How to check your earthing system

[Forkinhades]

You want fused leads in case of lightening strike as you are testing a socket? Which takes seconds to do.

God give me strength

Sent from my SM-G900F using Thaivisa Connect Thailand mobile app

Seconds are very long time relatively speaking. God won't give you strength but a good priest may give the last rites!!

Take the piss all you want. I take electrical safety VERY seriously.

Of course fused leads would be no good in the case of a lighting strike,in fact with a direct lightning strike you are in real trouble.

However a direct hit is quite rare, but lightning striking a powerline or a static discharge (yes wind can create a static charge) or even an HV switching operation, many kilometres away can create a very high short duration voltage pulse (with current in the kilo amp range) that can destroy the lower rated meters. If you are making a measurement at the same time......luck of the draw. With a CAT III or CAT IV meter, the chances are you would never even know it happened.

I merely made mention of the fused leads to give some guidance to the amateur sparkys who read this thread. I have repaired many analogue meters in the old days from people measuring current while ohms are selected. The fused lead can help save the meter (and the user).

As I have posted on TV before, Fluke have a very good video about multimeters and show a few cheaper Cat I and Cat II meters being destroyed by a high voltage impulse - measured in micro/milliseconds. I would recommend watching it.

You've never seen the aftermath of an arc fault? - I have - not a pretty sight. One bloke had his eyes fused shut for quite a while, another bloke was luckier as he had PPE on.

Meggar have in built fuses, and technology that offer audible warnings that your leads are on live terminals when on the ohm setting.

The amateur sparky is not going to spend in the region of 50K Baht for this type of equipment.

[SeaVisionBurma]

A couple of posts (off-topic, nonsense) have been removed.

Stick to sensible contributions please

[tifino]

I had a sparky, a while back, mouth off to me the lowly householder, not to do regular manual tests of RCB or ELCB, as it wears them out?

While on this visit, he was in the process of replacing one that had been tripping a lot, due to some water ingress into an external power outlet box.

[jcisco]

Looks like a reasonable job, shame he didn't stick to an internationally recognised colour code

I don't know Crossy. when did exposed conductor pass as reasonable and safe

[Crossy]

Looks like a reasonable job, shame he didn't stick to an internationally recognised colour code

I don't know Crossy. when did exposed conductor pass as reasonable and safe

It wouldn't pass muster back home, but since the exposed conductors are in a box that needs a tool to open they present zero hazard to the normal user.

If someone has the lid off they should be aware that all conductors should be considered as live unless proven otherwise.

[Anthony5]

Just want to jump in with a quick question. The other day when I switched on an outside light, the breaker opened, but the safety cut of that circuit stayed engaged.

I tested the safety cut with the little button and it functions.

Is this normal?

[Crossy]

Just want to jump in with a quick question. The other day when I switched on an outside light, the breaker opened, but the safety cut of that circuit stayed engaged.

I tested the safety cut with the little button and it functions.

Is this normal?

Depends why the breaker opened, if it opened on overcurrent (duff bulb causing a short) it's possible that it acted quicker than the Safe-T-Cut.

Discrimination between safety devices can be very difficult to predict, just be happy that one of them acted.

[jcisco]

Looks like a reasonable job, shame he didn't stick to an internationally recognised colour code

I don't know Crossy. when did exposed conductor pass as reasonable and safe

It wouldn't pass muster back home, but since the exposed conductors are in a box that needs a tool to open they present zero hazard to the normal user.

If someone has the lid off they should be aware that all conductors should be considered as live unless proven otherwise.

I can accept that, however I also accept that everytime that something is idiot proofed or moved to the realms of improbability. The universe builds a better idiot and if they come to grief on that installation, natural selection will be the culprit.

[KhnomKhnom]

Just saw this on Amazon UK

http://www.amazon.co.uk/Martindale-EZ150-Check-Impedance-Indicator/dp/B002L651LY/ref=sr_1_4/276-8035793-9097428?ie=UTF8&qid=1388905735&sr=8-4&keywords=martindale+tester

That is just an awesome piece of kit

RS Malaysia might do one, but their site is down at present.

Also available from RS Thailand:

http://thailand.rs-online.com/web/p/mains-socket-testers/7190901/

but I like this one better:

http://thailand.rs-online.com/web/p/mains-socket-testers/7190905/

This is where the uninformed give dangerous advice. The meter in question is rated at category 2 only. Could be good for working on cars.

The slightest fault - lightning strike, overvoltage or static discharge on the system will have this blow up in your face. Agreed unlikely for the domestic user but I will stick with Cat 4 meters, Type A fused leads thanks!

Thanks for the correction. Overall, I am amazed at how much wrong, and even dangerous, info is given on TV and the pinned info is as useful to the average homeowner as those things on a bull.

[KhnomKhnom]

This pinned stuff asserts, I guess from the phrases used, that if the resistance in a ground is too low, something will blow up. This is the height of non-sense.

[KhnomKhnom]

I had a sparky, a while back, mouth off to me the lowly householder, not to do regular manual tests of RCB or ELCB, as it wears them out?

While on this visit, he was in the process of replacing one that had been tripping a lot, due to some water ingress into an external power outlet box.

Like any switch, the breaker will have a finite number of times to switch it on and off prior to failure. Probably the manufacturer of the breaker knows the range of this information. In a well designed and made breaker, higher cost, your number of cycle times should be in the thousands.

The breaker is not made to be a switch, but unless you test it three times a day for several years, your breaker will still be ok.

Under load, the switching off and on will also likely cause some minor arc which has the possibility of either building up insulating carbon on the conducting surfaces or pitting of those surfaces due to melting via the hot arc for a very short time. The switch should be built with a wiping action to wipe away carbon when switched. Hopefully, there is not a 10amp or more load on that circuit and if not, a melt arc should also not happen. Even 10amp once or twice should be ok.

[KhnomKhnom]

Every socket I ever looked into in Thailand has two wires the same colour for the power, and if you are lucky (not normally) a different colour for earth.

The concept for neutral and phase wires may work in the west, but not here.

Couple of years ago I bought a extension bar with a little light on it that tells me if earth is OK, it cost about 400 baht and works good.

The better terms are hot and neutral.

[KhnomKhnom]

OP, just where did you reference the earth being too low can cause an explosion? In fact, as far as I'm aware, the lower the better.

He is talking about a specific component failure which will be a bigger failure if the resistance to earth is very low. That type of failure is so rare that I would estimate the proverbial millionS to one chance.

[KhnomKhnom]

Dear reader of the electrical info on thaivisa........

There is so much wrong, contradictory, and confused and confusing information here that if you read it all, as I have, you will have no guidance about which writing to obey. I recommend that you do not use this site for solid info about electrical wiring, etc., in Thailand.

All the info a normal homeowner needs is not all in one place and what is there is either in EMQTC non-world standard abbreviations over blown gobbly goop or does not apply to your situation totally.

I can say one thing for certain... do not yourself connect Thai two-wire electric supply wires, the incoming power wires, to earth/ground/dirt.

Do not connect any ground to your neutral wire, usually white and do not connect the other wire, hot/black, to any ground.

I should write the homeowners guide to grounding in layman's terms but not on thaivisa because it will just be contradicted by the local guess specialists.

[Forkinhades]

^ The information that we offer here is a direct translation of the Thai code, and indeed is a requirement for any new installation to be connected.

You should not be confused with the codes of your relevant country.

The facts that I offer are indeed true, and can happen.

I do not agree with the way the PEA (Electric Company) tries to turn a 'TT' system into a a 'TNCS' system with the onus of the MEN link on the consumer, which of course in the UK would be totally illegal to do.

If you would like to start a new thread with such concerns as to why you should not connect Neutral to Earth, then I and Crossy will be happy to debate. Or even over a few beers?

[Crossy]

I have linked to this document all over the place http://www.crossy.co.uk/Handy%20Files/groundwire.pdf

It really is worth a look to see how it's supposed to be done here. It's an official PEA document, you may be able to get your own copy from your local PEA office.

[Forkinhades]

This pinned stuff asserts, I guess from the phrases used, that if the resistance in a ground is too low, something will blow up. This is the height of non-sense.

I am talking about the amount of current that will flow under fault conditions. Most protective devices can only handle 6kA of fault current.

If the system was TT then the value of earth will never be low enough to generate such currents. However once MEN is implemented then the value of the earth is lowered quite considerably.

I had my earthing arrangements changed from TT to MEN, and the value of earth was reduced by 20 ohms, although a significant reduction, it is still at an acceptable level where the MCB would open under fault conditions, whereas it would not with a TT system. This is where the Safety-Cut must be used for a TT system.

Thailand seems to want the best of both systems by insisting on a Front End Safety-Cut and MEN connection.

[Forkinhades]

I have linked to this document all over the place http://www.crossy.co.uk/Handy%20Files/groundwire.pdf

It really is worth a look to see how it's supposed to be done here. It's an official PEA document, you may be able to get your own copy from your local PEA office.

I just wish more people would try to understand that document, before they decide to comment.

[Forkinhades]

Dear reader of the electrical info on thaivisa........

There is so much wrong, contradictory, and confused and confusing information here that if you read it all, as I have, you will have no guidance about which writing to obey. I recommend that you do not use this site for solid info about electrical wiring, etc., in Thailand.

All the info a normal homeowner needs is not all in one place and what is there is either in EMQTC non-world standard abbreviations over blown gobbly goop or does not apply to your situation totally.

I can say one thing for certain... do not yourself connect Thai two-wire electric supply wires, the incoming power wires, to earth/ground/dirt.

Do not connect any ground to your neutral wire, usually white and do not connect the other wire, hot/black, to any ground.

I should write the homeowners guide to grounding in layman's terms but not on thaivisa because it will just be contradicted by the local guess specialists.

We welcome your 'homeowners guide' to grounding in layman's terms, and wait for your reply. Hopefully you have read the documents posted, and realize that we NOT guess specialists.

This is one of the main reasons that I have left this sticky open for debate!

[KhnomKhnom]

Dear reader of the electrical info on thaivisa........

There is so much wrong, contradictory, and confused and confusing information here that if you read it all, as I have, you will have no guidance about which writing to obey. I recommend that you do not use this site for solid info about electrical wiring, etc., in Thailand.

All the info a normal homeowner needs is not all in one place and what is there is either in EMQTC non-world standard abbreviations over blown gobbly goop or does not apply to your situation totally.

I can say one thing for certain... do not yourself connect Thai two-wire electric supply wires, the incoming power wires, to earth/ground/dirt.

Do not connect any ground to your neutral wire, usually white and do not connect the other wire, hot/black, to any ground.

I should write the homeowners guide to grounding in layman's terms but not on thaivisa because it will just be contradicted by the local guess specialists.

We welcome your 'homeowners guide' to grounding in layman's terms, and wait for your reply. Hopefully you have read the documents posted, and realize that we NOT guess specialists.

This is one of the main reasons that I have left this sticky open for debate!

Best not to ground the neutral wire at the home because it can become the best ground on your side of the local transformer, even better than the hoped for one at the transformer, because then your home ground will serve as ground for your whole neighborhood that are on your side of the transformer. That puts your system in danger of overload. I do not know if it makes your meter spin faster or not.

[Forkinhades]

Yes mostly valid arguments, but the PEA will not connect a new installation without the MEN connection, which they expect the homeowner to do. The danger of your earth becoming the best in village (with your MEN) is a scary thought especially with the workmanship of the companies installing this from the transformer. For this reason it is best to talk to the PEA, and get the information that the earthing has been DONE (From the transformer) and indeed installed to the thai code. So yes I do agree that the MEN connection should not be done by DIYers.

So maybe now people will realise that earthing is not easy subject, and is indeed a science.

[Crossy]

The two previous posts highlight the reason that TNC-S (with or without PME) took a long time to be accepted in the UK, and then only as a cost saving as the outers of old cables (which provided the earth return) corroded and the TN-S ground became unreliable.

Like Forky, I'm not a lover of the way it's done here, but that's how it's done where you are.

If already on a permanent supply, and DIYing, I agree with KK, don't connect ground and neutral unless you KNOW that the neutral is grounded at the poles, but as Forky notes, you'll never get a permanent supply connected if you don't. Damned if you do, damned if you don't.

By the way, our village neutral is grounded at every third pole so little danger of our rod becoming the best ground in the village.

[jcisco]

From what I have seen around bkk it appears that MEA are on average installing great equipment with startling levels of consistently high workmanship. Is this not the same in the PEA areas,

And it appears that in the consumer side all bets are off when it comes to workmanship and safety practices.

How is this possible, it baffles me.

Pants the Great Wall

[Charly2008]

How to check your Earthing.

Earthing is very important, and will have many different values in an installation, these values are important, as if they are too low (<0.038 ohms) under fault conditions can cause explosions, and if they are too high (>1677 ohms for Safe-T-Cut set at 30mA) then our safety devices will not open. If you do not have a Safe-T-Cut installed then a 32A Type C MCB requires a value <0.71 ohms to open in time.

For reference I will use phase to describe the live/hot

The easiest way to test is with a multimeter at a socket.

First we should check between phase and neutral, this will tell us that there is voltage there on the phase, and indeed that the meter is working.

Set the multimeter to the 750Vac setting

Insert one probe into neutral first. As we do not want the other probe to become live, and then the other into phase, you should get a reading around 220V

Now you can check between phase and earth

You need to insert one probe into the earth terminal first. As we do not want the other probe to become live, then the other into the phase.

If you get a reading of around 220V, then you have a good indication of an earth.

You can also check between Neutral and Earth, and will possibly have 1 or 2 Volts

Doing this test will also prove polarity

How to calculate incoming ‘values’ of earth

If you have your MEN connection at your DB then your values will be low, we can calculate this as we know the resistance of different cable sizes.

R1R2 Chart.pdf

From the chart above I will give my example.

From my PEA meter I have a 10mm cable supply, for the full earth path we use the neutral as we have done our MEN connection.

The cables are 20 meters in length, so from my chart I know that the phase and cpc (Circuit protective conductor (MEN connection)) is 3.66 milli ohms per meter.

So a simple calculation 20x3.66/1000 = 0.0732 ohms so all good there.

This does not take into consideration that the meter will have a value as well, whichn would need to be added to the 0.0732 already calculated. You would also need to take off your resistance for your parallel earth rod. Mine was 15 ohms, so product over subnm would bring the resistance down to 0.0728 ohms

Again this calculation can only really give us an indication as to what we might have.

EDIT : added product over sum calculation for the earth rod.