Domestic Electrical Wiring

[dotcom]

If the local electricity authority feel like the load is about to reach capacity they will install an additional transformer.

I'll get a picture & post it up.

Where do you live jojo?

[jojothai]

If the local electricity authority feel like the load is about to reach capacity they will install an additional transformer. I'll get a picture & post it up. Where do you live jojo?

hi dotcomgood idea. now I am back in the province looking at things.the house is in prachuab khirikhan about 30km north of the city.I now see 3 phase and two series on the main road. one must be higher voltage going up to quarries and the mountain national park.the local feeder is 3 phase but my problem could be the distance to the house.the line already in is 2 wire and feeds 2 houses but at the distnce noted before.I will do my installation needing 100A but will have to get the locals to ask what happens if I cannot achieve. ie extra wiring may be needed to the main road.not seen my electrician yet. he should be able to say what is possible.hope to find out more in the next few says.'regardsjojo

[Crossy]

WARNING!! Counterfeit Schneider MCBs

The Schneider UK site has this warning http://www.schneider-electric.co.uk/intern...02573F3004D040C

Although there is no evidence that any of these are in Thailand it can do no harm the check what you have installed as these fake units provide ZERO protection against overload. Nasty!

Edited September 15, 2008 by Crossy

[dotcom]

Yeah jojo. Consider & discuss with your electrician using double runs. 2 of everything. 2 Meters on the pole & all.

3 phase power to your house would be great but expensive. Not sure it's really needed.

That's bacause of the long run & 2 houses. At least you are thinking & making a plan. Congrats.

Crossy. I am using 16mm2 from ploe to CU. What larger sizes are available? 35 mm2? any larger?

Big wires like that will be a pain to run overhead. Running along a boundry wall or buried are other options.

[jojothai]

Yeah jojo. Consider & discuss with your electrician using double runs. 2 of everything. 2 Meters on the pole & all. 3 phase power to your house would be great but expensive. Not sure it's really needed. That's bacause of the long run & 2 houses. At least you are thinking & making a plan. Congrats. Crossy. I am using 16mm2 from ploe to CU. What larger sizes are available? 35 mm2? any larger? Big wires like that will be a pain to run overhead. Running along a boundry wall or buried are other options.

thanks dotcomas you say I think going to 3 phase may not be justified. but could ask how much anyway.if I do have problems it will mean bigger cables to the distribution line,however it may not be much more for 2 extra wires to 3 phase,if cable size is then the same as existing. need to think ahead a little in the "what if" mode.re: your query on cable size after 35 mmsq I believe next is 50 then 70.jojo

[dotcom]

I personally feel that unless you are going to use 3 phase appliances such as air conditioner or cooking stove - benefits might be marginal. Maybe the experts can weigh in.

Sorry I got a little confused too. It's longball that has the long runs of wire from pole to house - 50 meters - wow!!!

I went out into the street & took some pictures where MEA (Bangkok Metro) added a transformer next door to my house.

[dotcom]

I can tell you from looking at it that the input is 3 wires - from the topmost (on the right in the first picture) set of wires. Then the output is 4 wires. The MEA ran the new supply (3 wires) from the nearby Soi & the dead legs pictured terminate in front of my house. This way everyone nearby has more current available - should they need it.

I was watching discovery channel the other day. They were saying that USA homes used to be wired for 100 AMPS. But today 200 amps is minimum (@ 120 volts) & 400 amp is not uncommon at all.

Let the experts tell us. The power coming into the transformer - is it 480? or higher?

[Crossy]

Let the experts tell us. The power coming into the transformer - is it 480? or higher?

Just a bit

IIRC in Thailand it will be 25kV (25,000V) 3-phase 3-wire, that's the 3 wires at the top on insulators.

Coming out is 3-phase 4-wire, 220V phase-neutral, 380V phase-phase.

[dotcom]

Thanks for that.

So if I want to make a 50 meter run from pole to Load Center - 100 amps - what size wire should I run?

[dotcom]

P.S. During a lightning storm - hurricane etc it's these transformers (oil filled) that explode in a shower of sparks - when they take a direct hit.

Then your lights go off for a few hours.

[Crossy]

Thanks for that.

So if I want to make a 50 meter run from pole to Load Center - 100 amps - what size wire should I run?

OK, it depends on how far your take off point is from the transformer, i.e. what the voltage has dropped to before you start your 50m run.

Some numbers (all are copper):-

25mm² (the smallest you should consider for a 100A supply) will drop 9V (4%)

35mm² will drop 6.5V (3%)

50mm² will drop 4.8v (2%)

Personally I'd go for the 35mm² provided the supply isn't already on the low side. Your electrician may be able to advise Check the relative cost of 50mm² (the fatter the better).

[longball53098]

I can tell you from looking at it that the input is 3 wires - from the topmost (on the right in the first picture) set of wires. Then the output is 4 wires. The MEA ran the new supply (3 wires) from the nearby Soi & the dead legs pictured terminate in front of my house. This way everyone nearby has more current available - should they need it.

I was watching discovery channel the other day. They were saying that USA homes used to be wired for 100 AMPS. But today 200 amps is minimum (@ 120 volts) & 400 amp is not uncommon at all.

Let the experts tell us. The power coming into the transformer - is it 480? or higher?

Someone correct me if wrong here but I am pretty sure the supply from the street to the home meter and Panelboard in the USA is typically 240 volts not 120. They stopped supplying 120 many years ago. The 240 comes in with a neutral and the Panel splits the two legs into 120 down each buss bar for the home. There are 240 volt breakers designed to cross both bus bars to supply a clothes dryer or other heavy draw appliance

[dotcom]

Definately 240 volt is available in most US homes to run a clothes dryer. Massive socket & plug. Would give Crossy the flutters.

[jojothai]

& took some pictures where MEA (Bangkok Metro) added a transformer next door to my house.

hi dotcomthanks for the pics and infi.my situation is over 100m already from the local distribution line to the pole where I will take my 70m cable into the CU.not so good.I wanted to get the local electrician to comment but since I got back he doesnot seem to be now interested in the job anyway! TITlooking for somebody else again.have to b patient and keep with it.regardsjojo

[jojothai]

OK Jojo, you're going the right way

I would look very carefully at 3-phase if it's available on the poles. You immediately divide the currents by 3 at the expense of more complex wiring of your consumer units.

Don't get 3-phase aircons, just balance them between the phases then if you lose a phase (quite common) you just lose one unit rather than all of them.

Hi again Crossy, longball, dotcom.

I'm now in a position to see the local electicity authority when I go back next week and discuss whether to go to 3 phase. A few more queries come to mind.

You can see the 3 phase at the main road picture left below. The two wires go off single phase to the existing few small houses. via two poles. it is about 100meters to the last existing pole where I will have to connect from. then about 50 m to the new house. The two existing poles are as big as 3 phase poles and have sufficient height clearance for the 3 phase matching the main line. So I think I should be able to get 3 phase on the existing poles if necessary.

Questions:

1. If I get the 3 phase, what wire sizes apply, is it one big neutral and 3 phase wires a third of the size, eg assuming I am looking at 100A load and 150m. Is it 1 neutral @ 70mmsq and + 3 phase wires a third of the size eg 25mmsq.

2. If I get 3 phase I presume the 4 wires go to the meter and do they go right through to the house or how does it work?

3. Then what do I need for the main circuit breaker a 3pole or 4 pole breaker?

4. Why is it people may need a transformer? ( other threads show this)? what determines it?

5. Do i then need to have a load center for 3 phase or can I still use consumer boxes combined to get the full load. ie Can I still connect 2 consumer units like the sense R3 as I would with single phase. I could go to 3 consumer units sense R2 if necessary (one for each phase).

If can use 2 x R3 can you tell me how would the wiring go from the 3 phases to the 2 consumer units?

I know the local people should be able to say what I should do, but may not communicate it well, so it is best if I can get some idea of what is likely.

Grateful for your help, thanks

jojo

[Crossy]

Questions:

1. If I get the 3 phase, what wire sizes apply, is it one big neutral and 3 phase wires a third of the size, eg assuming I am looking at 100A load and 150m. Is it 1 neutral @ 70mmsq and + 3 phase wires a third of the size eg 25mmsq.

2. If I get 3 phase I presume the 4 wires go to the meter and do they go right through to the house or how does it work?

3. Then what do I need for the main circuit breaker a 3pole or 4 pole breaker?

4. Why is it people may need a transformer? ( other threads show this)? what determines it?

5. Do i then need to have a load center for 3 phase or can I still use consumer boxes combined to get the full load. ie Can I still connect 2 consumer units like the sense R3 as I would with single phase. I could go to 3 consumer units sense R2 if necessary (one for each phase).

If can use 2 x R3 can you tell me how would the wiring go from the 3 phases to the 2 consumer units?

Ok here we go:-

1. If you get 3-phase your load currents will be reduced to about 33% in each phase, so the equivalent of a 100A single-phase supply would be about 33A per phase. Wires would be sized accordingly. You would probably get a 15/45A 3-phase supply which would be the rough equivalent of a 130A single phase supply. The neutral is normally the same size as the phases in a domestic situation. In fact, in a properly balanced 3-phase supply the neutral current is actually zero

2. It is not normal to run 3-phase all over the house. Treat it as 3 single phase supplies except where you have real 3-phase appliances (best avoided if possible). Split the house into zones (by room is easy) and feed each zone from one phase, try to get the load on each phase about the same but avoid having two phases in a single room (kitchen for example) as herein lies the danger of getting a phase-phase shock which WILL be lethal (our apartment in Delhi had triple outlets with each outlet on a different phase, scary!!).

3. You would use a 4 wire incoming breaker.

4. Transformers come into play when the existing transformer does not have sufficient capacity or is too far away from your house. The important distance for your cable sizing calculations is the distance to the nearest transformer. The transformer takes the big 3-phase (25kV or thereabouts) that runs along the top of the poles on big insulators and converts it to small 3-phase (3x220V P-N) that runs on smaller insulators lower down and is then run to the houses as either single-phase 2 wire or 3-phase 4 wire.

5. You can use a 3-phase load centre populated with single phase breakers or 3 single phase units one on each phase, depends how many circuits you end up with. Using single phase boxes simply wire each one between a phase and neutral. In either case you still must have a 4-pole incoming breaker so you can isolate the entire system with one switch.

Edited September 29, 2008 by Crossy

[jojothai]

Ok here we go:-

1. If you get 3-phase your load currents will be reduced to about 33% in each phase, so the equivalent of a 100A single-phase supply would be about 33A per phase. Wires would be sized accordingly. You would probably get a 15/45A 3-phase supply which would be the rough equivalent of a 130A single phase supply. The neutral is normally the same size as the phases in a domestic situation. In fact, in a properly balanced 3-phase supply the neutral current is actually zero

2. It is not normal to run 3-phase all over the house. Treat it as 3 single phase supplies except where you have real 3-phase appliances (best avoided if possible). Split the house into zones (by room is easy) and feed each zone from one phase, try to get the load on each phase about the same but avoid having two phases in a single room (kitchen for example) as herein lies the danger of getting a phase-phase shock which WILL be lethal (our apartment in Delhi had triple outlets with each outlet on a different phase, scary!!).

3. You would use a 4 wire incoming breaker.

4. Transformers come into play when the existing transformer does not have sufficient capacity or is too far away from your house. The important distance for your cable sizing calculations is the distance to the nearest transformer. The transformer takes the big 3-phase (25kV or thereabouts) that runs along the top of the poles on big insulators and converts it to small 3-phase (3x220V P-N) that runs on smaller insulators lower down and is then run to the houses as either single-phase 2 wire or 3-phase 4 wire.

5. You can use a 3-phase load centre populated with single phase breakers or 3 single phase units one on each phase, depends how many circuits you end up with. Using single phase boxes simply wire each one between a phase and neutral. In either case you still must have a 4-pole incoming breaker so you can isolate the entire system with one switch.

Thanks Crossy,

1. understand that therefore I could assume 125 A load, it will be 4 wires all the same size.

for 33A at 150meters Actually 25 mmsq or 35mmsq.

2. Understood, but would the rules about same phase in each room apply just to sockets/outlets or is it lighting also. What about aircons and what about water heaters. Is it still very risky having any of those on another phase.

They have their own breaker but which in some cases is sited adjacent to lighting switches.So I presume that this is the thing to avoid. If near each other then get them on the same phase.

So if I have an aircon breaker remote from other sockets/ lights it could be on a different phase without being too much danger. Would that be the case?

3.Ok

4.Understood, will have to see what the local electricity authority say.

5. If I go for 3 phase, Looks simplest to use the 3 consumer units if I want to be keeping each phase in an area.

For Your info I plan 24 circuits.

5 lighting (1 circuit non-ELCB)

6 Socket radials

6 aircons (4 fitted + 2 possibly for future) all non ELCB

4 water heaters

Kitchen oven + refridgerator Non-ELCB

Kitchen Hob (6.3 Kw) Non-ELCB

Pump

I am assuming the pump has ELCB protection to its circuit. IS THAT APPROPRIATE OR NOT?

Thanks for your help.

By the way please note I put some photos and remarks on a"new house build" thread for putting wiring conduit down the cavity of double block wall. I know some people who did the same before but could not tell me any advice on what problems it can cause. So I had to find out for myself.

I have summarized some key points in the pdf file. The thread is

http://www.thaivisa.com/forum/House-Build-Plan-t214093.html

jojo

[jojothai]

Hi Crossy

Something else I need to finalize now is what I allow for aircon circuits, previously indicated on my design as 20A circuits.

I am planning on 4 fitted approx

18000 BTU in lounge

2 x 13000 BTU in bedrooms

1 x 9000 BTU in study

What do you think I should be allowing for load / breaker size for 9000 BTU, 13000 BTU, 18000 BTU.

jojo

[Crossy]

Ok.

1. If you get a 3-phase 15/45 supply it will likely be fused at 63A so you need to rate your cables for this fusing and distance. 35mm2 is suitable and will drop about 3% at 33A, 25mm2 may well be adequate if your incoming supply isn't already low (bigger is always better assuming cost is not excessive). Subject to local conditions which your electrician should advise.

2. The main hazard occurs when you have outlets on different phases whatever you do keep outlets on different phases seperate by 3m (or a wall) and if you have outdoor outlets keep them all on one phase.

I would try to keep all the appliances in each zone on one phase, so lights, outlets, aircon and water heater in each bed/bath pair go on a single phase, same in the kitchen. Use single phase appliances wherever possible.

Your biggest loads are the water heaters and aircon so try to spread them evenly.

5. Pump needs an ELCB for safety.

Put your non-ELCB lighting in the common area of the house and on the same phase as the aircon, outlets etc in that area.

Wire all your aircons with 4mm2 and 25A breakers, you never know when you may want to upgrade

Edited September 29, 2008 by Crossy

[technocracy]

3. You would use a 4 wire incoming breaker.

Just a note on this in general all the Square D systems are 3 pole and have a permanent non breakered Neutral.

4 pole breakers are few and very far between in Thailand.

[Crossy]

3. You would use a 4 wire incoming breaker.

Just a note on this in general all the Square D systems are 3 pole and have a permanent non breakered Neutral.

4 pole breakers are few and very far between in Thailand.

Good point, I've not looked for 3-phase 4 pole breakers here

A 3 pole incomer would be OK as jojo intends using multiple consumer units each of which will have its own 2 pole isolator that will open the neutral.

Edited September 29, 2008 by Crossy

[jojothai]

3. You would use a 4 wire incoming breaker.

Just a note on this in general all the Square D systems are 3 pole and have a permanent non breakered Neutral.

4 pole breakers are few and very far between in Thailand.

Good point, I've not looked for 3-phase 4 pole breakers here

A 3 pole incomer would be OK as jojo intends using multiple consumer units each of which will have its own 2 pole isolator that will open the neutral.

Thanks Crossy, and good point from Technocracy. I need to look at it. I have seen on my brochures what was called a switch isolatar 4 pole 100A. T&B HL34

Have to go to the electrical store and check it out.

regards

jojo

[Crossy]

3. You would use a 4 wire incoming breaker.

Just a note on this in general all the Square D systems are 3 pole and have a permanent non breakered Neutral.

4 pole breakers are few and very far between in Thailand.

Good point, I've not looked for 3-phase 4 pole breakers here

A 3 pole incomer would be OK as jojo intends using multiple consumer units each of which will have its own 2 pole isolator that will open the neutral.

Thanks Crossy, and good point from Technocracy. I need to look at it. I have seen on my brochures what was called a switch isolatar 4 pole 100A. T&B HL34

Have to go to the electrical store and check it out.

Yup.

http://www.tbe.co.th/t&b.htm

The HL34/100A should do the job nicely and be available in Thailand

[dotcom]

jojo. Did you decide to go 3 phase?

Cuz after I read what Crossy said it looked to me like single phase would suit your requirements.

[jojothai]

jojo. Did you decide to go 3 phase?

Cuz after I read what Crossy said it looked to me like single phase would suit your requirements.

Yes single phase would be ok if the existing wires are large enough for the increased load.

I now pretty much realize that it may be necessary to go to 3 phase and Crossy has helped me to understand what need to do if this is the case.

I go back to the province at the weekend and this is now a priority so I will get PEA out to look at what is possible. I suspect the existing wires may be too small to consider all the new load on the existing line. If so then I will have to upgrade the line to 3phase or add a new 3 phase feed.

Will keep you posted as to what PEA advise.

thanks

jojo

[mdechgan]

I was also thinking about the 3 phase system but I couldn't justify the costs. 35 sqmm x 4 wires or 50 sqmm x 2 wires I think 50 sqmm x 2 is more cost effective. You halve the distances and the conduits and pvc pipes and clamps. Also you save on the breaker box.

Also it depends if you can balance the load. 1 phase for the bedroom, living room and kitchen? But still rarely do I use all 3 roooms at once. Then you have to balance the lights and each circuit. It just was too much trouble. If it were a big office then no question. But for a home one starts to think unless you have like 7 air conditioners and swimming pool equipment and like 100 lights.

[Crossy]

Agreed ^^^

An average 'farang' home should be fine on a 15/45 or possibly 30/100 single phase supply.

The only time to consider 3-phase is if your existing local supply won't handle the load on single (and PEA want you to buy a transformer), then it's time to do a cost-benefit analysis.

If you do end up using 3-phase, you only need a rough balance, the neutral current fixes any imbalance between the phases.

Edited October 3, 2008 by Crossy

[jojothai]

Agreed ^^^

An average 'farang' home should be fine on a 15/45 or possibly 30/100 single phase supply.

The only time to consider 3-phase is if your existing local supply won't handle the load on single (and PEA want you to buy a transformer), then it's time to do a cost-benefit analysis.

If you do end up using 3-phase, you only need a rough balance, the neutral current fixes any imbalance between the phases.

Thanks Mdechgan and Dotcom.

I dont look at 3 phase being the solution unless necessary. However I got that feeling I have to be prepared for it. So, thanks to Crossy for advising how I need to deal with it. Got to go speak to PEA in the next week.

will keep you posted

jojo

[jojothai]

Hi All - Crossy Dotcom, Longball, Mdechgan, et al

Looks like the DIY section has been a bit quiet recently.

Time to report on what I found from PEA for my connection.

The house is about 10Km along a secondary road from the main highway no4 going south to Prachuab Khiri Khan. The secondary road is very good going to the mountain national park, quarries and to the large water reservoir.

There are transformers along the road about every 1Km some big where there are many houses, others small.

Near us there is a small transformer. There are not many houses yet but a few have only just been completed in the last year. The transformer is about 200m away from the branch connection point of single phase feed to the existing house. There is about 100m from there to the post nearest the new house. PEA say the wire is 50 sqmm aluminium. The new house has about 60 m cable run from the post to the consumer unit.

So the new house CU will be about 360m from the transformer.

1. The small transformer is 25 KVa and PEA say no way we can get 100A. We could take up to about 50A - and put in a 15 / 45 A meter.

2. If we want 100A we could put in a new transformer, needs a 50KVA ( could cost about 115,000 Baht).

It is best to do this as 3 phase. Single phase not good at 100A and also existing cable too small, we would have to increase to about 100sqmm. For 3 phase we can upgrade only needing 2 more wires.

3. The engineer we spoke to seemed to be saying to my Thai GF that there are load problems sometimes at present and they are considering the increase of the transformer size. If thsi happened at say 66KVa we still would not cope for 100A single phase we would have to go 3 phase.

We needed to see the manager to discuss.

4. The manager was very good to speak to. He explained that there are not enough houses for the new transformer project and it will be very long until it may be done. He said that if we wanted 100A we should put in our own transsformer and again reasoned that we should go 3 phase.

5. Both the engineer and manager considered we could connect up to about 50A single phase which I said we may need to do initially. They also agreed with considerations to plan for going to 3 phase. Using 3 CUs Ok and MEN link (but showing it the thai way on the hot side). Both helpful pointing out that we must balance load and segregate the phases in areas of the house.

Thanks also to CROSSY for all the advice which helped me to understand what they were saying.

And with the 3 CUs we can put in everything for the 3 phase balance, but initially on single phase we just need to interconnect the 3 CUs to live and limit the load + use a smaller breaker. No problem I can work this out.

6. I am reluctant to put in the transformer now, partly because I dont have the extra money to hand at present until I go get more work. ( I should be OK to get it done in several months time).

However more importantly I reason that if I need 50KVa for 100A then the existing transformer will only support not a lot more than 50A. Considering that two recently built houses are probably 15 / 45 A load and the other few houses are 5 / 15 Amp the existing is over its limit and when we take 50 A then the manager has a big problem. So he may well prefer we get our own transformer and relieve him of the problem.

We are closest to the transformer and I get the impression from the engineerr that the other houses further away will have more problem than us getting their load. CAN ANYBODY COMMENT ON THIS?

In this case I will take my chance on the poker game to see what happens when we take say 45 amps. If it is a problem then either PEA will need to upgrade the transformer, or all houses have to contribute to the cost of a much bigger transformer.

7. I now have found another electrician for the installation. He appears to be reasonable and says best we go underground for connection to the existing pole. I dont see any problem but understand best we use NYY cable.

He was asking whether I should go with one very big custom load center instead of 3 CUs. Considering costs, I can get the 3 SENSE R2 ELCB CUs fitted cheaper. I also feel much clearer safety wise fixing the 3 phases in 3 distinct compartments rather than trying to fiddle the 3 phase wirings around in one big load center. I dont know if there are other good reasons to instead use the big load center.

8 All parties agreed I will be OK with 35 sqmm cable for the 60 m long 4 wire 3 phase connection to the new house. However i have to work out if I will need to put 2 cables out of the 4 as 50 sqmm for initial single phase set up.

Trust I have explained sufficiently and would welcome any debate on the above.

jojo

[Crossy]

8 All parties agreed I will be OK with 35 sqmm cable for the 60 m long 4 wire 3 phase connection to the new house. However i have to work out if I will need to put 2 cables out of the 4 as 50 sqmm for initial single phase set up.

If you're likely to go for 3-phase any time soon, why not run the required 4x35mm cables and pair them up (giving 2x 70mm equivalent) for the initial single-phase set up?