3 Phase Electric

[basjke]

I'm building a house with swimmingpool.Do I need 3 phase or will 2 phase be enough.I hear that when you use 3 phase that your electric appliances will use less electric but from the other hand the kilowatt price will be higher.So is it worth to have 3 phase installed.Some advice please.

[elkangorito]

I'm building a house with swimmingpool.Do I need 3 phase or will 2 phase be enough.I hear that when you use 3 phase that your electric appliances will use less electric but from the other hand the kilowatt price will be higher.So is it worth to have 3 phase installed.Some advice please.

What you have heard is not quite correct.

The only way to tell the size of your prospective incoming electrical supply mains is to do a maximum demand calculation. To do this, I need some specific information from you.

Do not attempt to guess the cable size as you may waste lots of money on cable that is too big or you may be in trouble because the cable is too small.

Please PM me for further info.

[tjo o tjim]

If you are going to have any motors over 1kW then 3ph is better for the motor. From a practical standpoint, 3ph doesn't make much sense unless you have over 30kW of load. This is enough for about a 400 m2 home.

You are better off sticking with single phase power. Having 380V power around a house is dangerous. Unfortunately, the electricians working on home installations really aren't qualified to work with higher voltages.

[elkangorito]

If you are going to have any motors over 1kW then 3ph is better for the motor. From a practical standpoint, 3ph doesn't make much sense unless you have over 30kW of load. This is enough for about a 400 m2 home.

You are better off sticking with single phase power. Having 380V power around a house is dangerous. Unfortunately, the electricians working on home installations really aren't qualified to work with higher voltages.

Let's not guess about this...let's talk fact.

First, single phase (neglecting Power Factor);

30kW at 220 volts = about 136 Amps.

So, if you did a maximum demand calculation for your installation (which I can accurately do instead of guessing the load) & it exceeded 100 Amps, it warrants the use of 3 phase.

3 phase (neglecting Power Factor);

30kW at 380 volts = 45.6 Amps per phase.

Cable size & insulation type for 220 volts less than or equal to 100 Amps - 25 to 35mm squared, 0.6/1kV.

Cable size & insulation type for 380 volts less than or equal to 50 Amps - 10 to 16mm squared, 0.6/1kV.

The above sizes are for aerial cables. Length is limited.

380 volts is NOT high voltage. It's still Low Voltage. Medium voltage starts at about 750 volts.

380 volts is marginally more dangerous than 220 volts.

So, how many kilowatts equal 100 Amps at 220 volts? For single phase, 22kW (neglecting Power Factor).

Generally speaking, if you wish to use kilowatts as an "estimate" of maximum demand, anything above about 20kW & it might be wise to think about 3 phase. But don't guess. Get it calculated properly. Your maximum demand CANNOT be equated to the size of your home. This approach can lead to a very significant error & possible extra unnecessary cost or a hazardous installation.

Again, if you want it calculated properly, contact me.

[GuestHouse]

Again, if you want it calculated properly, contact me.

Or me.

Or better still, let's keep this in the open forum and away from Private Messages so that others can benefit from the example of how this works and why it is necessary.

[elkangorito]

Again, if you want it calculated properly, contact me.

Or me.

Or better still, let's keep this in the open forum and away from Private Messages so that others can benefit from the example of how this works and why it is necessary.

Sure but how do you plan to calculate maximum demand?

[GuestHouse]

Sure but how do you plan to calculate maximum demand?

I take it you mean, how do I plan to ESTIMATE maximum demand.

Well I might open my browser, go to our engineering procedures/electrical/calculations/..... and use either the calculations software package we have available, or print out a load estimation table, sharpen my pencil and do it long hand.

Or I might lean backwards and take my copy of the IEE Regs of my bookshelf and use their guide to estimating maximum load.

Which ever, I like to think of it as a no nonsense, no mumbo jumbo exercise that is pretty straight forward. The sort of thing that deserves to be in the open forum for others to learn from.

[chownah]

One way to calculate total demand for a dwelling is to use the method as described in the 2002 NEC (National Electric Code) as found at this link:

http://www.selfhelpandmore.com/homewiringu...dcalc/index.htm

I've never done this before since I'm always wanting more electricity for my shop tools I just got a 100Amp service knowing I'd need it someday...but if my farming activities should even out some day and I have time to do some serious shop work I might be eyeing 3 phase.

Does anyone have an opinion about the adequacy of this method?

Chownah

[basjke]

Thaks everybody for your help.At this moment we start building so haven't reached the the point that I have full details of the electrical installation yet.Although I got already an idea about what I will have to take in consideration.I will keep this topic updated whenever I have more details so that everyone can benefit from the information given to me.

[elkangorito]

I have done a maximum demand calculation based on the following information issued by the OP;

3 x 'plug-in' air conditioning units (less than 10 amps each).

3 x bedrooms (2 x DGPO's each, 2 x 50 watt halogen lights each).

3 x 3.6kW instantaneous hot water units.

8 x ceiling fans (each not exceeding 150 watts).

3 x bathrooms. NOTE - power outlets are not installed in these bathrooms (2 x 50 watt halogen lights each).

1 x lounge room (6 x DGPO's, 6 x 50 watt halogen lights).

1 x kitchen (4 x DGPO's, 6 x 50 watt halogen lights).

1 x dining room (4 x DGPO's, 6 x 50 watt halogen lights).

1 x laundry. NOTE - only one DGPO has been installed in the laundry, at a height well away from water outlets & water collection areas (1 x standard light fitting).

1 x single 15 amp SGPO (whirlpool?).

2 x 500 watt swimming pool lighting, plus pool pump & ancillary pool equipment.

1 x whirlpool. NOTE - no allowance has been made to heat the water in the whirlpool.

Total calculated maximum demand as per Australian Standard AS/NZ 3000:2000;

53 Amps.

The above result does not allow for any changes to above listed equipment. Any change in equipment will require a recalculation of maximum demand.

The above result indicates that for the given equipment, a 3 phase supply is not required. However, it is advised that a single phase 80 Amp service be installed.

DGPO = double power outlet ie 2 sockets in each fixing.

SGPO = single power outlet.

[scottie dog]

I have done a maximum demand calculation based on the following information issued by the OP;

3 x 'plug-in' air conditioning units (less than 10 amps each).

3 x bedrooms (2 x DGPO's each, 2 x 50 watt halogen lights each).

3 x 3.6kW instantaneous hot water units.

8 x ceiling fans (each not exceeding 150 watts).

3 x bathrooms. NOTE - power outlets are not installed in these bathrooms (2 x 50 watt halogen lights each).

1 x lounge room (6 x DGPO's, 6 x 50 watt halogen lights).

1 x kitchen (4 x DGPO's, 6 x 50 watt halogen lights).

1 x dining room (4 x DGPO's, 6 x 50 watt halogen lights).

1 x laundry. NOTE - only one DGPO has been installed in the laundry, at a height well away from water outlets & water collection areas (1 x standard light fitting).

1 x single 15 amp SGPO (whirlpool?).

2 x 500 watt swimming pool lighting, plus pool pump & ancillary pool equipment.

1 x whirlpool. NOTE - no allowance has been made to heat the water in the whirlpool.

Total calculated maximum demand as per Australian Standard AS/NZ 3000:2000;

53 Amps.

The above result does not allow for any changes to above listed equipment. Any change in equipment will require a recalculation of maximum demand.

The above result indicates that for the given equipment, a 3 phase supply is not required. However, it is advised that a single phase 80 Amp service be installed.

Does three phase not imply an earth is available and therefore more safety?

DGPO = double power outlet ie 2 sockets in each fixing.

SGPO = single power outlet.

[Naam]

Having 380V power around a house is dangerous. Unfortunately, the electricians working on home installations really aren't qualified to work with higher voltages.

volts don't kill! amps kill! a 20,000 volt shock from your car ignition distributor might not even give you a small blister but it's not a problem to kill somebody with a 12volt car batterie. moreover, a three-phase connection does not necessarily mean you have anywhere in your home 380volts. using three phases each 220volts is the best possible way to evenly distribute the load on the different phases.

big advantage with three phases is that if one "goes off" (happens in my area quite often) you still have light, airconditioners and whatever other users running on the remaining three phases.

[Naam]

Does three phase not imply an earth is available and therefore more safety?

*****

NO! earth grounding in electrical outlets in thailand is available only when you are standing next to the electrician and make sure he wired the sockets accordingly. next thing is to check whether all these ground wirings are "REALLY GROUNDED" and do not end somwhere in "nowhereland" such as your attic or hanging loose and unseen behind the breakers in the breaker box. i have also never seen a three-phase outlet anywhere in thailand as we use them for special purposes in Europe.

sad but true!

[Naam]

I just got a 100Amp service knowing I'd need it someday...but if my farming activities should even out some day and I have time to do some serious shop work I might be eyeing 3 phase.

Does anyone have an opinion about the adequacy of this method?

Chownah,

are you quite sure you got a SINGLE phase 100 AMP connection??? i have strong doubts.

[chownah]

I just got a 100Amp service knowing I'd need it someday...but if my farming activities should even out some day and I have time to do some serious shop work I might be eyeing 3 phase.

Does anyone have an opinion about the adequacy of this method?

Chownah,

are you quite sure you got a SINGLE phase 100 AMP connection??? i have strong doubts.

Well, I have two wires only coming to my house and the power company told me I could use 100 amps. Isn't this a single phase 100 amp connection?

Chownah

[elkangorito]

Well, I have two wires only coming to my house and the power company told me I could use 100 amps. Isn't this a single phase 100 amp connection?

Chownah

It sure is.

[Naam]

I just got a 100Amp service knowing I'd need it someday...but if my farming activities should even out some day and I have time to do some serious shop work I might be eyeing 3 phase.

Does anyone have an opinion about the adequacy of this method?

Chownah,

are you quite sure you got a SINGLE phase 100 AMP connection??? i have strong doubts.

Well, I have two wires only coming to my house and the power company told me I could use 100 amps. Isn't this a single phase 100 amp connection?

Chownah

what puzzled me two years ago when i planned my home in Thailand was that you can draw CONTINOUSLY 80-100% more amps than the actual rated capacity installed. at first i thought it was a fairy tale what the developer told me but i enquired personally with the local electricity provider that this is indeed the case. in fact i was told that even 120% is possible for a short time (1-2 hours). anyway, i entered a clause in my contract for the land purchase that the developer has to provide (at my cost) a three-phase connection each phase 30amps. paid an additional 30k Baht for that connection. the main reason for my demand was that i was used to live in a fully airconditioned home. have 15 split units installed which of course are not running simultaneously all the time.

your "100 amps" might be just a single phase 50amp connection but you have to make sure that the cable diameters from the meter to your points of use are appropriately dimensioned. going over the rated capacity in Europe is virtually impossible as each phase has a sealed breaker which trips already at 10% overload.

[chownah]

your "100 amps" might be just a single phase 50amp connection but you have to make sure that the cable diameters from the meter to your points of use are appropriately dimensioned.

Yes, I believe that you want to be sure the cable diameters are appropriate regardless of the number of amps and phases that are delivered in your service. If you think you will be drawing 100 amps for even one second you should size the wires to accomodate that load....same for 15 amps....meaning that if you want to draw a maximum of 15 amps for even one second you should size the wires to accomodate THAT load.

Chownah

P.S. It is confusing for me also that my meter is rated 45/100 amps. I'm hoping that Elkangorito or some other knowledgeable person can explain EXACTLY what this means and its implications for what loads can be drawn and for what time intervals.

Chownah

[elkangorito]

P.S. It is confusing for me also that my meter is rated 45/100 amps. I'm hoping that Elkangorito or some other knowledgeable person can explain EXACTLY what this means and its implications for what loads can be drawn and for what time intervals.

Chownah

I spoke to my colleague today about KWH meters. He seemed to agree with me in that the first figure means little and the last figure is important. For example, a 45/100 Amp meter means that the highest amount of current that can be passed through it is 100 Amps. The lower figure seems almost meaningless.

Also, another poster suggested that these meters have a built in overload. To me, this does not seem probable because unless the overload device is a similar mechanism to that of a circuit breaker, it will not be able to safely open the circuit under even the smallest amount of fault current. As a matter of fact, I think it would be dangerous to have an overload device in this application UNLESS it is a proper switchgear mechanism, which is quite large & the physical size of the meter would need to be increased substantially to accommodate the device.

[lopburi3]

Basic (max.) current (A): 5(15)10(30)15(45)20(60)

[scottie dog]

Does three phase not imply an earth is available and therefore more safety?

*****

NO! earth grounding in electrical outlets in thailand is available only when you are standing next to the electrician and make sure he wired the sockets accordingly. next thing is to check whether all these ground wirings are "REALLY GROUNDED" and do not end somwhere in "nowhereland" such as your attic or hanging loose and unseen behind the breakers in the breaker box. i have also never seen a three-phase outlet anywhere in thailand as we use them for special purposes in Europe.

sad but true!

I find your reply to be very negative (pun intended!) I asked a very serious question: Is a three phase earthed circuit safer than an non earthed circuit. Let us assume the builder/contractor can do a propper job and not degenerate all Thais in one FALSE statement!

[basjke]

I have done a maximum demand calculation based on the following information issued by the OP;

3 x 'plug-in' air conditioning units (less than 10 amps each).

3 x bedrooms (2 x DGPO's each, 2 x 50 watt halogen lights each).

3 x 3.6kW instantaneous hot water units.

8 x ceiling fans (each not exceeding 150 watts).

3 x bathrooms. NOTE - power outlets are not installed in these bathrooms (2 x 50 watt halogen lights each).

1 x lounge room (6 x DGPO's, 6 x 50 watt halogen lights).

1 x kitchen (4 x DGPO's, 6 x 50 watt halogen lights).

1 x dining room (4 x DGPO's, 6 x 50 watt halogen lights).

1 x laundry. NOTE - only one DGPO has been installed in the laundry, at a height well away from water outlets & water collection areas (1 x standard light fitting).

1 x single 15 amp SGPO (whirlpool?).

2 x 500 watt swimming pool lighting, plus pool pump & ancillary pool equipment.

1 x whirlpool. NOTE - no allowance has been made to heat the water in the whirlpool.

Total calculated maximum demand as per Australian Standard AS/NZ 3000:2000;

53 Amps.

The above result does not allow for any changes to above listed equipment. Any change in equipment will require a recalculation of maximum demand.

The above result indicates that for the given equipment, a 3 phase supply is not required. However, it is advised that a single phase 80 Amp service be installed.

DGPO = double power outlet ie 2 sockets in each fixing.

SGPO = single power outlet.

Thank you for the calculation Elkangorito,however I have the intention to install direct waterheaters.They are available in 6-8 and 12 kw.I have 2 bedrooms at one side of the house and 1 bedroom and kitchen at the other side.Which waterheater will I need to fill a whirlpool bathtub and should I install one heavy waterheater or one at each side of the house.Also I see from your calculation that a 3 phase is not required but if I install a 3 phase supply will it make me significant savings in electric or not when I install 3 phase aircons,waterheaters and swimmingpool pumps.

[Naam]

I find your reply to be very negative (pun intended!) I asked a very serious question: Is a three phase earthed circuit safer than an non earthed circuit. Let us assume the builder/contractor can do a propper job and not degenerate all Thais in one FALSE statement!

*****

Scottie,

of course my statement is negative but i only stated facts. during construction period i lived in a rented penthouse and later in a detached home near the construction site. NONE of the sockets in these homes were ground wired. NONE of the hot water heaters or electrical outlets serving the bathrooms were connected to a GFCI switch (adjustable from 10 to 30 milliamps) and none were grounded. one faulty connection of the water heaters developing over a period of time could cause immediate death when having a shower!

in my country a builder handing over a home like this would face a prison sentence or if he is lucky a huge fine.

GFCI switches are available in Thailand and cost peanuts. the same goes for the ground wiring of all electrical outlets.

your question "Is a three phase earthed circuit safer than an non earthed circuit?"

my answer: "NO, IT IS NOT! you don't have normally any electric appliance in your home that requires a three-phase connection although i have two of these appliances (attic fan and whole-house fan). the phases are split in to 'normal' single phase 220v and if the sockets or your electric appliances are not connected to the ground/earth conduit (which is the normal case) you are back to square one (namely exactly what i described above).

this is what my electric setup looks like. but of course i am only a bloody german who likes to spent a few thousand Baht to protect the lives of my wife, my guests and of course mine.

[chownah]

When I grew up in the US there were no ground wires on anything and there were no GFI units on anything....anywhere......but.....somehow my generation survived. My house in Thailand is just the same...no ground wires and no GFI's.....I do have a gas water heater though so I have completely avoided the major risk factor.

Chownah

[percy2]

But of course i am only a bloody german who likes to spent a few thousand Baht to protect the lives of my wife, my guests and of course mine.

How come you have a sense of humour

[elkangorito]

Thank you for the calculation Elkangorito,however I have the intention to install direct waterheaters.They are available in 6-8 and 12 kw.I have 2 bedrooms at one side of the house and 1 bedroom and kitchen at the other side.Which waterheater will I need to fill a whirlpool bathtub and should I install one heavy waterheater or one at each side of the house.Also I see from your calculation that a 3 phase is not required but if I install a 3 phase supply will it make me significant savings in electric or not when I install 3 phase aircons,waterheaters and swimmingpool pumps.

For your purposes, I would advise against installing any electric powered storage hot water heaters. Thailand has the perfect environment for solar heated hot water, which will virtually cost you nothing to heat in Thailand. They come in different types but by far the best type is the storage solar hot water heater. The integral storage tank can hold up to about 400 Litres of water. These units also come with an electric/thermostatic overide, that is, you can either operate the system on electricity or it will change to electric power if the water in the storage tank drops below a certain temperature.

I've seen quite a number of these units in Thailand on the roves of buildings. The most popular brands are Solarhart & Rheem.

Whether your supply is single phase or 3 phase, you will pay the same for electricity. The installation of 3 phase is more expensive than single phase.

3 phase motors are generally more efficient & smaller than single phase motors of the same size but are more expensive to buy. You will not not need 3 phase air conditioners, motors or water heaters for an average domestic premises.

[Naam]

But of course i am only a bloody german who likes to spent a few thousand Baht to protect the lives of my wife, my guests and of course mine.

How come you have a sense of humour

after two glasses of Sherry or Port i find it quite hard to suppress my humour

[elkangorito]

In summary, I would recommend that an 80 Amp single phase supply be requested if the residence is 'average' ie not a 3 storey mansion or not utilise any large electrical equipment like electric motors over 5 kW in size.

Single phase @ 80 Amps is ample for most 'average' modern Australian homes. It is rare that a consumer will need to upgrade their consumer mains (incoming cables) from this size.

It is always a good idea to calculate the maximum demand & add between 10% & 20% for future.

A three phase supply is not required if your maximum demand is not likely to exceed 80 Amps.

Match the kilowatt hour meter to the maximum rating of the incoming supply cables ie incoming is supply rated at 80 Amps. KWH meter should not be less than 80 Amps. Since this size is not available (are they?), use a 100 Amp KWH meter - 45 (100).

[scottie dog]

I find your reply to be very negative (pun intended!) I asked a very serious question: Is a three phase earthed circuit safer than an non earthed circuit. Let us assume the builder/contractor can do a propper job and not degenerate all Thais in one FALSE statement!

*****

Scottie,

of course my statement is negative but i only stated facts. during construction period i lived in a rented penthouse and later in a detached home near the construction site. NONE of the sockets in these homes were ground wired. NONE of the hot water heaters or electrical outlets serving the bathrooms were connected to a GFCI switch (adjustable from 10 to 30 milliamps) and none were grounded. one faulty connection of the water heaters developing over a period of time could cause immediate death when having a shower!

in my country a builder handing over a home like this would face a prison sentence or if he is lucky a huge fine.

GFCI switches are available in Thailand and cost peanuts. the same goes for the ground wiring of all electrical outlets.

your question "Is a three phase earthed circuit safer than an non earthed circuit?"

my answer: "NO, IT IS NOT! you don't have normally any electric appliance in your home that requires a three-phase connection although i have two of these appliances (attic fan and whole-house fan). the phases are split in to 'normal' single phase 220v and if the sockets or your electric appliances are not connected to the ground/earth conduit (which is the normal case) you are back to square one (namely exactly what i described above).

this is what my electric setup looks like. but of course i am only a bloody german who likes to spent a few thousand Baht to protect the lives of my wife, my guests and of course mine.

I do not need a lecture on your experiences! I have asked a VERY simple question which is applicable to any person installing electricity in any building (assuming competent installation) IS THREE PHASE SAFER than the other options?

[Crossy]

IS THREE PHASE SAFER than the other options?

NO!!!!

Three-phase is no safer (nor more hazardous) than single phase in a domestic environment.

However, as previously intimated, you really are unlikely to need it