How to test house electrical

[Forkinhades]

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.

A good electrician will ALWAYS check his work before the power gets switched on, and will provide certification.

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[Forkinhades]

@ jackflash

Indeed DMM is not a good piece of equipment to fully test your electrical system.

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[Forkinhades]

NOTE:

The electrical testing and inspecting exam in the UK is quite a diificult exam for qualified electricians to pass, and indeed has quite a high failure rate.

To try to explain here in laymen terms would be quite a task indeed!

CPC= Circuit Protective Conductor

Continuity of circuit protective conductors (CPCs) at all metal accessories and equipment.

Continuity of all bonding conductors and earth clamps.

Continuity of all ring circuit conductors, including CPCs.

R1 + R2 continuity test or R2 test on every final circuit. (phase/hot and CPC)

Insulation resistance between live conductors and earth of all circuits collectively, excepting any circuits supplying electronic equipment which may be damaged by the test. These shall be listed separately as not having been tested.

An electrical separation test on all electrically separated circuits.

Polarity at the board and all lighting switches and equipment to ensure that switches interrupt only phase conductors.

Earth fault loop impedance (Ze) at the main intake position.

Earth fault loop impedance (Zs) at the distribution board.

Earth fault loop impedance (Zs) test on every final circuit and every socket outlet.

Test all Residual Current Devices.

The resistance of every earth electrode.

Prospective fault current

A manual operation test on all MCBs, RCDs, switch fuses andisolators.

[Crossy]

I don't believe there is any argument that:-

1. A DMM is not the best bit of kit for testing an installation.
2. A good electrician will always check his work before power on.

BUT

1. Our OP asked a specific question about checking his new installation, he has only a DMM.
2. Try finding one here who does not use the bang method.

If anyone has any dead tests to add to my procedure in Post #3 please post them here.

If you can find a locally configured 3-light (Martindale) tester (or use a UK or Oz one with a suitable adapter) that's the next process.

As Forky notes, test and certification in the UK is a complex (some would say too complex now) process requiring specialist equipment (costing several thousand $) along with the knowledge of how to use it and how to interpret the results. Sadly we don't have anything similar here.

[bankruatsteve]

Since I wouldn't win an argument, my opinion regarding DMM is that it IS the best kit for testing a new installation esp. for the DIY. Although I've never owned one myself, I'm thinking a megger is basically a DMM using higher voltage - well, and several more testing options. (?) And, for a new installation, it seems one can ASSUME the insulation is good and that a properly installed ground rod is a good earth. Actually, I wonder how many "electricians" actually know how to properly test and interpret results from a megger. (?)

For me, a short-cut to Crossy's circuit integrity tests (meaning not as thorough) is to first check for no continuity at the CU between N-L-E, then to short N-L-E at the furthest outlet and test for continuity at the CU (and any spurs).

[Forkinhades]

A Meggar can test your cables up to a 1000V, and get ohmic values of 1000 Meg ohms (100,000,000 ohms) a DMM cannot not get anywhere near them values. As we are talking about RCBOs which are rated at 30mA, your DMM will not pick up values that can open the RCBO.

If you can assume that the insulation of the cables have not been damaged by burning or charring then a DMM will give an indication for the DIYer.

A Meggar will also test the function of your RCBO's by applying a fault current of 30mA on the circuit to open the RCBO, and record the time it takes to open. For me this is more important than the insulation resistance test. A DMM cannot

A Meggar can measure the resistence of your earth rod (Za), your impendance at the DB (Ze), and your impedance at your last socket/light/appliance (Zs). A DMM cannot.

A Meggar can also provide the PFC (Prospective fault current), getting this reading will tell somebody whether or not an explosion will happen under fault conditions. Something that seems to be totally overlooked here in LOS. A DMM cannot.

[Crossy]

Note that Forky is talking about a Megger INSTALLATION tester as opposed to the classical megger which is a simple INSULATION tester.

Something like this http://www.amazon.co.uk/Megger-MEGGER-MFT1730-BS-Multifunction-Tester/dp/B00DOTZUTU/ref=pd_sim_sbs_diy_3/275-7590307-4278813?ie=UTF8&refRID=08H9P4P2CRW97XNT9JYW at nearly 1,300 Quid probably a bit out of the average DIY'ers price range.

[Forkinhades]

To test a circuit for insulation, and continuity.

OK we have 1 socket on 1 RCBO (to keep things simple)

You disconnect the phase/hot, and Neutral at the RCBO, and CPC from within the Fuseboard (DB) enclosure.

You can then use your DMM Meggar and test between the cables, you will be ooking for 0 on a DMM and >200 meg ohms on a meggar

You should then join together phase and CPC at your DB, and test at the socket, you should get a low reading on both DMM, and Meggar

Whislt the cables are connected at DB, you can then test 'other' equipment, sockets, light etc, to make sure that they are not connected to circuit under test.

You should then join together phase and neutral at the DB and test at the socket, again a low reading should be obtained.

This test will also give you polarity.

[Forkinhades]

Just to add

A meggar will pick up the slightest of damage to a cable, and so we know whether to replace the cable or not. This is where the DMM will fail. So the circuit could work for a period, but will eventually break down and fail. Could be very costly to replace the cable.

[Forkinhades]

Note that Forky is talking about a Megger INSTALLATION tester as opposed to the classical megger which is a simple INSULATION tester.

Something like this http://www.amazon.co.uk/Megger-MEGGER-MFT1730-BS-Multifunction-Tester/dp/B00DOTZUTU/ref=pd_sim_sbs_diy_3/275-7590307-4278813?ie=UTF8&refRID=08H9P4P2CRW97XNT9JYW at nearly 1,300 Quid probably a bit out of the average DIY'ers price range.

good piece of kit.

Was looking for something like that to post in my post

Meggar is associted to testing, same as Safe-T-Cut is to RCBO

You can get fluke meters from RS Thailand (same price mind)

[Crossy]

I gave up house-bashing many years ago when these nice toys didn't exist, the testing requirements were somewhat less onerous too mind

I did buy a Robin '16th Edition' tester on Ebay when we built the house, unfortunately I was in India when the 'electrician' did his first fix and (no) testing, the ceilings were up when I actually got around to doing some tests.

Hundreds of borrowed neutrals and a number of deliberate N-E shorts (one of which I've still not found) which caused all sorts of interesting tripping of the RCDs. The circuit with the N-E short has it's earth disconnected in the CU and 2-pin outlets fitted until I can investigate further.

[Forkinhades]

http://thailand.rs-online.com/web/p/electrical-installation-testers/0573400/

[Forkinhades]

I gave up house-bashing many years ago when these nice toys didn't exist, the testing requirements were somewhat less onerous too mind

I did buy a Robin '16th Edition' tester on Ebay when we built the house, unfortunately I was in India when the 'electrician' did his first fix and (no) testing, the ceilings were up when I actually got around to doing some tests.

Hundreds of borrowed neutrals and a number of deliberate N-E shorts (one of which I've still not found) which caused all sorts of interesting tripping of the RCDs. The circuit with the N-E short has it's earth disconnected in the CU and 2-pin outlets fitted until I can investigate further.

oh that could be a fun afternoon with a few beers

[Forkinhades]

I have both the fluke and meggar equipment, and IMO the meggar is much better, as it can still get readings on 'noisy' circuits.

[Crossy]

http://thailand.rs-online.com/web/p/electrical-installation-testers/0573400/

A significant investment for a local sparky

The equivalent of me shelling USD 200,000 on a single piece of kit, not going to happen.

[thomasteve]

Note that Forky is talking about a Megger INSTALLATION tester as opposed to the classical megger which is a simple INSULATION tester.

Something like this http://www.amazon.co.uk/Megger-MEGGER-MFT1730-BS-Multifunction-Tester/dp/B00DOTZUTU/ref=pd_sim_sbs_diy_3/275-7590307-4278813?ie=UTF8&refRID=08H9P4P2CRW97XNT9JYW at nearly 1,300 Quid probably a bit out of the average DIY'ers price range.

good piece of kit.

Was looking for something like that to post in my post

Meggar is associted to testing, same as Safe-T-Cut is to RCBO

You can get fluke meters from RS Thailand (same price mind)

Megger is a trade name for an insulation resistance test meter. Other manufacturers make similar test meters and just as Hoover is often used when referring to a vacuum cleaner the names are often interchanged.

They use a low voltage battery, with inbuilt circuitry, to apply 500V or 1000V to the test probes used for measuring resistance. This is much more likely to show up faults than a cheap DMM where the voltage being applied is usually below 9 volts.

However as already stated a cheap DMM is better than nothing.

If nothing else is available you could do continuity tests with a simple battery and bulb circuit (torch).

[thomasteve]

I gave up house-bashing many years ago when these nice toys didn't exist, the testing requirements were somewhat less onerous too mind

I did buy a Robin '16th Edition' tester on Ebay when we built the house, unfortunately I was in India when the 'electrician' did his first fix and (no) testing, the ceilings were up when I actually got around to doing some tests.

Hundreds of borrowed neutrals and a number of deliberate N-E shorts (one of which I've still not found) which caused all sorts of interesting tripping of the RCDs. The circuit with the N-E short has it's earth disconnected in the CU and 2-pin outlets fitted until I can investigate further.

i have also come across something I suspect is similar with live supply appearing when it's not expected - is this what 'borrowed neutrals'

causes ? If so is there an easy way to locate or is it best to go back and rewire everything from the start ?

Also is it done to save on wiring costs ?

[Forkinhades]

^ This is where individual RCBO's are really good, as any crossed neutral will cause 1 or 2 RCBO's to open, thus making finding the fault a lot easier to find.

Neutral Earth faults are a pain in the butt, and these faults can be fatal to the DIYer, who has 'thought' he has isolated a circuit, and then 'splits' 2 neutrals one of which is borrowed!

However they can be solved, not going to go into the procedure here, as its too long, as indeed the test is itself!

EDIT : Borrowed neutrals are very dangerous, not so much neutral earth faults!

[Crossy]

Yes Thomasteve, unexpected appearance of a hot wire is a symptom of borrowed neutrals where several circuits share a single neutral.

They're not dangerous per-se in normal operation unless you have several power circuits sharing the same neutral which may cause it to be over loaded, it's only when some poor sparks disconnects and touches what he thinks is an isolated neutral that the fun starts.

Thai sparks will pick up any convenient neutral, the concept of 'circuits' is completely alien, I've given up trying to remove all of them and simply isolate the whole installation at the main breaker if I'm working on it.

I HAVE determined that the water heaters and aircon are definitely wired correctly with no borrowed anythings and RCD protection that works

[JesseFrank]

http://thailand.rs-online.com/web/p/electrical-installation-testers/0573400/

A significant investment for a local sparky

The equivalent of me shelling USD 200,000 on a single piece of kit, not going to happen.

2000 US$

[Crossy]

oh that could be a fun afternoon with a few beers

Indeed, myself and JAS21 spent a happy afternoon working out why turning on the patio lights caused the fan plugged in to an outlet in the small bedroom to stop whilst the LED reading light plugged into the other half of a double outlet remained on.

Let's just say that after sparky had spent hours with his limited test kit (neon screwdriver) we fixed it in about an hour with a bulb, 12V battery and a long trailing flex with a modicum of common sense and a methodical approach.

[thomasteve]

Yes Thomasteve, unexpected appearance of a hot wire is a symptom of borrowed neutrals where several circuits share a single neutral.

They're not dangerous per-se in normal operation unless you have several power circuits sharing the same neutral which may cause it to be over loaded, it's only when some poor sparks disconnects and touches what he thinks is an isolated neutral that the fun starts.

Thai sparks will pick up any convenient neutral, the concept of 'circuits' is completely alien, I've given up trying to remove all of them and simply isolate the whole installation at the main breaker if I'm working on it.

I HAVE determined that the water heaters and aircon are definitely wired correctly with no borrowed anythings and RCD protection that works

Looks as if all the Thai 'electricians' went to the same school as I have the same situation where water heaters and air-con circuits are all good with each on separate circuits, individual breakers and wired with unbroken lengths of 2.5 or 4mm flat twin and each has a separate earth wire.

Problem is with the socket-outlets and too many downlighters/circular fluorescents where inaccessible twisted wires and birds nests are used.

[Pieter1964]

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

yes, some of them are grounded

depending on the amount of amperes you official get from the company.

my gf's house had 5 amp band nothing grounded.

she wanted to change to 15 amps, and she first needs to ground the electric wiring from house, so they put a rod in the ground, 1.5 meter long

that is not realy grounding, but it works a little bit.

what they again not have, a decent 0.02amps ground circuit breaker.

that is not needed, but the house is grounded

strange people those thai

[Mike45]

Had my first look at the house project today. The wires are run but the CU isn't installed yet nor are the outlet plugs installed. I looked at the wires and found they are made by Bangkok Cable. The wires for the AC were 8mm.

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[Crossy]

Had my first look at the house project today. The wires are run but the CU isn't installed yet nor are the outlet plugs installed. I looked at the wires and found they are made by Bangkok Cable. The wires for the AC were 8mm.

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8mm² is a non-standard size which Bangkok Cable do not make, you either misread the size (hopefully) or you have fake cable of unknown pedigree

[Mike45]

I guess I'll go back and take a better look. I was perched on the top of a 5 gallon bucket when I looked at it.

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[Crossy]

I guess I'll go back and take a better look. I was perched on the top of a 5 gallon bucket when I looked at it.

Don't beak your neck, it's probably 6mm² adequate for up to about 8kW water heater.

Is the heater grounded (green wire)?

[Mike45]

I guess I'll go back and take a better look. I was perched on the top of a 5 gallon bucket when I looked at it.

Don't beak your neck, it's probably 6mm² adequate for up to about 8kW water heater.

Is the heater grounded (green wire)?

I'll look at it later today. Its not for a heater its for an air conditioner so the wires are up high. I'll look for the ground wire.

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[Crossy]

Sorry Mike, misread your post, most aircons will be fine on 4mm² (or even 2.5mm²) so if it's that or larger no worries.

[Forkinhades]

^ most be enjoying the beer in HH

sorry back on topic......