US Electrical power

Discussion in 'General Electronics Chat' started by JDT, Sep 3, 2013.

  1. JDT

    Thread Starter Well-Known Member

    Feb 12, 2009
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    Hi, I'm looking for some advice from you American guys about power outlets in the US.

    Over here in the UK our electricity is 240V AC 50 Hz. In Europe it's usually 230V. I know over your side of the Atlantic it's 110V 60Hz - or is it 115V? I don't know who you blame for this: Edison? Westinghouse? One of the disadvantages of being an early adopter, I suppose.

    What I want to know is how do you run larger electrical appliances? For example in every British kitchen you will find an electric kettle (we like our tea). Usually rated at 3kW. This draws about 13A from the power outlet here.

    A similar appliance running from 110V will draw 27A! I have seen your little 2-pin plugs and I don't know what current they are rated at but I wouldn't like to put more than 10A through them. 27A will probably start a fire! I don't know if you have kettles but you must have heaters, dishwashers, vacuum cleaners, washing machines, etc. How do you do it?

    I have heard that you can use an extra phase giving you 220V for high-power appliances. How common is this? Does every house have both types of outlets?

    I ask this because the company I work for are producing a piece of equipment which is now going to be sold worldwide. It consumes about 2kW. Do we make it for 220V or 110V? What standard connectors do you use?

    Actually, this equipment will normally be used in a laboratory environment. Same outlets there? What type of connectors? Part numbers?

    Thanks for your help.
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Most houses have two types of outlets. The one in the middle is seldom seen here.

    [​IMG]
     
  3. cabraham

    Member

    Oct 29, 2011
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    I believe the one in the middle is 115 volts and 20 amps. The top and bottom outlets look correct.

    Claude
     
  4. Kermit2

    AAC Fanatic!

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    I think you are right. The flat blade is on the wrong side for 220V

    Here is another image of NEMA types that I believe is correct.

    [​IMG]
     
  5. JDT

    Thread Starter Well-Known Member

    Feb 12, 2009
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    Thanks for your quick replies.

    So, if we make our equipment for 220 - 240VAC (the frequency doesn't matter) it should be OK world-wide.

    What is the technical part number of the 220V connector? Is it a NEMA or UL standard?

    Ta.
     
  6. JDT

    Thread Starter Well-Known Member

    Feb 12, 2009
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    Kermit2 don't confuse me with that lot!

    Just the 3-pin 220V 30A will do. If that is the most common one.

    Thanks
     
  7. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    The 220V in the US is very unusual in a kitchen or through out the house. It is mostly found in laundry rooms and garages or basements. The 220V is mainly reserved for electric stoves and laundry dryers.

    How large are your "electric kettles" that they use 3KW? Just went and looked at my coffee maker, 975W@120V 60Hz.
     
  8. JDT

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    Feb 12, 2009
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  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Kettles here are typically 1500w, the 'cordless' type are becoming popular here as I believe in the UK now.
    By cordless I mean you lift them off a disconnect, mains powered base.

    The domestic supply in N.A. is residences are fed from a single phase 240v centre tap transformer supplying a grounded neutral (centre tap) and two 120v 1ph legs.
    As opposed to the 1ph from a 3ph supply and star neutral in the UK.

    When I first came to N.A. I was supprised at the small size of the AC plug, but have never really seen any heating effect, this is contrary to the large brass pin 13a amp plug in the UK, I had quite a few white plugs turn brown because of poor contact and heating of the pins!.

    Max.
     
    Last edited: Sep 3, 2013
  10. JDT

    Thread Starter Well-Known Member

    Feb 12, 2009
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    Update: Just been looking at what some others do and it seems for USA 220/240V they use a NEMA 6-15P plug (as shown on Kermit2's diagram).

    Does this look correct? Is this general in not just the USA but in the whole of North and South America? Anyone from Brazil, Mexico, Canada, etc. care to comment?

    Thanks again.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    In Canada, if there is no need for a neutral then the 6-15 is popular for 240v domestic use up to 15a.
    Max.
     
    Last edited: Sep 3, 2013
  12. Kermit2

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    Closer examination has revealed that both diagrams are correct.

    The first one shows an 'OLD' method of installation with the ground socket below the power sockets

    New methodology has dictated outlets be installed with the ground pin above the power sockets. This is how the NEMA diagram shows the outlets.

    When you account for the orientation, the first picture does show a 220V outlet configuration.
     
  13. #12

    Expert

    Nov 30, 2010
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    One of the limiting factors is wire gauge and circuit breaker sizes. NEC demands that no single load require more than 80% of the capability of the circuit breaker.

    14 gauge wire can be connected to a 15 amp breaker and the design limit is 12 amps.
    12 gauge wire is connected to a 20 amp breaker and the design limit is 16 amps.
    10 gauge wire is connected to a 30 amp breaker and the design limit is 24 amps.

    Power line voltage has been changing over the decades. In 1970, it was rare to get 115 volts per leg. Now, I get 125 volts per leg at my home. The "standard" is: 240 VAC RMS +/- 5%, center tapped, as recited to me by the local electric power company.

    The common 120 volt receptacles come in 2 sizes, 15 amp and 20 amp. Still, no single load can be designed for more that 80% of the capability of the outlet.

    Set your design to comply with these standards and you will not need the customer to install special wiring to your device.
     
  14. shortbus

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    And in my area it measure 127V most days, though it does fluctuate between 122V and the 127V, depending on the day.
     
  15. poopscoop

    Member

    Dec 12, 2012
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    To be clear, if you're designing an appliance for use in US households and it is not a dryer, electric stove, or an A/C, it needs to use 120V. There are usually 2-4 220v receptacles in a house and they are almost always in use.

    I believe the greatest continuous draw is 1.5kw. The breakers are rated for 20 amps but code demands substantially less for continuous operation.

    Edit: Just saw the laboratory environment line. That's a totally different game, and opens up many more options. Someone here will know a lot more about it than I.
     
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  16. JDT

    Thread Starter Well-Known Member

    Feb 12, 2009
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    To be fair, I said "households" just to find out what was the most common. This equipment is not a household appliance but will be used mainly in laboratory or industrial situations.

    Think I'm going with the 6-15P for the Americas. Supply voltage of 220V to 240V should cover everywhere (except possibly Japan).

    Thanks for your help, folks.

    John
     
  17. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    then you'll want to go with a twistlok configuration
     
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  18. JDT

    Thread Starter Well-Known Member

    Feb 12, 2009
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    Tell me more!
     
  19. #12

    Expert

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    You can get "twist-lock" connectors, but the 6-15P is commonly used on window air conditioners, and it works. In other words, I am disagreeing with GetDevice. I say you don't need the higher quality of the twist-lock connector. Still, it's your decision.
     
  20. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Some more.
    NEMA 6-15 (green is ground).
    All NEMA 6 devices are three-wire grounding devices (hot-hot-ground) used for 208 V and 240 V circuits and rated for 250 V maximum, with the 6–15, 6–20 and 6–30 being grounding versions of the 2–15, 2–20 and 2–30, respectively.
    The 6-15 resembles the 5-15, but with collinear horizontal pins, spaced 23⁄32 in (18.256 mm) center-to-center.

    Generally 6–series non-locking plugs are used for such appliances as large room air conditioners, commercial kitchen equipment, and the occasional home arc welder.
    Single phase 6-50 is commonly used on farms for the silo unloader, and is used with a 6 gauge flexible power cord up to 200 ft long (61 m).
    NEMA 6 devices, while specified as 250 V, may be used for either 208 V or 240 V circuits, generally depending on whether the building has a three-phase or split-phase power supply.
    The NEMA 6–20R or 6–30R found in many hotel rooms is often supplied with 208 V and without a neutral.

    Ref:
    http://en.wikipedia.org/wiki/NEMA_connector
     
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