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    210.52(A) – Wall Space Questions
    [LIST][*]Do I have to include wall space that is exclusively behind doorswings when laying out receptacles?[/LIST]Yes, in dwelling units. Mobile Homes have different (but similar) rules in 550.13, and in mobiles, the space behind the doorswing is permitted to be excluded by 550.13(G).

    A receptacle behind a doorswing is a natural space for a user to plug in appliances that move around the dwelling unit, such as vacuum cleaners.[LIST][*]Are foyers included in 250.52(A)?[/LIST]Foyers have generated some discussion. Some see them as a hallway, others as a habitable room. Given the difficult language of this section, it has been unclear as to whether some "similar areas" were intended to be covered by the wall-space requirements.

    However, in the 2008 code cycle some proposals were submitted that cleared up some confusion about the CMP's intent, even if they were rejected. Proposal 2-195 suggested including foyers in the requirements of 210.52(A), and the panel replied, "The submitter ’s concern about the receptacle outlet requirements in foyer areas is already addressed in 210.52(H)."

    The panel believes that a foyer is a hallway. [LIST][*]Can a receptacle serving a kitchen countertop also serve as the wall space receptacle for the wall space next to the countertop, sharing the same wall?[/LIST]No. 210.52(A)(1) states that no point measured along the floor line in any wall space be more than 6 feet from a receptacle. If the receptacle doing the serving is not contained in that wall space then as far as this section is concerned, there is no receptacle present.

    Further, CMP statements on proposals to this section confirm the idea that they are very aware of potential damage to cords that go over the edge of a counter, which they bear in mind as the amend the sections each cycle. This is explored further in the kitchen FAQ.

    Related Links:
    How high is normal for wall space receptacles? - Aug 2006. Started by Jaman, with 49 replies
    Foyers - Feb 2005. Started by Explorer136, with 77 replies.
    Kitchen Wall Receptacle - Aug 2006. Started by Malachi Constant, with 36 replies. It reinforced the idea that each wall space was independent - a "counter wall space" receptacle cannot perform double duty as a "wall space" receptacle.

    Island Receptacles - Dec 2004. Started by Nascar03, with 31 replies. Nascar asked the question, "Is the side of an island facing habitable rooms considered a wall space of that room?"
    Last edited by Dennis Alwon; 09-02-11, 01:46 PM.


      210.52(B), (C) – Kitchen, Dining and Similar Area Questions

      Foreword: 210.52(B) and (C) tread deeper into design than most sections of the NEC. As a result, it can be confusing to determine the right course of action when dealing with some custom kitchens that are not designed with the electrician in mind. Designers take a form of sadistic glee in designing kitchens that are attractive to the eye and bear innovative ideas that make applying the NEC to them a somewhat arduous task. I will attempt to provide a number of links to odd kitchens presented in different threads, to give you something to work with in coming to your own conclusions. -George

      210.52(B)(1): Requires all wall, counter, and fridge receptacles in these areas to be on the two or more required SABCs.
      Exception 1 permits a receptacle installed to replace a lighting outlet, to be supplied from a lighting circuit.
      Exception 2 permits the receptacle for a fridge to be on it's own individual branch circuit 15A or greater. So the fridge is either on an SABC or on it's own, two options.

      210.52(B)(2): Forbids us from using the SABCs for other outlets.
      Exception 1 allows an SABC to serve a receptacle for a wall clock.
      Exception 2 allows an SABC to serve small loads on fixed gas cooking appliances.
      These two exceptions make it clear that receptacles behind fixed (or cumbersome) appliances are not "wall receptacles". They are receptacles for specific appliances.

      210.52(B)(3): The group of receptacles serving countertops in a kitchen shall be served by two SABCs. (Each receptacle is served by one; the group of receptacles by no less than two).

      210.52(C): Did you ever notice counters in dining rooms are to comply with the 2'/4' spacing rules, just like kitchens?

      210.52(C)(1): "Wall Counter Space" is defined. This is different than "Wall Space".

      210.52(C)(2): There is only one receptacle required on an island, unless a sink or a cooktop divides the island into two "islands". Notice that if there is a foot or more of counter space behind the sink or cooktop, then the entire area becomes one island again.

      Proposals were submitted for the 2008 cycle to get rid of the island requirement completely, due to potential injury to small children pulling appliances down on themselves. The panel viewed the potential risk "to both children and adults" from extension cord use as cause to reject them.

      Proposals were also submitted to increase the numbers of receptacles required to be installed on islands, and they were rejected as well. The panel indicated that one receptacle on an island is the best-fit between extention cord danger and accidental snagging of appliance cords.

      210.52(C)(3): The same goes for peninsulas as islands. Only, a sink or a cooktop would create an "island" at the end of the peninsula. Most AHJs do not require a receptacle on the "peninsula" portion of such a counter space, but the wording would require a receptacle on the wall-less countertop on either side of the sink or cooktop. With an overhang for a bar top, this becomes exceedingly difficult to comply with.

      210.52(C)(4): This section makes it clear that sinks, ranges and cooktops seperate counters for the purposes of this section.

      Note that appliance garages are not listed. Proposals have been submitted to permit an appliance garage to seperate counter spaces, and have been rejected on the premise that there is usually counter space in front of the appliance garage large enough to facilitate food preparation.

      However, in all but the same breath, they have rejected proposals to require counter-spacing requirements to be observed inside appliance garages. As in, the receptacle inside the appliance garage should not be considered serving the counter space in front of the appliance garage.

      The panel has never clarified (to my knowledge or satisfaction) how exactly we are to serve this counter space.

      In practice, generally the space in front of an appliance garage is considered served by receptacles with the garage. In general, GFCI protection seems to be required for these receptacles. Given the confusion, it would be good to get the AHJ's input before setting any design into stone, if it is questionable.

      In my opinion, the space in front of an appliance garage is not wall counter space, as it backs up to cabinetry and not a wall. Therefore, it should be considered a break in the counterspace and also have the 2'/4' rule enforced inside the garage as well. However, the words at this point are not there.

      210.52(C)(5): This section requires all receptacles serving counter spaces to be above the counter. Only where impracticable are receptacles below the countertop allowed, due to damage that could result from the cord on the edge of the countertop.

      Related links:

      Here we go again: Hallway or Not? - May 2007. Started by Dennis Alwon, still in progress as of addition.
      Appliance Garages on SABCs - Oct 2006. Started by Volt102, with 65 replies. "Are appliance garages required, permitted, or prohibited to be on the SABCs? GFCI protected?"
      Can I put a microwave on a SABC - Feb 2005. Started by ethwinfir, with 31 replies.
      Switched Dining Room Outlet? - Mar 2005. Started by davedottcom, with 513 replies. An exhausting odyssey through the interrelationship between 210.52 and 210.70. Pack a lunch.
      Undercabinet Lights - Apr 2005. Started by Electrofelon, with 277 replies. "Can a luminaire be plugged into a countertop receptacle?" How innocent a beginning for such a bloodletting.
      Since you guys are so smart... - Apr 2005. Started by Electricmanscott, with 35 replies. Addressed an odd kitchen with difficult customer requests surrounding an appliance garage.

      For more related threads, search for the term "210.52". As of this writing, it comes up with 151 threads, most of which are dealing with some aspect of complying with the NEC in kitchens and similar areas.

      If dealing with this section has you frustrated, click here for a discussion about how really, it's not easy writing code.
      Last edited by Dennis Alwon; 09-02-11, 01:56 PM.


        [LIST][*]Can I install a television over a bathtub in a bathroom?[/LIST]Yes, but the receptacle for the television cannot be over the tub space (406.8(C)). Regardless of receptacle location, if in the bathroom, it requires GFCI protection (no exceptions) 210.8(A)(1).

        Related Links:
        Question posted 11/23/06
        Question posted 07/01/06
        Last edited by Dennis Alwon; 09-02-11, 01:57 PM.




          Click Here for wire insulation types and letter designation

          AC- Armored Clad (cable Type AKA BX)
          AFCI – Arc Fault Circuit Interrupter
          AHJ – Authority Having Jurisdiction
          AHU - Air Handling Unit (as in, Air Conditioning)
          AIC – Amps Interrupting Capability
          AC - usually Air Conditioning; also Armored Cable, Alternating Current
          AFAIK - As far as I know
          AFAICT - As far as I can tell
          BTW - By The Way
          CB – Circuit Breaker
          CCC - Current Carrying Conductor
          CMP - Code Making Panel
          DIY – Do It Yourself
          EC – Electrical Contractor
          EGC – Equipment Grounding Conductor
          EMT- Electrical Metallic Tubing
          ENT- Electrical Nonmetallic Tubing
          ESI - Electricians Success International - an organization
          FAP (FACP) - Fire Alarm (Control) Panel
          FLA – Full Load Amps
          FMC- Flexible Metal Conduit
          FMT- Flexible Metal Tubing
          FWIW - For What It's Worth
          GC – General Contractor
          GEC – Grounding Electrode Conductor
          GFCI – Ground Fault Circuit Interrupter
          GFI – Ground Fault Interrupter (technically GFCI)
          GFPE - Ground Fault Protection of Equipment- This is for protection to equipment not personnel
          HI - Home Inspector
          HO – Home Owner
          HVAC – Heating, Ventilation, and Air Conditioning
          IIRC - If I Recall Correctly
          IMC- Intermediate Metal Conduit
          IMHO – In My Humble Opinion
          IMO – In My Opinion (used by those who are not humble)
          IOW - In Other Words
          KVA - kilo-volt-amps
          KW - kilo-watt
          LABCPB - Lighting & Appliance Branch Circuit Panelboard (408.34)
          LFMC- Liquidtight Flexible Metal Conduit
          LMAO – (I'll not translate this one)
          LFNC- Liquidtight Flexible Nonmetallic Conduit
          LOL – Laughing Out Loud
          LOTO - Lock Out Tag Out
          LRA – Locked Rotor Amps
          MC- Metal Clad (cable type)
          MCA- Minimum Circuit Ampacity
          MCB – Main Circuit Breaker

          MCC – Motor Control Center
          MDP - Main Distribution Panelboard
          MI- Mineral Insulated (Cable Type)
          MLO – Main Lugs Only
          MOCP- Maximum Over Current Protection
          MV- Medium Voltage (Cable Type)
          MWBC - Multiwire Branch Circuit (see definition in Article 100)
          NEC – National Electrical Code
          NECH - NEC Handbook
          NEMA = National Electrical Manufacturers' Association
          NETA – National Electrical Testing Association

          NFPA – National Fire Protection Association
          NM- Non Metallic (cable Type) There are different types-- NM-B, NMC, NMS
          OCP – Overcurrent Protection
          OCPD – Overcurrent Protection Device
          OP – Original Poster (i.e., the person who started the thread)
          OTOH – On the Other Hand
          POCO – Power Company
          PPE – Personal Protection Equipment
          PV- Photovoltaic
          PVC- Rigid Polyvinyl Chloride Conduit
          RCI - Residual Current Interrupter (like GFPE, but European)
          RMC_ Rigid Metal Conduit
          ROP- Report on Proposals
          RTU - Roof Top Unit (as in, air conditioning)
          ROFL - Rolling On Floor Laughing
          SA (SABC) – Small Appliance (as in "SA Branch Circuit")
          SDS - Separately Derived System
          SFD- Single Family Dwelling
          SE- Service Entrance
          SEU (3 wire SE cable) - service entrance ungrounded
          SER (4 wire SE cable)- service entrance round
          TC- Tray Cable
          UF- Underground Feeder and Branch Circuit (Cable Type)
          UL – Underwriter's Laboratory
          URD - A cable assembly with no outer sheath, composed of three or more conductors of USE for direct burial.
          USE - See Article 338- underground service entrance
          VFD- Variable Frequency Drive (could be Volunteer Fire Department too)
          WTG - Way to go
          List compiled by Charlie Beck, with help from others.
          Last edited by Dennis Alwon; 08-16-13, 04:17 PM.


            Equipotential Bonding & Hot Tubs
            [LIST][*]Under the 2005 NEC, is an equipotential bonding grid required around a hot tub?[/LIST]Yes, it is. 680.42 states that outdoor installations shall comply with Parts I and II, except as amended by 680.42's subsections. Nothing in the subsections remove the requirements of 680.26.

            Enforcement is not widespread, possibly due to the hopscotch back-and-forth references of this Article. However, the CMP has made statements to the effect that they do intend for hot tubs outdoors to be covered under 680.26. Click here to see an example of a panel statement confirming this.

            Related Links:
            8-3 NM-B for Hot Tubs?, Oct 2006. Started by SLC James, with 77 replies. NM is questioned, Equipotential bonding for hot tubs is questioned, fur flew.
            Hot Tub Equipotential, Sep 2006. Started by Shelco, with 87 replies. Covered the bases on the question.
            Hot Tubs & Equipotential Bonding - Aug 2006. Started by me, with 11 replies. "What about hot-tub prewires? Should we worry about equipotential bonding in a prewire?"
            Last edited by Dennis Alwon; 09-02-11, 01:58 PM.


              [LIST][*]Am I required to install a Concrete-Encased Electrode if one isn?t already present?[/LIST]No. 250.50 requires the installer to make use of all electrodes present. If there is no CEE to begin with, then there's none to bond.

              If there is not one present, you are free to add one if you'd like, two methods are offered in 250.52(A)(3).

              The change in the 2005 text was to make it more evident to installers that covering a CEE in concrete does not alleviate our need to connect to it for our grounding electrode system. The CEE (or "Ufer" as it's commonly called) is a very effective grounding electrode for an almost negligable additional cost in most cases, and proposals were submitted to force everyone into noticing.

              Some areas may require CEE's to be installed by amending the NEC in their locality. Be sure to check local codes before concrete is poured.

              Related links:

              2005 Grounding Electrode System - the history of the Ufer electrode and it's inclusion in the NEC.
              Last edited by Dennis Alwon; 09-02-11, 02:11 PM.


                [LIST][*]Is a green ground screw required in metal boxes?[/LIST]
                No. There is a requirement for the main bonding jumper screw of a service to be green: 250.28(C). There is also a requirement for the grounding terminal for a device to be green, 250.126.

                250.8 forbids the use of sheet metal screws for connecting EGCs to enclosures.

                250.148 (C) requires the screw used to bond a metal box not to be used for another purpose.

                Related Threads:
                Grounding Screw? - Mar 2005. Started by Jason32, with 23 replies.
                Last edited by Dennis Alwon; 09-02-11, 02:12 PM.


                  Metal Water Pipes in Detail
                  [LIST][*]Is a metal water pipe a primary grounding electrode, and others secondary?[/LIST]
                  An electrode is an electrode. Some perform better than others, but the NEC takes a basic stance that all present shall be used, and the order does not matter.

                  250.64(F) says that a GEC can run to any convenient electrode, and then "daisy-chain" from electrode to electrode if we like. The GEC for some electrodes is not required to be larger than a certain size, like #6 for a ground rod. If you were to pull a GEC to the ground rod first, then run a bonding jumper from the ground rod to a water pipe, then you would be forced to pull a larger-than-6 conductor to the ground rod due to the sequence of electrodes pulled to.

                  The water pipe needs a full sized GEC all the way back to the service. Therefore, it's a little counterintuitive to run to a ground rod first.

                  We can also pull GECs to each grounding electrode if we prefer.[LIST][*]Are we required to install ground rods when a metal water pipe is present?[/LIST]Not exactly. A metal water pipe grounding electrode is required to be supplemented by another electrode (250.53(D)(2)). If there is a concrete-encased electrode and a water pipe in the same structure, then no additional grounding electrodes are necessary.

                  If a metal water pipe grounding electrode is the sole electrode at the structure, then it must be supplemented somehow, and the easiest is a ground rod.[LIST][*]Are two ground rods required to augment a metal water pipe?[/LIST]If a ground rod is driven to augment a water pipe, and the single ground rod's resistance to ground is greater than 25 ohms, then a second is to be driven, according to 250.53(D)(2).

                  If you can't afford expensive testing equipment, you can drive a second rod and walk away regardless of the resistance of the system.

                  The NEC does not have any requirement for the overall resistance of a system. It only has a rule that states that a single ground rod must be augmented if it's resistance is over 25 ohms. Proposals to eliminate this requirement, or to increase the requirement have both been rejected.[LIST][*]What if the water pipe is replaced for plastic later?[/LIST]That's why we supplemented it with ground rods (or other electrodes) - by the nature of it's use, it's vulnerable to changes later in it's life, unlike the other electrodes.[LIST][*]If the water pipe entering the building is plastic, and the water pipes inside the building are metallic, do the metallic water lines require grounding?[/LIST]No, but they do require bonding. See 250.104(A).

                  The bonding conductor does not have to be to any specific area of the water piping (as opposed to the metal water pipe grounding electrode described in 250.52(A)(1), which has to be connected to within 5' of the entrance to the building).[LIST][*]Does this mean that all metal water piping in a structure has to be bonded, per 250.104?[/LIST]All metal water piping systems are required to be bonded. Therefore, plastic piping with metallic fittings do not require bonding per the NEC.[LIST][*]Does this mean that I have to bond around a water heater - isn't there a hot system and a cold system?[/LIST]This is not clear in the NEC. One thing that is indisputable (in my opinion) is that if there are metallic mixing valves at the sinks and/or tubs, then the piping is electrically continuous.

                  Click here to see a discussion on the topic, which was never resolved, IMO. It may help you to form your own opinion. Essentially, the debate was what constituted a "system", and what may go legally unbonded by the NEC. According to a panel statement that Mike Whitt (jwelectric) found, the hot water pipes would need to be bonded only if likely to become energized, by 250.104(B).
                  Last edited by George Stolz; 07-30-07, 07:12 AM.


                    [LIST][*]What codes apply when replacing old non-grounding receptacles in an existing structure?[/LIST]Device replacement of the receptacles themselves are covered in 406.3(D). Some more flexible rules for installing an EGC in an existing structure are given in 250.130(C).

                    Please note that the goal when using one of these alternate methods is to ensure that an effective ground-fault-current path is provided. Care should be taken to be absolutely sure that the electrode connected to is in fact connected to the neutral of the service of the building served. The earth is of no consequence to a receptacle, a normally non-current-carrying solid connection back to the electrical source is what we desire.

                    Related threads:
                    Grounding of Rec.
                    What is the benefit of upgrading an old structure to circuits containing an EGC?
                    Last edited by Dennis Alwon; 09-02-11, 02:13 PM.


                      [LIST][*]Am I required to run an equipment grounding conductor to a detached structure?[/LIST]Under certain conditions, no, you do not have to. Section 250.32(B)(2) allows the neutral to serve as the effective ground fault clearing path under three conditions. If the installation complies, then you may omit pulling an EGC with the feeder conductors to a detached structure.

                      This is Mike Holt's site, I would be remiss if I didn't quote his note from Grounding Vs. Bonding:

                      CAUTION: Using the grounded neutral conductor as the effective ground-fault current path poses potentially dangerous consequences and should only be done after careful consideration. Even if the initial installation doesn't result in dangerous objectionable current on metal parts, there remains the possibility that a future installation of metal piping or cables between the buildings or structures could create unwanted parallel neutral current paths.

                      Author's Comment: The preferred practice (or at least my preferred practice) is to not use the grounded neutral conductor as the effective ground-fault current path, but to install an equipment grounding (bonding) conductor with the feeder conductors to the building or structure in accordance with 250.32(B)(1 ).
                      Last edited by George Stolz; 03-10-07, 09:19 PM.


                        [LIST][*]Am I required to upsize the Equipment Grounding Conductor when upsizing for voltage drop?[/LIST]Yes, see 250.122(B).

                        In fact, it does not matter why the conductors have been upsized (as in, voltage drop). If you decide to use 10 AWG ungrounded conductors on a 20A circuit from sheer eccentricity alone, you are still required to upsize the EGC proportionately.

                        Given that Table 250.122 requires the same size EGC as the ungrounded conductors, then we are faced with having to directly upsize the EGC to the same size as the ungrounded conductors the whole way, because the proportion is 1:1.

                        With larger circuits it is not so extreme. Example:

                        A 50A circuit is wired with CU THHN in EMT. The required conductor size is #6. The installer chooses to upsize the conductors three times to #1, due to distance and voltage drop.

                        #1 is 83680 circular mils.
                        #6 is 26240 circular mils.
                        Difference is 57440 circular mils, or a factor of 3.1894 (83680 / 26240) proportionately.

                        Prior to upsizing the circuit for voltage drop, 50A circuit normally requires a #10 CU conductor (Table 250.122). A #10 has 10380 circular mils (Table 8).

                        10380 x 3.1894 = 33106 circular mils. The installer must use a #4 EGC (41740 cm) for this circuit.
                        A primary reason for this requirement is that when you upsize the ungrounded conductors, you increase the available fault current at the same time. The short and sweet explanation for this is, fault current is determined by the size of the conductors supplying the fault, along with other factors.

                        To go for a plumbing analogy, imagine one day you decided to upgrade the 3/4" main water pipe coming into your house with a 4" main, from the street. To carry this a bit further, let's say you upsized the piping all the way to your master bathtub. You are into extreme showers.

                        You've upgraded all the supplying pipes, but didn't bother with the drains because they're not as interesting. It's hard to envision an extreme shower drain. You'll never see one in a Mountain Dew commercial.

                        What happens? The bathtub can't drain as fast as it takes water in, so the tub fills.

                        Moving back to conductors and electricity, Table 250.122 is based on normal conductor sizes. If you increase the ungrounded conductor size, leave the EGC at the normal small size, then you increase the likelyhood of burning up the EGC in the event of a ground fault.
                        People that first hear of the rule often remark, "That's stupid! Why would a #10 not work for a 20A branch circuit using #6 wire, when it will be just fine on a 20A breaker?" Here's a quote from Don:
                        Originally posted by don_resqcapt19
                        There is no technical rationale for this issue. It is just a result of the oversized equipment grounding conductors that are required by 250.122 for 15, 20 and 30 amp circuits. To write a rule to cover these wire sizes would complicate this issue even more that it is now.

                        Related Links:
                        Voltage Drop and the EGC - Oct 2006. Started by me, includes the explanation from Don above. 30 replies.
                        Raceway as EGC - Mar 2004. Started by Ryan Jackson, with 54 replies
                        Code in your area? "Grounds" - Oct 2006. Started by Brightidea, with 11 replies. The link brings you to a post, also from Don, that clarifies why EGCs are smaller than ungrounded conductors, and includes a link to a Bussman document.
                        Last edited by Dennis Alwon; 09-05-11, 08:14 AM.


                          [LIST][*]How do I calculate voltage drop?[/LIST]There are several calculations available.

                          The formula I use most frequently is:

                          VD = 2 x R x I x D (single phase)
                          (2 x Resistance x Amps x Distance)
                          VD = 1.73 x R x I x D (three phase)
                          (Square root of three x Resistance x Amps x Distance)

                          It's easy to remember, to rid yourself of voltage drop.

                          The 2 in the single-phase equation above is due to the number of conductors of the circuit: there is a hot and a neutral, two conductors. If the load is three phase, the current travels along all three wires, so it is more efficient.

                          Example: You want to know what the voltage drop is for a single phase 120V 16A load on a 20A branch circuit wired with THHN, 300 feet from the load.

                          Look at Table 8:

                          Remember, the circled number is the resistance for solid wire, 1000' long, so this number must be divided by 1000' to get the resistance per foot.

                          Plug this into the formula:

                          Vd = 2 x R x I x D
                          Vd = 2 x .00193 x 16 x 300
                          Vd = 18.5V dropped
                          120V - 18.5V = 101.5 V at the load
                          120V / 101.5V = 84.58% available, or
                          1 - .8458 = .1541 = 15.41% voltage drop.

                          Too lazy for math? Try this Online Voltage Drop Calculator. (Link ctsy of Dennis Alwon).

                          Related Threads:
                          Voltage Drop Calculation Question - Feb 2008. Started by FloridaSun, 7+ Replies. How do you calculate voltage drop on light poles, since the load is less as the circuit reaches it's end?
                          Attached Files
                          Last edited by Dennis Alwon; 09-02-11, 02:18 PM.


                            [LIST][*]When is voltage drop required to be considered in the NEC?[/LIST]In 695.7, you are required to consider voltage drop when dealing with fire pumps.

                            In 647.4(D), you are required to consider voltage drop when dealing with sensitive electronic equipment.

                            That's it.

                            99% of installations performed under the NEC do not have any mandatory rule concerning voltage drop. There are Fine Print Notes in 210.19(A)(1), 215.2(A), and elsewhere in the NEC. However, FPN's are not enforceable rules, they are informational only. See 90.5(C).

                            Related links:
                            Voltage Drop at Receptacle - Dec 2004. Started by ldbelec, with 33 replies.
                            Last edited by Dennis Alwon; 09-05-11, 08:13 AM.


                              Standard Load Calculation
                              [LIST][*]What are the steps to a basic standard load calculation?[/LIST][COLOR=black]Step 1: Demanded General Lighting Load - (including SABCs and Laundry if applicable)[LIST][*]Determine the type of structure, and look at Table 220.12 to determine the general lighting load by occupancy.[/LIST]For example, a church requires 1VA/square foot for lighting.

                              A dwelling unit requires 3 VA/square foot for lighting - but notice the reference to footnote a of the table. Receptacle outlets are included in this 3VA/square foot number. Also, notice that 220.52(A) and (B) allow the SABCs and the Laundry circuits to be included in the general lighting load (prior to demanding the load).

                              Looking at Annex D (on page 717 of the 2005 NEC), the first example is a one family dwelling. The general lighting load is added to the SABCs and the Laundry, and then "demanded" down to a lower number. What this means is that the actual demand load will be lower, because it is highly unlikely that all the lights, SABCs and Laundry circuits will be in use and used to their capacity at the same time. The writers of the NEC realize this, and allow us to reduce the service size somewhat on account of that fact.

                              A bank requires 3.5 VA/square foot - but notice the reference to footnote b of the table? Be sure to keep an eye on details such as this, it makes a difference in the calculation. Some test questions are geared towards testing the individual's attention to details such as these notes. Depending on the situation, the real number could be 4.5VA/square foot for a bank.

                              Step 2: Fixed Appliances - In a dwelling unit, four or more appliances may be demanded down to 75% of their nameplate rating (220.53).

                              Step 3: Range - Ranges may be calculated in accordance with Table 220.55.

                              Step 4: Dryer - The minimum load for a dryer in a calculation is 5kW (220.54). They can be demanded down according to Table 220.54.

                              Step 5: Heating - A/C - Calculated at 100% of the larger load. (220.51, 220.60)

                              Step 6: 25% of largest motor load - Add 25% of the largest motor load per 220.18(A).

                              Last edited by George Stolz; 03-10-07, 09:23 PM.


                                [LIST][*][COLOR=black]How do I calculate box fill? [/COLOR][/LIST][COLOR=black]The requirements for box fill are given in 314.16(B). The easiest way I've found is just to take it step by step:[/COLOR]

                                (1) Conductor Fill. (Each conductor counted once, unless it's a long unbroken one (twice)).
                                (2) Clamp Fill. (On the inside of box counted once, outside not counted, based on largest conductor in box).
                                (3) Support Fittings Fill. (In the box counted once, based on largest conductor in box).
                                (4) Device or Equipment Fill. (Each device counted twice, based on conductor connected to device).
                                (5) Equipment Grounding Conductor Fill. (The biggest EGC is counted once.)

                                The total number of conductors are then multiplied by the cubic inches used, as given in Table 314.16(B).
                                Last edited by George Stolz; 05-11-07, 12:53 PM.