Domestic Electrical Wiring

[Crossy]

One for the rogues gallery, anyone care to explain what happened to this piece of flexible conduit. I think I've worked it out but ideas would be fun.

NOTE this is a new construction (still ongoing)

[elkangorito]

One for the rogues gallery, anyone care to explain what happened to this piece of flexible conduit. I think I've worked it out but ideas would be fun.

NOTE this is a new construction (still ongoing)

The black cable on the left looks unaffected. Methinks it hasn't been connected yet. The conduit doesn't seem to have any cables in it & the wall or surrounding structures do not seem to show any obvious burns (although I can see something on the blue RSJ) so my guess is that some pratt has attacked it with heat in some way. A blowtorch or heat gun?

EDIT I've just thought of it. I'll bet it was electric welding that caused it. Somehow, the metal flex conduit was involved in the 'work' circuit of the welder.

Edited March 30, 2007 by elkangorito

[Crossy]

The black cable on the left looks unaffected. Methinks it hasn't been connected yet. The conduit doesn't seem to have any cables in it & the wall or surrounding structures do not seem to show any obvious burns (although I can see something on the blue RSJ) so my guess is that some pratt has attacked it with heat in some way. A blowtorch or heat gun?

It's more subtle than that. Note it's screwed to a steel structure. On the other side of the wall is another steel structure (actually the lift shaft). The lift installation chap had his welder grounded out to the blue RSJ and was welding on the lift. The only electrical connection between the two was that poor bit of flexy, the welding current was flowing through it, it was glowing red. Needless to say he had the filippino version of mai pen rai, somebody elses problem.

I hate to think what his welds were like with all that extra resistance in the circuit (makes note to self, don't use the lift at Doroteo Jose station).

[elkangorito]

The black cable on the left looks unaffected. Methinks it hasn't been connected yet. The conduit doesn't seem to have any cables in it & the wall or surrounding structures do not seem to show any obvious burns (although I can see something on the blue RSJ) so my guess is that some pratt has attacked it with heat in some way. A blowtorch or heat gun?

It's more subtle than that. Note it's screwed to a steel structure. On the other side of the wall is another steel structure (actually the lift shaft). The lift installation chap had his welder grounded out to the blue RSJ and was welding on the lift. The only electrical connection between the two was that poor bit of flexy, the welding current was flowing through it, it was glowing red. Needless to say he had the filippino version of mai pen rai, somebody elses problem.

I hate to think what his welds were like with all that extra resistance in the circuit (makes note to self, don't use the lift at Doroteo Jose station).

What a dolt!!! The 'we can do anything' attitude here will or has most likely killed or injured somebody. Are they really that bad/wittless over there?

[Crossy]

What a dolt!!! The 'we can do anything' attitude here will or has most likely killed or injured somebody. Are they really that bad/wittless over there?

I have many more similar, when I get a spare minute I'll put up a rogues gallery on the wiring website. Yes they are that witless

[Nawtilus]

I got an electric shock from that power point/switch I put a pic up of a few pages back, second time in my life now and I hate even tiny electric fence shocks.

Other guys I knew could touch or hang on to the fencing wires to see if it was working, I had to place a piece of green grass on it to feel it, still hated it.

Years ago while wrecking a bathroom in an old farmhouse I was bashing away with the hammer, the hammer connected with the bare light wires hanging from the ceiling, sent me accross the room.

[technocracy]

On the topic of PVC conduit I can confirm from 1st hand experience that it is a ###### sight stronger than what you would expect. As I've been going round pulling the wires through I've come around a few where I have had installed conduit to long and requiring cutting. However cutting ain't that easy when it's situated in a channel with an inch of cement render over the top of it! So I though hmmmmm sharpen up a cold chiesel and whack it an in theory it would cut through it being as it's gripped tight . . . . the conduit just dinked slightly and bent a little bit!

Next I decide to make it easy why not just smash the main excess with the hammer then use the trust wire snips to tidy it up ready for the connector. Yep the hammer bounced (1lb lump hammer). Anyway in the end I snapped a spare hacksaw blade down taped it to a piece of conduit and it was small enough to allow me to cut it . .. although I did use the cold chiesel to cut the back on the brick.

So in short to 'accidently' smash through the yellow conduit they sell over here would take some doing!

Oh yeah as I've just come back from a trip over to Udon Thani to buy some odds and sods from Global Home and HomePro I had a look at the price of the TPS mentioned before on this thread and I was very suprised it's 1000 baht more expensive in HomePro than my local shop here in Vientiane!! Exact same make the lot!

I was thinking it's expensive here!!!

[elkangorito]

On the topic of PVC conduit I can confirm from 1st hand experience that it is a ###### sight stronger than what you would expect. As I've been going round pulling the wires through I've come around a few where I have had installed conduit to long and requiring cutting. However cutting ain't that easy when it's situated in a channel with an inch of cement render over the top of it! So I though hmmmmm sharpen up a cold chiesel and whack it an in theory it would cut through it being as it's gripped tight . . . . the conduit just dinked slightly and bent a little bit!

Next I decide to make it easy why not just smash the main excess with the hammer then use the trust wire snips to tidy it up ready for the connector. Yep the hammer bounced (1lb lump hammer). Anyway in the end I snapped a spare hacksaw blade down taped it to a piece of conduit and it was small enough to allow me to cut it . .. although I did use the cold chiesel to cut the back on the brick.

So in short to 'accidently' smash through the yellow conduit they sell over here would take some doing!

Oh yeah as I've just come back from a trip over to Udon Thani to buy some odds and sods from Global Home and HomePro I had a look at the price of the TPS mentioned before on this thread and I was very suprised it's 1000 baht more expensive in HomePro than my local shop here in Vientiane!! Exact same make the lot!

I was thinking it's expensive here!!!

This is why I think it is better to run cables in PVC conduit. Can you imagine belting a nail into a wall & not feeling any resistance as the nail ploughs through the unprotected cable, & thence receiving a 'zap'?

Better safe than sorry, I think...unless you like to gamble or play with 'statistics'.

[chownah]

When pounding in masonry nails I always expect alot of resistence....odds are if I hit a conduit I'd probably just think the concrete was hard and drive right through it. I think it is likely that some Thai worker would do the same. If you want to avoid this then when you cut your channels and put in your conduit you could place a strip of steel (1/8 inch thick or more should do) directly over the conduit before plastering in the slot. Personally, I don't worry about it...I think before driving masonry nails and I generally don't let hired help do this on their own. If you are driving them into a wall then you could turn off the power and proceed....you might have to cut a wall open and fix the damage but at least it won't kill you...not that it would anyway if you were wearing rubber soled shoes and had a hammer with a rubber grip.

Of course this is not what a QUALIFIED person would do...but then I'm just a rice farmer and the only reason I'm still alive is out of shear luck....I guess I'm just a lucky guy!!!

Cheers,

Chownah

[Crossy]

Of course this is not what a QUALIFIED person would do...but then I'm just a rice farmer and the only reason I'm still alive is out of shear luck....I guess I'm just a lucky guy!!!

Do I detect just an eensy-weensy bit of a dig at certain members of this board?

I wish I'd kept my big gob shut about buried wiring, just wanted to confirm if the UK practice was acceptable in LoS domestic installations.

To be honest, the actual chance of putting a nail through a cable is so miniscule that it's not worth worrying about. I have a cable detector (brought from the UK) as insurance against the point-to-point wiring I noted in my OP re. buried wiring, in the end it cost me far less that I'd save by not using conduit

[technocracy]

Of course this is not what a QUALIFIED person would do...but then I'm just a rice farmer and the only reason I'm still alive is out of shear luck....I guess I'm just a lucky guy!!!

Do I detect just an eensy-weensy bit of a dig at certain members of this board?

I wish I'd kept my big gob shut about buried wiring, just wanted to confirm if the UK practice was acceptable in LoS domestic installations.

To be honest, the actual chance of putting a nail through a cable is so miniscule that it's not worth worrying about. I have a cable detector (brought from the UK) as insurance against the point-to-point wiring I noted in my OP re. buried wiring, in the end it cost me far less that I'd save by not using conduit

Crossy,

The problem you will have (as with most things) is actually getting the plastic shielding as used in the UK. I certainly haven't seen it - hence why I went down the yellow conduit route - and to be honest it is actually easier!

On the subject of concrete nails and conduit (trying not to pour petrol on the fire here ..... ) - what would actually happen is when the nail is first hit the thinner layer of render over the conduit would shatter and fall off the conduit revealing the conduit, since the render doesn't grip to the conduit.

[Crossy]

Crossy,

The problem you will have (as with most things) is actually getting the plastic shielding as used in the UK. I certainly haven't seen it - hence why I went down the yellow conduit route - and to be honest it is actually easier!

On the subject of concrete nails and conduit (trying not to pour petrol on the fire here ..... ) - what would actually happen is when the nail is first hit the thinner layer of render over the conduit would shatter and fall off the conduit revealing the conduit, since the render doesn't grip to the conduit.

Agree with the scenario of the render shattering when the conduit rebounds.

The plastic shield is not actually required by the UK regs and its purpose is actually to prevent cables being damaged by the plasterer rather than stop nails being bashed through it.

[chownah]

Of course this is not what a QUALIFIED person would do...but then I'm just a rice farmer and the only reason I'm still alive is out of shear luck....I guess I'm just a lucky guy!!!

Do I detect just an eensy-weensy bit of a dig at certain members of this board?

I wish I'd kept my big gob shut about buried wiring, just wanted to confirm if the UK practice was acceptable in LoS domestic installations.

To be honest, the actual chance of putting a nail through a cable is so miniscule that it's not worth worrying about. I have a cable detector (brought from the UK) as insurance against the point-to-point wiring I noted in my OP re. buried wiring, in the end it cost me far less that I'd save by not using conduit

Crossy,

The problem you will have (as with most things) is actually getting the plastic shielding as used in the UK. I certainly haven't seen it - hence why I went down the yellow conduit route - and to be honest it is actually easier!

On the subject of concrete nails and conduit (trying not to pour petrol on the fire here ..... ) - what would actually happen is when the nail is first hit the thinner layer of render over the conduit would shatter and fall off the conduit revealing the conduit, since the render doesn't grip to the conduit.

This way when you give the nail that first good whack the last thing you will realize before you die from electocution is the color of the conduit!!!...a fitting end I say!!

[elkangorito]

[Crossy]

From the 'Thai domestic Electrical Work' thread, probably a better place to put the answers

Just brought a place from Sansiri and moved in over Songkran.

First morning woke up, jumped in the shower and got an elecrtic shock from the metal shower faucet when I tried to turn it off!

I don't know much about domestic electrical work but I assume that this is not normal! I suppose they haven't grounded the plumbing, but how could I check? What should I look for?

Edited April 24, 2007 by Crossy

[Crossy]

Just brought a place from Sansiri and moved in over Songkran.

First morning woke up, jumped in the shower and got an elecrtic shock from the metal shower faucet when I tried to turn it off!

I don't know much about domestic electrical work but I assume that this is not normal! I suppose they haven't grounded the plumbing, but how could I check? What should I look for?

Are you in a house or a condo?

OK, there is certainly an earthing issue, but simply having no ground alone should not result in shocks. Do you get a tickle from your PC casework?

1. TURN OFF THE POWER TO THE WATER HEATER!!!!!

2. Open up the heater where the supply wires go in, do NOT touch any wires (just because the breaker is off doesn't guarantee that all the cables are dead).

3. You will see, a black live wire, a white or grey neutral and (hopefully) a green ground wire. Check the ground is well attached to the metalwork.

4. At the distribution board (switch off the main breaker before removing the cover) locate the green wire from the heater (often easier said than done ). It should go to a ground bar, which in turn should be grounded to some form of ground spike (in a condo you should see a thick ground going off with your incoming supply cables).

Let us know what you see

EDIT What is your electrical competence level? I really don't advise anything more than a visual inspection unless you are at least confident using (and have) a simple digital multimeter and some basic electrical knowledge and safety training.

Do you have an ELCB (or Safe-T-Cut), if not consider getting one installed as part of your work (you are going to need an electrician).

Edited April 24, 2007 by Crossy

[quiksilva]

Thanks Crossy, I'm in a house, the wife and maid have reported little shocks from the fridge but I haven't noticed anything myself, or from the PC.

I will report back shortly, and will try to do so without touching anything!

Edited April 24, 2007 by quiksilva

[Crossy]

Thanks Crossy, I'm in a house, the wife and maid have reported little shocks from the fridge but I haven't noticed anything myself, or from the PC.

I will report back shortly, and will try to do so without touching anything!

A house makes life easier as you should be able to find the ground spike.

I forgot to ask, do you have two or three pin outlets? If three pin open one (POWER OFF) and check that there actually is a green ground wire going somewhere.

Also, have a look here http://www.crossy.co.uk/wiring/

EDIT Got a digital camera? Post some photos of what you see

Edited April 24, 2007 by Crossy

[technocracy]

3. You will see, a black live wire, a white or grey neutral and (hopefully) a green ground wire. Check the ground is well attached to the metalwork.

4. At the distribution board (switch off the main breaker before removing the cover) locate the green wire from the heater (often easier said than done )

If you lucky if might be green but be advised it could be red, black or whatever colour building cable (single core) the Thai sparkie used.

[quiksilva]

After closer inspection ALL the outlets appear to be two pins, what on 'earth' were they thinking? (and this from Thailand's 'leading' developer, Sansiri) I have the sparkies coming around on Saturday, I'll get the digi camera out and will post pics at that time.

Looks like we have some work on the horizon. They apparently hooked up the ground for an a/c unit in another room to the same ground wire the water heater used.. could that be an issue?

BTW Crossy your website is very informative and easy for non-techies like myself to grasp. Great job. Mods?? I think there needs to be a sticky to it somewhere. This information could save lives.

Edited April 25, 2007 by quiksilva

[Bannawk]

Guys, very informative stuff, but a little over my head I'm afraid.

I'll be building a new home next year, does anyone know of a competent, qualified, electrician in the Chiang Mai area? What I've seen in the homes under construction in this area is really....well, shocking! (sorry, couldn't help it.) But seriously, any names?

Thanks.

[Crossy]

After closer inspection ALL the outlets appear to be two pins, what on 'earth' were they thinking? (and this from Thailand's 'leading' developer, Sansiri) I have the sparkies coming around on Saturday, I'll get the digi camera out and will post pics at that time.

Looks like we have some work on the horizon. They apparently hooked up the ground for an a/c unit in another room to the same ground wire the water heater used.. could that be an issue?

BTW Crossy your website is very informative and easy for non-techies like myself to grasp. Great job. Mods?? I think there needs to be a sticky to it somewhere. This information could save lives.

Typical Thai I'm afraid, two pole outlets save 30% on wire

The grounds should all go to a ground bar in your distribution board / consumer unit and thence via a nice fat wire to a ground stake. A new construction should also have a MEN link between the incoming neutral and the ground bar. I suspect that you've got two 'grounds' tied together but not actually grounded

This thread is referenced in the useful information sticky, unfortunately there were so many sticky threads at one time that the real threads were in danger of ending up on page 2, so the descision was made to put all the links in one thread. Just takes the occasional post to bump this onto page 1

I really need to maintain the website properly. Another sparks (Elkangorito) provided a lot of the info and I've still got some of his drafts to sanitize (de-tech), it's just finding the time

EDIT You may want to print this diagram http://www.crossy.co.uk/wiring/CU-2.jpg to show the sparkies and compare with what you've actually got

Edited April 25, 2007 by Crossy

[Luckydog]

I get no kick from Champaigne, but I certainly get one from my PC!

Bought it from Liberty Computers off 2nd Rd.

Told the owner there about it to which he replied "Yes, we always get that here. Don't worry".

What should I do ?

[Crossy]

I get no kick from Champaigne, but I certainly get one from my PC!

Bought it from Liberty Computers off 2nd Rd.

Told the owner there about it to which he replied "Yes, we always get that here. Don't worry".

What should I do ?

A very common problem, caused by poor or non-existant earthing

Read this site http://www.crossy.co.uk/wiring/ particularly this page http://www.crossy.co.uk/wiring/2pin.html and come back with any questions/problems

[robint]

fyi

the power supplies in PCs are inherently leaky because of the type of power supply used (its called a switched mode power supply SMPS). Its a complex component and prone to failure especially if run near its maximum power output - vulnerable to instability. A cheapo 250W unit is barely adequate for a modern pc with video cards and other addons. specify at least 350W+ unit

You are alsways likely to get a shock from an unearthed PC because the power supply contain special filter circuits which leak to earth. This means that you pc may not work with an RCD. You must use an earth rod (especially if you have young children around)

BTW I was really surprised to get a tingle off my PC (which I havent earthed yet cos Ive just moved in and there is no earth lead). The surprise was that i was standing in bare feet on a wood block floor, so should have been insulated - just goes to show what can happen

You can never be too careful in LOS with electrics

[chownah]

You are alsways likely to get a shock from an unearthed PC because the power supply contain special filter circuits which leak to earth. This means that you pc may not work with an RCD. You must use an earth rod (especially if you have young children around)

Are you sure that the filters leak to earth....or do they leak to the neutral? If they have to leak to earth and there is no earth like on the computer I am using right now.....then how do they function? Also, it seems to me that in a properly earthed outlet the earth and neutral will be at almost the same potential (assuming nothing is amiss) so I can't see the necessity of a filter leaking to earth rather than neutral. It is unreasonable for me to expect you to have a circuit diagram for one of these things....so I don't expect that you do....but....do you?

Chownah

[Crossy]

Are you sure that the filters leak to earth....or do they leak to the neutral? If they have to leak to earth and there is no earth like on the computer I am using right now.....then how do they function? Also, it seems to me that in a properly earthed outlet the earth and neutral will be at almost the same potential (assuming nothing is amiss) so I can't see the necessity of a filter leaking to earth rather than neutral. It is unreasonable for me to expect you to have a circuit diagram for one of these things....so I don't expect that you do....but....do you?

Chownah

Yes they do. Dr Naam posted a circuit somewhere on one of the numerous 'shock from my PC' threads. There are (amongst other things) small capacitors between live-earth and neutral-earth (IIRC there's also one live-neutral). These form a potential divider with the earth terminal in the middle. With no ground connection the chassis hangs around 50% of mains, pretty high source impedence but still enough ooomph to give you a strong tickle.

True that neutral and ground are at roughly the same potential but since live and neutral are interchangeable on a switching PSU (they are not polarity sensitive) you still need both capacitors.

EDIT Here we go, it's the two 220pF caps on the right that do the biting :-

BTW Without the ground connection these filters do not work correctly. Although you will see nothing on your PC (the filter stops noise getting OUT of the PSU) you may well see the effects on your TV or audio system.

Edited April 29, 2007 by Crossy

[chownah]

Crossy,

Thanks for that. I'm really surprised to learn this. I thought that the only connection to a chasis on any appliance would only be a straight and unobstructed path to ground.

It does look like this creates a nuisance more than a danger....is that right? If so, then could this nuisance be elimitated by not connecting the earth conncetion on the load side?

Chownah

Edited April 29, 2007 by chownah

[Crossy]

Crossy,

Thanks for that. I'm really surprised to learn this. I thought that the only connection to a chasis on any appliance would only be a straight and unobstructed path to ground.

It does look like this creates a nuisance more than a danger....is that right? If so, then could this nuisance be elimitated by not connecting the earth conncetion on the load side?

If you open up your PC PSU you should se that it's wired with a direct connection from the casework to the incoming ground

Theoretically you could remove the connection between the node of the capacitors and the chassis which would then remove the possibility of the chassis floating at 50% mains.

In practice this is not possible as the capacitors are in the form of a 'feed-through' device that bolts directly to the can containing the filter assembly which is then bolted to the chassis. You'd need to open up the filter (which is usually a sealed unit) and perform some surgery on mains wiring inside, really not recommended.

Remember, the manufacturers don't put in unnecessary components, these capacitors are there for a reason. The ONLY fix for a 'tickly case' is to properly ground the supply

[robint]

Thanks crossy, I didnt want to come across too technical and bamboozle peeple like chownah and his self confessed ignorance of the subject. I am merely emphasizing the potential dangers of an unearthed PC, especially to a small child.

After all, thats what this thread is really about - safety.

We cant turn round and educate the layman on electrical technology based on a few passing observations and explainations on specific details, when it takes 10's of year of theoretical study and practical experience to understand the subject properly and professionally.

I am still unable to get the message across to the average punter that the domestic fuse does not protect you against shock, You need proper earthing and preferably some RCD's.

I was told that it is now Thai law from late last year that all new electrical installations must be 3 wire.

Presumably using the pattern of socket typically available from Homepro (and used on PC equipment)

Well the joke is

a) Its not easy to get twin core and earth cable. You have to run a separate earthwire - messy)

Where can you buy 3 pin re-wireable plugs (I did spot some once in a bkk Homepro last year, but never again since then)