400V3ph4W,230V L-N is it OK with NEC ?

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davidv

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Dear Experts
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)
2. 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.
3. 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 using 400V for a 600V wire instead of 230V, while both are safe.) 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 plug 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. The NEC being mentioned here 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. A friend told me that this is voltage system is not approved in the US.
My question now is why is the 400V 3ph 4W / 230V L-N is not allowed by the NEC for residential occupancies? What are they afraid of ? If ever this is allowed by NEC will the Utility provide this voltage?

DavidV
Electrical Supervisor
 
My question now is why is the 400V 3ph 4W / 230V L-N is not allowed by the NEC for residential occupancies? What are they afraid of ? If ever this is allowed by NEC will the Utility provide this voltage?
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I doubt they're afraid of anything.

The 120/240 1? system is the standard for residences in the US. Providing some other voltage would mean the homeowner would have a heck of a time buying a new TV. Keeping things simple makes things easier on everyone.

120/208 (derived from 3? 120/208Y) is another not uncommon residential voltage, in certain situations. It's acceptable because the line-to-neutral voltage is the same. Large appliances such as ranges and dryers are infrequent purchases, and can be had in 208V.
 
FWIW Most residential appliances, dryers, stoves, water heaters, baseboard heaters etc. that are rated 240 are also rated 208 at a reduced KW.

A 30 story apartment building in this area would likely be served with a 480/277 Wye service. Elevators, Lighting HVAC equipment outside of the dwelling units would run off the 480 system.

The dwelling units themselves would be served via transformers located on the same floor (or close) as the units at 208/120 volt.
 
Gentlemen,
I'm not convince by the reasons above, majority of domestic appliances have dual voltage options, why not take advantage of these, even ranges and other heavy appliances run on 240.

Using 208/120 transformer from 480/277 is not energy effective, Its a known fact. why should a customer pay for the power loss of these transformers.
The NEC should allow this voltage so that US installations would be more energy efficient, minimizing the burden on our power resources.

As for safety issues, is there something I should know aside from the fact that other advance nations such as UK,Germany,Switzerland are using this for a long time that no alarming accident rate that can be attributed.

But if the reason is that the industry cannot afford the cost to change its products or make make some obsolete. And also to protect US manufacturers from foreign competition. I can understand.

Dear Moderator, I know this topic is not new, may be there's a previous thread where the NEC had given its position on this subject. Please let me know. Thanks

Guys what do you think, your comments or suggestions are very much welcome ,no matter what it is.
 
Let's picture a scenario:
  • GC "A" has built condos in a great location, for a reasonable price, with nice options and upgrades. Some are ready for express move in.
  • GC "B" has built condos next door, in a similarly great location, for a slightly lower price, with the same nice options and upgrades. Some are ready for express move in. You're informed that when you purchase the condo, you're going to have to throw most of your small appliances in the dumpster, because they won't plug into the wall.

How many units will GC "A" sell?
How many units will GC "B" sell?
 
buddy,
if the gadets are small then dump it. if its new manufacture or asian then its autovolt no problem,
as I said its better for new appliances than pay 20 years for electric power even when its not in use.
The condo "B" will sell more.
May be there are other reasons by NEC, or has anybody has experience this kind of requirements. I'd really like to know.
 
David, welcome to the forum. Where are you from? What do you do?

I wasn't trying to be combative, it comes naturally. :D
davidv said:
as I said its better for new appliances than pay 20 years for electric power even when its not in use.
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How much is paid in energy loss? I can't imagine it's that much.

May be there are other reasons by NEC, or has anybody has experience this kind of requirements. I'd really like to know.
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The NEC seldom gives us the "why", which is why I find this place to be valuable. I don't know why the NEC frowns on it (NEC-2005 210.6(A)).

Here is a quick link with some history. It kind of indicates why everyone but the US wound up with a higher voltage to their residences. Another good post by Bryan. :)
 
hi George,
being combative was never on my mind, I'm the one who is treats adversaries as friends coz they reveal hidden facts from fixed minds.
didn't mean to offend you & rather have you as a partner in trade.
I've aquired citizen@ hawaii, but much of my experience is in middle east -oil&gas industries & asian countries electrical installations As construction supervisor & design evaluator.

I'm interested on what transpires during the course of NEC deliberations, of course we can still demand explanations from them. they are not the sole "authority" on electrical discipline. The electrical practitioners also has a say on things. I mean concensous. & They must answer the why.
Thanks for the link. Its good to know the roots.

till nxt time
 
Re: 400V3ph4W,230V L-N is it OK with NEC ?

davidv said:
My question now is why is the 400V 3ph 4W / 230V L-N is not allowed by the NEC for residential occupancies? What are they afraid of ? If ever this is allowed by NEC will the Utility provide this voltage?

DavidV
Electrical Supervisor
Click to expand...

We can get 240v line-to-line. But everyday utilization devices use 120v. There is certianly a cost benefit to utilizing a higher, rather than lower everyday voltage. Perhaps we don't because we have always favored life over slightly lower initial installation and operating costs.
 
Hmmm, the NEC does not forbid voltages under 600VAC, commercial or residential. The local POCO may have stated what they will provide, but there's nothing stopping a user from installing their own transformer for whatever voltages or single/three phase enduser requirements there are. Any disagreement with this?

EXCEPT 210.6(A)
 
Section 210.6(A) is indeed the "culprit." Other branch-circuit voltage limitations are described in the rest of 210.6.

Whether it is protectionist or not, it is the basis for the product safety standards and third-party certification in the US.

Since the construction is in Thailand, the product standards are different. George's analysis would be the reverse there. This would be a ripe opportunity to apply 90.4 "Special Permission."

My personal opinion, having worked with both systems, is Europe/Asia got the voltage right and we got the frequency right. There is very little conclusively identifiable safety differences up to about 1000V (yes 1000V) where properly applied materials and equipment are used.
 
I believe the NEC is just protecting the homes where the folks are not aware of the hazards. When I was 5yrs old, I slip a finger on a pin while plugging bread toaster, I got my first shock and manage to pull my finger out. It was 220 coz later I let my dad teach me how to read volts on appliance and outlets and never interchange. didn't told him of the accident though, I wonder where would I be if it were the hot of the 230LN, coz what I got was a 110LN shock. Is it equivalent if two fingers touch both pins of a 240 plug on a 120/240 1ph? How do the European engineers view this? I' try to get as many facts,
Meanwhilie I will still used the 400/230 system for my project, its safe, and pursue it here in the US if possible. The electrical practitioners should not be burdened by injuries resulting from improper use & unsafe handling. I guess the folks at home just have to learn, "yes even at my home"
Thanks to all of you guys.
George, Bob, Lawnguy, Mark & Bob(Mod)
 
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