220VAC Single Phase in American Home?

Reply

  #1  
Old 09-27-04, 03:50 AM
Boxxcar
Visiting Guest
Posts: n/a
220VAC Single Phase in American Home?

I am purchasing a new home that is being built near New Braunfels, Texas. I have been living in Europe (DoD) for some time and have accumulated a number of 220V items, which quite frankly, I really don't want to get rid of.
I am not an electrician, but I have tinkered with electrics for a number of years, mostly 220V single phase here in Europe. I've installed outlets, lights, ceiling fans, most of your common do-it-yourself type things and when I refer to single-phase, I mean 1 hot, 1 neutral, 1 gnd.
The new home is obviously being wired for 110V throughout, but is it possible to get 220V single phase to a number of separate outlets (4) in the house and garage? I realize 220V is available to perhaps the dryer or the stove, but I believe that is two-phase.
Would a 220V single-phase line be within local building codes?
Any info would help on this subject.
 

Last edited by Boxxcar; 09-27-04 at 05:32 AM.
Sponsored Links
  #2  
Old 09-27-04, 05:31 AM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
The 220 volts used in Europe is quite different from the 220 volts used in the US.

Firs and foremost. For residential service, all power is single phase. Your house has incoming power at 240 volts AC. This 240 volts is measured line to line, between two incoming hot lines. These two lines are 120 volts each, exactly opposite each other, which makes 240 volts. There is a a neutral return that is grounded between the two. When you use either hot wire and the neutral you have 120 volts, which is what the bulk of household electric appliances and lights run on. It is only for high load appliances that 240 volts is used. These include (in a residence) heating water, electric heat, air conditioning, and cooking.

In Europe the 240 volts used is measured with respect to ground.

There is also a frequency difference. In North America 60 Hz is used. In Europe 50 Hz is used.

While it is possible to convert North America's 240 volts to match Europe's appliances, it is not advisable. First and foremost, it is expensive to convert from 50 Hz to 60 Hz. It can be done, but you need to decide if the cost is worth it. If you skip the frequency conversion, you will have some devices that won't work, and other that won't work properly.


You will be better off in the long run if you sell those European appliances and start over, buying 120 volt appliances.
 
  #3  
Old 09-27-04, 05:46 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
First, some terminology:

Power to US homes is 240V _center tapped_ single phase, not _two phase_. We had a recent discussion on this in a previous thread. (Note, you sometimes find 2 phases of a 3 phase system, different thread.)

If you have a proper transformer installed, I do not believe that there is any NEC code reason restricting you from getting 240V, single phase, line to neutral wiring installed.

However I believe that this is a bad idea, and will result in un-necessary expense. Proper transformer grounding is not simple, transformers consume current all the time, even when all of your other loads are off, and you will essentially be installing a duplicate wiring system in the home.

What you need to do is examine each of the 240V appliances that you wish to use. You will divide these into four catageories:

Those appliances with universal power supplies. Work at 100V to 240V 50 to 60 Hz. Change the cords on these appliances, and just use them on 120V. These are electronic items such as laptops.

Those appliances that require 50Hz line frequency. US power is 60Hz line frequency, so these appliances won't work without an expensive frequency converter. Chuck 'em. These are items such as clocks.

Those appliances that require 240V, and care about supply polarity. This is anything that uses one of the supply terminals as a ground reference, or anything that has exposed metal connected to one of the supply terminals. You might, for example, have a lamp with a screw shell bulb holder; the screw shell _must_ be at ground potential for safety reasons, so this item cares about polarity. These devices would require the transformer setup described. Think carefully about the value of being able to operate them unmodified. If something such as a lamp, replace the bulbs with 120V bulbs!

Finally, those appliances which require 240V, but _don't_ care about polarity. Many European receptacles are _not_ polarized, and there are many plug standards throughout Europe. Net result: it is hard to be sure about the supply polarity, and many appliances are built to function safely with either leg hot. These appliances will also function with 240V center tap (both legs hot at 120V). For these appliances, get standard US 240V receptacles installed, and replace the cord caps on the supply leads.

Regards,
Jonathan Edelson
 
  #4  
Old 09-27-04, 07:24 AM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Jon, very interesting post. I especially like your four category way of looking at it.
 
  #5  
Old 09-27-04, 03:57 PM
sjr
Visiting Guest
Posts: n/a
I agree with John. That was probably the clearest way I have heard to explain it. I moved back from the UK about 8 months ago and went through the process described to determine which appliances I could use and which ones wouldn't work out. I was pleasantly surprised to find that I could use a NEMA 6-15 plug (with associated kitchen outlets) on a significant number of my appliances (especially kitchen ones with grounded plugs).
 
  #6  
Old 09-27-04, 05:00 PM
HandyRon's Avatar
Member
Join Date: Dec 2001
Location: New York
Posts: 1,365
You will find 210.6 limits regular receptacles to 120V max between conductors.
 
  #7  
Old 09-27-04, 06:21 PM
sjr
Visiting Guest
Posts: n/a
210.6(A)(2) seems to allow cord-and-plug connected loads more than 1440VA to have more than 120 volts between conductors.

I'd really like someone to explain why it is unsafe to use my 1320VA cappuccino maker at 240V and safe to use my 1500VA electric kettle at 240V when each is on a 240V 6-15 outlet. That one just doesn't make much sense.
 
  #8  
Old 09-27-04, 06:50 PM
HandyRon's Avatar
Member
Join Date: Dec 2001
Location: New York
Posts: 1,365
Your kettle would fall under 210.6(C)(6) and be permitted as an additional receptacle when counting required receptacles from the NEC.
I think the reasoning is to have the general purpose receptacles limited to 120V and specific utilization equipment can be more with the special receptacle.
You wouldn't be able to circuit the entire dwelling without 120V receptacles and still be in compliance with the NEC.
 
  #9  
Old 09-27-04, 07:31 PM
sjr
Visiting Guest
Posts: n/a
I'm not sure I put my question in the right form.

Suppose the following: you have a 1320VA cord-and-plug device and a 1500VA cord-and-plug device. Both of them are 240V and have 6-15 plugs, and both of them are plugged into 6-15 receptacles on dedicated branch circuits installed specifically for those devices.

What makes the 1320VA device less safe (or even less desirable) than the 1500VA device?

If the point was to make sure that all of the required general use, small appliance, etc, branch circuits were installed as 120V, then just explicitly state as much in the code.

Why impose the additional restriction of minimum power usage on branch circuits with 240V between conductors?
 
  #10  
Old 09-28-04, 10:10 AM
Member
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
Relevant Code Articles---

(Branch-Circuits-----) 210.23, Permissible Loads-------"The load (shall not) exceed the (B-C) rating. An individual B-C shall be permitted to supply ANY LOAD for which it is rated" (A), 15 & 20 amp B-C's----(1),Cord & Plug connected---"The rating of any (cord-connected load) shall not exceed 80% of the B-C rating"

240.5,( Over-current protection) Protection of Flexible Cords, (B), B-C Over-current device, (1) Supply Cord(s)----" Where a flexible-cord is (used) for an (appliance) it shall be permitted to be supplied with a B-C in accordance with the following---- (1), 20-amp (B-C)--- #18 cord or larger"

***********************

The concept that a 3-wire, 120/240 volt single-phase system has 2 "out-of-phase" voltages is erronous. Equal, but "opposite" voltage-values do not indicate "out-of-phase".

If you arrange a 3-wire D.C. system with 2 120-volt batteries with the Neutral as the "reference-point" for voltage-values, you will read both +120 volts and -120 volts, "outside legs-to-Neutral" voltage-values. Similiar "readings" at an A.C. "source" are no more "out-of-phase" than the D.C. connection is "out-of-phase".

In general, an "out-of phase" system has 2 or more un-equal voltage-values at a given "instant", a condition unique to A.C. systems. At the "instant" Phase-leg "B" reads 120 -volts-to-Neutral, Phase-leg "A", with a voltage-values that "leads" "B", will read a different voltage-value.
 
  #11  
Old 09-28-04, 11:42 AM
sjr
Visiting Guest
Posts: n/a
PATTBAA, so what you are saying is that in a three-wire 120/240V single-phase system, the voltage does not exceed 120 volts, nominal, between the two phase conductors and that therefore 210.6(A) would not apply?
 
  #12  
Old 09-28-04, 12:19 PM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
PATTBAA,

I think that you missed the point that Handy Ron made. 210.6 is an additional restriction placed on receptacle outlets in homes only.

In any other occupancy, you could install a 240V receptacle to run an 50W hand blender. But in a home it is a code violation to install a 240V receptacle for any appliance smaller than 1440 VA.

For what its worth, I don't see how this particular bit of code could be enforced, because you could always claim that the receptacle is for your 1600W kettle. And I agree with sjr that I don't see the safety issues with having low power 240V appliances. Clearly, if one were buying appliances in the US, most would be 120V appliances, and only extremely power hungry devices would require 240V, so 210.6 pretty much doesn't matter for most home applications.

I guess it just boils down to 'the code is the code''; there is probably some historic reason for the cut-off.

Also I'd like to note that the safety issues in UK wiring are somewhat different that those of US wiring. In general, the 240V circuits have higher ampacity (32A is common) but the cord caps have fuses in them that more directly protect the load. In the US, we depend upon the circuit breaker for the circuit to also protect the appliance cords. If you install a US cord cap on your UK cords, you will lose that fuse protection.

-Jon
 
  #13  
Old 09-28-04, 12:55 PM
Member
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
I stand corrected on Art 210.6--- "good to know" I am more knowlegable on the NEC today then I was yesterday, thanks to "winnie" and "ron".Thanks guys for sharing your knowledge.

By argument pertaining to the concept of a singe-phase system with "out-of-phase" voltages has no relevancy at all to the NEC.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes