Domestic Electrical Wiring

[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?

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

Yes, the capacitors are there for a reason....you discussed that earlier....and my computer is not grounded so my capacitor is not working and frankly it doesn't seem to be a problem at all. You didn't respond to my inquirey about whether the capacitor leaking to ground is a nuisance more than a danger...so I'll assume its a nuisance since I'm sure if you thought it was a danager you would have said something. I think there is another fix for those who are concerned about it...and that is to insulate the psu case from the chasis by using nylon screws and washers...wouldn't that work?...for those unfortunate people who rent their dwelling space and have no ground available and are concerned that the tickle they are getting might be dangerous even though it seems from what has been posted so far it is only a nuisance.

I know that you guys are very concerned about safety and that you see me as not stressing safety enough....and that sometimes some of you have a hard time maintaining your cool around this...believe me the overly cautious attitude that some people display here from time to time makes it hard for me to maintain my cool around it sometimes too...but I do...or at least I think I do. Your continued efforts to stay calm and civil are very much appreciated!!!!...I hope my efforts are appreciated too!!!

Chownah

Edited April 29, 2007 by chownah

[Crossy]

Yes, the capacitors are there for a reason....you discussed that earlier....and my computer is not grounded so my capacitor is not working and frankly it doesn't seem to be a problem at all. You didn't respond to my inquirey about whether the capacitor leaking to ground is a nuisance more than a danger...so I'll assume its a nuisance since I'm sure if you thought it was a danager you would have said something. I think there is another fix for those who are concerned about it...and that is to insulate the psu case from the chasis by using nylon screws and washers...wouldn't that work?...for those unfortunate people who rent their dwelling space and have no ground available and are concerned that the tickle they are getting might be dangerous even though it seems from what has been posted so far it is only a nuisance.

I know that you guys are very concerned about safety and that you see me as not stressing safety enough....and that sometimes some of you have a hard time maintaining your cool around this...believe me the overly cautious attitude that some people display here from time to time makes it hard for me to maintain my cool around it sometimes too...but I do...or at least I think I do. Your continued efforts to stay calm and civil are very much appreciated!!!!...I hope my efforts are appreciated too!!!

Chownah

OK, 115V from a high impedance source is probably not going to harm a healthy adult, although as you are aware it will give you a pretty strong nudge. Substitute 'healthy adult' with 'small child with wet feet' or 'healthy adult with hot coffee' and you could have a disaster!

It's not always the shock that causes the injury, it's the involuntary action that results e.g. spill boiling coffee on your wedding tackle, "aaarrrggghhhh - can you kiss it better please dear?" (actually, could be an idea there :D ).

Isolating the case metalwork will certainly stop you getting a zap, but bear in mind that the 0V line from your PSU output will most likely be internally connected to the PSU ground and will therefore still be at 115V. The upshot is that all the metal parts of your USB, VGA, audio ports etc. may still be at bitey voltages. There is a slight possibility that components with metal casework (disk drives for example) may not like their casework and 0V lines being at such different voltages (and will protest by going fizzzz!), they may even connect the two together, negating the effect of your isolation efforts.

It is of course entirely up to you what you do in your own home, far be it from me to tell you otherwise. But I don't believe you can EVER be over cautious around electric power.

Perhaps it's caused by being around rail traction-power systems 750VDC @ 3000A (SkyTrain, BKK Metro), 1500V DC @ 5,000 Amps (Seoul subway, HKK Airport Rail Link) or 25kVAC @ 500amps (BKK ARL, most surface electric railways), that's made me this way. I don't work on these systems, just tooooo dangerous, but I get rather nearer to them than most people.

Good luck with your isolation efforts.

Hey, dumb idea, get a plastic case (still wont solve the ports issue but has to be easier (and safer) than mucking around inside the PSU)

Edited April 29, 2007 by Crossy

[chownah]

Isolating the case metalwork will certainly stop you getting a zap, but bear in mind that the 0V line from your PSU output will most likely be internally connected to the PSU ground and will therefore still be at 115V.

I don't/can't seem to get a shock from the case on my computer and my outlets do not have ground wires. Could it be that my 0V line is not connected to ground? Since you say "most likely" does this mean that sometimes it is and sometimes it isn't?

I think I'll go find my mulitmetre and see what kind of voltages I've got on my case and port hardware and report back.

You imply that it could be disasterous to children....do you have any evidence of this or a link discussing this (in relation to the problem we are discussing) or had anyone ever heard of anyone having a disaster of this type with children? There are millions of children huddled around thousands of computers here in Thailand and I'm willing to bet that the majority of the computers are not grounded....have there been lots of reports of disasters coming form this?...or any reports? I'm just trying to find out if there is a real problem here and if so what is its magnitute or if its only a potential problem (pun intended).

Chownah

[Crossy]

I don't/can't seem to get a shock from the case on my computer and my outlets do not have ground wires. Could it be that my 0V line is not connected to ground? Since you say "most likely" does this mean that sometimes it is and sometimes it isn't? Don't forget, that there has to be a path to ground through yourself and the building structure before you get a shock, could be that you are just a bad conductor It's possible that the 0V is not connected internally to ground, just not likely.

I think I'll go find my mulitmetre and see what kind of voltages I've got on my case and port hardware and report back. You'll need a good ground to check against. Or you could use your neutral as that should be within a few volts of ground.

BTW it's a multimeter a meter being a device that measures, a metre being the unit of length

You imply that it could be disasterous to children....do you have any evidence of this or a link discussing this (in relation to the problem we are discussing) or had anyone ever heard of anyone having a disaster of this type with children? There are millions of children huddled around thousands of computers here in Thailand and I'm willing to bet that the majority of the computers are not grounded....have there been lots of reports of disasters coming form this?...or any reports? I'm just trying to find out if there is a real problem here and if so what is its magnitute or if its only a potential problem (pun intended). Oh come on sir, even reports of children being killed by faulty water coolers in hospitals don't make the front page (mid last year IIRC). A few tickles or even a tragedy are going to get little coverage so no, I don't have any direct evidence of injury or even spilt coffee

Chownah

EDIT I've posted a query on the IEE / IET forum, if there are any credible reports of injury then someone there will have links.

Edited April 30, 2007 by Crossy

[technocracy]

On to an old topic .. .. flickering fluorescents!

I have just finished of wiring up the house i.e. installing all the sockets and lights etc. - the installation is 3 phase using a Square D consumer unit which has a permanent none breakered neutral just a 3 pole live main breaker.

So when I had finished putting all the sockets on I plug in a fluorescent light into a socket as I need a bit of light - however I can't remember why - but I flicked the main breaker off and hey presto the fluorescent was flickering!

I grabbed my multimeter and stuck in the neutral and read just over 50 volts on the neutral!!! I was slightly confused any way all was disconnect as it was late and I thought I'd check it out in the morning in daylight.

The next day I head in connect up stick in the probe on the neutral. . . 0v (well between -1v and 1v) - this time I didn't think much of it.

But continued with my work installing the lights - the live and neutral were left connected whilst I worked - obviously the individual MCBs were off (I ain't stupid!)!! When I was installing a ceiling extractor fan I got a medium size tickle off the neutral. As I was up in the roof space I didn't have the multimeter at hand just the trusty testing screwdriver - I stuck it on the neutral and hey presto the light glowed! I sat and thought for a minute where the hel_l this sudden power could be coming from! Anyway I shouted down to the wife tell everyone disconnect ANYTHING that is connect to the power. A few minutes later I check again - no glow - it's gone!

I now knew something was leaking live down the neutral! Anyway to cut a long story short I tonight discovered after receiving numerous not so pleasant tickles that the culprit was a fan connected in the builders house outside. Luckily this afternoon nothing else was connected (well nothing outside of my control!) at the time so it allowed quick identification!

So what I am saying if you're suffering the flickering fluoresents at night - when fans are most likely to be used test your fan and what voltage there is on the neutral!

Other than that the house wiring has gone like a dream other than the normal shifty trouser feelings when you first switch on the breakers - regardless of how many times you've checked things!!

The number of workers and visitors who stood looking and asking why is there so many wires for the lights has been highly amusing. I am beginning to think my house is the only one in Laos with individual lighting radials!!

[Crossy]

The number of workers and visitors who stood looking and asking why is there so many wires for the lights has been highly amusing. I am beginning to think my house is the only one in Laos with individual lighting radials!!

You'd probably want to include Thailand as well as Laos

You really shouldn't get a nibble off the neutral even with a leaky appliance and N-E of 50V is frightening, you sure it's properly grounded at the Tx??

You may want to install a nice fat MEN link as well, just to be sure.

[technocracy]

The number of workers and visitors who stood looking and asking why is there so many wires for the lights has been highly amusing. I am beginning to think my house is the only one in Laos with individual lighting radials!!

You'd probably want to include Thailand as well as Laos

You really shouldn't get a nibble off the neutral even with a leaky appliance and N-E of 50V is frightening, you sure it's properly grounded at the Tx??

You may want to install a nice fat MEN link as well, just to be sure.

The outside run of cable is a bit of a mess due to it being a leftover from the building time on the house - it only remains as they haven't finished the walls around the land yet, once I've got my arse in gear and wired up the outside it'll be removed. In terms of grounding and this being Laos I would hazard a guess that there is sod all grounding anywhere!

In terms of a MEN link - I understand it's earthing of the neutral but since I've never installed one I am not 100% certain about it. But I am guessing that I'd just need to whack in an earthing rod (handily I have a spare 2m one and some 25mm2 cable) and connect the Neutral to the rod at the point where the overhead comes down to my meter? I assume then I'd connect the neutral to the house to the same rod?

50v down the Neutral is certainly frightening and also bloody uncomfortable when it bites you!

Cheers in advance!

[mosquitoman]

The number of workers and visitors who stood looking and asking why is there so many wires for the lights has been highly amusing. I am beginning to think my house is the only one in Laos with individual lighting radials!!

Sounds like you have been very thorough

Does this mean you have run a cable back to the consumer unit for each individual light circuit in your house, and have you then put each individual light circuit on its own breaker?

MM

[lopburi3]

If you have unprotected wires outside that is most likely the problem. In my case it was attic vermin deciding to eat the wires - neutral is grounded so when the amperage got high enough the breaker tripped. As problem was intermittent took awhile to isolate as removed wire from fixture and then found both leads hot.

Photo here

[Crossy]

In terms of a MEN link - I understand it's earthing of the neutral but since I've never installed one I am not 100% certain about it. But I am guessing that I'd just need to whack in an earthing rod (handily I have a spare 2m one and some 25mm2 cable) and connect the Neutral to the rod at the point where the overhead comes down to my meter? I assume then I'd connect the neutral to the house to the same rod?

Have a look here for how to connect a MEN link

http://www.crossy.co.uk/wiring/Consumer.html

Are there other buildings operating off the same 3-phase Tx? Your large N-E potential MAY be caused by a big phase imbalance causing excessive neutral current.

[technocracy]

In terms of a MEN link - I understand it's earthing of the neutral but since I've never installed one I am not 100% certain about it. But I am guessing that I'd just need to whack in an earthing rod (handily I have a spare 2m one and some 25mm2 cable) and connect the Neutral to the rod at the point where the overhead comes down to my meter? I assume then I'd connect the neutral to the house to the same rod?

Have a look here for how to connect a MEN link

http://www.crossy.co.uk/wiring/Consumer.html

Are there other buildings operating off the same 3-phase Tx? Your large N-E potential MAY be caused by a big phase imbalance causing excessive neutral current.

Ahhh it's even simpler than I was thinking - just hook the Neutral to the earth in the consumer unit. Be done tomorrow.

Lopburi - nope, it's definately this dodgy fan. I am now routinely checking the neutral for a whiff of any voltage and if I just tell them UNPLUG THAT F'ING FAN - and hey presto as if by magic the voltage on the neutral disappears!

Mosquito - Yep, I have 3 lighting circuits - Left and right side of house and upstairs each on their very own 10amp breaker - on 1.5mm2 cable with earth throughout.

As for what might be hooked up to my Tx - I ain't exactly sure but tonight a big old show stopper reared it's head - that being the actual amps on the village grid! Since what there was tonight wouldn't start the newly installed 8kw (25000btu) aircons. The blower units work fine on the fan but when it tried kick the compressor into life the lights in the house dimmed and the aircon turned itself off . .. . oh deep joy - time to talk to the Laos Electric Company. We have the Volts (a nice and rosey 223v at the Aircon unit) but just not the Amps .... so it seems which is a royal pain in the butt. I really don't want my own transformer - I already have my own pole - I'll own half the grid at this rate!!!!

The aircon installs worked this afternoon - obviously when there is minimal load around, so before folks start questioning that side of it.

[chownah]

I don't/can't seem to get a shock from the case on my computer and my outlets do not have ground wires. Could it be that my 0V line is not connected to ground? Since you say "most likely" does this mean that sometimes it is and sometimes it isn't? Don't forget, that there has to be a path to ground through yourself and the building structure before you get a shock, could be that you are just a bad conductor It's possible that the 0V is not connected internally to ground, just not likely.

I think I'll go find my mulitmetre and see what kind of voltages I've got on my case and port hardware and report back. You'll need a good ground to check against. Or you could use your neutral as that should be within a few volts of ground.

BTW it's a multimeter a meter being a device that measures, a metre being the unit of length

You imply that it could be disasterous to children....do you have any evidence of this or a link discussing this (in relation to the problem we are discussing) or had anyone ever heard of anyone having a disaster of this type with children? There are millions of children huddled around thousands of computers here in Thailand and I'm willing to bet that the majority of the computers are not grounded....have there been lots of reports of disasters coming form this?...or any reports? I'm just trying to find out if there is a real problem here and if so what is its magnitute or if its only a potential problem (pun intended). Oh come on sir, even reports of children being killed by faulty water coolers in hospitals don't make the front page (mid last year IIRC). A few tickles or even a tragedy are going to get little coverage so no, I don't have any direct evidence of injury or even spilt coffee

Chownah

EDIT I've posted a query on the IEE / IET forum, if there are any credible reports of injury then someone there will have links.

Have there been any reports yet? I'm beginning to feel more sure of my original hunch that the tingle one might get from an ungrounded computre case is only a nuisance and not a real danger. Unfortunately I have not had time to hunt down my mulitmetrer to see what's up with my ungrounded computer and why I get no shock from it....my excuse is that the rains have come early this year and I've been busy ploughing the rice fields.

Chownah

[quiksilva]

Update on my thrilling showers, all is well the sparky's came around and got together with the project's resident sparky and fixed it all up.

Ever cautious I insisted that they take their socks off and stand in the shower to prove to me it worked, and voila no more shocks! I understand it was a problem stemming from poor grounding of the water heater which has now been sorted.

They also fixed my ungrounded PC and I was mistaken in fact ALL of my sockets are indeed grounded

So good grades all round for my developer Sansiri.

Edited May 10, 2007 by quiksilva

[Crossy]

Have there been any reports yet? I'm beginning to feel more sure of my original hunch that the tingle one might get from an ungrounded computre case is only a nuisance and not a real danger. Unfortunately I have not had time to hunt down my mulitmetrer to see what's up with my ungrounded computer and why I get no shock from it....my excuse is that the rains have come early this year and I've been busy ploughing the rice fields.

Chownah

Well, I'm quite sure you'll be happy to know that nobody has posted any documented cases, a couple of anecdotal stories but nothing that would satisfy a determined rice farmer

There ARE well documented cases of deaths caused by other Class-1 appliances (that's metal cased appliances that are not double-insulated) that were operated without grounds but these were all related to internal faults that connected the casework to the phase.

Please continue to utilise your ungrounded PC as it will cause you no harm whatever (until a real fault conects the casework to phase that is).

[Crossy]

Update on my thrilling showers, all is well the sparky's came around and got together with the project's resident sparky and fixed it all up.

Ever cautious I insisted that they take their socks off and stand in the shower to prove to me it worked, and voila no more shocks! I understand it was a problem stemming from poor grounding of the water heater which has now been sorted.

5555 love it, perhaps we should include this advice on the website

[Sparks46]

Thanks for your post Robin but there some things that you said that need to addressed. My comments are in red.

Electrical wiring is one of many pet hates in the los. thai wiring at the user level is completely incompetent and unsafe judged against europeean stands - i wont even beging to mention on how many accounts but its a national disgrace. I fully agree.

the flang can best protect his domestic residence by installing an RCD safety breaker (earlier called an ELCB and also named a GFI in the states. Its around 1500 baht in homepro and can be part of proper distribution board (as made by Square D, one of the better makes). This is not entirely true. The BEST & FOREMOST form of protection is a correctly earthed MEN system employed at the installation. Earth Leakage Protection devices are electronic & are therefore, apt to fail. To put your life TOTALLY in the hands of one of these devices is foolishness.

It is an invaluable ADDED protection for your family BUT

be aware

a) Much of thai electrical goods is very shoddy electrically which means that you will get earth leaks in time - a rice cooker is a typical example - sometimes lethal. so this may result in nuisance trips or intermittant trips. A proper earthing system & an MEN link will fix this provided the appliance is adequately earthed.

Most existing witring will be 2 wire and the RCD is an essential protection, but a 3 wire Euro pattern system is preferable (available in homepro and typically seen on PC peripherals. but this needs a proper earth rod installed in the ground. this may increase the number of nuisance trips. The addition of Earth rods do not cause nuisance trips...unless equipment is faulty. In such a case, the fault is easily detected & the device is repaired/replaced.

c) If you use an earth rod, dont put it anywhere near an aerail mast as a lightening strike may blow your safety breaker without you knowing. this happened to me on my shower heater and the safety trip no longer worked - and I DIDNT KNOW i was unprotected. There is absolutely no evidence to say that earth rods attract lightning. On the other hand, a lack of earth rods will increase the risk of death should lightning strike an installation. After a lightning strike (secondary or primary), the user is advised to have all electrical protection tested for correct operation. The safest option is to replace all protection devices. This is rarely done as it is not generally necessary unless a direct strike has destroyed equipment.

d) RCDS are essential for electric showers (usually built in to the unit) and also for any equipment to be used outside in the yard. To be really safe you should use a step down transformer 200/110 and 110 volts machinery but its diifficlt to find here. If you indicate the use of a 'stepdown transformer', be sure to know what you are talking about. The technically safe 'low' voltage is any voltage less than 32 volts RMS. Contrary to popular belief, 110v is as dangerous as 220v.

e) PC power supplies are notoriously leaky and shocking so you may not be able to use this via you RCD cisrcuit. You will have to provide a separate supply and its own earth rod - as i do. Many appliances are 'leaky & shocking' because an appropriate earthing system is not used together with an appropriate MEN link. Again, the installation of an appropriate earthing system & an MEN link will resolve these problems. There is no such thing as a 'non leaky' appliance. For this reason, the MEN system together with appropriate earthing was introduced.

Still alive but I know of some who are not. If you continually trust your RCD's, you may not be alive much longer.

Hello again from Barry

The surge protection system you enquired about is:

Tesco - http://www.tesco-online.com/products/se/TES240R.htm - 240 VAC Surge Arrester for residential and light industrial usage. Installed at wattmeter, service entry, or weatherhead, safety clamps and dissipates lightning induced safely AC line high voltage current impulses going to a residence.

In the discussion above keep in mind - if you increase voltage you lower current - and voltage doesn't kill you - its the current.

Barry

hope this works

There are two problems here

1 gfci ground fault protection is to limit current to mili amps. much over 15ma is enough to kill a person. the higher the volts and the lower the resistance the higher the amps. as low as 49 volts has caused death

2 surge protection protects equipment, not people, from excesive voltage that can cause damage

[technocracy]

Back again. . . .

First off - I stuck in the MEN/PME link in the consumer unit and bingo! Not a sniff of voltage on the neutral . . lovely jubbly! That's the happy bit.

The other bit . . .

Transforms . .. oh deep joy! Just when I thought all wasa going to be done and dusted this huge inconvienience appears on the horizon!

Basically now after the highly skilled Laos Electrical team came around to check the power into the house. It has been determined that we don't have enough juice in the local transform to supply our needs. Just to note the skilled technicians appeared with a run of the mill multimeter with one of the probes missing just a bare bit of wire!!!

Even though I stood there and told them we have the volts but not the amps they still insisted on prodding around (at this point I got my multimeter complete with probes!). They got highly confused and cue much head and arse scratching when they saw 220 volts but the aircon wouldn't start . . . - they even went and got an aircon guy - even though the aircon will start sometime when the local transform is heavily loaded.

Amps just wasn't a word that was getting through - neither to them or my aircon! Anyway then the discussion turned to 'maa fai' (transforms) . . . at this point they were saying a 50 or 30, I asked 50 what? - Yes Watts was the reply!!! Ok they don't know amps but they knew Watts, Kilowatts at that.

So the upshot of it all is that I will soon be purchased my own personal 50Kw transform . .. . I might just about use 20Kw - dunno what the other 30Kw will be used for!!! I might start selling power around the village!!!

But out of curiosity you sparkies do you know any companies which sell smaller 3 phase transforms than 50Kw? As I am being told that the smallest I can get is 50 or next is 100.

[suanprig]

Ok Ok Ok. This techie stuff is all great if you know what your saying and reading about. However. If you have absolutly no idea about electricity like myself its not much fun.......

I have had a 16 year old house in Chiang Mai for 2 years and quite frankly am sick of being zapped. So far i have been electrocuted by the kettle, the Refrigerator, the back of computer, the computer monitor and the most recent the TV ariel. The TV ariel??? Is this actually possible? Well it is now.. it happened.

I recently ventured into my roof space to find a Junction box full of exposed, twisted together wires that was obviously prepared by little kid and not an electrician.

My question is? If i want to pull all this crap out of the house and have a decent safe system installed who do i approach to carry out the work? I am in Central Chiang Mai. There must be a person in this city that can make my electricity supply just a bit safer. but buggered if i can find him/her.......

i read of a guy named Prathom in another section of this site. Is he the man to contact or is there a electrical contracting mob that any one reading this forum can recommend in CM?

Any help would be much appreciated.

[technocracy]

Ok Ok Ok. This techie stuff is all great if you know what your saying and reading about. However. If you have absolutly no idea about electricity like myself its not much fun.......

I have had a 16 year old house in Chiang Mai for 2 years and quite frankly am sick of being zapped. So far i have been electrocuted by the kettle, the Refrigerator, the back of computer, the computer monitor and the most recent the TV ariel. The TV ariel??? Is this actually possible? Well it is now.. it happened.

I recently ventured into my roof space to find a Junction box full of exposed, twisted together wires that was obviously prepared by little kid and not an electrician.

My question is? If i want to pull all this crap out of the house and have a decent safe system installed who do i approach to carry out the work? I am in Central Chiang Mai. There must be a person in this city that can make my electricity supply just a bit safer. but buggered if i can find him/her.......

i read of a guy named Prathom in another section of this site. Is he the man to contact or is there a electrical contracting mob that any one reading this forum can recommend in CM?

Any help would be much appreciated.

I would hazard a small guess to the fact that you house purely has 2 pin sockets everywhere so not having any earth in the house - also by the sounds of it you might have a dodgy device that is causing the shocks as the leaked current has nowhere to go without earthing it just hangs around in the metal casing ready for the next someone to touch it who'll do the earthing (i.e. you!)!

As for a box full of twisted together wire - I'd also guess that around all of them was a load insulation tape? As unfortunately this is standard in Thailand and Laos - connectors are just too technical!

... Back to my previous post - I've just re-read it and it appears I missed the 'er' out of all the spellings of Transformers!

So anyone know of companies in Thailand that sell 30Kw Transformers?

[S3Iraq]

Hi Crossy,

Over the past month or so, I've very much enjoyed reading the posts on this board, I'd like to express my gratitude to yourself, enkangorito and others who have contributed their time and knowledge.

After living in Issan for the past couple of years, I have finally decided to take the plunge and build a house... I already had a good idea of how this would progress, so even though my patience has and no doubt will continue to be throroughly tested, I'm resigned to that fact and can often be found taking long walks 'around the block' so to speak rather than confronting issues head on...

I do have a question for you pertaining to an auxilliary power supply. As I type, the power has been down for about 12 hours here... again... it's red hot and I'm sweating like a dog in a chinese chip shop, despite it being overcast.... this time of year the electrical storms are quite vicious and power outages are all too common.

I know that the conventional approach would be to have a large diesel standby generator, but I have been considering another approach and would appreciate your comments/suggestions.

Many years ago, I worked with large radio rebroadcast stations and we had a backup electrical system which consisted of a large bank of batteries connected in series-parallel (to provide sufficient voltage and amps to run the equipment for about 12 hours in the event of an outage) which would replace the domestic supply should it fail, the batteries were trickle charged from mains current.

My question is, does this sound like a reasonable option for a standby option in the event of the failure of domestic supply here? I would like to put a system together that will continue to power all the essentials, fridge, lights etc, and possibly a couple of luxury items, TV, DVD for about 12 hours... I like the fact that this would be noise free, not requiring the generator to run, and perhaps it could be trickle charged from a solar panel? Mains supply or a small generator should the power be down for a sustained period.

I would be interested on your thoughts about the voltage required, I know that domestic appliances can be run from a 12v battery through an inverter, but would be like to know what kind of ampere hour capacity you think this would require... also does a system exist that would allow this to be permanantly connected and come online automatically should power fail...?

Thank you in advance for taking the time to respond to this.

[elkangorito]

A little info on transformers & phase balance. If a password request window appears, click on the 'read only' button.

Edited June 5, 2007 by elkangorito

[Crossy]

My question is, does this sound like a reasonable option for a standby option in the event of the failure of domestic supply here? I would like to put a system together that will continue to power all the essentials, fridge, lights etc, and possibly a couple of luxury items, TV, DVD for about 12 hours... I like the fact that this would be noise free, not requiring the generator to run, and perhaps it could be trickle charged from a solar panel? Mains supply or a small generator should the power be down for a sustained period.

I would be interested on your thoughts about the voltage required, I know that domestic appliances can be run from a 12v battery through an inverter, but would be like to know what kind of ampere hour capacity you think this would require... also does a system exist that would allow this to be permanantly connected and come online automatically should power fail...?

What you require is an Uninteruptable Power Supply (UPS), very common in the IT world to keeps stuff alive during power outages. Available in various sizes from a few hundred Watts to many kilowatts, priced accordingly. Usually they have internal batteries but are available with connections for external batteries (you will need this option if you're wanting 12 hours of autonomy), have a look at the APC Home UPS (not sure if it's available in Thailand as yet though).

First thing to do is decide what you want to run and add up all the power ratings, do NOT expect to be able to run your aircon, multiply your total power by 1.5 and source the next bigger UPS.

To determine your battery requirements, convert your power requirement into Amps at 24V (most UPS's of the sizes we're interested in use a 24V supply).

Say you want 1500Watts, Watts=Volts x Amps so Amps = Watts/Volts = 1500/24 = 62.5A

You want 12 hours of run time so you will need 62.5 x 12 = 750 Amp Hours of battery at 24V, you don't want to fully discharge the batteries so add 30% = 1000AH

You are going to need 20 x 100AH 12V batteries, ideally, sealed lead-acid type, although you may be frightened by the price You could use car batteries to cut the cost, but they are really not designed for this purpose and won't have the life of the sealed units. BTW, if you're connecting in series-parallel arrangement make sure you have plenty of fusing, a lead-acid battery array of this size contains a serious amount of energy, more than enough to burn your house down (ever accidentally shorted even a single car battery?). Ideally all the batteries should be identical.

THEN, you have to charge this lot, to charge your 1000AH in six hours you'll need to push in approaching 200Amps (not going to get that from solar).

IMHO you're better off using smaller batteries (50AH) and spending the money saved on a small GenSet.

NOTE Before anyone jumps in with things like Power Factor and the difference between VA and Watts, along with the inefficiency of the UPS and batteries, I've taken these into account with the over-rating factors, we are, after all, looking at a ball-park size.

Edited June 6, 2007 by Crossy

[S3Iraq]

My question is, does this sound like a reasonable option for a standby option in the event of the failure of domestic supply here? I would like to put a system together that will continue to power all the essentials, fridge, lights etc, and possibly a couple of luxury items, TV, DVD for about 12 hours... I like the fact that this would be noise free, not requiring the generator to run, and perhaps it could be trickle charged from a solar panel? Mains supply or a small generator should the power be down for a sustained period.

I would be interested on your thoughts about the voltage required, I know that domestic appliances can be run from a 12v battery through an inverter, but would be like to know what kind of ampere hour capacity you think this would require... also does a system exist that would allow this to be permanantly connected and come online automatically should power fail...?

What you require is an Uninteruptable Power Supply (UPS), very common in the IT world to keeps stuff alive during power outages. Available in various sizes from a few hundred Watts to many kilowatts, priced accordingly. Usually they have internal batteries but are available with connections for external batteries (you will need this option if you're wanting 12 hours of autonomy), have a look at the APC Home UPS (not sure if it's available in Thailand as yet though).

First thing to do is decide what you want to run and add up all the power ratings, do NOT expect to be able to run your aircon, multiply your total power by 1.5 and source the next bigger UPS.

To determine your battery requirements, convert your power requirement into Amps at 24V (most UPS's of the sizes we're interested in use a 24V supply).

Say you want 1500Watts, Watts=Volts x Amps so Amps = Watts/Volts = 1500/24 = 62.5A

You want 12 hours of run time so you will need 62.5 x 12 = 750 Amp Hours of battery at 24V, you don't want to fully discharge the batteries so add 30% = 1000AH

You are going to need 20 x 100AH 12V batteries, ideally, sealed lead-acid type, although you may be frightened by the price You could use car batteries to cut the cost, but they are really not designed for this purpose and won't have the life of the sealed units. BTW, if you're connecting in series-parallel arrangement make sure you have plenty of fusing, a lead-acid battery array of this size contains a serious amount of energy, more than enough to burn your house down (ever accidentally shorted even a single car battery?). Ideally all the batteries should be identical.

THEN, you have to charge this lot, to charge your 1000AH in six hours you'll need to push in approaching 200Amps (not going to get that from solar).

IMHO you're better off using smaller batteries (50AH) and spending the money saved on a small GenSet.

NOTE Before anyone jumps in with things like Power Factor and the difference between VA and Watts, along with the inefficiency of the UPS and batteries, I've taken these into account with the over-rating factors, we are, after all, looking at a ball-park size.

Outstanding response Crossy,

Really, thank you very much for that, you've given me much to work with and I appreciate you taking the time to figure that out...

Cheers, J

[Khonwan]

As described in other posts, I have a very long (1,556m) 3-phase supply. The concrete pole supporting my 50kVA transformer also supports my kWh-meter. The high voltage lines are protected with an overhead ground-wire. Unfortunately, the overhead ground wire terminates at this pole (due to lack of budget, PEA did not extend the long overhead ground to the transmission poles beyond my location). The transformer is grounded at this pole. So too is the meter. Both earth-ground rods are therefore only inches apart. At the other end of the system, my house is electrically earth-grounded.

My kWh-meter exploded again last week during a thunder storm. This is the third time in less than one year...the second time in less than two months (always due to lightning strikes).

The local PEA manager now wants me to earth my neutral cable every 500m. He also wants me to install phase-to-neutral surge protectors across the cables just after the meter and again just before entry to the house (rated at 2.5kA 500V).

I'm concerned that this remedy may not help. I think the real cause is the location of the grounded kWh-meter on the same lightning-grounded transformer pole. I think the kWh-meter should be re-located to the next pole (my low voltage pole) and earth-grounded.

I'd appreciate comments from the sparkies before Tuesday since the local PEA manager is to visit me then.

Thanks

Khonwan

[lopburi3]

S3Iraq:

I seriously doubt that the radio station received UPS power from battery source for 12 hours. The normal configuration would be battery power until generators up to speed and then they take over the load until commercial power returns. Here in Thailand the batteries have a very short life (because of the heat). As you mention storms as the most likely cause of outages solar is probably not an option. Suspect you would be best served with a small generator unit if you can not ride out the outages.

[elkangorito]

As described in other posts, I have a very long (1,556m) 3-phase supply. The concrete pole supporting my 50kVA transformer also supports my kWh-meter. The high voltage lines are protected with an overhead ground-wire. Unfortunately, the overhead ground wire terminates at this pole (due to lack of budget, PEA did not extend the long overhead ground to the transmission poles beyond my location). The transformer is grounded at this pole. So too is the meter. Both earth-ground rods are therefore only inches apart. At the other end of the system, my house is electrically earth-grounded.

My kWh-meter exploded again last week during a thunder storm. This is the third time in less than one year...the second time in less than two months (always due to lightning strikes).

The local PEA manager now wants me to earth my neutral cable every 500m. He also wants me to install phase-to-neutral surge protectors across the cables just after the meter and again just before entry to the house (rated at 2.5kA 500V).

I'm concerned that this remedy may not help. I think the real cause is the location of the grounded kWh-meter on the same lightning-grounded transformer pole. I think the kWh-meter should be re-located to the next pole (my low voltage pole) and earth-grounded.

I'd appreciate comments from the sparkies before Tuesday since the local PEA manager is to visit me then.

Thanks

Khonwan

It is up to the energy authority to ensure that their supply is protected & associated equipment is protected. Does the kWh meter belong to you? If so, then you are responsible for it. If not, the PEA is.

They installed the supply system & you shouldn't have to pay for any part of their installation.

Having said all this, it may help if you;

1) as you suggest, relocate your kWh meter.

2) ensure that it is protected by either a BS 1361 HRC fuse or an appropriately rated circuit breaker. If the Tx is 50 kVA then a 10kA (fault current rating) CB should do the job. Either of these devices should be placed UPSTREAM of the kWh meter.

Surge protection of the supply is up to the energy authority, not you.

The local PEA manager now wants me to earth my neutral cable every 500m. He also wants me to install phase-to-neutral surge protectors across the cables just after the meter and again just before entry to the house (rated at 2.5kA 500V).

The PEA supply cables should be earthed every 500m. Surgeis required at Txers & at various locations along the local power grid/supply. They are trying to pass the cost onto you. The system here is TT &, according to my sources, it is an MEN system. As such, the energy authority should earth THEIR supply neutral every so often along the power pole route. This would solve an enormous number of problems.

Since this is a tropical climate & therefore prone to storms, it would be a good idea to buy a transient protection device (MOV). Good brands are Critec & Procel. Schneider may have some similar devices for sale.

[Khonwan]

As described in other posts, I have a very long (1,556m) 3-phase supply. The concrete pole supporting my 50kVA transformer also supports my kWh-meter. The high voltage lines are protected with an overhead ground-wire. Unfortunately, the overhead ground wire terminates at this pole (due to lack of budget, PEA did not extend the long overhead ground to the transmission poles beyond my location). The transformer is grounded at this pole. So too is the meter. Both earth-ground rods are therefore only inches apart. At the other end of the system, my house is electrically earth-grounded.

My kWh-meter exploded again last week during a thunder storm. This is the third time in less than one year...the second time in less than two months (always due to lightning strikes).

The local PEA manager now wants me to earth my neutral cable every 500m. He also wants me to install phase-to-neutral surge protectors across the cables just after the meter and again just before entry to the house (rated at 2.5kA 500V).

I'm concerned that this remedy may not help. I think the real cause is the location of the grounded kWh-meter on the same lightning-grounded transformer pole. I think the kWh-meter should be re-located to the next pole (my low voltage pole) and earth-grounded.

I'd appreciate comments from the sparkies before Tuesday since the local PEA manager is to visit me then.

Thanks

Khonwan

It is up to the energy authority to ensure that their supply is protected & associated equipment is protected. Does the kWh meter belong to you? If so, then you are responsible for it. If not, the PEA is.

They installed the supply system & you shouldn't have to pay for any part of their installation.

Having said all this, it may help if you;

1) as you suggest, relocate your kWh meter.

2) ensure that it is protected by either a BS 1361 HRC fuse or an appropriately rated circuit breaker. If the Tx is 50 kVA then a 10kA (fault current rating) CB should do the job. Either of these devices should be placed UPSTREAM of the kWh meter.

Surge protection of the supply is up to the energy authority, not you.

The local PEA manager now wants me to earth my neutral cable every 500m. He also wants me to install phase-to-neutral surge protectors across the cables just after the meter and again just before entry to the house (rated at 2.5kA 500V).

The PEA supply cables should be earthed every 500m. Surgeis required at Txers & at various locations along the local power grid/supply. They are trying to pass the cost onto you. The system here is TT &, according to my sources, it is an MEN system. As such, the energy authority should earth THEIR supply neutral every so often along the power pole route. This would solve an enormous number of problems.

Since this is a tropical climate & therefore prone to storms, it would be a good idea to buy a transient protection device (MOV). Good brands are Critec & Procel. Schneider may have some similar devices for sale.

Thanks for your reply, elkangorito. The supply cables and installation is mine...not PEA's. PEA supplied & installed the 50kVA 3-ph transformer and kWh-meter (at my cost). I then purchased & installed the full low voltage system to my home (1,556m between my transformer and my home - all my [wife's] land). I did, however, take advice from PEA at the time and followed that advice to the verbal letter.

Although I paid for the meter also, they appear to take responsibility for its replacement in case of lightning strike (three times now already) - I pay for the labour and HV & LV fuse replacements. My capacitor and HV surge protectors were also destroyed this time - I think PEA want me to pay for these.

Earthing the neutrals every 500m is easy enough for me to do (I had originally considered doing so every 200m). I also don't mind installing the MOV's myself...so long as the problem is resolved and that I don't have to replace the MOV's too regularly (I've no idea of the price of these!). However, if the meter should not have been located on the transformer pole causing immediate proximity of the lightning ground and meter ground, I'll insist that PEA relocate the meter at their expense.

Do you know, were they wrong to locate the meter as they did? Am I correct to assume the lightning strike to the overhead ground (above the HV supply cables) earthed to a point in immediate proximity (two inches) to the meter's ground would likely destroy the meter?

Regards

Khonwan

[elkangorito]

As described in other posts, I have a very long (1,556m) 3-phase supply. The concrete pole supporting my 50kVA transformer also supports my kWh-meter. The high voltage lines are protected with an overhead ground-wire. Unfortunately, the overhead ground wire terminates at this pole (due to lack of budget, PEA did not extend the long overhead ground to the transmission poles beyond my location). The transformer is grounded at this pole. So too is the meter. Both earth-ground rods are therefore only inches apart. At the other end of the system, my house is electrically earth-grounded.

My kWh-meter exploded again last week during a thunder storm. This is the third time in less than one year...the second time in less than two months (always due to lightning strikes).

The local PEA manager now wants me to earth my neutral cable every 500m. He also wants me to install phase-to-neutral surge protectors across the cables just after the meter and again just before entry to the house (rated at 2.5kA 500V).

I'm concerned that this remedy may not help. I think the real cause is the location of the grounded kWh-meter on the same lightning-grounded transformer pole. I think the kWh-meter should be re-located to the next pole (my low voltage pole) and earth-grounded.

I'd appreciate comments from the sparkies before Tuesday since the local PEA manager is to visit me then.

Thanks

Khonwan

It is up to the energy authority to ensure that their supply is protected & associated equipment is protected. Does the kWh meter belong to you? If so, then you are responsible for it. If not, the PEA is.

They installed the supply system & you shouldn't have to pay for any part of their installation.

Having said all this, it may help if you;

1) as you suggest, relocate your kWh meter.

2) ensure that it is protected by either a BS 1361 HRC fuse or an appropriately rated circuit breaker. If the Tx is 50 kVA then a 10kA (fault current rating) CB should do the job. Either of these devices should be placed UPSTREAM of the kWh meter.

Surge protection of the supply is up to the energy authority, not you.

The local PEA manager now wants me to earth my neutral cable every 500m. He also wants me to install phase-to-neutral surge protectors across the cables just after the meter and again just before entry to the house (rated at 2.5kA 500V).

The PEA supply cables should be earthed every 500m. Surgeis required at Txers & at various locations along the local power grid/supply. They are trying to pass the cost onto you. The system here is TT &, according to my sources, it is an MEN system. As such, the energy authority should earth THEIR supply neutral every so often along the power pole route. This would solve an enormous number of problems.

Since this is a tropical climate & therefore prone to storms, it would be a good idea to buy a transient protection device (MOV). Good brands are Critec & Procel. Schneider may have some similar devices for sale.

Thanks for your reply, elkangorito. The supply cables and installation is mine...not PEA's. PEA supplied & installed the 50kVA 3-ph transformer and kWh-meter (at my cost). I then purchased & installed the full low voltage system to my home (1,556m between my transformer and my home - all my [wife's] land). I did, however, take advice from PEA at the time and followed that advice to the verbal letter.

Although I paid for the meter also, they appear to take responsibility for its replacement in case of lightning strike (three times now already) - I pay for the labour and HV & LV fuse replacements. My capacitor and HV surge protectors were also destroyed this time - I think PEA want me to pay for these.

Earthing the neutrals every 500m is easy enough for me to do (I had originally considered doing so every 200m). I also don't mind installing the MOV's myself...so long as the problem is resolved and that I don't have to replace the MOV's too regularly (I've no idea of the price of these!). However, if the meter should not have been located on the transformer pole causing immediate proximity of the lightning ground and meter ground, I'll insist that PEA relocate the meter at their expense.

Do you know, were they wrong to locate the meter as they did? Yes. In Australia & I dare say other countries, the kWh meter is placed as close to the consumer load as possible. The main reason being is that you will pay for any supply cable losses incurred to supply the installation with electricity. Also, the meter has a noticeable impedance between it & the supply Tx, which could theoretically reduce the impact of a lightning strike upon the installation. Am I correct to assume the lightning strike to the overhead ground (above the HV supply cables) earthed to a point in immediate proximity (two inches) to the meter's ground would likely destroy the meter? In Australia, the neutral cable (which is earthed) is placed above the HV supply cables for the reason as you state; to help protect the phase cables from lightning damage. All this is well & good but there are not many devices that can withstand a direct lightning strike. Secondary strikes are a different matter. MOV protection at the installation is usually adequate to protect against secondary strikes. As for your kWh meter, my only suggestions would be;

1) relocate it as close to your house as possible.

2) ask the PEA if LV transient protection can be placed between your kWh meter & their Tx. If so, ask them to recommend the protection system. This way, if it is not adequate, you have a 'come back' to them.

Normally, energy authorities do not allow consumers to have any input to electrical design whatsoever. This includes the consumer hiring an electrical engineer/consultant. I would try, as much as possible, to place most of the responsibility in their hands, otherwise they may be able to blame you for other local supply problems.

Regards

Khonwan

Khonwan, mycomments in blue.

[stickyb]

A slightly different question. I have a number of dimmer switches controlling incandescent lights ( not flourescent). The dimmers are rated at 300W, and the bulbs are at the most 150 watts, some only 50 watts.

I have noticed that the dimmer switches get quite warm to the touch when the light is off - there is no separate click off position as on Uk ones.

Am i drawing current when the lights are off? i don't know what the circuitry inside them is.

[chownah]

A slightly different question. I have a number of dimmer switches controlling incandescent lights ( not flourescent). The dimmers are rated at 300W, and the bulbs are at the most 150 watts, some only 50 watts.

I have noticed that the dimmer switches get quite warm to the touch when the light is off - there is no separate click off position as on Uk ones.

Am i drawing current when the lights are off? i don't know what the circuitry inside them is.

If the dimmer STAYS WARM all the time then you are drawing current... I capitolize STAYS WARM because the dimmer might feel warm when you turn the lights out as a residual from the running of the lights, but if it stays warm all the time (check in the morning before the lights get turned on) then power is being consumed all the time. If the dimmer does stay warm all the time then you might consider installing a switch in series with the dimmers (if they are all on the same circuit) to turn lights off....and you might even consider some other lighting alternative in that incandescents not only use more power in operating but they also create more waste heat which makes more work for an air con unit.