the language. Early next week I start again.

In Europe (Spain) I started already with a very sophisticated and expensive installation to avoid damages by atmospheric (over)-tensions / sparking which I shall not do here. I start, as showed, in the second phase and try to protect the third phase, the contacts, also a bit where it's necessary with low protection. It means that I extend the earthing also a lot more.

One question remains if I can stick to the single-pole breakers as I don't have enough space to replace them all by double-pole. Only the main-breaker can be double.

http://www.antoni-uni-photography.com/THAILAND/TECHNICAL-STUFF/Various/16175222_p7gJ73#!i=1771580132&k=4gSLV3p&lb=1&s=A

Anyway the most annoying part of the whole story is to get the chosen parts together in this country................

[dhrobertson]

Ground rods should be 3m long copper clad steel. Drive them down to 0.5m BELOW the surface. We need to maximise surface contact with the earth. Usually, 3 rods in a 3m triangular array are sufficient for a very good ground.

Only use double pole, double width breaker for main breaker. All others can be single width. If you use some 30mA RCBOs(known as ELCBs) to protect individual circuits, these connect to both phase and neutral but only disconnect the phase. These are single width devices.

If you do not use TN-C-S (I recommend that you do) and wish to rely upon the ground rods alone (TT system) use a 300mA RCD at the main incoming. These are available as a combined 40A 2 pole breaker and 300mA RCD (in other words, an RCBO)

Do investigate the neutral connection. I suspect there may be a high resistance joint here. This will result in high ground currents in a TN-C-S system.

Good luck!

[Crossy]

The top of the rod and it's connection to the ground wire must NEVER be in contact with the earth. This is purely to prevent corrosion, if you put it in an earth pit (a length of 4" PVC soil pipe) it can be below ground level. Paint the connection with acrylic paint to help prevent corrosion.

Most regulations suggest that a single 2m rod is adequate (indeed many regulations prohibit multiple rods) although testing of the actual ground is always advised. The rod can be copper ($$$$), copper clad steel or hot-dip galvanised steel.

Do NOT link N and E unless you KNOW that TN-C-S with MEN/PME is implemented in your area. TT with an RCD is safer than the potential issues of having the only N-E link on the system.

[dhrobertson]

At the risk of causing further confusion, which I want to avoid......

Yes, a ground pit is good practice. However, normal procedure here is to use exothermic welding fo connect the ground conductor to the rods and burying the lot.

Thai EIT code states that, with normal soil conditions, a resistance to earth of less than 5 ohms is required. This is NOT easy to achieve with a single ground rod.

We have already established that every 3rd pole has a ground connection in this particular case and that is in line with Thai practice.

The issue that I have with TT systems is this:-

Often an RCD rated at 30mA is selected to provide system wide protection against shock. As soon as nuisance tripping occurs, which it often will, the end user often disables the RCD or dials in a value like 500mA. I often see Safe-T-Cuts set to 500mA or off.

In general, these are NOT, in my opinion, issues for the DIY person. I would always recommend getting a qualified engineer or technician to deal with these sort of issues.

Finally, and at the risk of sounding pedantic, the size of the ground conductor is important. A ground conductor can be a fire hazard if required to handle a large current due to a fault. In general,assume not less than 50% of main feeder size.

[Crossy]

If you find a qualified engineer / tech doing domestic installations on 400 Baht a day let us know, all the good guys are on major projects or O&G earning megabucks.

For most of us DIY is the only option when Sparky Somchai owns two screwdrivers and a pair of industrial scissors.

Do you have a copy of the Thai EIT code for domestic installations? Seems to be a rare beast, an ISBN or other reference would be very handy.

Out of interest where is 'here' in regards to using exothermic welds to the ground rod/mat? I've never seen it used in a domestic installation, invariably clamp and bolt.

[dhrobertson]

Exothermic welding is referenced in the EIT code and shown on most Thai EE drawings. problem is that it is often badly executed with severe porosity and inclusions. Frankly, you are correct and brass compression joints are often more reliable in my opinion.

I work as a consultant all over Thailand but most frequently in Phuket. My clients need to comply with the local code but require the additional comfort of complying with international standards (IEC 60364). Fortunately, with increased harmonisation, most first world codes are very close (BS, AS/NZS, D DIN, FN etc). Sadly, Thailand started out with a code based on the American NEC code which is very different (witness black phase and white/grey neutral).

The Thai EIT Code 2002 is quite hard to get hold of. I usually get multiple copies from Chulalongkorn University bookshop. ISBN 974-7197-59-1. They're only 300TBT per copy and I give them away to Thai "electricians". The scarcity of, and lack of knowledge of, this book is the single most important fact underlying the poor standards here. (It's in Thai but the numbers are in English! Ha!)

Trying to impart useful information to people without going into too much technical detail is difficult and frankly fraught with danger. The UK tightened up on DIY electrical work some years ago and now certification is required.

My main aim in replying occasionally on web boards is to try and head off dangerous misunderstandings. Sadly, I all to frequently end up as an expert witness when there has been a fatal electrocution......

[Crossy]

Great information DH. I wonder why they make it so difficult to find. I scatter copies of the PEA 'groundwire' http://www.pea.co.th/pdf/groundwire.pdf document to any an all Somchai sparkies I encounter, most have never seen it.

For 300 Baht I'll see if I can get a copy as distil out the information that's useful to us involved with domestic stuff.

[longball53098]

One Google search produced this link,,,,,,,

http://www.eit.or.th/book_detail.php?id=17&gid=2

[mistitikimikis]

At the risk of causing further confusion, which I want to avoid......

Yes, a ground pit is good practice. However, normal procedure here is to use exothermic welding fo connect the ground conductor to the rods and burying the lot.

Thai EIT code states that, with normal soil conditions, a resistance to earth of less than 5 ohms is required. This is NOT easy to achieve with a single ground rod.

We have already established that every 3rd pole has a ground connection in this particular case and that is in line with Thai practice.

The issue that I have with TT systems is this:-

Often an RCD rated at 30mA is selected to provide system wide protection against shock. As soon as nuisance tripping occurs, which it often will, the end user often disables the RCD or dials in a value like 500mA. I often see Safe-T-Cuts set to 500mA or off.

In general, these are NOT, in my opinion, issues for the DIY person. I would always recommend getting a qualified engineer or technician to deal with these sort of issues.

Finally, and at the risk of sounding pedantic, the size of the ground conductor is important. A ground conductor can be a fire hazard if required to handle a large current due to a fault. In general,assume not less than 50% of main feeder size.

"qualified engineer or technician" (who is interested in small jobs and in his work)

[mistitikimikis]

Reading all this with big respect and helpful not to get in dangerous situations, WHERE one finds, even a "professional" wholesaler (I'm not speaking about Home"Pro" "mai mee"), with this stock, interested and skilled sales-staff and even an interested owner to sell those "difficult" things??? A supplier where the whole low-paid Burmese sales-staff leaves you alone with your "difficult" demand and the Taiwanese owner isn't even interested to avoid that you leave his shop empty-handed and your whole shopping-list (Minburi) or a "respectful" wholesaler where the staff hands you a cable over of 6 mm2 (YES, the outside diameter............) but the wire 4 mm2 after half an hour waiting for the queue (soi next to Symphaet Ramintra). And same same in a big shop Ramintra next to Symphaet manned with fully uninterested sales-staff. We know what we need but to get what we need is a big and frustrating challenge.