Announcement

Collapse
No announcement yet.

Frequently Asked 2005 NEC Questions

Collapse
This topic is closed.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Frequently Asked 2005 NEC Questions

    Frequently Asked Questions



    Based on the 2005 National Electrical Code






    If you post a similar question to the questions that follow, the thread will not be closed because of it: but a link to the appropriate FAQ may be posted. There is usually an avenue to a question that has not been explored, new members arrive daily, and new perspectives are always welcome.

    General QuestionsBranch Circuits, Devices, and Layout QuestionsServices, Feeders, PanelboardsGrounding Code QuestionsCalculation QuestionsThe Taboo Questions that will be promptly closed, due to exhaustion of the topic (or because of Forum Rules):-----------


    If you notice a technical error, have a question you believe belongs here, or have a different opinion on a topic addressed by the FAQs that you feel should be included, feel free to start a thread on it with "FAQ" in the title. Or, you can send George a PM or post feedback in this thread if it's a small issue.

    If you do not understand an answer in the FAQ, feel free to start a thread on any of the topics (except for the taboo topics mentioned above).
    Last edited by Dennis Alwon; 09-02-11, 04:17 PM.

    #2
    The NEC Cycle Process
    • How is the NEC created? How can I propose a change to the NEC? Can anyone propose a change?
    Every three years, the code making panels of the NFPA convene to go over submitted proposals, accept them or reject them, and report their conclusions. The ROP is generated from this meeting, and then made available for comment. The CMPs then review the comments, and their final decisions create the next edition of the code. There are hundreds of codes that undergo this process from the NFPA, the most popular and widely used is the NEC.

    Anyone can submit a proposal or comment to the NEC. Proposal forms (and the schedule for the next cycle) are included in the back of each NEC. If you would like to submit a proposal and have the members discuss it before you send it, you can use the Proposal Forum here to do just that.
    • What is an ROP, and an ROC? Where can I find ROPs/ROCs online?
    An ROP (Report on Proposals) is the report that shows all proposals submitted, and the CMP's decision on each.
    An ROC (Report on Comments) is the report that shows all comments received, and the CMP's final decision on each.
    The ROPs and ROCs can be found at this link to the NFPA website.
    The NFPA Manual of Style (basically, the rules for writing rules) can be found at this link.
    A downloadable proposal form is here.
    A downloadable comment form is here.

    Once I download the forms in a word doc. I fill out all the fields that will remain the same, ie. name, address, etc. I even scanned my signature and placed it in the box then saved the file for the next go round. BTW, I don't believe you need to sign it if you file the form electronically.
    • Is there a website at which you can get a free copy of the NEC, either in HTML or PDF format?
    The NFPA recently made the decision to make the 2005 NEC accessible, without cost, directly from their web site. The information is available as a "read only" page. It is not possible to copy, print, or otherwise duplicate what is given to you for free. Access requires you to agree to their terms and conditions. Here is the page (copy this web address to your browser's address bar): https://www.nfpa.org/catalog/service...%3Fid%3D7008SB . There is a table of contents available; it pops up as a separate window. You can click on a paragraph title, and the window that contains the code book will open to that page. You can also turn pages, one by one, using arrow buttons at the bottom of the page.This version has no "search" feature. If for example you want to find the rule about AFCI protection, you cannot search for that term. You have to look at the table of contents, and then read page by page until you find what you want.
    Last edited by Dennis Alwon; 09-05-11, 08:10 AM.

    Comment


      #3
      Grounds Up or Down?
      • Should a receptacle be installed with its ground connection point up or down?
      The NEC does not address this question. Both configurations are equally acceptable. It is a matter of choice, and the choice can be made by the designer, the installer, or the owner. There may be some aesthetic advantages in being consistent throughout a given project, but even that is not a code requirement. There have been reasonable arguments made in favor of “ground up.” There have been reasonable arguments made in favor of “ground down.” However, not one of the arguments is any more compelling than any other.

      Related threads:
      Counter Receptacles Proposal - Mar 2007. Started by Al Ewaldt, asks if a proposal to add this to the code would be a good idea. Includes text from previously rejected proposals.
      Ground Pin Up? - Nov 2007. Started by George Everett, casts light on a rumored OSHA requirement regarding ground up or down. Numerous replies including links to manufacturer's statements.
      Last edited by Dennis Alwon; 09-02-11, 01:08 PM.

      Comment


        #4
        Is pigtailing a receptacle required?
        • Is it legal to use a receptacle’s screws or back-stab connections for continuity of the circuit, or is pigtailing the conductors required?
        First, the NEC does require certain conductors to be "pigtailed", to not depend on the device to carry the current flowing through the entire circuit. For grounded (neutral) conductors in a multiwire branch circuit, pigtailing is required, see 300.13(B).

        For equipment grounding conductors, there is a similar requirement in all circumstances. See 250.148.

        The UL listing information for receptacles can be found by clicking here. Here is an excerpt from that information:

        Screwless terminal connectors of the conductor push-in type (also known as "push-in-terminals") are restricted to 15 A branch circuits and are for connection with 14 AWG solid copper wire only. They are not intended for use with aluminum or copper-clad aluminum wire, 14 AWG stranded copper wire, or 12 AWG solid or stranded copper wire.

        Single and duplex receptacles rated 15 and 20 A that are provided with more than one set of terminals for the connection of line and neutral conductors have been investigated to feed branch circuit conductors connected to other outlets on a multi-outlet branch circuit, as follows:
        • Back wire (screw actuated clamp type) terminations with multiple wire access holes used concurrently to terminate more than one conductor
        • Side wire (binding screw) terminals used concurrently with their respective push-in (screwless) terminations to terminate more than one conductor
        Single and duplex receptacles rated 15 and 20 A that are provided with more than one set of terminals for the connection of line and neutral conductors have not been investigated to feed branch circuit conductors connected to other outlets on a multi-outlet branch circuit, as follows:
        • Side wire (binding screw) terminal with its associated back wire (screw actuated clamp type) terminal
        • Multiple conductors under a single binding screw
        • Multiple conductors in a single back wire hole
        Duplex receptacles rated 15 and 20 A that are provided with break off tabs may have those tabs removed so that the two receptacles may be wired in a multi-wire branch circuit.
        "Not investigated" is not the same as "not permitted", it means the AHJ must make the decision on approval.

        In general, it is considered a superior practice to pigtail all conductors, but many don't and it is not required.

        Related Threads:
        Recent thread
        Receptacle Stabs (anti-backstabbing thread)
        Last edited by Dennis Alwon; 09-02-11, 01:10 PM.

        Comment


          #5
          Smoke Detectors
          • Where are smoke detectors required to be installed, and where do I find this information?
          NFPA 72 and various building codes have different specific requirements.

          Here is a rough summary of what Chapter 11 of NFPA 72 (specifically 11.5.1) requires:
          • One in each bedroom (to wake people up).
          • One on each level, including basement.
          • A smoke in a basement shall be on the ceiling, near the entry to the stairs.
          • One outside each sleeping area, within 21 feet of the door to any sleeping area. If the hallway is closed off from the sleeping and living areas by doors, then smokes are required on both the living and hallway sides of the door.
          • When a door is installed in a stairway, smoke rising up the stairwell cannot be obstructed from a detector by the door.
          • One in the living area of a guest suite.
          • When a given level of a living area is 1000 sq.ft. or greater, one is required for every 500sq.ft. of floor area for that space, no greater than 30 ft apart.
          • If a ceiling on any level has an elevation change of 24", each elevation needs one. Example: Vaulted living room on same floor as 8' ceiling for back hall, den, laundry.
          • No closer than 3' to any cold air return or supply, or ceiling fan. Nuisance alarms due to dust attraction are common when this is done, and the sensitivity can diminish.
          • No closer than 4" and no farther than 3' to peak of vaulted ceiling. Smoke rolls in corners, bypassing detector.
          • No farther than 3' from peak of vaulted ceiling.
          • No closer than 4" from wall on a flat ceiling.
          • No closer than 4" from ceiling and no farther than 12", when wall mounted.
          • Ambient temperature cannot exceed 100 F, or below 40 F, as in attics and garages.
          • Interconnection of detectors is required.
          • Per NEC 210.12, AFCI protection required. Per NFPA 72 11.6.3(7), if the smoke is supplied by an AFCI, then battery backup is required. By 11.6.4(1), the smoke must audibly report a low battery condition.
          • The instruction booklet supplied with the smoke detector is required to be provided to the occupant. (72 11.8.4(1).)
          • Smokes should be replaced every ten years. (72 11.8.5(b).)
          Many smoke detectors come with instructions that mirror NFPA 72's requirements, so they could also be considered a 110.3(B) listing issue, if NFPA 72 has not been adopted in your area.

          Here are some related threads, or you can search for the term "smoke detector" and find many results.

          A free online viewable copy of NFPA 72, is available by clicking on this link (Click "I agree" to see the read-only document).

          Thanks to Mark Henderson for the link and correction on the list above. :cool:

          forums.mikeholt.com/showthread.php?t=81410
          forums.mikeholt.com/showthread.php?t=78988
          forums.mikeholt.com/showthread.php?t=81410
          Smoke detector placement in dwellings - started 05/07. Includes quotes from the IRC and other building codes.
          Last edited by Dennis Alwon; 09-02-11, 01:18 PM.

          Comment


            #6
            AFCI's

            All About AFCI's

            Click here for a link to the NEMA FAQs on AFCIs.

            The requirements for AFCIs can be found in 210.12:

            210.12 Arc-Fault Circuit-Interrupter Protection.
            (A) Definition: Arc-Fault Circuit Interrupter. An arc-fault circuit interrupter is a device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.
            (B) Dwelling Unit Bedrooms. All 120-volt, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit bedrooms shall be protected by a listed arc-fault circuit interrupter, combination type installed to provide protection of the branch circuit.

            Branch/feeder AFCIs shall be permitted to be used to meet the requirements of 210.12(B) until January 1, 2008.

            FPN: For information on types of arc-fault circuit interrupters, see UL 1699-1999, Standard for Arc-Fault Circuit Interrupters.

            Exception: The location of the arc-fault circuit interrupter shall be permitted to be at other than the origination of the branch circuit in compliance with (a) and (b):
            (a) The arc-fault circuit interrupter installed within 1.8 m (6 ft) of the branch circuit overcurrent device as measured along the branch circuit conductors.
            (b) The circuit conductors between the branch circuit overcurrent device and the arc-fault circuit interrupter shall be installed in a metal raceway or a cable with a metallic sheath.
            This requirement covers receptacle outlets, lighting outlets, and outlets for other equipment such as smoke detectors. Bear in mind, local jurisdictions have the authority to amend the NEC as they adopt it, so local enforcement may vary.

            This does prompt questions of how to define a bedroom, and how to define an outlet for practical purposes. Easy answers would be, if it is called a bedroom on the plans, then it's a bedroom. There is no NEC definition for a bedroom, so it is up to the AHJ to determine how to enforce this section (90.4).

            When polled, 75 percent of respondents on a forum poll stated they believed that a switch is not an outlet. Therefore, if the AHJ in your area agrees with the majority here, then a switch controlling a load not in a bedroom would not require AFCI protection.

            Note that Article 760 fire alarm systems are not allowed to be supplied by GFCI or AFCI. This is not usually relevant to dwelling units, because smoke detectors are not Article 760 fire alarm systems.

            Old Work: In general, the NEC that is in effect today, when you do the work today, is applicable to the work completed today. If you add a new outlet to an existing circuit, then you have to determine what cycle NEC is currently in effect (in Colorado, for example, we're under the 2005 NEC).

            Then, you determine what is new: if it's a new receptacle outlet, then the circuit supplying this new receptacle outlet is to be AFCI protected. If other receptacles are already existing in the same room, on a different circuit, then that existing circuit would not require AFCI protection.

            If you install a new outlet in an existing dwelling unit bedroom, then technically you would need to provide AFCI protection for the entire circuit supplying that new outlet. This can pose problems for an installer because there is limited (or no) availability of AFCI breakers for older existing panelboards. Some jurisdictions do require the protection regardless of the existing equipment, so a solution would be to install another panelboard in line to get AFCI protection on the new outlet.

            Some jurisdictions might require that AFCI protection be added if you change the service or the panelboard inside. The only way to know is to ask the AHJ of the installation in question. There is no set agreement among states, counties, cities or towns, and it's not addressed at all in the NEC.

            Troubleshooting: AFCI Branch/Feeder circuit breakers come equipped with 30-50mA GFPE. What this means is that there is a device similar to a GFCI (but not as sensitive) inside the AFCI breaker, which will trip under load if the neutral is touching the EGC on the load side of the circuit breaker. Usually, a "bootleg neutral" is the cause for nuisance tripping under load, and can be detected by normal troubleshooting methods.

            What is the difference between a "branch/feeder type" and a "combination type" AFCI?
            Both types examine the waveform signature of the loads they supply, and compare the signatures supplied to signatures they are designed to interrupt. An arcing fault is usually the result of a bad connection, or damaged wiring/cords, which creates a high-resistance connection ("glowing connection") that heats up and combusts surrounding material.

            The branch/feeder type AFCI was the original style of AFCI that was first introduced to the market. They look for arcing faults in loads exceeding 75 amps, which greatly limited their ability to discover and disconnect arcing faults. Most of the nuisance-tripping issues that occurred when the device was introduced was a result of the built-in ground fault protection (GFPE) detecting bootleg neutrals (an EGC carrying neutral current inadvertently).

            Given the low amperage of most household appliances, and the high threshold for the branch feeder AFCI, there is virtually no protection beyond the outlet when using a branch/feeder AFCI.

            The combination-type AFCI is to be required starting 01/01/2008, by the 2005 cycle of the NEC. It will examine all loads exceeding 5 amps for arcing faults. There are currently (07/26/2007) no combination-type AFCIs available for installation, so the branch/feeder AFCIs are still in use.

            The combination type will be able to offer protection to cord-and-plug connected loads even through cords, according to the manufacturers.
            ------------------------------------------
            al hildenbrand 224 - charlie b 109 - jwelectric 85 - LarryFine 66 - marc deschenes 48 - allenwayne 38 - jeff43222 31 - iwire 31 - electric_instructor 28 - peter d 25 - roger 24 - don_resqcapt19 15 - electricmanscott 11 - georgestolz 9 - jimwalker 6 - sandsnow 5 - sparky_magoo 4 - dillon3c 2 - ronaldrc 2 - paul 2 - magoo66 2 - hbiss 2 - mark32 2 - tkirk911 1 - macmikeman 1 - JES2727 1 - aelectricalman 1 - pierre 1 - realboss 1 - steve66 1 - busman 1 - petersonra 1 - j_erickson 1 - ryan_618 1




            Incidentally, the "is a switch an outlet" discussion continues to hold the honor of garnering the most replies ever on the Mike Holt Forum, at 781 posts.






            The guilty are listed above with their counts.

            Last edited by George Stolz; 11-12-07, 10:58 PM.

            Comment


              #7
              GFCI's / GFPE

              All About GFCI’s






              GFCI's are intended to protect people from electrical shock in many different situations.

              The main requirements for GFCIs can be found in 210.8. There are additional requirements scattered throughout the NEC for various specific occupancies and equipment, such as elevators, swimming pools, temporary installations, etc.

              Looking at 210.8, the key to note is that all receptacles in the listed locations are required to have GFCI protection, and then the exceptions allow some receptacles to go unprotected. One notable example is bathrooms in dwelling units. There are no exceptions, so therefore a single receptacle or a receptacle not readily accessible still requires GFCI protection.
              • When was GFCI protection required for __________ ?
              Click here to see when GFCI protection was required by various cycles of the code, compiled by Jerry Peck for Mike Holt.
              • How do GFCI's work? Do they require an EGC to work?
              GFCI's have coils inside them that continuously measure the current leaving the GFCI on the ungrounded (hot) conductor, and measure the current returning on the neutral conductor. If more current leaves on the ungrounded conductor than returns on the neutral conductor, then the GFCI will trip. GFCI's are set to trip when the imbalance between the conductors is from 4-6 milliamps.

              They do not trip under a short circuit, because in a short circuit, all current is still travelling along the normally current-carrying conductors.

              Since GFCI's monitor the ungrounded and grounded conductors of a circuit, they do not use the EGC of the circuit for any purpose. That is why GFCI's are permitted to replace two-wire non-grounding receptacles in existing structures. Click here for the FAQ discussing this.


              GFPE (Ground-Fault Protection of Equipment)





              GFCI is different than GFPE, in that GFPE is designed to minimize damage to equipment during a ground fault. The requirements for GFPE can be found in various locations in the NEC. Here's an excerpt from the index of the NEC:





              Ground-fault protection
              Deicing and snow-melting equipment, 426.28
              Emergency systems, not required, 700.26
              Equipment, 215.10, 240.13
              Definition, Art. 100–I
              Health care facilities, 517.17
              Personnel. see Ground-fault circuit interrupters
              Pipeline heaters, 427.22
              Service disconnecting means, 230.95
              Solar photovoltaic systems, 690.5

              Related links:





              Vending Machines

              How GFCI's Work

              Evolution of GFCI's from IAEI. Thanks to M. D. for the link!
              Sump Pumps & GFCI's - May 2007.
              Last edited by Dennis Alwon; 09-02-11, 01:29 PM.

              Comment


                #8
                210.21(b)(3)









                Yes, provided that it is not an individual branch circuit. The requirements are found in 210.21.

                210.21(B)(1) states that a single receptacle on an individual branch circuit shall have a rating equal to or greater than the rating of the branch circuit.

                210.21(B)(3) states that when connected to a branch circuit supplying two or more receptacles or outlets, the receptacles shall conform to Table 210.21(B)(3).

                [ATTACH]755[/ATTACH]

                Note that a circuit rating must be chosen first, and then a suitable receptacle rating can be determined. The table does not work in reverse, and this is a common misunderstanding.

                Related threads:
                Why is it legal to install 15A receptacles on a multioutlet 20A circuit?
                Last edited by Dennis Alwon; 09-02-11, 01:30 PM.

                Comment


                  #9
                  How many cables per staple / connector?



                  It depends upon the listing of the connector/staple. Most connectors are listed to have a maximum of two cables per connector. Most staples are listed for two cables, but some are listed for one.


                  Section 110.3(B) requires listed equipment and material be used according to it's listing.

                  Some staples are unlisted, so it falls on the AHJ to approve/disapprove of the installation (90.4). Most people feel that three cables under a staple is acceptable.

                  How many NMs under a staple, with code references - Mar 2007.
                  Stacking Runs of Romex - Feb 2007.
                  Plastic Vs. Metal Staples - Mar 2005.
                  Stak-Its - Feb 2005.
                  Last edited by George Stolz; 09-02-07, 12:51 PM.

                  Comment


                    #10
                    How many receptacles per circuit?




                    In 220.10, it states that branch-circuit loads shall be calculated according to the requirements of 220.12, 220.14, and 220.16.

                    220.14(J) states that the receptacles in a dwelling unit are already included in the "Lighting and Receptacle Load" specified in 220.12. From this, most users of the NEC agree that there is no limit in the NEC for the number of receptacles that can be placed on a circuit in a dwelling.

                    However, most users of the NEC view this as proof that in a commercial setting, you must assume that there will be 180VA per receptacle, per 220.14(I). Therefore, they draw the conclusion that you may not have more than 13 receptacles on a 20A branch circuit (assuming that there are no continuous loads on the branch circuit at all.) This is the popular textbook perspective on the issue of how many receptacles are allowed on a circuit in a commercial setting.

                    However, there are some users of the NEC who believe that the provisions of Article 220 are to be used solely for determining the "calculated load for the service", and not for the "load to be served". (George's note: I consider this to be a minority opinion but worthy of mention. In one of the threads below (Number of Receptacles), a poll showed 75% of members who voted believe there is a 180VA limit in commercial. )

                    Bear in mind, the NEC is a minimum standard and it's scope makes clear that we are free to design and install at an above-code level. (90.1). Specifications developed by an engineer may be replied upon by the AHJ for final approval of a project, and the specs may also be used as a contract standard as well.

                    Related Threads:
                    GFCI Receptacles- Jan 2007. Moderator Charlie Beck offers the viewpoint that the commonly held belief may not be correct about the max in a commercial setting.
                    Max Number of Receps per Circuit - Mar 2006. Started by Dnem, currently ranks #4 all time for number of posts in the NEC forum at 294 posts.
                    Outlets Per Breaker - May 2005. Started by rmatc4, currently ranks #14 all time in the NEC forum at 167 posts.
                    Number of Receptacles - Jun 2007. Started by dSilanskas, still in progress as of 6/28/07.
                    __________________________________________________ __________
                    __________________________________________________ __________



                    Honorable mention - Click here for entire thread:

                    Originally posted by iwirehouses
                    Is there anywhere in a dwelling unit where you are restricted to the number of receptacles you put in?
                    Originally posted by iwire
                    No.
                    Originally posted by winnie
                    Bob's answer is correct only with respect to the electrical codes.

                    Various other building codes clearly set limits on the number of receptacles which you may put in. For example, fenestration requirements dictate that at least some portion of the wall area be used for windows, similarly egress requirements dictate space dedicated for doors. (Though I suppose that you could mount receptacles upon the doors.)

                    The effect of device boxes on any required thermal insulation would need to be considered, and large numbers of device boxes on firewalls will require special design.

                    -Jon
                    Last edited by Dennis Alwon; 09-02-11, 01:33 PM.

                    Comment


                      #11
                      Lighting Outlet Requirements
                      • Do I need a light fixture in a habitable room, or just a blank over a box?
                      210.70 lays out requirements for lighting outlets in different situations. In 210.70(A)(1), the requirements for lighting outlets in habitable rooms is outlined.

                      The key is, the primary term used is lighting outlet. A lighting outlet is defined in Article 100 of the NEC as:
                      Lighting Outlet. An outlet intended for the direct connection of a lampholder, a luminaire (lighting fixture), or a pendant cord terminating in a lampholder.
                      So, essentially, the box that a luminaire is attached to is the lighting outlet. Therefore, the most commonly held belief is that a box with a blank is perfectly acceptable for meeting the requirements of the NEC. Here are some Code-Making-Panel Comments regarding this section, from the 2008 Report on Proposals:
                      Proposal 2-251: The objective of the NEC is to provide the requirement for the lighting outlet. The requirements specific to illumination are in the building code.

                      Proposal 2-252: The location and number of switches is a design requirement that is determined by the designer, user or installer. The panel disagrees with the submitter’s example in the substantiation relative to the switch at the top of the basement stairs. If there are six risers or more, a switch is required at the top and bottom of the stairs.

                      Proposal 2-253: Closets are not intended to be covered in the present rule (210.70(A)(3). The submitter has not substantiated a requirement for a lighting outlet in every closet.
                      The requirement for illumination is believed by the CMP to be dictated by the building code. However, to date no one (to my knowledge) has come forward with IBC/UBC requirements to confirm this. It also would not mesh with the allowances of a switched receptacle in lieu of a lighting outlet as permitted by the exceptions.

                      In the state of Massachusetts, a luminaire in a hallway is required. Click here for a PDF (link ctsy of M. D.) confirming this.

                      Related threads:
                      Habitable Rooms - Lighting Outlet, Feb 2007. Started by MrMark, with 6 pages as of this addition.
                      Last edited by George Stolz; 05-04-07, 03:23 PM.

                      Comment


                        #12
                        The Six Handle Rule

                        The Six-Handle Rule
                        Services, Feeders to detached structures, etc.




                        The rules for the number of switches allowed to disconnect all ungrounded conductors of a structure are given in different locations depending on the application.

                        For services, 230.71(A) dictates that no more than six handles shall disconnect a service from the structure served. Throughout all of Part V of Article 230 are several rules dictating how large the disconnecting means must be, how to determine how large the service is, where it must be located and what may be attached to the line and load sides of a service disconnect.

                        For detached buildings that are fed from another building, the rules are given in Part II of Article 225. Section 225.33(A) also requires no more than six handles to a structure.

                        Please note that the key to both 230.71(A) and 225.33(A) is the number of handles present, not the number of spaces available. Therefore, based on this fact, you can install a 40-circuit panelboard, install a single 100A breaker to feed an interior panelboard inside a structure, and comply with these rules. This is widely considered a practice that may be legal but should be avoided. However, by the NEC such an installation should be approved.

                        However, 225.36 requires the disconnecting means to be marked as suitable as service equipment. When closely examined, most panelboards have instructions that they are suitable as service equipment when less than six handles are installed and the panelboard is not used as a Lighting & Appliance Branch Circuit Panelboard (L&ABCPB). This is a crucially overlooked key to detached structures on a feeder. A panel containing three branch circuit handles would make the panel not "suitable for service equipment", so a main would be required.

                        L&ABCPB's are defined in 408.34. They have 10% or more of the overcurrent protective devices supplying L&ABC loads, which are defined in 408.34. In most small installations, this will limit the number of handles for a detached structure disconnect to one handle.

                        Grounding requirements for services are found in Article 250, Parts I and III.

                        Bonding and Grounding requirements for detached structures are found in 250.32, and are discussed in detail in this FAQ.

                        Related threads:
                        6 Disconnect Rule Violation?- Nov 2005. Started by mdshunk, #3 number of posts in the NEC forum at 347 posts.
                        230.71, 90.4 and an MLO panel - Aug 2005. Started by Dnem, #13 number of posts in NEC forum at 169 posts.
                        400A Service With No Main - Apr 2007. Started by Romeo, still in progress as of this addition.
                        Last edited by Dennis Alwon; 09-02-11, 01:39 PM.

                        Comment


                          #13
                          Detached Garages

                          Detached Garages

                          There are many different desired designs for detached buildings, perhaps as many as people who build and wire them. For clarity, I will put some examples up and explain each example.

                          Example #1: A small outbuilding calls for a 15A circuit for lighting, and a 15A circuit for a receptacle. A multiwire branch circuit is selected, a 12-3 UF cable. In this case, no grounding electrode system is required to be connected to the electrical system of the detached structure.

                          According to 250.32(A), exception, no grounding electrode system is required for a single circuit, and the multiwire branch circuit is considered one circuit. 225.33 requires a disconnecting means for all ungrounded conductors supplying the building. The EGC in the UF cable is the effective ground fault clearing path required by 250.4.



                          Example #2: A small outbuilding calls for one 15A lighting circuit and four 20A circuits for receptacles. Five runs of two-wire UF cable are selected. In this case, we have several circuits supplying the structure, so we can no longer use the exception to 250.32(A). Each branch circuit is still to be disconnected according to 225.33.

                          Connecting the branch circuits to the grounding electrode system is prohibitive, in that minimum of #8 AWG conductors are to be connected to the grounding electrodes, and only 12 AWG conductors are supplying the structure.

                          A feeder would have been a more normal choice.

                          Example #3: A customer desires a 100A panel in a garage. No other services are common between the structures. A three-wire (Hot, Hot, Neutral) USE feeder is selected. In this case, a grounding electrode system is required to be connected to the panelboard at the detached structure (250.32(A)). The panel should be a main-breaker panelboard, as explained in the Six-Handle-Rule FAQ.

                          Since there are no metallic paths continuous between the structures, then 250.32(B)(2) can be used: the neutral serves as the ground-fault current path for the detached structure, as it would if the detached structure were supplied by a service. The neutral is bonded to the EGCs of the branch circuits of the detached structure, just like a service.

                          Example #4: A customer desires a 100A panel in a garage, and is also bringing a metallic water pipe to the structure. In this case, it is the same as Example #3 - except that the metallic water pipe is connected to the electrical system of each building. Therefore, you must provide an equipment grounding conductor with the feeder conductors, and keep the neutral isolated from the EGCs at the detached structure.

                          Please note that the grounding electrodes are for the purposes outlined in 250.4(A)(1) only, and are not a ground-fault current return path! They do nothing when a energized conductor touches the normally non-current-carrying metal of the equipment grounding system.

                          Example #5:(Click here to see the picture)

                          Wait, that's not a frequently asked question, nevermind.

                          However, the installation pictured is not legal, because there are two neutral paths connected to the house's Grounding Electrode System. Therefore, there are multiple metallic paths between buildings, and EGCs should be installed (and the neutrals kept isolated from the EGCs of the house)because of it.

                          As I said, there are many different ways to deal with a detached structure.

                          Also see The Six-Handle Rule FAQ and the grounding question for detached garages.

                          Related Links:
                          Last edited by Dennis Alwon; 09-02-11, 01:43 PM.

                          Comment


                            #14
                            Lighting fixture (luminaire) taps?
                            • Is it legal to use 14 AWG conductors on a 20A breaker for lighting switchlegs?
                            No. All parts of a 20A circuit for lighting are included in 240.4(D), which includes conductors between a switch and a luminaire.
                            Last edited by George Stolz; 09-02-07, 12:53 PM.

                            Comment


                              #15
                              Distance Limit for conduit runs
                              • Is there a distance limit for conduit runs, between junction boxes?
                              No. However, all conduit/tubing wiring methods are restricted to no more than 360 degrees of bend between pull boxes or junction points. See xxx.26 (as in, 358.26 for EMT, etc).
                              Last edited by George Stolz; 03-03-07, 12:45 PM.

                              Comment

                              Working...
                              X