How to test house electrical

[Mike45]

I expect to be back in Thailand in a couple of weeks for a few days only and I would like to try to test the electrical wiring while I'm there.

I purchased a Schneider MCB RCBO that the electrician will install in the CU. I'm concerned that when eventually powered up that it might immediately trip and my electrician won't know what to do to get it to operate.

I don't know if there will be power available in the new build house.

I have a DMM available to do the testing. I don't know if the probes fit into a socket. I haven't tried it yet.

Is there a procedure I can perform either at each power outlet or in the CU to insure proper operation and protection of the circuits?

Thanks

[gerry123]

over to you CROSSY and co

[Crossy]

OK I'm pretty busy right now so a Quick and Dirty answer.

With only a multimeter you're limited, but should be able to verify that it won't go bang and will stay on

Equip yourself with a long length of single core wire, preferably flexible, that will reach from the distribution board to any point in your home.

With ALL the breakers OFF.

Open each outlet and light switch and visually check that the wires are correctly connected.

Using the multimeter (or better an insulation tester), verify that none of the wires is shorted to any other wire.

Clip one end of your long lead on to the neutral bar in the distribution board.

Using the multimeter check that you have continuity from each outlet neutral back to the board.

Do the same for each light fitting.

Clip one end of your long lead on to the earth bar in the distribution board.

Using the multimeter check that you have continuity from each outlet earth back to the board.

Do the same for each light fitting (if you're taking an earth to the fitting).

Clip one end of your long lead on to the output side of each breaker in turn in the distribution board.

Using the multimeter check that you have continuity from each outlet (on that circuit) live back to the board.

Do the same for each light switch.

Verify that you have continuity from the earth bar to your earth rod.

If all looks OK you should be able to progressively power on circuits without doing a 'bang test'.

[Mike45]

OK I'm pretty busy right now so a Quick and Dirty answer.

With only a multimeter you're limited, but should be able to verify that it won't go bang and will stay on

Equip yourself with a long length of single core wire, preferably flexible, that will reach from the distribution board to any point in your home.

With ALL the breakers OFF.

Open each outlet and light switch and visually check that the wires are correctly connected.

Using the multimeter (or better an insulation tester), verify that none of the wires is shorted to any other wire.

Clip one end of your long lead on to the neutral bar in the distribution board.

Using the multimeter check that you have continuity from each outlet neutral back to the board.

Do the same for each light fitting.

Clip one end of your long lead on to the earth bar in the distribution board.

Using the multimeter check that you have continuity from each outlet earth back to the board.

Do the same for each light fitting (if you're taking an earth to the fitting).

Clip one end of your long lead on to the output side of each breaker in turn in the distribution board.

Using the multimeter check that you have continuity from each outlet (on that circuit) live back to the board.

Do the same for each light switch.

Verify that you have continuity from the earth bar to your earth rod.

If all looks OK you should be able to progressively power on circuits without doing a 'bang test'.

Crossy

Thanks for that thorough procedure. I'll give it a try.

I've read about other peoples electrical problems and I remember someone saying that a ground fault protected circuit would trip because the electrician had "borrowed grounds". I don't understand that or how to test for it. I'm concerned about my MCB tripping.

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[Crossy]

'Borrowed' grounds shouldn't cause an issue, but a N-E short will cause intermittent tripping and will totally flummox a local sparks trying to fix it with a neon screwdriver.

[Mike45]

'Borrowed' grounds shouldn't cause an issue, but a N-E short will cause intermittent tripping and will totally flummox a local sparks trying to fix it with a neon screwdriver.

Will the testing procedure you described find that problem? In a MEN installation the N and E are supposed to be shorted in the CU. I'm supposed to measure a short at an outlet measuring N - E....right?

[Crossy]

'Borrowed' grounds shouldn't cause an issue, but a N-E short will cause intermittent tripping and will totally flummox a local sparks trying to fix it with a neon screwdriver.

Will the testing procedure you described find that problem? In a MEN installation the N and E are supposed to be shorted in the CU. I'm supposed to measure a short at an outlet measuring N - E....right?

Yes, the procedure will find a N-E short because your N-E link is on the incoming supply and all your breakers (including the incomer) are open.

[bankruatsteve]

Seems like he would temporarily need to un-bond the Neutral and Ground bars in the CU to test for N-E fault in the circuits by simply checking for continuity between N and E ??

[Crossy]

Look at Forky's drawings.

There is no connection between the N and E bars when the main breaker is open.

[bankruatsteve]

But I thought supply N was connected to Ground bar? I'm getting confused about MEN implementation in LOS.

Oh OK. So the "bonding" of N and E is through the breaker. Got it.

[Crossy]

Sorted

[bankruatsteve]

I guess what confuses me is the comparison to the US NEC. Except for the transformer grounding, I don't see much similarity at all. ??

[Crossy]

I guess what confuses me is the comparison to the US NEC. Except for the transformer grounding, I don't see much similarity at all. ??

I think I'll stop using that reference, I'm not sure exactly where the 'NEC' drawings I have came from.

[jackflash]

I think I would recommend a different approach to Crossy

Crossy is perfectly correct, but I feel nervous about people poking about in switch boxes.

I would make up a simple test lead consisting of a 60 Watt incandescent light globe (and socket) with two short leads fitted with test probes (similar to those on your multimeter).

Then draw a simple diagram of a power outlet with the correct arrangement of Active, Neutral and Earth marked.

I am assuming that the Electrician has previously switched on the system and there are no problems evident.

Go to each power outlet: With the switch OFF, use the probes to make sure there is no power between any of the three points.

Next turn the switch ON and make sure there is power between Active and Neutral, and that there is NO power between Neutral and Earth.

Then test between Active and Earth. The Safety Switch should immediately trip and there should be no power anywhere.

If any of the above tests fail, then there is a serious wiring fault. If it passes, reset the Safety Switch and move on the the next outlet and test again.

The advantage of this practical test is you can demonstrate the fault to your Electrician and confirm later that he has actually fixed it.

Keep in mind that the test lamp described can itself be lethal.

Make sure that your fingers don't contact anything live.

Use only one hand and keep your other hand in your pocket.

When finished, make sure its disassembled or locked away so the kids can't get to it.

[Pieter1964]

go to each wall socket and take a nail in each hand.

stick it in there and if you feel some sparkling in your body, there is juice.

if you not feel anything

then it is not good.

other option.

better ask a real electrician to do the work for you if you not know how to do it.

and if you not trust the man who installed it all, why the hell did you let him install it for you.

[jackflash]

> if you not trust the man who installed it all, why the hell did you let him install it for you?

Because in most countries you must use a local Electrician do the work,

and the problem is that Electricians are notorious for screwing things up, even in the West.

I could tell you dozens of stories of Electricians making stupid mistakes which were potentially lethal.

In Thailand it seems that few Electricians have much in the way of safely training.

[David Barker]

Just had a house tested for a potential purchaser 2 days ago. 4 electricians!!! Arrived with him with an electric drill they proceeded to plug it into every socket in the house to make sure it worked switched on every light in the house . Final verdict everything ok sir but one bulb in this light no good need new.

When I suggested testing breakers etc. Oh no have meter for that.

[Crossy]

@ Jackflash (appropriate username if ever I saw one)

It pays to read the OP, 'assume' makes an ass out of u and me.

1. System has never been powered.
2. Supply may not be available.

My advice stands, a thorough Visual Inspection followed by reasonably comprehensive dead testing using the equipment available (a DMM).

At least our OP will know that it won't go bang on power up and that the RCD has a fighting change of staying engaged.

Nobody ever died from a multimeter on 'Ohms'.

[asdecas]

I use the "finger probe" method - preferably someone else's.

[soalbundy]

Stand in a bucket of water and then stick two fingers in the plug holes, you will know real quick,but not for long

[shrimpythailand]

is any house here in Thailand actually grounded? ok ok I don;t know all the tech details of above posters but...i read all you need is a 6 ft deep copper wire to ground a house electric power out - but seriously - is any thai electrian EVER grounded a house?

i do always wear sandals when in my place - i hate getting the voltage rush when plugging something into my computer 5 5 5

[ChiangraiTony]

@ Jackflash (appropriate username if ever I saw one)

It pays to read the OP, 'assume' makes an ass out of u and me.

• System has never been powered.
• Supply may not be available.

My advice stands, a thorough Visual Inspection followed by reasonably comprehensive dead testing using the equipment available (a DMM).

At least our OP will know that it won't go bang on power up and that the RCD has a fighting change of staying engaged.

Nobody ever died from a multimeter on 'Ohms'.

Would you concur or not that only testing for continuity does NOT ensure a bang on power-up as I think you're suggesting?

Even with having good continuity (all wires connected and verified using the meter), and then you turn on power, if there is an excessive load and/ or surge in current, i.e., wiring configured incorrectly with one or more A/C units drawing to much current, this has the potential of going bang on power-up. Agree or disagree?

[wayned]

Nobody ever died from a multimeter on 'Ohms'.

But I did have a "near miss"! I was on a ladder doing a continiuty test V cable that I had just installed and the leg on the ladder broke. I ended up on the floor with a broken hip and now have a steel femur head in my leg. If I had ended up on my head it might heve been different but most likely it would only have cracked the floor!

[Crossy]

@ Jackflash (appropriate username if ever I saw one)

It pays to read the OP, 'assume' makes an ass out of u and me.

• System has never been powered.
• Supply may not be available.

My advice stands, a thorough Visual Inspection followed by reasonably comprehensive dead testing using the equipment available (a DMM).

At least our OP will know that it won't go bang on power up and that the RCD has a fighting change of staying engaged.

Nobody ever died from a multimeter on 'Ohms'.

Would you concur or not that only testing for continuity does NOT ensure a bang on power-up as I think you're suggesting?

Even with having good continuity (all wires connected and verified using the meter), and then you turn on power, if there is an excessive load and/ or surge in current, i.e., wiring configured incorrectly with one or more A/C units drawing to much current, this has the potential of going bang on power-up. Agree or disagree?

I would concur (but it's better than NO testing), but I'm not advocating ONLY continuity, did you read my post?

And one would not simply turn on the supply with all breakers closed, as I also note in my post, progressive power up is order of the day.

Our OP is limited by having only a (probably cheap) DMM and does not have access to a comprehensive set of installation test equipment (and the knowledge of how to use it).

[DrDave]

How about using one of these - although it requires the breakers to be turned on.

Does this perform a thorough enough test to ensure that the house has been properly wired?

[Crossy]

How about using one of these - although it requires the breakers to be turned on.

Does this perform a thorough enough test to ensure that the house has been properly wired?

These are a handy way of checking an existing installation (when you move in to a rental for example), or a new one that sparky has powered up without a bang.

BUT, finding a 220V one with a US style plug is easier said than done.

Martindale and a couple of other manufacturers do them with flying leads which you can fit local plugs to, but they are not cheap ($50 and up).

There is no substitute for comprehensive dead testing, including an insulation test if you have a suitable tester, before the big moment.

[kurnell]

I would love for a qualified electrician to come and look at the wiring in our house as we have some external lighting, water features etc that are more than likely not grounded properly.

[jackflash]

Crossy,

Surely the first switch on is up to the Electrician? If it goes bang, it's up to him to fix it.

Testing before hand-over seems counter productive to me.

I was going to write a longish piece on why using a Multimeter is a bad idea for electrical tests,

but judging by the reception my last post received, there's not much point.

Once again I'm reminded how posting T.V. is such an infuriating waste of time.

[Crossy]

@Jackflash.

You are more than welcome to post whatever you like here, but poor advice or dangerous posts will be removed (note that your previous post is still here, so it wasn't that bad).

Do remember that there are many wiring faults that won't go bang on power up, may not stop appliances working (but still be potentially deadly), but will be found by simple dead tests with a DMM. Yes it's not ideal, but it's what most people have, or if they don't it's cheap and readily available.

We would all love to leave it to the sparks (I hesitate to call him an electrician), but the guys who wire houses here are rarely competent or properly trained. There ARE good Thai electricians but all are earning pots working on major projects or O&G and wouldn't deign to do house wiring for the pittance these guys are paid by the building contractors.

[Forkinhades]

Seems like he would temporarily need to un-bond the Neutral and Ground bars in the CU to test for N-E fault in the circuits by simply checking for continuity between N and E ??

Correct

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