50 amp breaker for kitchen appliances

Discussion in 'Electrical Forum discussion & Blog' started by jvstevens, Aug 1, 2013.

  1. jvstevens

    jvstevens Member

    Messages:
    46
    I have a rental property that has a 50 amp 220 VAC circuit that supplies power for both an electric cooktop and wall oven. I would like to replace both appliances with new ones. The cooktop I have in mind requires a 30 amp breaker per the specs. For the wall oven, I would like to install an electric oven/microwave combo unit, and it requires a 30 amp breaker per the specs. Doing just a simple addition, it would seem I need a 60 amp breaker. Which is, of course, problematic, since I only have a 50 amp breaker. But, I started to wonder, in a situation like this, is there any sort of "derating" (I think that's the proper term) factor that can be applied to this arrangement, such that 50 amps would be considered adequate? After all, it would be rare to have all 4 cooktop burners, the oven and microwave all going full bore at the same time. I looked briefly in some electrical references I have, but haven't come across anything that addresses this.

    Even if no such allowance is allowed per the code, is it really a bad, unsafe idea to put both of these appliances on a 50 amp circuit? Would there be problems, other than tripping the breaker once in a while?

    I guess if worse comes to worse, I could just go with a separate wall oven and microwave, and put the microwave on its own 120 VAC circuit.

    Thanks in advance for all your help.
  2. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    There should be a VA rating on each unit that would help.

    Using the 30 amps of each unit we can come up with something general.

    30 times 240 equal 7200. 7200 times 2 equals 14,400

    14,400 subtract 12,000 equals 2,400
    Now increase the demand found in column “C” by 5% for each KW or fraction thereof
    8,000 times 115% equals 9,200 divided by 240 equals 38.33

    210.19 says that a fifty amp circuit can be tapped as you propose so it looks as though what you propose would be code compliant. Always remember that anything less than code compliant is not safe.
  3. jvstevens

    jvstevens Member

    Messages:
    46
    Thanks! I will look up the VA rating myself on the appliances. I would like to do the calculations like you just did for the appliances I'm considering. Can you refer me to this table online so I can understand the theory behind what you just did? Much appreciated!
  4. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,127
    Location:
    Houston, TX
    I would not change the breaker size, and just replace the appliances.

    Then test the load for "Normal Use"

    Chances are you will be OK.

    If you need more power, then another breaker and wire run will be required. For safety.


    When putting in new appliances a person should be decreasing power usage, Not Increasing it.


    Have Fun.
  5. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,974
    Location:
    NW Ontario, Canada
    Let me see if I got this straight. You have two appliances that each require 30 amp breakers but you want to use only one 50 amp to protect both? If either of the appliances malfunctioned and drew more than 30 amps, the current would be greater than what it was designed for since the single breaker would allow 50 amps. I would think that each appliance would need its own 30 amp breaker.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,631
    Location:
    Cave Creek, Arizona
    Since the breaker is to protect the wire from overload, and your appliances will not likely require the full amperage at any one time, just as the breakers in a panel can exceed the rating for the main breaker, you will be okay. IF you should exceed the amperage, which is unlikely, the breaker will trip and terminate the overload. To avoid the problem of a 50 amp breaker protecting a 30 amp device, you could install a subpanel fed by the 50 amp breaker with two 30 amp breakers in it.
  7. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,974
    Location:
    NW Ontario, Canada
    The wires of the individual appliances may be sized only for 30 amps since the specs call for a 30 amp breaker.
  8. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    There might be some additional factors applied, for an electric oven and cooktop, as they are constant resistive loads not unlike my baseboard electric heaters, which are only allowed to draw 80 percent of the branch circuit capacity.
  9. leejosepho

    leejosepho DIY scratch-pad engineer

    ...and for a 30A outlet. There is nothing wrong with connecting a 30A load (or even a potential 60A load) to a 50A circuit, but connecting two outlets of 30A each (or even of whatever size) at the end of a circuit intended for one does not sound right to me.
    Last edited: Aug 2, 2013
  10. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    See the NEC at 220.55 and table 220.55 including notes
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    Come on now people let’s think a little. We install multiple 15 amp receptacles on 15 and 20 amp circuits so what is the problem with installing a cooktop and oven as outlined in the NEC?

    210.19 allows a #12 or larger tap for a cooktop or oven to a 50 amp circuit or you can pull individual circuits which ever you choose. What that is included in the manual does not count for much unless it is included in the listing and labeling of the appliance and no it does not void a warranty. The instructions included in the listing and labeling of an appliance can be found in the UL Guides and Whitebook
  12. leejosepho

    leejosepho DIY scratch-pad engineer

    So then, I could put a 30A welder outlet in the tool closet in my carport and directly behind the 50A receptacle for our oven (with gas top) in the kitchen? I know that would work, but I did not know it is legal!
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    no that would not be legal but wiring a cooktop and oven to a 50 amp circuit is legal


    210.19 Conductors — Minimum Ampacity and Size.
    (A) Branch Circuits Not More Than 600 Volts.

    (3) Household Ranges and Cooking Appliances. Branch-circuit conductors supplying household ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances shall have an ampacity not less than the rating of the branch circuit and not less than the maximum load to be served. For ranges of 8¾ kW or more rating, the minimum branch-circuit rating shall be 40 amperes.

    Exception No. 1: Conductors tapped from a 50-ampere branch circuit supplying electric ranges, wall-mounted electric ovens, and counter-mounted electric cooking units shall have an ampacity of not less than 20 amperes and shall be sufficient for the load to be served. These tap conductors include any conductors that are a part of the leads supplied with the appliance that are smaller than the branch-circuit conductors. The taps shall not be longer than necessary for servicing the appliance.


    Table 220.55
    Note 4. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55. The branch-circuit
    load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch-circuit load for a
    counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room,
    shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range.
  14. leejosepho

    leejosepho DIY scratch-pad engineer

    Okay, clarified.
  15. jvstevens

    jvstevens Member

    Messages:
    46
    The cooktop VA rating is 7200, and the oven/microwave combo VA rating is 6400. So, I'm a bit better off than you calculated. Thanks again, everyone for all the input. Learned something new!
Similar Threads: breaker kitchen
Forum Title Date
Electrical Forum discussion & Blog Possible "broken breaker" miswiring kitchen splits Sep 29, 2011
Electrical Forum discussion & Blog Sizing Kitchen Range Breaker Size & Wire Gauge Apr 12, 2011
Electrical Forum discussion & Blog AFCI breaker (in Wisconsin) needed for dedicated light circuit? Jul 30, 2014
Electrical Forum discussion & Blog Can I use 2 single pole 30 amp pushmatic breakers as a double pole set up May 28, 2014
Electrical Forum discussion & Blog piggyback 20A breakers May 15, 2014

Share This Page