208 Volt single phase oven/from 208 Volt 3 phase Breaker Panel

Discussion in 'The Projects Forum' started by Bob in VA, Jan 27, 2016.

  1. Bob in VA

    Thread Starter New Member

    Jan 27, 2016
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    Just need a confirmation here. Purchasing a commercial Pizza Oven that is listed as 208v single phase. There are "spares" in the 120/208 (three-phase) breaker panel.

    I am correct that I will need to add a two-pole breaker (rated at the correct amperage) in order to provide the oven with 208 voltage/single phase. ?

    Thanks!
    Bob
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yes, If you go across two phases (208) then yes that should be OK.
    Max.
     
  3. Bob in VA

    Thread Starter New Member

    Jan 27, 2016
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    Max... Thanks! I was pretty sure that I had it right. Just needed a confirmation. Bob
     
  4. Bob in VA

    Thread Starter New Member

    Jan 27, 2016
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    OK some other confirmation needed?

    OK now.... Let's determine the breaker size and the wire size?

    The rating on the Pizza Oven is listed as: "208/240V, 1PH, 7.2KW, 26/30 Amps"

    7.2 kw equals a "heating wattage" of 7200 watts - correct? For 7200 watts I would divide the wattage by the voltage (208) 7200/208=34.615 amps.

    Assuming I tie into the 120/208 3 Phase Breaker Panel using a 2-pole breaker, I need the breaker to be a 30 Amp? Is that Correct? Or should it be a 40Amp 2-pole breaker?

    And if the run from the box to the outlet (oven location) is 30 feet, (I double the length ... say 60 feet), then the recommended wire size should be #8AWG copper? Or should I go with #6?

    Thanks!
     
    Last edited: Jan 28, 2016
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,565
    2,379
    I would go with the 40amp breaker to avoid nuisance tripping, #8 should be fine as this has a 40amp ampacity rating.
    Max.
     
  6. ebeowulf17

    Active Member

    Aug 12, 2014
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    Resistive loads operate with a fixed resistance, not a fixed wattage, which leads to a lot of misunderstandings. Looks like you've got an 8 ohm load (240/30 and 208/26 both equal 8) and your wattage spec is the max wattage based on 240V supply (240*30=7200.) Your actual wattage, assuming 208V supply, should be 5408 (208*26.)

    Sorry for nit-picking, but I work on coffee and espresso machines and techs are constantly confused by the fact that heading elements are listed by their wattage, instead of their resistance. It's become a pet peeve of mine.

    Regardless, none of this really changes how you safely wire it up in your situation. Max's advice is solid.
     
    Bob in VA likes this.
  7. Bob in VA

    Thread Starter New Member

    Jan 27, 2016
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    Thank you both!
     
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