Tested Earths With Meter, But Not Sure If It'S Safe.

[thaibeachlovers]

Bought a meter from Lotus, but impossible to understand the instructions!

Anyway, know enough to be able to see if there is a resistance in the wiring by touching the probes together, reading the result and then putting probes on either end of the wire and checking result. All my wiring has same resistance as when just touching probes together, so can't get better than that.

However, when testing the earth rod by putting one probe in the N outlet and the other to the earth wire I get a completely different result, which is what I need some help with, please.

With the meter on the 200 ohm setting I get between 11 and 17 for the shower and between 35 and 45 in the kitchen ( They have different earth rods on either side of the house ). Is that safe?

I can't get a steady reading when testing the earth rod to N, and the meter flicks up and down constantly- is that normal? When just testing a wire it's steady.

On my shower thread there was some discussion of the water transmitting electricity. The washing machine gives a good tingle if you put your hand in the water while it's filling. That's even when it's "earthed", which is why I went up to Lotus on a special trip and got the meter. If the above results are safe, despite the washing machine being earthed via the plug and the casing, is it possible that the machine is leaking electricity that can't be earthed?

Thanking you for some help.

[InterestedObserver]

Readings of 11-17 and 35-45 ohms between neutral (N) and the earth rods is a little on the high side but better than no earth altogether. What does the green earth wire measure to earth rod? Also a simple multimeter is not the best of earthing testers. The tingle from the washing machine is a dead give away that you are not adequately earthed, the case to earth voltage should be no more than 5VAC - preferably zero VAC. The flickering ohms reading between neutral and earth rod is because there is a voltage present, resulting in an unreliable reading on the ohms scale.

Edited October 7, 2011 by InterestedObserver

[Crossy]

I agree with IO, the tickle is a dead giveaway.

Visually check that the earth wire is connected to your washing machine outlet, check the machine has the correct plug for the outlet (or an adaptor), post photos here if in doubt, check that the earth wire actually goes to your rod (use your meter and an extension if the leads are not long enough). Finally check all the way from a screw on the machine to the earth rod. All readings should be as close to zero ohms as makes no odds. Make these measurements with the power OFF.

I think we are rapidly concluding that trying to test the quality of an earth using a regular multimeter is not practical, the proper kit is not cheap and won't get much use, so we will have to come up with an alternative means, give me a while to think about this.

A thought, since you have two rods try measuring the resistance between them (with the wires disconnected), let us know how you get on.

[thaibeachlovers]

Readings of 11-17 and 35-45 ohms between neutral (N) and the earth rods is a little on the high side but better than no earth altogether. What does the green earth wire measure to earth rod? Also a simple multimeter is not the best of earthing testers. The tingle from the washing machine is a dead give away that you are not adequately earthed, the case to earth voltage should be no more than 5VAC - preferably zero VAC. The flickering ohms reading between neutral and earth rod is because there is a voltage present, resulting in an unreliable reading on the ohms scale.

Thanks for the reply.

There is no resistance ( same reading as putting the probes together ) anywhere in the wiring till the rods are reached, including the wire between the rods, and measuring from the wire to the rod itself, so the problem must be from rod to ground. Perhaps it will help if I soak the ground around the rods.

[Crossy]

Thanks for the reply.

There is no resistance ( same reading as putting the probes together ) anywhere in the wiring till the rods are reached, including the wire between the rods, and measuring from the wire to the rod itself, so the problem must be from rod to ground. Perhaps it will help if I soak the ground around the rods.

It's more likely that the meter is unable to overcome the initial breakdown resistance between the rod and the mass of the earth. Have you tried rod to rod with the wiring disconnected?

[thaibeachlovers]

I agree with IO, the tickle is a dead giveaway.

Visually check that the earth wire is connected to your washing machine outlet, check the machine has the correct plug for the outlet (or an adaptor), post photos here if in doubt, check that the earth wire actually goes to your rod (use your meter and an extension if the leads are not long enough). Finally check all the way from a screw on the machine to the earth rod. All readings should be as close to zero ohms as makes no odds. Make these measurements with the power OFF.

I think we are rapidly concluding that trying to test the quality of an earth using a regular multimeter is not practical, the proper kit is not cheap and won't get much use, so we will have to come up with an alternative means, give me a while to think about this.

A thought, since you have two rods try measuring the resistance between them (with the wires disconnected), let us know how you get on.

Thanks Crossy.

The washing machine is connected by an old style earth plug ( I was using an adaptor, but have now put in a "proper" socket for the old style plug ) and a wire to the casing. However, I haven't as yet checked for any resistance in the washing machine earth wiring- will do that tomorrow.

Yes, the earth wire goes to the rod. I know that because till I put them there there weren't any earths in the house.

I'll try measuring the resistance between rods tomorrow. I'll also try that trick you recommended of putting a bulb between L and the earth wire ( disconnected from everything else of course ).

[InterestedObserver]

The washing machine gives a good tingle if you put your hand in the water while it's filling. That's even when it's "earthed",..............

Was the washing machine tingling, have a stray voltage on it, when you touched it before you installed the "proper" socket and earth rod? Or did this stray voltage just appear after you earthed (grounded) the machine. What is the resistance from the wash machine casing to the earth rod? Are you sure the "proper" socket is wired correctly and matches the machine plug?

Edited October 9, 2011 by InterestedObserver

[thaibeachlovers]

Tested the resistance between the two rods with wire disconnected. It was about 400 on the 200 ohm scale. I say 400, but kept rising slowly. I tried wetting the ground around the rods, and the meter went down to about 245. I got no reading at all on the 2000 ohm scale.

I also tested for voltage between N and E- 2 volts present on the 200v scale of my Lotus meter.

I was about to move the washing machine to make some readings, but my wife came home and spread the groceries all over the kitchen floor, then started making dinner, so that will have to wait till tomorrow.

[Crossy]

That reading between rods is good, providing you have an RCD you're good to go.

I'm still worried about your washing machine, getting shocks from the water is scary, please verify the ground is OK.

[lopburi3]

If you have the same cheap Lotus meter I have (Yogo DT-830B) you need to use the ACV 750 setting to measure voltage. You should get the same reading between L-N and L-E if the earth is working.

[bankruatsteve]

And, let's remember that almost all Thai electronics don't even have 3-prong plugs (and if they do - it's likely there is nothing connected to the ground). So, if your washing machine doesn't have a 3-prong plug, or if it does and there's no connection to the gournd, then you need to connect the external ground (which some products do have) to the ground in the outlet. Otherwise, it really doesn't matter what your ground system b/c nothing is connected to it! BTW: putting the probes together on an ohm meter should get a reading of ZERO - short circuit and is a simple and effective test in a MEN system for G-N (but doesn't say how good the "ground" is).

[InterestedObserver]

Tested the resistance between the two rods with wire disconnected. It was about 400 on the 200 ohm scale.

Are you sure?

[electau]

Trying to measure the resistance of the soil is of no practical value and is a waste of time.

We are dealing here with an individual electrical installation within a building or structure.

Earthing for HV installations , HV/LV distribution transformers and LV network earthing are covered by different requirements.

Providing the earth electrode has sufficient area in contact with the soil that is all that is required. The minimum is 1 x 13mm copper clad electrode a minimum of 1.2/1.8 M in the ground located in an area exposed to the weather and visible for inspection.

The resistance from the electrode to any exposed conductive parts of the electrical installation including the earth terminals of 3 pin socket outlets should not exceed 2 ohms. (From the electrode not the soil).

Protection is provided by an RCD with a TT or direct earthing system as in the event of an earth fault the fault current flows from the RCD through the fault, the PE conductor, and the main earth and electrode. While the fault exists a touch voltage is created and if this is over 50VAC automatic disconnection must occur in less than 0.4secs. Touch voltage only exists under fault conditions.

With the MEN system the fault path does not return to the source of supply via the ground but through the consumers main neutral and distribution neutral conductor. Current through the main earth and electrode is negligible and may be disregarded.

[electau]

With a TT system there wil always be a voltage from neutral to earth depending on how far one is from the source of supply.

With a compliant MEN system the voltage between the neutral and earth will be between 0 and 1 volt.

These AC voltages will distort any readings that you are trying to read using the low ohms range on a multi meter, you are effectively trying to read AC current.

If you have voltage between N and E you must have current it may only be mA

[thaibeachlovers]

If you have the same cheap Lotus meter I have (Yogo DT-830B) you need to use the ACV 750 setting to measure voltage. You should get the same reading between L-N and L-E if the earth is working.

Thank you. I did as you said and it is indeed the same for both the kitchen earth and the shower earth.

So unless someone wants to dispute the above method, I am earthed.

Now I'll just have to pull the back off the washing machine and see if there is an earth wire attached to anything from the plug wire.

Thanks for all the advice, everyone.

[InterestedObserver]

If you have the same cheap Lotus meter I have (Yogo DT-830B) you need to use the ACV 750 setting to measure voltage. You should get the same reading between L-N and L-E if the earth is working.

Thank you. I did as you said and it is indeed the same for both the kitchen earth and the shower earth.

So unless someone wants to dispute the above method, I am earthed.

Now I'll just have to pull the back off the washing machine and see if there is an earth wire attached to anything from the plug wire.

Thanks for all the advice, everyone.

As long as you continue to get a "good tingle" from the washing machine it is not earthed.

[electau]

If you have the same cheap Lotus meter I have (Yogo DT-830B) you need to use the ACV 750 setting to measure voltage. You should get the same reading between L-N and L-E if the earth is working.

Thank you. I did as you said and it is indeed the same for both the kitchen earth and the shower earth.

So unless someone wants to dispute the above method, I am earthed.

Now I'll just have to pull the back off the washing machine and see if there is an earth wire attached to anything from the plug wire.

Thanks for all the advice, everyone.

One does not use the voltage ranges of a multimeter to check earthing. the voltage L to N, N to E and L to E is to verify polarity tests.

To verify the earthing conductor. 1. Visibly check it and the electrode/electrode connection and 2. Use the low ohms range of the multimeter to verify continuity.

To do this you will require a trailing lead ( point to point test) and zero out the resistance of the leads first.

If you are receiving mild shocks similiar to a slight burning sensation the electrical equipment is not earthed. However the touch voltage will be very low, ie, probably less than 25VAC.

[lopburi3]

You surly can make a good check using voltage and it is much safer than trying to use ohm meter. We are talking home tests not an oil rig or commercial exam test.

[bankruatsteve]

No matter where you are testing - the initial tests should be x-live for continuity etc which is best for the ohm meter. After live, those tests, having been completed, don't need to be verified by anything else (like voltage potential between N-E.) And, if everything is perfect or in MEN - there is zero resistance between N-E and therefore zero voltage. So, I don't agree that voltage test for that is any value whatsoever.

[thaibeachlovers]

Oh dear, now I'm confused!

Leaving aside the washing machine, I have no readable resistance anywhere in the wiring, using low ohms setting, as far as the earth rods, and between the wires and the exposed rod, so there is no resistance as far as the actual rods.

So until someone can hopefully come up with an agreed method of testing the rod to earth resistance that does not involve thousands of baht, I'll just have to make like a Thai and trust in Buddha that everything is OK. At least I do have rods in the ground, so that's 100% more than before.

Thanks everyone.

[bankruatsteve]

Just to re-state, when you do that type of testing (continuity) it should be with the power off (the knife breaker open). If you're doing it correctly and you get zero ohms in your earth tests, that is perfect (although hard to believe unless you have MEN). Anyway....

Since your problem seems to be the washer (with a bit of a buzz when you touch the chassis, yah?) - then that is what you need to check out. Again, you can have the best grounding system in your ampur, but if nothing is connected to it - it's not doing anything to help. Here's a suggestion: no matter what your plug is or is not connected to a ground, you could connect a single core copper wire of any size you might have laying around from a screw in the washing machine frame and/or the metal foot to the ground screw in the receptacle. If that doesn't remove the buzz then you might need the monks to spray it with holy water. Cheers.

[electau]

You surly can make a good check using voltage and it is much safer than trying to use ohm meter. We are talking home tests not an oil rig or commercial exam test.

To check earthing one uses an ohms range of a multimeter in this case. the resistance must be less than 2 ohms.

You must carry out a visual check of the earthing and electrode.

The earth resistance must be low so as to mimimise the touch voltage, with the TT system the RCD will provide automatic disconnection in the event of an earth fault.

IEC, AS and BS standards all give the requirements for earth testing.

An ohmmeter is a device which measures resistance in ohms, with a normal multi meter this test voltage is about 300mVDC. A multimeter on the voltage ranges is a high impedance device and may give correct voltage readings L-N. L-E even when the resistance is many thousands of ohms.

There are no such tests as "home tests".

[electau]

Oh dear, now I'm confused!

Leaving aside the washing machine, I have no readable resistance anywhere in the wiring, using low ohms setting, as far as the earth rods, and between the wires and the exposed rod, so there is no resistance as far as the actual rods.

So until someone can hopefully come up with an agreed method of testing the rod to earth resistance that does not involve thousands of baht, I'll just have to make like a Thai and trust in Buddha that everything is OK. At least I do have rods in the ground, so that's 100% more than before.

Thanks everyone.

If you have less than 2 ohms resistance between the earth electrode (NOT the soil around it) and any earthed point eg washing machine , socket outlet etc you will have an earthing system that will be functional.

A 2.5sqmm earth conductor has a resistance of 0.008ohms per meter.

Why are you so concerned with the resistance of the general mass of earth/ground soil? All that is required is that the electrode has sufficient contact area with the surrounding soil.

Edited October 14, 2011 by electau

[thaibeachlovers]

Oh dear, now I'm confused!

Leaving aside the washing machine, I have no readable resistance anywhere in the wiring, using low ohms setting, as far as the earth rods, and between the wires and the exposed rod, so there is no resistance as far as the actual rods.

So until someone can hopefully come up with an agreed method of testing the rod to earth resistance that does not involve thousands of baht, I'll just have to make like a Thai and trust in Buddha that everything is OK. At least I do have rods in the ground, so that's 100% more than before.

Thanks everyone.

If you have less than 2 ohms resistance between the earth electrode (NOT the soil around it) and any earthed point eg washing machine , socket outlet etc you will have an earthing system that will be functional.

A 2.5sqmm earth conductor has a resistance of 0.008ohms per meter.

Why are you so concerned with the resistance of the general mass of earth/ground soil? All that is required is that the electrode has sufficient contact area with the surrounding soil.

I was testing the ground resistance because that was one of the suggestions given on this post. As Crossy said somewhere else, I'm just an enthusiastic DIYer, and somethings take a while to define, but if I understand you correctly then I am earthed.

Thank you for your helpful replies, though I don't always understand the more technical side of what you write.

Edited October 15, 2011 by thaibeachlovers

[thaibeachlovers]

Just to re-state, when you do that type of testing (continuity) it should be with the power off (the knife breaker open). If you're doing it correctly and you get zero ohms in your earth tests, that is perfect (although hard to believe unless you have MEN). Anyway....

Since your problem seems to be the washer (with a bit of a buzz when you touch the chassis, yah?) - then that is what you need to check out. Again, you can have the best grounding system in your ampur, but if nothing is connected to it - it's not doing anything to help. Here's a suggestion: no matter what your plug is or is not connected to a ground, you could connect a single core copper wire of any size you might have laying around from a screw in the washing machine frame and/or the metal foot to the ground screw in the receptacle. If that doesn't remove the buzz then you might need the monks to spray it with holy water. Cheers.

Thanks.

The tingle is actually from the water as it enters the machine, but not anywhere else in the plumbing system, so just the WM.

I've been up north getting a new visa entry, but I'll be checking everything out once I get back.

Thanks for your reply.

[Kwasaki]

Since your problem seems to be the washer (with a bit of a buzz when you touch the chassis, yah?) - then that is what you need to check out.

Thanks.

The tingle is actually from the water as it enters the machine, but not anywhere else in the plumbing system, so just the WM.

I've been up north getting a new visa entry, but I'll be checking everything out once I get back.

Thanks for your reply.

Open the back a check internal wires and for mice nests etc which I'm sure you will do and see if it checks out OK.

If the water entry is a metal set up try putting a wire to it and then to earth and see what happens.

I have earthed our washer but there was nothing from the metal back or water even before I earthed it.

[thaibeachlovers]

Finally got to test the earth with the light bulb between L and E. Works spectacularly well. So hopefully that is OK then.

Had a minor glitch when the light tripped the CB. Found that whoever assembled the bulb holder had not folded over the center contact, so it was shorting to the metal thread that holds the bulb. Never a dull moment!

As for the W M. Tipped it upside down to get at the electrics, but first had to drill out the pop rivets that someone used to secure the home made rat proof grill underneath, sigh ( now it is secured with screws ), Did a visual search and couldn't find anything. Checked every metal point, including the casing, that I could find with the ohm meter to the wire ( disconnected from the outside earth wire ) that goes to earth, and all are OK. Only the main electric motor and the pump motor didn't register, and they are insulated from the chassis. Anyone know how I can check them to see which is faulty?

So now it's earthed through a casing wire and the plug wire. Seems to be OK now, so not sure where the problem was.

[thaibeachlovers]

Since your problem seems to be the washer (with a bit of a buzz when you touch the chassis, yah?) - then that is what you need to check out.

Thanks.

The tingle is actually from the water as it enters the machine, but not anywhere else in the plumbing system, so just the WM.

I've been up north getting a new visa entry, but I'll be checking everything out once I get back.

Thanks for your reply.

Open the back a check internal wires and for mice nests etc which I'm sure you will do and see if it checks out OK.

If the water entry is a metal set up try putting a wire to it and then to earth and see what happens.

I have earthed our washer but there was nothing from the metal back or water even before I earthed it.

Thanks, but it appear to be all plastic. Only the pump motor would be metal, and I'm not sure how to check that.

[InterestedObserver]

Thanks, but it appear to be all plastic. Only the pump motor would be metal, and I'm not sure how to check that.

AND

Only the main electric motor and the pump motor didn't register, and they are insulated from the chassis. Anyone know how I can check them to see which is faulty?

With the power turned OFF and wash machine unplugged, test the insulation resistance from L and N, on unplugged cord, to motor and pump metal frame. The insulation resistance should be quite high.

Edited October 25, 2011 by InterestedObserver

[Pacificperson]

What is the voltage between the water and ground? Is there anything that could be in contact with the water such as an electrically operated valve that could be leaking current?