wire guage

oh I forgot, the receptacles I was refering to was from the same asian products,there are 10A 30A but not the nema config. these are universal type blade & pin type plugs can go in. has 250V rating. Any chance I can use it here in the USA.

Also do you know that insulating stregnth of thermoseting plastics are the same for 220 and 440v up to 600v, they behave the same within that voltage range. the only detriment will be the temperature to which they might be subjected to or build up. Safety & capacity(i.e. lower 1st cost ) Its the amount of power that can be transmitted to the wire, especially for large residentials such as high rise condominiums, long multistory apartments which the advantage can taken.Safety is the same whether 220 or 440 v is on a 600v wire.

Also why is 400LL/230LN vac service not available , in europe this is available, is it due to the cost of maintning an invetory of different transformers ratings that most utility company objects?

Appliances today are autovolt types 110/220, lamps of 220v are already common. If only 230 v utilization voltage was used, will the Inspector approve it?

Also fault current is lower at 400v or 480v than on 240v, basing on cb catalogs and by point method calculation.

Not if they don't have agency approval, from UL or equal. But regrdless, why would you want to if NEMA plugs won't fit them?

I am not sure what your point is here. I said that 600V wiring is used regardless of the system voltage. It would be safe at 440 volt.

US voltages are all based on 120V L-N. The standard voltages are all multiples of 120 or 1.73 times 120. This is how the US does it. Other countries are different. To see our standard low voltage systems, visit

220V lamps are not common in the US. 120 or 240/120 volts are the standard residential voltages. The NEC restricts the voltage for lighting and cord-connected units under1440 VA in a dwelling unit to 120 volts, so an inspector will not approve a straight 240 volt system.

True, if all else is equal. My point was that when a utility runs a three-phase supply to your house, they very likely will use larger lines and a larger transformer than just what your needs are. As a result, even at the higher voltage you may get higher available fault current. You would be going to industrial boxes and breakers, which are more expensive. And, you still didn't say how you plan on powering all of the 120 volt single-phase loads. What is the point of all of this?

Ben Miller

Dear Ben Sorry to get u into this trouble, a year ago my american friend ask me about the electrical system of a 30 story condo.His business partners are planning to put it near a beach in Thailand.Since I worked there for quite sometime, they ask me for my recommendation.

1.The Utility practice there is that all energy meter is at ground floor,(otherwise its a private meter if located per floor and utility will have main meter at transformer secondary, building admin will bill the occupants)

1. All service above 500KVA, Client will have to give 60% deposit for service transformers to be deducted on billings for 10 years. Secondary Voltage is per client request. My recommendation to him is the following.
2. Use utility metering so that Building admin will not bother itself with billing the occupants.This mean that each Unit feeder will run down to the Utility meter room. a. I suggest to use the 400V 3PH 4W distribtion voltage, with 230V L-N as utilization voltage, central split-AC for each units can use the

400V 3ph. this will give maximum savings on materials such as feeder wires,( higher load capacity for same size of wire, lower power loss due to voltage drop. this is the point that I'm stressing on our previous correspondence on using 400V for a 600V wire instead of 230V, as we agreed both are safe.) and smaller breaker ratings, b. All lightings and appliances are on 230V, this is the normal voltage here, and I think on other asian countries as such as Japan, Singapore. and that no shock fatalities have been of significant occurences on these countries using this voltage. c. With a single voltage, Universal type ( can accept pin or blade plugs) receptacles can be used, all nema types except locking can be used. d. The percent impedance for a distribution type Padmouted Transformer (used by Utility ) is the same for 400 or 230V secondary at same KVA. So the fault duty is smaller for 400V dist.voltage. Also cascade ratings can be applied for branch CB's since this is mostly lighting & receptacle loads. Industrial type CB's are not necessary. e. For wiring method I suggested the used of Cu-XLPE-PVC multicore cable (also common here ) feeder run on vertical cable trays.Generally they are also using the NEC but as a guide only. If things push through I may be the have to design the plan for this, they are already processing the acquisition of the property. Thanks for pointing out that this will not be approved here in the US, However if I use a dry type transformer at 120V for each unit (for lighting & 1 duplex outlet per area) will it be approved? Thanks for your generous replies, Mr Ben , I really appreciate and truly treasure the insights you gave. Good Luck and may you prosper more on your business.

Dsky Electrical Supervisor

There is nothing wrong with using a transformer, but you will need more than one duplex receptacle. The NEC requires a number of them within a dwelling unit (Kitchen counters, bathrooms, along walls, etc.). You really need to study up on the national and local codes that will affect your project, or else hire a local consultant to assist you.

Good luck

Ben Miller

Dear Ben, if however, it were not in the US and with no 120V xfmr, are the rest of my recommendations agreable to you personally? My friend is cutting cost on consultants and will hire a PE only to sign the plans after I prepared them. Thanks again. dsky

I can't really comment without seeing the plans.

Tell your friend he will get what he pays for. No legitimate PE will sign your plans, as it violates the law. PEs can only sign plans prepared by them or under their direct supervision.

Ben Miller

Most PE's I know liked it better that way, but must let them have it their way. Usually no big problem. If things went ok, I'll show it. Thanks again, Ben

Dsky