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  1. #1
    Join Date
    Feb 2009
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    Southern Vancouver Island
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    Default Combining two 120v circuits

    A client has two 120 volt 15 amp circuits going from his breaker panel to a detached cottage, what we call a garden cottage. I called out the use of a portable space heater. He should install a 120 volt wall heater for safety.
    He wants to know if he can install a 240 volt baseboard heater by combining the two feeders in a junction box. I agree he can get 240 volts this way because the breakers are on opposing bus bars. But I believe this is prohibited by the Canadian EC. He needs to install a new 240 feeder and a breaker panel if he wants 240 volts in the cabin. What does the NEC say about this?
    What is the reasoning for not allowing the two branch circuits to be combined downstream?

    2018 ASHI InspectionWorld
    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  2. #2
    Join Date
    Aug 2008
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    Maryland
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    Default Re: Combining two 120v circuits

    The NEC limits an outbuilding to one circuit or feeder. A MWBC counts as one circuit.

    All answers based on unamended National Electrical codes.

  3. #3
    Join Date
    Aug 2012
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    Rock Hill S.C.
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    94

    Default Re: Combining two 120v circuits

    Why combine the circuits? Could you not use a double pole breaker on one of the circuits for the 240v heater, or is the baseboard heater 120/240?


  4. #4
    Join Date
    Mar 2007
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    Ormond Beach, Florida
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    Default Re: Combining two 120v circuits

    Quote Originally Posted by Jim Port View Post
    The NEC limits an outbuilding to one circuit or feeder. A MWBC counts as one circuit.
    Jim,

    (bold and underlining are mine)
    "The NEC limits an outbuilding to one circuit or feeder."

    I must have missed that part, which section is that? Thank you.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  5. #5
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    Southern Vancouver Island
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    Default Re: Combining two 120v circuits

    Quote Originally Posted by Chris McIntyre View Post
    Why combine the circuits? Could you not use a double pole breaker on one of the circuits for the 240v heater, or is the baseboard heater 120/240?
    You are right, Chris. The load has to be kept below 15 amps, not hard to do.

    The CEC allows for ONE 15 amp branch circuit to a detached building. These guys got two somehow.
    I checked the pics and it turns out this guy has a 240 volt circuit, not presently in use in the cabin.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  6. #6
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    Default Re: Combining two 120v circuits

    I'll ask a different question.
    'May' a 240 volt circuit be supplied by two separate 120 volt circuits, on single, adjacent breakers, by bringing the far ends together in a junction box?
    He'll have 120 v appliances on two branches and a 240 volt heater at the ends of the two branches.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  7. #7
    Join Date
    Aug 2008
    Location
    Maryland
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    Default Re: Combining two 120v circuits

    Quote Originally Posted by Jerry Peck View Post
    Jim,

    (bold and underlining are mine)
    "The NEC limits an outbuilding to one circuit or feeder."

    I must have missed that part, which section is that? Thank you.
    225.30. I could have worded this a little more clearly.

    All answers based on unamended National Electrical codes.

  8. #8
    Join Date
    Mar 2007
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    Default Re: Combining two 120v circuits

    Quote Originally Posted by Jim Port View Post
    225.30. I could have worded this a little more clearly.
    You mean like the part which says: "unless" ... got it now.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  9. #9
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    Default Re: Combining two 120v circuits

    I was more referring to the one circuit part. Someone may take that as the outbuilding could only have one circuit, instead of being supplied by one circuit or feeder.

    I doubt that any of the conditions in (A) through (E) would have applied so I did not even mention them.

    All answers based on unamended National Electrical codes.

  10. #10
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,252

    Default Re: Combining two 120v circuits

    Quote Originally Posted by Jim Port View Post
    I was more referring to the one circuit part. Someone may take that as the outbuilding could only have one circuit, instead of being supplied by one circuit or feeder.

    I doubt that any of the conditions in (A) through (E) would have applied so I did not even mention them.
    Got what you mean now:
    - Instead of 'only one circuit', you were meaning:
    - - The outbuilding would most likely be supplied by only one feeder ... but that the outbuilding is allowed to have multiple circuits originating from the panel supplied by that one feeder set.

    Yes, I was thinking you were going with the 'one circuit' and did not realign my thinking with your followup 'one circuit or one feeder' comment until now.

    Thank you for clarifying what you were meaning.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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