3 Phase Electric

[elkangorito]

Why should the main breaker be limited to 80 amps....seems to me that bigger would not cause a problem?...would it?...and if so what problem?

Chownah

Since I believe that the KWH meter to be used should be 100 amps & since these KWH meters do not have built-in overcurrent protection, the only thing that will prevent damage to the KWH meter is the MCB (Main Circuit Breaker). The next size CB up from 80 amps is 100 amps, which in not a good selection for this case. His max demand is less than 80 amps. In most installations (not in Thailand), the energy authority protects their KWH meter with an HRC fuse, aka the 'consumers fuse' or the 'service fuse'. This fuse is located before the KWH meter & is usually to BS 88 or BS 1361 standard. Its job is to protect the consumers mains from overload & to limit the fault current to the domestic installation. These fuses are normally rated the same (or slightly less) as the current carrying capacity as the consumers mains.

It seems that a 100 amp main circuit breaker would be the right size to protect the KWH meter since they are both 100 amp rated....so I'm still not seeing why you indicated that 80 amps is the max main circuit breaker to be used....what problem does the 100 amp main circuit breaker cause...I still don't get it. In your post you said " The next size CB up from 80 amps is 100 amps, which in not a good selection for this case. His max demand is less than 80 amps. "...I can't tell if you are saying that a 100 amp beaker is not good because of the 100 amp meter rating or if you are saying he onliy needs 80 amps so a 100 amp breaker is not necessary. When I got my service (with a 100 amp meter) I was told that a 100 amp main circuit breaker was the largest I should use....and that's what I've got...so I'm trying to anticipate what problem this may cause. The advantage of the 100 amp breaker is more room for future build out compared to an 80 amp breaker.

My main concern is protecting the meter. If the current coils are damaged (due to overload), the meter may read incorrectly or fail, which may lead to bigger power bills. This is an inconvenience either way you look at it.

The accuracy of Thermal Magnetic circuit breakers is affected by ambient temperature. Will the breaker trip at 95 Amps or 105 Amps? I prefer to err on the safe side rather than to gamble on the accuracy of a protective device. Another option is to use a Hydraulic Magnetic CB. They are quite accurate & are not affected by ambient temperature but are difficult to source in Thailand. They are also physically bigger & more expensive than a Thermal Magnetic CB.

Also, this is why an HRC Service fuse is used. It allows you to have whatever size Main Switch you want. It also allows you to choose either an automatic CB or a non-automatic CB as a Main Switch. A non-auto CB is simply a switch & therefore does not have any trip devices within it. This way, if your consumer mains are upgraded as a result of an increased demand, the only thing you'll need to do is change the size of the fuse, which is a very cheap option.

A 100 Amp CB protecting a device rated at 100 Amps offers no margin for error.

I think that from now on, I will be strongly suggesting the use of Service Fuses in all installations. This will solve many problems.

Thanks for the clarification. I take it that this is your gut feeling and is not based on any codes or manufacturer's specs. Could it be that a 100 Amp meter is rated at 100 Amps meaning that it is compatible with a 100 Amp main breaker?....that seems to be what I was told. This could mean that the meter could actually take more than 100 Amps but its rating contains a safety factor. If you think about it it would not make sense to rate a meter at 100 Amps if that was its "failure" current....it would seem to make sense that there would be some safety factor in the rating. Has it been positively determined yet exactly what the 100 Amp rating means for a kwh meter?

Well, it's not really a gut feeling.

If the KWH meter is a 100 Amp meter, it means that the current coils within the meter are designed to handle up to 100 Amps, without being damaged. While it is not possible to tell how current will actually damage the coils, it is therefore common sense to not exceed this figure of 100 Amps but it is also good practice to use a device that will adequately protect this accurate device. In this case, it would be best to use a 100 Amp HRC fuse because it is a much faster acting device compared to a 100 Amp CB, thereby affording better protection than the 100 Amp CB. If the HRC fuse is not employed, I would choose a CB that is rated lower than the 100 Amp capacity of the meter. In this case, the next size down CB is 80 Amps.

[chownah]

Why should the main breaker be limited to 80 amps....seems to me that bigger would not cause a problem?...would it?...and if so what problem?

Chownah

Since I believe that the KWH meter to be used should be 100 amps & since these KWH meters do not have built-in overcurrent protection, the only thing that will prevent damage to the KWH meter is the MCB (Main Circuit Breaker). The next size CB up from 80 amps is 100 amps, which in not a good selection for this case. His max demand is less than 80 amps. In most installations (not in Thailand), the energy authority protects their KWH meter with an HRC fuse, aka the 'consumers fuse' or the 'service fuse'. This fuse is located before the KWH meter & is usually to BS 88 or BS 1361 standard. Its job is to protect the consumers mains from overload & to limit the fault current to the domestic installation. These fuses are normally rated the same (or slightly less) as the current carrying capacity as the consumers mains.

It seems that a 100 amp main circuit breaker would be the right size to protect the KWH meter since they are both 100 amp rated....so I'm still not seeing why you indicated that 80 amps is the max main circuit breaker to be used....what problem does the 100 amp main circuit breaker cause...I still don't get it. In your post you said " The next size CB up from 80 amps is 100 amps, which in not a good selection for this case. His max demand is less than 80 amps. "...I can't tell if you are saying that a 100 amp beaker is not good because of the 100 amp meter rating or if you are saying he onliy needs 80 amps so a 100 amp breaker is not necessary. When I got my service (with a 100 amp meter) I was told that a 100 amp main circuit breaker was the largest I should use....and that's what I've got...so I'm trying to anticipate what problem this may cause. The advantage of the 100 amp breaker is more room for future build out compared to an 80 amp breaker.

My main concern is protecting the meter. If the current coils are damaged (due to overload), the meter may read incorrectly or fail, which may lead to bigger power bills. This is an inconvenience either way you look at it.

The accuracy of Thermal Magnetic circuit breakers is affected by ambient temperature. Will the breaker trip at 95 Amps or 105 Amps? I prefer to err on the safe side rather than to gamble on the accuracy of a protective device. Another option is to use a Hydraulic Magnetic CB. They are quite accurate & are not affected by ambient temperature but are difficult to source in Thailand. They are also physically bigger & more expensive than a Thermal Magnetic CB.

Also, this is why an HRC Service fuse is used. It allows you to have whatever size Main Switch you want. It also allows you to choose either an automatic CB or a non-automatic CB as a Main Switch. A non-auto CB is simply a switch & therefore does not have any trip devices within it. This way, if your consumer mains are upgraded as a result of an increased demand, the only thing you'll need to do is change the size of the fuse, which is a very cheap option.

A 100 Amp CB protecting a device rated at 100 Amps offers no margin for error.

I think that from now on, I will be strongly suggesting the use of Service Fuses in all installations. This will solve many problems.

Thanks for the clarification. I take it that this is your gut feeling and is not based on any codes or manufacturer's specs. Could it be that a 100 Amp meter is rated at 100 Amps meaning that it is compatible with a 100 Amp main breaker?....that seems to be what I was told. This could mean that the meter could actually take more than 100 Amps but its rating contains a safety factor. If you think about it it would not make sense to rate a meter at 100 Amps if that was its "failure" current....it would seem to make sense that there would be some safety factor in the rating. Has it been positively determined yet exactly what the 100 Amp rating means for a kwh meter?

Well, it's not really a gut feeling.

If the KWH meter is a 100 Amp meter, it means that the current coils within the meter are designed to handle up to 100 Amps, without being damaged. While it is not possible to tell how current will actually damage the coils, it is therefore common sense to not exceed this figure of 100 Amps but it is also good practice to use a device that will adequately protect this accurate device. In this case, it would be best to use a 100 Amp HRC fuse because it is a much faster acting device compared to a 100 Amp CB, thereby affording better protection than the 100 Amp CB. If the HRC fuse is not employed, I would choose a CB that is rated lower than the 100 Amp capacity of the meter. In this case, the next size down CB is 80 Amps.

It seems that our sources of information disagree. Your source seems to be saying that the coils are designed to fail at 100 amps and my source seems to be saying that the kwh meter is designed so that it can be adequately protected by a 100 amp main breaker. At any rate the risk being taken is limited to the meter. If the meter coils are damaged then maybe the meter will stop functioning, or maybe it will start charging you too much, or maybe it will start charging you too little.

I got my information from the electric utility which provides my power. Having lived in Thailand for a few years I know that this does not mean that the information is reliable.....where did you get your information?

Chownah

[marc11]

I would just like to add my experience with 3 phase.

While building the house we told the electrician that we wanted to install many A/C units in different rooms amongst other appliances at a later date, he said oh you’ll need 3 phase and gave us an estimate of 58000 bt, this was to include 3 phase from the main road up to (which was to be installed by the local elec company) and in the house (done by the electrician). I was not around during the installation and it wouldn’t have mattered as I don’t know much about elec wiring etc anyway. Needless to say the day came when we wanted to install the A/C units (2 years later), the A/C company came round to take a look at the wiring etc in the house and promptly told us we only have single phase in the house and from the main road, was I surprised "No" pissed off that I had been ripped off, you bet. I don't know what the answer would have been to prevent this happening as we had employed the electrician to do his job, we have tried to locate him but as you can imagine this is proving very difficult and a complete waste of time.

Marc, it may be that only the 3 phase "supply" was installed but your installation was not wired using the 3 phases. The way to tell if you have 3 phase distributed within your home is to see how many cables go into your main distribution board (breaker box) from the supply. There should be 4 cables - 3 phases & a neutral. The 3 'active' phases will go into the top of your main switch (or main circuit breaker).

I'm not sure you should trust the A/C guy any more than than that

"electrician". How many cables go into your meter?

The amount of cables that go into your kilowatt hour meter will not tell you if your installation has been wired using the 3 phases.

ProThaiExpat, my comments in red (easier to see against blue).

I diligently read almost every one of the 92 posts in this thread to make sure I am not missing something, so if I have, please be kind.

I saw nowhere the mention of the "demand", in general, that an appliance requires. Perhaps the ohms, watts or volts tell it all, but for us "civilians" without electrical engineering degrees or manuals on our bookshelves, a simpler approach would be helpful.

Maximum Demand was actually mentioned in post number 10 & from then on at various stages.

When I built my house, the developer and most falangs in the developemnt opted for 3 phase systems as the developers experience was that most falang have so much "demand" for electricity that three phase was worth the initial investment. More expensive panel, more expensive meter and connection charge but well worth it when high demand is present and when electric power diminishes from the utility.

Not all farangs actually require 3 phase. If a Maximum Demand calculation is done BEFORE the home is wired, it may prove that single phase will suffice. As a general rule, anything above an 80 amp demand may require 3 phase. Anything OVER 100 amps WILL require 3 phase. When I do a Maximum DEmand calculation, I always allow about 20% extra load for future expansion.

I do know that "resistance" type of appliances, ie. toasters, hot water kettles, hot water heaters in bathrooms, electric clothes dryers, hair dryers, etc. draw a great deal more power than simple motors. Since I have two Siemens Automatic Electric water heaters (by the way, they are three phase) and an electric clothes dryer as well as many "resistance coil" small applicances, I went along with the initial additional cost of a 3 phase.

My system never goes down due to too much "demand" and I thank the electric gods for the three phase when the power supply for our development diminishes and only parts of my house have electricity.

The number of electic outlets, outside kitchen, hair dryers etc. have only increased since I moved in, but I do not worry as the three phase will cover any addition or add ons.

Since 3 phase doesn't increase your electric bill, it seems to me that any quality home of 200 sq. meters or larger for a falang should be three phase. My guess is that the three phase cost me about 60k more than two phase.

I am of the opinion that a "normal" farang home should have a minimum 80 amp single phase supply. This will be more than enough for the average farang & his/her family.

First image is of the main supply coming down from the overhead cables (2 wires)

These are then spliced (as you can see from the black tape) to produce 4 wires (as if by magic)

which then continues to the house

I couldn't quite see where the wires come into the house and connect to the junction box

but the wires you can see are from the grey box above. Apparently the grey box is a transformer of some kind and we were told when the power is of a low voltage we can push the handle up and increase the voltage using the dial. I only used it once as the heat generated was very high, also i was unsure of what would happen if the voltage went back to 220 etc.

I was away when the box was installed, instructions were not provided, cost 25000 bt (thank you very much)

Edited March 25, 2007 by marc11

[elkangorito]

Marc, from your photos & descriptions, you are being supplied with single phase. If so, how can you end up with 3 phases? I see the red, yellow & blue supply cables going into the top of what looks to be an Email breaker. What is the fault current rating of the breaker? Also, what are those 3 round things to the right of the breaker? Are they fuses? Are they for the voltmeter?

That voltage adjustment device sounds a bit iffy to me. It's obviously electronic. It indicates a value of 80 amps. How do you limit the current to not exceed this value? Do you often get voltage drops?

Your installation looks rather complicated for a domestic supply. Is it domestic?

[marc11]

Marc, from your photos & descriptions, you are being supplied with single phase. If so, how can you end up with 3 phases? I see the red, yellow & blue supply cables going into the top of what looks to be an Email breaker. What is the fault current rating of the breaker? Also, what are those 3 round things to the right of the breaker? Are they fuses? Are they for the voltmeter?

That voltage adjustment device sounds a bit iffy to me. It's obviously electronic. It indicates a value of 80 amps. How do you limit the current to not exceed this value? Do you often get voltage drops?

Your installation looks rather complicated for a domestic supply. Is it domestic?

What is the fault current rating of the breaker? = No idea

Also, what are those 3 round things to the right of the breaker? = No idea

How do you limit the current to not exceed this value? = No idea

Do you often get voltage drops? = Yes, but i don't switch the machine on for fear of a fire

Is it domestic? = Yes

[Crossy]

Marc, from your photos & descriptions, you are being supplied with single phase. If so, how can you end up with 3 phases? I see the red, yellow & blue supply cables going into the top of what looks to be an Email breaker. What is the fault current rating of the breaker? Also, what are those 3 round things to the right of the breaker? Are they fuses? Are they for the voltmeter?

That voltage adjustment device sounds a bit iffy to me. It's obviously electronic. It indicates a value of 80 amps. How do you limit the current to not exceed this value? Do you often get voltage drops?

What's the betting the man wired for 3-phase then found it wasn't available in the street so he just connected all three 'phases' to a single incoming line. I'm worried that the neutral does not appear to be go through the isolator (I'd expect a 4-pole beast). The round things do indeed look like fuses, who knows what for though.

That regulator does seem odd, if it's a recent installation I would have expected an automatic regulator (motorised variac) they are very efficient (don't get hot) although I've never seen one rated at 80A certainly not in a domestic environment. EDIT Actually if it is a 3-phase one and is wired as I suspect it may well get VERY hot!!

Most interesting and not a little scary.

Where are you Marc. a visit from a competent person (Elkangorito) may be in order

Edited March 26, 2007 by Crossy

[marc11]

Where are you Marc. a visit from a competent person (Elkangorito) may be in order

Phuket

And I would like to deal with a Farang electrician, no offence to our Thai brothers

Oh yeh I also had a fire above the ceiling in the attic space, this was due to the wires being taped together i am led to believe.

[Crossy]

Phuket

And I would like to deal with a Farang electrician, no offence to our Thai brothers

Oh yeh I also had a fire above the ceiling in the attic space, this was due to the wires being taped together i am led to believe.

IIRC Elkangorito is in Pattaya, I'm in Pathum Thani (actually in Manila at the mo. then Delhi on 10th April), so I think we're both off the list

There are a few sparks on this forum, has to be someone in Phuket who would have a butchers for a beer or two, anyone??

[marc11]

Phuket

And I would like to deal with a Farang electrician, no offence to our Thai brothers

Oh yeh I also had a fire above the ceiling in the attic space, this was due to the wires being taped together i am led to believe.

IIRC Elkangorito is in Pattaya, I'm in Pathum Thani (actually in Manila at the mo. then Delhi on 10th April), so I think we're both off the list

There are a few sparks on this forum, has to be someone in Phuket who would have a butchers for a beer or two, anyone??

Oh forget the beers, how does Glenfiddich 15 YO or Ballentine's 17 YO sound

There's no real rush either as i'm back to Europe for a couple of months soon and would definitely want to be around when the butchery starts.

I'll post again here when I return to Thailand.

Thanks again guy's for your help.

Best regards

Marc

[elkangorito]

Marc, from your photos & descriptions, you are being supplied with single phase. If so, how can you end up with 3 phases? I see the red, yellow & blue supply cables going into the top of what looks to be an Email breaker. What is the fault current rating of the breaker? Also, what are those 3 round things to the right of the breaker? Are they fuses? Are they for the voltmeter?

That voltage adjustment device sounds a bit iffy to me. It's obviously electronic. It indicates a value of 80 amps. How do you limit the current to not exceed this value? Do you often get voltage drops?

What's the betting the man wired for 3-phase then found it wasn't available in the street so he just connected all three 'phases' to a single incoming line. I'm worried that the neutral does not appear to be go through the isolator (I'd expect a 4-pole beast). The round things do indeed look like fuses, who knows what for though.

That regulator does seem odd, if it's a recent installation I would have expected an automatic regulator (motorised variac) they are very efficient (don't get hot) although I've never seen one rated at 80A certainly not in a domestic environment. EDIT Actually if it is a 3-phase one and is wired as I suspect it may well get VERY hot!!

Most interesting and not a little scary.

Where are you Marc. a visit from a competent person (Elkangorito) may be in order

I think you may be right Crossy...sounds like a single phase installation but wired for 3 phases.

About the neutral...even though it isn't necessary to switch the neutral, I think it's a good idea to do so in Thailand (via a 2 pole or 4 pole CB, depending on the number of phases).

About the round things...I've seen them before & I'm pretty sure they're fuses. I'd also bet that they are for the voltmeter but my only problem with these fuses is that they are connected directly to the incoming supply. Even though they are wired in double insulated cable (it looks double insulated), the fuses are not HRC & therefore may not be able to cope with a high prospective fault current. Of course, should a fault occur, these will explosively 'blow' & who knows what the further effect of this explosive situation will be!!

And what about the ammeter? Is it CT connected or direct wired? I'd love to know! If it is CT connected, I hope shorting links have been installed. EDIT I see a switch directly beneath the ammeter. Is this to switch off the ammeter or select phase currents? If the ammeter is CT connected, switching off the ammeter without shorting the CT will cause a dangerous voltage (higher than 220 volts) to be present at the ammeter switch. 2nd edit Also, an open circuited CT will eventualy burn out. It may even catch fire. My bet is that it is CT connected since a direct connected ammeter cannot be switched off plus I think it is too small to be a direct connected unit to handle 80 amps.

As for your roof space fire, Thais seem to never use proper cable/wire connectors. I'm glad that you can give us a good example of what happens if cables/wires are not connected properly. Many people say things like, "I don't need to worry...I've never had a fire or heard of anyone who has had a fire because of bad cable connections." To all those people who think this, you have now heard of the first case.

Edited March 26, 2007 by elkangorito

[marc11]

As for your roof space fire, Thais seem to never use proper cable/wire connectors. I'm glad that you can give us a good example of what happens if cables/wires are not connected properly. Many people say things like, "I don't need to worry...I've never had a fire or heard of anyone who has had a fire because of bad cable connections." To all those people who think this, you have now heard of the first case.

The best of it is while the electrician was wiring the house during construction I happened to be around, all be it briefly, I saw him twisting wires together and taping them (only on the ground floor), I asked what he was doing and he said this is how we do it in Thailand, I immediately went to home pro and bought some blocks to show him, he said he had never seen them before, I said I want proper connections and the next day he came back with cap type that you screw the wires into.

I never did check the attic to see if he had used the cap type. The fire was only small and burnt away half of the insulating that lies on top of the ceiling, the fire must have used up most of the O2 as it extinguished itself and the only reason I found out was that one of the ceiling lights kept blowing, needless to say I now have smoke detectors fitted in the house and THESE ARE A MUST regardless who does your wiring.

Edited March 26, 2007 by marc11

[elkangorito]

As for your roof space fire, Thais seem to never use proper cable/wire connectors. I'm glad that you can give us a good example of what happens if cables/wires are not connected properly. Many people say things like, "I don't need to worry...I've never had a fire or heard of anyone who has had a fire because of bad cable connections." To all those people who think this, you have now heard of the first case.

The best of it is while the electrician was wiring the house during construction I happened to be around, all be it briefly, I saw him twisting wires together and taping them (only on the ground floor), I asked what he was doing and he said this is how we do it in Thailand, I immediately went to home pro and bought some blocks to show him, he said he had never seen them before, I said I want proper connections and the next day he came back with cap type that you screw the wires into.

I never did check the attic to see if he had used the cap type. The fire was only small and burnt away half of the insulating that lies on top of the ceiling, the fire must have used up most of the O2 as it extinguished itself and the only reason I found out was that one of the ceiling lights kept blowing, needless to say I now have smoke detectors fitted in the house and THESE ARE A MUST regardless who does your wiring.

Marc, do you think you can provide a photo of one the cap type connectors you purchased? If my guess is correct, they are BP connectors (what they're called in Australia). I think it would be beneficial for Thaivisa posters to know what they look like.

[Crossy]

Marc, do you think you can provide a photo of one the cap type connectors you purchased? If my guess is correct, they are BP connectors (what they're called in Australia). I think it would be beneficial for Thaivisa posters to know what they look like.

Elk et al.

Anyone seen this type of junction box in LoS? http://www.mkelectric.co.uk/products/range...mp;rangeid=1002 The top one in particular is ideal for drop cables down to your outlets, no more taped joints.

They're not expensive in the UK, I may just import some but then I've got to teach the locals how to use them

EDIT Insert link, idiot!

Edited March 26, 2007 by Crossy

[Pink Mist]

Marc, do you think you can provide a photo of one the cap type connectors you purchased? If my guess is correct, they are BP connectors (what they're called in Australia). I think it would be beneficial for Thaivisa posters to know what they look like.

Elk et al.

Anyone seen this type of junction box in LoS? http://www.mkelectric.co.uk/products/range...mp;rangeid=1002 The top one in particular is ideal for drop cables down to your outlets, no more taped joints.

They're not expensive in the UK, I may just import some but then I've got to teach the locals how to use them

EDIT Insert link, idiot!

Pm me I live in the city where Clipsal manufacturers exist

[Gary A]

About the round things...I've seen them before & I'm pretty sure they're fuses. I'd also bet that they are for the voltmeter but my only problem with these fuses is that they are connected directly to the incoming supply. Even though they are wired in double insulated cable (it looks double insulated), the fuses are not HRC & therefore may not be able to cope with a high prospective fault current. Of course, should a fault occur, these will explosively 'blow' & who knows what the further effect of this explosive situation will be!!

-----------------------------------------------------------------------------------------------------------------------

I too think those little round things are fuses. If they are what I think they are, they are time delay and will allow a surge such as a motor starting without immediately blowing out. I used similar ones in the US in my shop.

[chownah]

Marc11,

Did you personally go and inspect the wiring which caused the fire to determine precisely what the problem was? I'm asking becaue you posted "this was due to the wires being taped together i am led to believe." and I'm wondering how you were led to believe this....whether someone (who fixed it maybe) said this....or if you saw it yourself....or you assumed that was the case based on your previous observations of the electricians inadequate methods.

Chownah

[elkangorito]

Marc, do you think you can provide a photo of one the cap type connectors you purchased? If my guess is correct, they are BP connectors (what they're called in Australia). I think it would be beneficial for Thaivisa posters to know what they look like.

Elk et al.

Anyone seen this type of junction box in LoS? http://www.mkelectric.co.uk/products/range...mp;rangeid=1002 The top one in particular is ideal for drop cables down to your outlets, no more taped joints.

They're not expensive in the UK, I may just import some but then I've got to teach the locals how to use them

EDIT Insert link, idiot!

Never seen 'em here yet. I prefer PVC J-Boxes myself with BP connectors. I wouldn't trust Thai electricians with metal ones. Are they PVC or what? I do agree, they would help to solve the 'wire taping' problem but they may introduce another problem...can cables be connected to them without the use of crimp lugs? If so, how?

About the round things...I've seen them before & I'm pretty sure they're fuses. I'd also bet that they are for the voltmeter but my only problem with these fuses is that they are connected directly to the incoming supply. Even though they are wired in double insulated cable (it looks double insulated), the fuses are not HRC & therefore may not be able to cope with a high prospective fault current. Of course, should a fault occur, these will explosively 'blow' & who knows what the further effect of this explosive situation will be!!

-----------------------------------------------------------------------------------------------------------------------

I too think those little round things are fuses. If they are what I think they are, they are time delay and will allow a surge such as a motor starting without immediately blowing out. I used similar ones in the US in my shop.

I'm inclined to agree with you Gary. I think that in Marcs installation, it is hazardous & needs to be addressed.

About CT's (current transformers)...I have seen 1 CT installation in Thailand. It was without shorting links & the cabling was too small. Also, 1 side of the circuit was not earthed, which is always recommended when using CT's (one leg of the secondary circuit must be earthed for safety). These transformers can be quite dangerous if not installed correctly.

Edited March 26, 2007 by elkangorito

[Khonwan]

Marc11

Despite my extremely low opinion of Thai electricians (especially ALL P.E.A. electricians I have met), it beggars belief that anyone, never mind an electrician, would install a three-phase system (which is exactly what has been done) where a three-phase supply does not exist.

Out of interest, and just to help me make sense of this, could you please describe the power supply outside your home? Where 2 cables come down, do you see 4 running overhead? If there are only 2 rather than 4, do you perhaps have 3 high voltage cables running above your 2 supply cables?

I originally suggested (correctly) to check the supply first rather than just the indoor installation. I now assume that you do in fact have 4-cable 3-phase public supply available but that your electrician decided not to install a 3-ph meter after having installed a 3-ph distribution system indoors, and then decided to connect a manual step-up transformer to deal with the under-voltage. Completely stupid, of course, but....

Alternatively, if you only have 2-cable single-phase supply with 3 high voltage cables above, I assume he originally intended that you install a 3-ph transformer (very expensive).

[elkangorito]

Marc11

Despite my extremely low opinion of Thai electricians (especially ALL P.E.A. electricians I have met), it beggars belief that anyone, never mind an electrician, would install a three-phase system (which is exactly what has been done) where a three-phase supply does not exist.

Out of interest, and just to help me make sense of this, could you please describe the power supply outside your home? Where 2 cables come down, do you see 4 running overhead? If there are only 2 rather than 4, do you perhaps have 3 high voltage cables running above your 2 supply cables?

I originally suggested (correctly) to check the supply first rather than just the indoor installation. I now assume that you do in fact have 4-cable 3-phase public supply available but that your electrician decided not to install a 3-ph meter after having installed a 3-ph distribution system indoors, and then decided to connect a manual step-up transformer to deal with the under-voltage. Completely stupid, of course, but....

Alternatively, if you only have 2-cable single-phase supply with 3 high voltage cables above, I assume he originally intended that you install a 3-ph transformer (very expensive).

I must agree with these assumptions...sad that they are (not having a go at you, Khonwan).

3rd Edit Marc, did you have a maximum demand calculation done PRIOR to your electrical installation? I don't want to be the bearer of bad news but you may not need 3 phase if your max demand is low enough.

Edited March 26, 2007 by elkangorito

[Crossy]

Never seen 'em here yet. I prefer PVC J-Boxes myself with BP connectors. I wouldn't trust Thai electricians with metal ones. Are they PVC or what? I do agree, they would help to solve the 'wire taping' problem but they may introduce another problem...can cables be connected to them without the use of crimp lugs? If so, how?

Yep, they're PVC.

You can insert solid or stranded conductors (not flex) without crimps, you don't need to twist the wires together either. The clamp screws are wider than the wire slot and push down evenly across the width ensuring a large contact area between the cores, unlike the choc-bloc type connectors that tend to spread the cores and cause overheating. Very British, very safe. You can even tee off a spur without cutting the 'through' cable athough it needs careful activity with your trusty Stanley knife

IIRC there are actually special tools avaialble to remove the jacket and insulation for this purpose, never seen one used though

[technocracy]

Never seen 'em here yet. I prefer PVC J-Boxes myself with BP connectors. I wouldn't trust Thai electricians with metal ones. Are they PVC or what? I do agree, they would help to solve the 'wire taping' problem but they may introduce another problem...can cables be connected to them without the use of crimp lugs? If so, how?

Yep, they're PVC.

You can insert solid or stranded conductors (not flex) without crimps, you don't need to twist the wires together either. The clamp screws are wider than the wire slot and push down evenly across the width ensuring a large contact area between the cores, unlike the choc-bloc type connectors that tend to spread the cores and cause overheating. Very British, very safe. You can even tee off a spur without cutting the 'through' cable athough it needs careful activity with your trusty Stanley knife

IIRC there are actually special tools avaialble to remove the jacket and insulation for this purpose, never seen one used though

Crossy,

I have hunted high and low for trusty British junction boxes and they can't be found anywhere! On a different note I have also found another manufacturer of TPS called Standard - same colours at the other one. There is a severe lack of decent junction boxes or connectors in Thailand or Laos.

[Gary A]

It may just be the case that a German electrician installed the system. In that case you can just tear out a lot of things, have a large basket full of things that are not needed and still have a good installation.

[Crossy]

Crossy,

I have hunted high and low for trusty British junction boxes and they can't be found anywhere! On a different note I have also found another manufacturer of TPS called Standard - same colours at the other one. There is a severe lack of decent junction boxes or connectors in Thailand or Laos.

We may be in luck, MK have outlets and manufacturing in Malaysia, I've got a mate investigating JBs (closer than the UK)

[eriksen]

I would guess that single phase is enough for MOST houses. If you have equipment that needs three phase that would be a different story. I base this on the fact that a friend of mine has a large villa. He has single phase. He has three fairly large air conditioners, four refrigerators, a large electric water heater and several microwave ovens. His swimming pool has two filters, both about 1,200 watts each as well as a 1,000 watt pump for a jacuzzi. He also has two well water pumps and MANY lights. He is a former British electrician and has no choice because three phase is not available out in the boonies.

Well I am not a household E but have a lot of on time with this. What happens here in LOS, a developer will take 3 P because it is more resellable to most. Meaning lets say he has one account and resells it (perhaps doubles it) being 3P sure costs more but allows him to sell /connect to more... what a great business.. and give a % to the PEA so the suckers cant get their own meter.... roll in the money...