advice on wire gauge for built in oven

Discussion in 'Electrical Forum discussion & Blog' started by jono604, Nov 1, 2011.

  1. jono604

    jono604 New Member

    Messages:
    11
    Location:
    vancouver, BC
    Hello,
    I 'm in the midst of a kitchen renovation and I'd like some advice on the wire gauge for a built in oven.

    The oven is the the only electrical appliance on the circuit and supplied directly from the panel. The cooktop is gas and it's electrical needs will be supplied by a separate 15A circuit.

    The oven manufacturer calls for a 30A circuit and lists 7300W in the specs.

    I'm inclined to use 10AWG because of the 30A circuit but in some other on-line material I've seen a suggestion that says 10AWG is suitable for 30A appliances with power draw lower than 7200W.

    I'm a little bit confused. Does the 7300W rating have any impact on the wire gauge selection of is the 30A circuit the overriding factor?

    appliance specs are shown below

    thanks
    Jonathan



    Bosch oven HBL5450UC
    http://www.bosch-home.ca/en/products/cooking/ovens/single/HBL5450UC.html?source=browse

    Energy source: Electric
    Watts (W): 7,300 W
    Current (A): 30 A
    Volts (V): 240/208 V
    Frequency (Hz): 60 Hz
    Approval certificates: CSA
    Power cord length (cm): 127.0 cm
    Plug type: Fixed connection, No plug
  2. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Well seeing how 30amps * 240 volts would be 7200watts, I think you're sort of crazy and over-thinking this whole thing...
  3. jono604

    jono604 New Member

    Messages:
    11
    Location:
    vancouver, BC
    "over-thinking" probably.
    "crazy" ... I don't know about that. ;-)
    I'm just a first time home-owner and first time renovator who's trying to do things the right way.
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    You admitted to having a lose screw (crazy) in the first sentence of your original post ie: I 'm in the midst of a kitchen renovation

    Always install a piece of equipment according to any instructions included in the listing and labeling of the equipment, 110.3 (B) of the NEC

    If the installation instructions say 30 amps are what are needed then a 30 amp is what is required to be installed regardless of the math we do. The appliance has been tested by a third party who says that the 30 amp circuit is all that is needed.
  5. leejosepho

    leejosepho DIY scratch-pad engineer

    I also have an electric oven with a gas top, but both draw power from the 240V connection. So, are you sure the gas top requires a separate 120V circuit?

    Sure. The 10ga wire can be used for anything *up to* 30A, and that means it is also fine with anything drawing less than your oven's possible maximum of 7300W.

    No. Volts X Amps = Wattage, and circuits are rated according to amperage while total wattage used is being measured out at the electric meter.
    Last edited: Nov 2, 2011
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    If volts times amps equals wattage would that not mean that wattage divided by voltage give us amps.

    In the equation we know the wattage 7300 and the volts 240 so what would the amperage be? 30.4

    Now a quick look at 220.5 (B) Fractions of an Ampere. Calculations shall be permitted to be rounded to the nearest whole ampere, with decimal fractions smaller than 0.5 dropped.

    Now we are back to 30 amps just as the instructions called for
  7. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Here is the watts breakdown of the components in the oven:
    Bake Element Wattages cavity 1 (W): 2000 W
    Broil Element Wattages cavity 1 (W): 3600 W
    Convection Element Wattages cavity 1 (W): 2000 W


    Add that up and it is 7600 watts, but would broil ever run concurrently with bake? Would convection run concurrently with both of the other two???


    That is why the "system" is listed as 7300 watts, which is probably at the very high end....and 30 amps is fine.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,680
    Location:
    Cave Creek, Arizona
    The circuit breaker determines the MINIMUM wire size, and #10 wire is adequate for a 30 amp breaker. That is ALL you have to know, once you determine that the unit is rated at 30 amps.

    Leejoseph; If that is a "hybrid" range, then the 120 control circuit for the cooktop is coming from the 240/120 electric supply. Even electric ovens use 120 for their circuit boards.
    Last edited: Nov 2, 2011
  9. jono604

    jono604 New Member

    Messages:
    11
    Location:
    vancouver, BC
    Thanks for the feedback everyone.

    This all makes sense. I just wanted to be thorough and understand everything before I slap drywall up.

    The oven (wall mounted) and cooktop are in different areas so it didn't make sense to have them on the same circuit even if that was allowed.

    And to "jwelectric" I guess you're right. I probably do have a screw loose. Not only am I renovating the kitchen, I'm renovating the whole house... as hj and dlarrivee can attest to from my plumbing questions in the other forum.
    fun fun fun ...
  10. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    It won’t be long until you will be ready for one of those pretty white coats that buttons in the back. You know the one with the extra-long sleeves.
  11. jono604

    jono604 New Member

    Messages:
    11
    Location:
    vancouver, BC
    I'm close. very close ... ;-)
  12. leejosepho

    leejosepho DIY scratch-pad engineer

    Yes, I understand, and I was just not sure whether the OP had the same or had separate oven and cooktop units. Either way, having a gas top means we can still cook something even while the power is out since our top only needs power for the igniters.
  13. bsperr

    bsperr Member

    Messages:
    74
    Location:
    Athens, GA
    If you have a gas range top, I believe the NEC allows you to put it on one of your 20A small appliance branch circuits, so you shouldn't need to run a 15A circuit just for that (I guess the manufacturer's instructions could trump that though).
  14. Electromen

    Electromen New Member

    Messages:
    17
    Location:
    Pittsburgh
    Run 10/3 with ground "kleenex®". Most of the new ovens have four wires, 2 hot, neutral and ground. Plan on connecting it in a 4" square, 2 1/8" deep metal junction box with 1/2" knock outs. The 10/3 will bit in a 1/2" romex connector. The oven will come with flexible metal conduit. You'll need to buy a 1/2" flex connector, also call a Greenfield connector. If the oven comes with just three wires, 2 hot and a ground, simply do not use the white neutral, cap it off with a wire nut. However most ship with four wires.

    ed. sorry you cannot use that other word for wire on here. their lawyers told us so.
    Last edited by a moderator: Dec 11, 2011
  15. Electromen

    Electromen New Member

    Messages:
    17
    Location:
    Pittsburgh
    Do not connect the gas cooktop to a GFCI protected circuit. The ignitor on the cooktop usually trips the GFCI. Connect it to 15 or 20 amp circuit.
  16. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    Where do I go to see this information? Even if it did it wouldn’t be much to reset it.
  17. Electromen

    Electromen New Member

    Messages:
    17
    Location:
    Pittsburgh
    It's just experience. I've never connected a cooktop to a GFCI circuit. I was called in on a new house to trouble shoot someone else's work. That person had the cooktop connected to a GFCI circuit. The ignitor would trip it every time. I installed a new circuit that was not GFCI protected and it's worked ever since.
    Last edited: Dec 11, 2011
  18. Electromen

    Electromen New Member

    Messages:
    17
    Location:
    Pittsburgh
    I wouldn't want it on a GFCI because if it did trip, gas could fill the room. You have to assume that your clients are going to make mistakes.
  19. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,202
    Location:
    Houston, TX


    I never could get kleenex® to conduct electricity very well, When it is wet it does conduct better.
  20. Electromen

    Electromen New Member

    Messages:
    17
    Location:
    Pittsburgh
    LOL that's pretty funny. Dog Gone auto-fil and my use of the Trade Marked ® word for nm-b
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