220 volt supplying two 110s

Discussion in 'General Electronics Chat' started by stevealtman, Mar 29, 2005.

  1. stevealtman

    Thread Starter New Member

    Mar 29, 2005
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    Hi out there. I have two questions and they are kind of related. This situation is thus. I am remodeling my kitchen and when I do a circuit analysis, the appliances easily take up double the amps supplied to the kitchen, however before the remodel I never seemed to have breaker tripping issues. How could this be and how much amperage should I have to run a standard fridge, microwave, dishwasher and several outlets?

    Additionally, I have replaced my electric range with a gas range. This opens up a 220 volt 30 amp circuit. Can each hot power a 110 circuit with the single white acting as the common return?

    Thanks for the input.

    Steve
     
  2. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1
    Last questions first: The range outlet should have been fed by it's own circuit breaker, and would therefore have no effect on the rest of the kitchen outlets. Though the size 10 or 8 awg wire would be pretty darn big for a 110volt circuit, yes, you can use this wire to feed other receps, providing that you reduce the breaker to two 15 or 20 amps.

    According to the NEC code, you need two small appliance circuit breakers, at 20 amps each. One of these is usually the fridge, the other can feed your counter tops and microwave. (I would recomend putting the microwave on it's own 15 amp circuit, but it may not be absolutely necesarry.) The counter top circuits must be GFCI protected, and may not have more than 48" distance between them (excluding the sink).

    Keep in mind that you will probably never run a small appliance from every outlet, as well as running the dish washer, disposal, and anything else in the kitchen, all at the same time. The "small appliance" part of the code just says no more than 12 amps at a time.

    Hope this helps. I can give the exact code and chapter later if you need. :)
     
  3. stevealtman

    Thread Starter New Member

    Mar 29, 2005
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  4. stevealtman

    Thread Starter New Member

    Mar 29, 2005
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    Thank you so much for your response. I hope I can trouble you once more to clarify a couple more questions.

    As you stated, I have a dedicated 30 amp circuit for the rangetop and the oven. In the future I will use a dual fuel oven thus eliminating the power required for the range top. Because the kitchen is old it is in despirate need of additional circuits (it has only one 20 amp circuit that was running the fridge, dishwasher, three outlets and the garbage disposal (I don't know how I didn't trip the breaker)).

    Because I have no basement or attic access in my house running new wiring is very destructive. Therefore, my plan was this: Because the old range circuit wiring was rated at 30 amps, I wanted to run an additional 20 amp line off of it. The range never draws more than ten, leaving this extra capacity.

    My understanding of 220 appliances is that the two hots provide the circuit and the white neutral is not a current carrying wire. I wanted to tap a 110 circuit into one of the hots and use the existing white to return to ground. I would just leave the 30 amp breaker in place as this is what the wires are rated for.

    Sound plausible?

    One last question. With an 8 amp fridge, 10 amp dishwasher, and 5 amp garbage disposal, how should they be devided up among two 20 amp circuits (lest the two outlets not be forgotten).

    Thanks for reading,

    Steve
     
  5. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1
    You must change the breaker from thirty amps to two, single pole, 15 or 20 amps breakers, if you want to feed 120 volt circuits. Otherwise, it would take thirty amps or more to trip the circuit, no matter how you have it divided up. Though the wire is rated for 30 amps, your small appliances are not. NEC code says you may have no more than 12.5 amps on small appliance branch circuits (220.52(A)), and that small appliance branch circuits be fused at no more than 20 amps, per circuit. (210.52(B))

    This is all academic because Code (and possibly common sense) also dictates that the range gets it's own circuit breaker. Though I couldn't find anything that specifically forbids using a tap conductor from a range supply to feed a small appliance branch circuit, the code only provides for (kitchen) tap conductors that feed ranges and cooking appliances. (210.19(3)) NOT small appliance outlets. You may be forced to run a new wire for your other appliance receptacles.

    Not to put too fine of a point on it: If you had a counter top range, and a seperate oven or other cooking appliance (both electric), then you could wire a 50 amp branch circuit and tap each of those two (cooking appliance) loads from that circuit (210.19(3)exception #1). It was not intended that you could tap a small appliance branch source from the 50 amp (or in your case, 30 amp) circuit, even though you are able to get the voltage from the tap.

    What ever you do, make sure that you're safe. A circuit fused at 30 amps requires an excess of 30 amps to trip it. Remember that if you tap 120 volts for a small appliance out of this circuit, the appliance could be overloaded to the point that it's on fire, and still not draw the 30 amps required to trip the breaker.

    Just an idea: Contact the local electrical inspector and ask if they'll allow you to tap the 30 amp circuit, and use the tap as a "feeder". Use the feeder to to feed 120 volts to a small branch box (hide it behind the fridge) that has it's own circuit breakers. There will be some neutral / grounding bonding issues, but if this is do-able, it will be much safer than a direct tap. Are you on a 120volt, two wire circuit? Or do you have a seperate ground wire for each neutral and hot?

    Once you've figured out how to safely get your 120 volts, put the fridge on it's own 15 amp breaker, and dishwasher / disposal on another 20 amp breaker. The fridge is the largest, single load.

    The reason you didn't trip before is because your three appliances were not all on at the same time, and probably weren't drawing full load when they were on.

    I know I haven't been full of good news, but I hope this helps you out.
     
  6. stevealtman

    Thread Starter New Member

    Mar 29, 2005
    5
    0
    Thanks so much for your input!

    I have decided on the following using your input for guidance. I will use one of my 220 v lines to run two 15 amp circuits ( 15 A breaker protected). The other 220 line will be left as is to run the dual fuel oven.

    Because the 220V lines have no fourth green grounding wire, I have added a #10 gauge wire (insulated and different routing to the breaker box) for grounding of this old circuit. Does stranded wire of the same gauge have the amperage capacity of solid?

    Best regards,

    Steve
     
  7. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1
    Stranded wire usually has a slightly higher amp rating than solid wire of the same gage. This is because the stranded wire porvides more total wire cross-section area than solid. This difference is slight, so with home wiring it shouldn't matter much.
     
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