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    harveymasons's Avatar
    harveymasons Posts: 10, Reputation: 1
    New Member

    Jul 27, 2005, 04:48 PM
    Question on 220 volt
    How can one identify 220 volt appliance besides looking on the appliance?
    Does 220 volt devices have the same 3 prong (with ground) or two prong configuration on the plug or does something look different indicating that it is 220 volts?

    Lastly, I know on 20 amp appliances the plug has one prong going sideways, can there be 120 volt devices w/ 20 amp or is all 20 amp devices 220 volt?

    Thanks in advance,

    labman's Avatar
    labman Posts: 10,580, Reputation: 551
    Uber Member

    Jul 27, 2005, 05:38 PM
    A 220, actually more like 240, appliance should have a funny looking plug. I think it is mostly to keep people from plugging in 120 stuff in a 240 outlet. They come is several varieties, some with 4 prongs. Dryers, stoves, and air compressors and maybe some larger window air conditioners are about all I can think of that come with cords and plugs. Most 240 stuff is hard wired. The air compressor I had with a dual voltage motor came with a regular plug.

    The generator I just bought has a 4 prong twist lock 240 outlet.

    If you buy a 240 appliance, don't plan on using it much except with it dedicated outlet. I guess you don't need to set the dryer or stove up in the living room much.
    brucesay54's Avatar
    brucesay54 Posts: 1, Reputation: 1
    New Member

    Aug 9, 2010, 06:38 AM
    I Have a heater powered by a 220 volt circuit and the input is 22 amps. What is my megewatts consumed by the heater?
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert

    Aug 9, 2010, 07:53 AM

    The easiest and best way to identify a device as 240 volt is to read the manufacturer's lable on the device. I know you said,"without looking at the device itself".

    The next easiest way is to look on the Branch Circuit Legend on the Main Panel Door. Each circuit is listed there. 240 V circuits will have a double breaker.

    I suggest that you go to a Lowe's, Barnes and Noble, Borders or Home Depot and pick up a book on wiring. These will have pictures of the various receptacles and their uses.

    Most 20A circuits are used off 120V. There are some 240V - 20A circuits but they are few when compared against the 120V uses.

    For example, you can use 120V-20A for lighting and general use receptacle. Also, the NEC require that there be two 20A circuits to service the counter top receptacles in the kitchen, at least 1 20A in the laundry (more likely 2).

    Code only requires 15A for general use circuits but if you don't mind the cost you could certainly buy 12 AWG cable instead of 14 AWG cable.

    With all that said, the NEC Code also allows the use of a 15 Amp receptcale on a 20A circuit. Some of the receptcales you are looking at are carying 20A already.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert

    Aug 9, 2010, 08:10 AM


    Please open a new post for a new question in the future.

    To begin with, Water Heaters 120 gals. Or less are considered to be a "Continously On" device and as such the Amperage needed is sized at 125% of the amperage required on the metal plate.

    For example - 20A X 1.25 = 25A

    So, if your faceplate requires 22A then the required amperage would be: 22 X 1.25 = 27.5A (round up to 28A)

    To figure out the wattage, use a deritive of Ohm's Law

    Watts are determined by multiplying the Voltage by the Amperage(and in some case by a third operator, power factor)

    So for your example:

    W (Power or Watts) = E (voltage) * I (Amperage)

    W = 240 X 28 = 6720 Watts or 6.72 kW (kilo Watts/ 10 to the 3rd power)

    I seriously doubt that there is any device in a residence that would require Mega watts (10 to the sixth power)

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