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Thread: How many neutral conductors do I need?

  1. #1

    Default How many neutral conductors do I need?

    Bringing electricity from main panel to sub-panel @ shed 20 feet away. I'm using #12 THHN conductors in 3/4" conduit with two conductors providing 240V to a dedicated air conditioner outlet and two conductors for two separate 120V, 20A outlet circuits for hand tools, etc. My question is do I need to run two separate neutral conductors for those 120V circuits or is one sufficient? Thanks in advance for your help.

  2. #2
    In the Trades Bob NH's Avatar
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    It isn't clear that you are installing a subpanel.

    It sounds like you are running complete circuits from the main panel.

    If you are installing a subpanel you run one circuit from main to the subpanel. If you have a subpanel you need one neutral + two hot + ground.

    If the calculated load doesn't exceed 30 Amps you can run a #10 circuit to the subpanel, and then run the 20 Amp circuits to the A/C and the other outlets. If you want more you can run #8 to the subpanel and put it on a 50 Amp breaker in the main.

    You don't need a neutral for the 240 Volt circuit.

    You can run the two 20 Amp circuits as a multiwire branch circuit which consists of two ungrounded (hot) conductors and one neutral. When you get to the point where the circuits diverge you will connect both of the circuits to the one neutral.

  3. #3

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    One will do it but @ 20 feet, I'd spend the extra 2 bucks and run separate neutrals just to avoid any issuers with the multi wire branch circuit.

    If you use one neutral and somehow, thru a loose connection loose the neutral going to the panel, you will end up with 240V at your 120V outlets (if there is a load on one circuit). Separate neutrals will eliminate that possibility.

  4. #4
    Electrical Contractor/Instructor jwelectric's Avatar
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    It never ceases to amaze me the BAD ADVICE given on these self help forums. Although what has been suggested would work it is totally wrong and BAD ADVICE.

    225.30 Number of Supplies.
    Where more than one building or other structure is on the same property and under single management, each additional building or other structure that is served by a branch circuit or feeder on the load side of the service disconnecting means shall be supplied by only one feeder or branch circuit unless permitted in 225.30(A) through (E). For the purpose of this section, a multiwire branch circuit shall be considered a single circuit.
    (A) Special Conditions. Additional feeders or branch circuits shall be permitted to supply the following:
    (1) Fire pumps
    (2) Emergency systems
    (3) Legally required standby systems
    (4) Optional standby systems
    (5) Parallel power production systems
    (6) Systems designed for connection to multiple sources of supply for the purpose of enhanced reliability
    (B) Special Occupancies. By special permission, additional feeders or branch circuits shall be permitted for either of the following:
    (1) Multiple-occupancy buildings where there is no space available for supply equipment accessible to all occupants
    (2) A single building or other structure sufficiently large to make two or more supplies necessary
    (C) Capacity Requirements. Additional feeders or branch circuits shall be permitted where the capacity requirements are in excess of 2000 amperes at a supply voltage of 600 volts or less.
    (D) Different Characteristics. Additional feeders or branch circuits shall be permitted for different voltages, frequencies, or phases or for different uses, such as control of outside lighting from multiple locations.
    (E) Documented Switching Procedures. Additional feeders or branch circuits shall be permitted to supply installations under single management where documented safe switching procedures are established and maintained for disconnection.
    Only one circuit is allowed to be installed and anything more could cause problems should there be a need to make a claim on the homeowner’s insurance.

    And people ask why Joe did what he did.

  5. #5

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    shall be supplied by only one feeder or branch circuit unless permitted in 225.30(A) through (E). For the purpose of this section, a multiwire branch circuit shall be considered a single circuit.
    Gah!

    Somewhere in there (not there specifically but in the code) it says you can also run a 240 circuit.....I was sure of it. It was covered a few months ago in a thread....somewhere.....I think.....maybe. There is an exception for lighting circuits also.



    Well....I couldn't find it.

    Looks like one circuit legal maximum. MWBC (2 hots+1 neutral) is considered one circuit. I don't see how it could hurt anything but I don't make the rules.
    Last edited by Alectrician; 08-14-2008 at 09:17 PM.

  6. #6
    In the Trades Bob NH's Avatar
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    Quote Originally Posted by Old Coot View Post
    Bringing electricity from main panel to sub-panel @ shed 20 feet away. I'm using #12 THHN conductors in 3/4" conduit with two conductors providing 240V to a dedicated air conditioner outlet and two conductors for two separate 120V, 20A outlet circuits for hand tools, etc. My question is do I need to run two separate neutral conductors for those 120V circuits or is one sufficient? Thanks in advance for your help.
    The original post said "sub-panel @ shed". That is the legal and correct way to serve the shed. It is also more convenient for the purpose of running multiple circuits. A 4-circuit subpanel is not that expensive.

    It would be easy to pull #10 to the subpanel and that would be enough for the A/C and hand tools. Not many people use a Skil Saw in the left hand and a SawZall in the right hand.

    If I wanted a compressor in the shed I would run #8s.

  7. #7
    Electrical Contractor/Instructor jwelectric's Avatar
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    Lord I sure understand why I go out every day and see things that were a joke from the first day. It is due to the theory that if it works it must be right.

    225.39 Rating of Disconnect.
    The feeder or branch-circuit disconnecting means shall have a rating of not less than the calculated load to be supplied, determined in accordance with Parts I and II of Article 220 for branch circuits, Part III or IV of Article 220 for feeders, or Part V of Article 220 for farm loads. Where the branch circuit or feeder disconnecting means consists of more than one switch or circuit breaker, as permitted by 225.33, combining the ratings of all the switches or circuit breakers for determining the rating of the disconnecting means shall be permitted. In no case shall the rating be lower than specified in 225.39(A), (B), (C), or (D).
    (A) One-Circuit Installation. For installations to supply only limited loads of a single branch circuit, the branch circuit disconnecting means shall have a rating of not less than 15 amperes.
    (B) Two-Circuit Installations. For installations consisting of not more than two 2-wire branch circuits, the feeder or branch-circuit disconnecting means shall have a rating of not less than 30 amperes.
    (C) One-Family Dwelling. For a one-family dwelling, the feeder disconnecting means shall have a rating of not less than 100 amperes, 3-wire.
    (D) All Others. For all other installations, the feeder or branch-circuit disconnecting means shall have a rating of not less than 60 amperes.

    If you're going to do something at least do it right of just leave it alone. If you are going to give advise give correct advise or just be quite.

    EDITED TO ADD:

    Let’s not forget all those answers to questions that have not as yet been ask such as the other requirements for this installation

    Article 225 requires that a disconnect be installed at the building that will disconnect all incoming ungrounded conductors, 225.31

    This disconnect is required to be rated as service equipment, 225.36

    If there is going to be more than one circuit in that building such as one for the lights and another for receptacles then a minimum of 30 amp circuit MUST be installed.
    Should there be more than two circuits out there then a minimum of 60 amp circuit MUST be installed and this will require at least a #6 copper conductor that CAN’T be NM nor SE cable.

    The circuit installed will require both a neutral and an equipment grounding conductor. 250.32

    A grounding electrode system is required at this building, 250.32.

    This list goes on and on. There are several questions that have not yet been asked about the PROPER way to make this installation that carries some very strong life safety issues.

    We need to stop giving out our opinions and “it will work” advice and start giving out correct advice to those who are seeking knowledge on how to make installations.
    Last edited by jwelectric; 08-15-2008 at 06:29 AM.

  8. #8
    DIY Junior Member Juan for the road's Avatar
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    Quote Originally Posted by jwelectric View Post
    Lord I sure understand why I go out every day and see things that were a joke from the first day. It is due to the theory that if it works it must be right.


    We need to stop giving out our opinions and “it will work” advice and start giving out correct advice to those who are seeking knowledge on how to make installations.
    Amen.

    The code is code for a reason,even if most of us can't understand it.
    Follow the code and you're in good shape...only an idiot would disregard it or not reference it.There's just too much at risk.

    I will only follow advice given along with specific code references.If the advice sounds "anecdotal" I skip it.

    The original question is very basic and common,been asked a thousand times over,everywhere in the country.Most electrical apprentices with 6months experience should nail this one.

    Rest easy if you follow JW.

  9. #9

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    The original post said "sub-panel @ shed".
    Oh yeah. I guess that since JW went all blah blah blah, I assumed that he read the post.

    So......Back to the original post and the original question, based on the info given.......you only NEED one neutral but two is better.

  10. #10
    Moderator & Master Plumber hj's Avatar
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    Default neutral

    So......Back to the original post and the original question, based on the info given.......you only NEED one neutral but two is better.

    You are therefore assuming that they are going to be on different legs of the power supply, otherwise a single neutral could be overloaded by usage of both feeds at the same time, also assuming it were not improper to do it in the first place and also more time and trouble than it is worth rather than installing a sub panel in the garage.

  11. #11

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    You are therefore assuming that they are going to be on different legs of the power supply, otherwise a single neutral could be overloaded by usage of both feeds at the same time, also assuming it were not improper to do it in the first place and also more time and trouble than it is worth rather than installing a sub panel in the garage
    Holy run on sentance Batman

    Try to keep up. He IS putting a sub in the shed.

    Bringing electricity from main panel to sub-panel @ shed 20 feet away
    It was a little unclear but that's what he said.

  12. #12
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Alectrician View Post
    Oh yeah. I guess that since JW went all blah blah blah, I assumed that he read the post.

    So......Back to the original post and the original question, based on the info given.......you only NEED one neutral but two is better.
    so you think it would be a good idea to parallel the neutral to the subpanel?

  13. #13
    Electrician Chris75's Avatar
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    Quote Originally Posted by Bob NH View Post

    It would be easy to pull #10 to the subpanel and that would be enough for the A/C and hand tools. Not many people use a Skil Saw in the left hand and a SawZall in the right hand.

    If I wanted a compressor in the shed I would run #8s.

    Quote Originally Posted by jwelectric View Post
    Lord I sure understand why I go out every day and see things that were a joke from the first day. It is due to the theory that if it works it must be right.

    225.39 Rating of Disconnect.

    (D) All Others. For all other installations, the feeder or branch-circuit disconnecting means shall have a rating of not less than 60 amperes.

    If you're going to do something at least do it right of just leave it alone. If you are going to give advise give correct advise or just be quite.

    EDITED TO ADD:

    Let’s not forget all those answers to questions that have not as yet been ask such as the other requirements for this installation



    This disconnect is required to be rated as service equipment, 225.36

    If there is going to be more than one circuit in that building such as one for the lights and another for receptacles then a minimum of 30 amp circuit MUST be installed.
    Should there be more than two circuits out there then a minimum of 60 amp circuit MUST be installed and this will require at least a #6 copper conductor that CAN’T be NM nor SE cable.



    Mike, not to burst your bubble, but no where in the NEC tells you what size conductors to run to a seperate structure, the only thing the NEC requires is the Rating of a Disconnect, not the rating of the conductor....



    4-26 Log #2194 NEC-P04

    Final Action: Reject

    (225.39, FPN )

    Submitter: David Williams, Lansing, MI

    Recommendation: Revise as follows:
    The rating feeder or branch-circuit disconnecting means shall have a rating of
    not less than the load to be supplied, determined in accordance with Parts I and
    II of Article 220 for branch circuits. Parts III or IV of Article 220 for feeders,
    or Part V of Article 220 for farm loads. In no case shall the rating be lower
    than specified in 225.39(A), (B), (C), or (D).

    FPN: The rating of the overcurrent device protecting the feeder does not need
    to be rated to the minimum rating in this section.

    Substantiation: The code section specifies the minimum rating of the
    disconnect and is not clear that the feeder or branch circuit needs to be rated
    for this minimum rating. As an inspector, I am not positive if this section only
    applies to the rating of the disconnect or does this mean that the minimum size
    of a feeder to a building should be 60 amperes.
    Just trying to clear up a concern.

    Panel Meeting Action: Reject

    Panel Statement: An additional FPN is not necessary. The title of 225.39
    defines the requirement as solely being the rating of the disconnect.


    Number Eligible to Vote: 10

    Ballot Results: Affirmative: 10
    Last edited by Chris75; 08-16-2008 at 04:05 AM.

  14. #14
    Moderator & Master Plumber hj's Avatar
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    Default ?

    Holy run on sentance Batman

    It is "sentEnce" since we are going pedantic. But not the king of runons. That was a whole page in an educational journal.

  15. #15

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    so you think it would be a good idea to parallel the neutral to the subpanel?
    I know a trick question when I see it

    I think separate neutrals is a better idea, especially when a HO is doing the work. They don't seem to be able to tighten wire nuts properly.


    It is "sentEnce" since we are going pedantic
    Now you want me to make me get out the dictionary?

    I know it's sentence. It is a common mistake of mine along with many others.

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