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QUESTION: Are motor branch circuit conductors sized at 125% of motor full load current to handle the motor starting current?

ANSWER: No. The motor starting or "inrush" currents, which are also called "locked rotor current", are only present during the acceleration period at the moment a motor is started. The inrush current decreases rapidly as the motor begins to rotate. The motor branch circuit overcurrent protection as calculated from Table 430-153 easily handles these currents within the limitations of the motor branch circuit conductors. These motor branch circuit overcurrent protective devices which are permitted to be sized much higher than the rated ampacity of the motor branch circuit conductors are also able to protect the motor branch circuit conductors from short-circuit or ground-fault currents because of the magnitude of the currents produced so rapidly by these types of faults.

SECTION: 430-152

ANSWER: In installations of motor circuits under 600 volts, each controller must have an individual disconnecting means and it shall be in sight from the motor controller. See Section 430-102(a). A new Exception No. 2 permits a single disconnecting means for a group of coordinated controllers that drive several parts of a machine or apparatus. The disconnecting means and controllers must be located in sight from the machine or apparatus.

SECTION: 430-102(a)

QUESTION: How is the overcurrent protective device sized in the motor disconnecting means?

ANSWER: No overcurrent protective devices are required in the motor disconnecting means. This disconnecting means is solely for the protection of persons maintaining the motor or its driven machinery and is not required if the controller disconnecting means is capable of being locked in the open position. See Section 430-102(b).

SECTION: 430-102(b)

QUESTION: How is the motor disconnecting means sized?

ANSWER: Section 430-110(a) requires the disconnecting means for motor circuits to have an ampere rating of at least 115% of the motor full load current.

SECTION: 430-110(a)

SOURCE: Charlie Trout

ANSWER: Yes, with one exception. Section 430-102(b) requires a separate disconnecting means to be located in sight from the motor and the driven machinery. This disconnecting means is not required if the controller disconnecting means is individually capable of being locked in the open position.

SECTION: 430-102(b)

QUESTION: Explain how when using Column "C" in Table 430-72(b) they can say a 60 ampere overcurrent device can protect a #12 copper control circuit conductor?

ANSWER: The motor control circuit conductors are protected from physical damage by the raceway in which they are enclosed. The coil circuit is current is small and overload is not a problem. Short-circuit and ground-fault currents rise rapidly and will open the motor branch circuit overload protective devices before any damage could occur.

SECTION: 430-72(b)

ANSWER: Overcurrent protection for motor control circuits is covered in Section 430-72(b). The requirements for conductors, which extend beyond the enclosure (remote) can be found in Table 430-72(b) in Column "C". For example, if your motor branch circuit protective device is rated at 60 amperes and you are using copper control circuit conductors, then you find 60 in the copper column and move to the left to control circuit conductor size where you find 12. This means that you need to install control circuit conductors not smaller than #12 copper. A smaller conductor would require supplemental overcurrent protection to protect that conductor.

SECTION: 430-72(b)

ANSWER: If you are tapping to a single motor and are not reducing the conductor size, overcurrent is not a problem. If you are reducing the conductor size, Section 430-52(d)(2) requires that the tap conductors have protection from physical damage, the conductors are not more than 25 feet in length and that the conductors have an capacity not less than 1/3 that of the feeder conductor with a minimum in accordance with Section 430-22. This means that the tap conductor must be sized at 125 percent of the motor full load current, and also not be less than 1/3 the capacity of the feeder conductor.

SECTION: 430-52(d)(2), 430-22

QUESTION: Regarding the question as to whether NM cable can be used in other than residential construction. Please explain your answer about using NM cable in any structure not exceeding three floors above
grade.

ANSWER: During the recent period when Code Question of the Day was having on-line problems, some previously used questions inadvertently got back into the system. These questions were answered using the 1996 Edition of the NEC. There is a change in Section 336-5(a)(1) relating to uses not permitted. The 1996 NEC said "In any dwelling or structure exceeding three floors above grade." This was changed in the 1999 NEC to read "In any multi-family dwelling or other structure exceeding three floors above grade." This of course means that type NM, NMC, and NMS cable can now be used in one-family and two-family dwellings regardless of height above grade. This change in the 1999 NEC renders the answer given as incorrect. Another reader challenged the answer based on "There are nine locations listed where this cable cannot be used." That is absolutely correct, but if the read had paid "better attention to detail" he would realize that those other prohibited locations are areas where NM cable cannot be used in buildings that have other areas where it is permitted if the building does not exceed three floors above grade. However, let's get back to the original question. Yes, nonmetallic-sheathed cable (Type NM)can be used in other than residential construction. Yes, it can be used in warehouses, doctors' offices, banks, schools, and shopping centers, except where prohibited by Section 336-5.

SECTION: 336-5(a)(1)

SOURCE: Charlie Trout

RELATED PRODUCT: 1999 National Electrical Code Tables

NECA Comment: "1999 National Electrical Code Tables"
NECA's most popular technical publication is a "must" for contractors, electricians, inspectors, and everyone else who uses the Code daily in their work. 1999 NEC Tablesputs the information you use every day - conductor properties, raceway dimensions and capacities, motor code letters and overcurrent device settings, plus much more - in a compact package that's handier to use in the field than the complete 650-page Code book. Tables are photographically reproduced from the 1999 NEC, to insure accuracy. Contact the NECA Order Desk at (301)215-4504 Tel, (301) 215-4504 fax, or sgw@necanet.org.  Index No. 5036 $7.50 (NECA-member and quantity discounts are available)

QUESTION:  I have a one-year-old multi-family dwelling that is three floors above grade. The building is wired with type NM cable. The owner is building two new penthouse apartments on top of the building. Can I use type NM cable to wire those new apartments?

ANSWER:  Are you putting me on? Well, if the building department permits this construction, I guess he can do it. But you must follow the code, unless the AHJ approves differently, and if it's the NEC this building now exceeds three floors above grade and you cannot use type NM cable. (See Section 336-5). Don't blame me, they own the store.

SECTION: 336-5

SOURCE:  Charlie Trout

RELATED PRODUCT:   State Electrical Regulations

NECA Comment:  "State Electrical Regulations: NECA Guide to State Electrical Codes, Enforcement and Licensing" An invaluable reference for contractors, manufacturers and others who operate in multiple jurisdictions around the country, NECA's State Electrical Regulations summarizes information about electrical codes, code enforcement, and contractor/electrician licensing in every state plus the District of Columbia. In addition, it gives you contact names and phone numbers for state agencies that regulate electrical construction. Contact the NECA Order Desk at (301)215-4504 Tel, (301) 215-4504 fax, or sgw@necanet.org.   Index No. 5060 $20  (NECA-member and quantity discounts are also available)

QUESTION:  I am wiring recessed fluorescent fixtures in a lay-in type ceiling in a two-story department store building. Can I use type NM cable for whips from the junction boxes to the fixtures?

ANSWER: Yes. A new Exception No. 3 was added to Section 336-18 in the 1999 NEC. The catch is that the whips cannot be longer than 4-1/2 feet. Allowing 6 inches on each end for connections, you only have about 3-1/2 feet to work with. I guess the good news is that the NM cable doesn’t have to be secured within 12 inches of the boxes. And yes, I know that the same exception to the basic support rule is provided for in Sections 337-7 and 334-10 but a length of 6 feet is allowed. I don't know, same panel, same situation, and different answer. Go figure.

SECTION:   336-18, 333-7, 334-10

SOURCE:  Charlie Trout

RELATED PRODUCT:  NECA/FOA 301-1997

NECA Comment:  NECA/FOA 301-1997, "Standard for Installing and Testing Fiber Optic Cables"
This publication describes installation practices for optical fiber systems used for communications purposes. NECA/FOA 301-1997 was jointly developed and published with the Fiber Optic Association. Contact the NECA Order Desk at (301)215-4504 Tel, (301) 215-4504 fax, or sgw@necanet.org and request.  Index No. NECA 400 $25
(NECA-member and quantity discounts are available)

QUESTION:  For a long time it has been common practice to mount closed-circuit video security cameras on site lighting poles and run the wiring down inside the pole. Explain how the addition of four words to 1999 NEC Section 410-15(b) prohibits this once-common practice.

ANSWER:  Adding the words "as a raceway to" in effect turns the metal support pole in to a raceway. Section 820-52(b) requires that CATV cable be separated from electric light and power conductors. Since there is no Code Article specifically for CCTV systems, Article 820 is applied to such installations.

SECTION:  410-15(b) and 820-52(b)

SOURCE:  Brooke Stauffer

RELATED PRODUCT:  1999 NEC Changes Video

NECA Comment: "1999 National Electrical Code Changes video"
This 60-minute video training course combines expert commentary, outstanding graphics, and footage of actual installation situations to bring new 1999 Code requirements to life right before your eyes, and provide the information contractors need to apply the NEC correctly on the job. Contact the NECA Order Desk at (301)215-4504 Tel, (301) 215- 4504 fax, or sgw@necanet.org.    Index No. 5016V $99  (NECA-member and quantity discounts are also available)

QUESTION: Is there a reason that Section 430-145(b) appears to allow 3/8" intermediate metal conduit and Section 345-6(a)says conduit smaller than 1/2" shall not be used?

ANSWER:  There could be several reasons. The panel may have inadvertently left out the type of exception that they put in Section 346-6. It may be an error in your Codebook (and mine) or maybe we're not reading 430-145 correctly or maybe they could improve the language. If all else fails, write a proposal for the 2002 Code and get a free Report on Proposals.

SECTION: 430-145(b), 430-146(a)

SOURCE:  Charlie Trout

RELATED PRODUCT:   NECA/IESNA 500-1998 (ANSI)

NECA Comment:  NECA/IESNA 500-1998, "Recommended Practice for Installing Indoor Commercial Lighting Systems" This publication describes installation procedures for lighting systems commonly used in commercial and retail buildings. It is one of a series of "National Electrical Installation Standards" published by NECA. NECA/IESNA 500-1998 was jointly developed with the Illuminating Engineering Society of North America, and is approved as an American National Standard (ANSI). Contact the NECA Order Desk at (301)215-4504 Tel, (301) 215-4504 fax, or sgw@necanet.org.  Index No. NECA 400 $25   (NECA-member and quantity discounts are available)

QUESTION:  I have a service to install. I calculated it at 495 amperes. According to Table 310-16, I will need to use 900 kcmil conductors. I want to parallel this service so I am using 3 sets of 300 kcmil. Will the Code allow this?

ANSWER:  Yes, the Code will, but I don't think your budget will. When paralleling conductors, don't divide the circular mils, divide the amperage required. In this case 495 amperes divided by 3 = 165 amperes. You can use #2/0 copper conductors to accomplish your job or if you want to put them in two raceways, 495 divided by 2 = 247 amperes. You could use 250 kcmil copper conductors in two raceways. There is no direct proportional relationship between amperage and circular mils.

SECTION:  Table 310-16

SOURCE:  Charlie Trout

QUESTION:  On a property where the service comes into a secondary building with a feeder to a one-family dwelling, what is the minimum capacity permitted for the feeder conductors?

ANSWER:  Section 225-39(c) requires that the feeder disconnecting means have a rating of not less than 100 amperes, 3-wire. If these were service conductors Section 230-42(b)would require the conductors to have an ampacity not less than the rating of the disconnecting means. However these are feeder conductors and are only required to be sized for the calculated load. At first thought the ampacity of these conductors would have to be not less than 61 amperes to be protected by a fuse that would fit in this switch but listed fuse reducers are available to allow smaller size fuses to be installed in the switch. Some local requirements do not allow the use of fuse reducers but I find nothing in the NEC to prohibit their use.

SECTION: 225-39(c), 230-42(b)

SOURCE:  Charlie Trout

QUESTION:  In a recent question you said that to ground a 3-wire Delta secondary you would have to "corner" ground the secondary. Isn't there some sort of transformer you can hook up to the secondary to get a groundable neutral?

ANSWER:   Yes,You're right. A ziz-zag transformer can be used to convert the secondary to a 3-phase, 4-wire way system. Generally a zig-zag transformer is used to gain the advantages of a grounded system and  is sized only to carry ground-fault current for a short duration. The grounded conductor can be used as a system grounded common/return conductor. If used for this reason the transformer must be sized for the calculated loads. It would be more to your advantage to use a standard transformer if you are attempting to get a 3-phase, 4-wire, way system. For more information see the IAEI Source Book on Grounding.

SOURCE:  Charlie Trout

QUESTION:  Can a "plug-in" meter and fitting be used in a fire pump circuit when the locked rotor current of the fire pump exceeds the rating of the meter?

ANSWER:  Yes. Locked rotor or inrush current is only present when the motor is started. As the motor accelerates the current decreases rapidly to the normal full load current. Overcurrent devices are selected to carry indefinitely the locked rotor current, which is an overload condition. A short- circuit or ground-fault would open the overcurrent device because of the magnitude of the currents produced by these faults. Motor overload protection is not permitted in fire pump circuits. The purpose of these requirements is, when the fire pump is called upon to operate, to get the pump started and keep it running regardless of equipment damage until manually shut down.

SECTION:   695-6(d), 695-3(1)695-6(c)

SOURCE:  Charlie Trout

QUESTION: How can you say that a separately derived system is "basically a new service" when the definition of a service requires that the electrical energy be delivered from a serving utility?

ANSWER: Well I guess to put it simply my terminology was incorrect. It is definitely NOT A NEW SERVICE as is clearly shown by the new definition of service in the 1999 NEC. And to make it worse, the reference to a "main bonding jumper" was also incorrect by definition, which says a main bonding jumper is "the connection between the grounded circuit conductor and the equipment grounding conductor AT THE SERVICE. And wait a minute, I also said the panel after the transformer was the main distribution or "SERVICE PANEL". It definitely is not a service panel as shown in the definition of service equipment. All this because service can only be made by a serving utility. So to sum this up: It is not a new service, it is a new system (separately derived). It is not a main bonding jumper, it is a bonding jumper. It is not a main service panel, it is a main distribution panel. There is a difference in requirements for a service as opposed to a separately derived system and the bonding and grounding requirements are also different.

SECTION: Article 100, 250-30

SOURCE:  Charlie Trout

QUESTION: Please explain why when equipment grounding conductors are run in parallel they have to be full size in each raceway but when a paralleled grounded conductor is brought to a service to provide a low impedance path for fault current it doesn't have to be full size in each raceway?

ANSWER: When conductors are run in parallel in multiple raceways, an equipment grounding conductor, where used, shall be run in each raceway. Each parallel equipment grounding conductor shall be based on the ampere rating of the overcurrent device protecting the conductors. Example: Three sets of 3-600 kcmil THW CU conductors run in three raceways protected by 1200 ampere fuses. Using 250-122(f)(1) and Table 250-122 it is required to run a #3/0 copper grounding conductor in each raceway. When a grounded conductor is not required for the system or circuit being supplied and the supply is derived from a grounded system, a grounded conductor must be brought to the service equipment. This grounded conductor must be sized according to Table 250-66 and if larger than 1100 kcmil copper it shall not be smaller than 12-1/2 percent of the area of the largest service entrance conductor. However, where installed in parallel the size of the grounded conductor in each raceway shall be sized on the size of the ungrounded conductor in the raceway but not smaller than #1/0. Example: Three sets of 3-600 kcmil THW CU ungrounded service entrance conductors run in three raceways to a 1200 ampere fused service disconnect switch. Using Section 250-24(b)(1) a grounded conductor must be brought to the service disconnecting means. Section 250-24(b)(1) requires that the grounded conductor be not smaller than 12-1/2 percent of the area of the largest phase
conductor. However, Section 250-24(b)(2) requires that the grounded conductor in parallel raceways be based on the size of the ungrounded service entrance conductors in the raceway. The size of the ungrounded service entrance conductor is 600 kcmil and using Table 250-66 a #1/0 copper grounded conductor must be used.   Two conductors of different sizes asked to do the same job? No. The job description may be the same but the work load is different. In the first instance the equipment grounding conductor in a single conduit may be asked to carry enough current to open the overcurrent protective device. Therefore it must be sized in accordance with the size or rating of the overcurrent protective device. In the second example the fault current will always be carried by the combined capacity of the grounded conductors. Remember the grounded conductor in the second example does not extend beyond the service disconnecting means. Whew!

SECTION:  250-122(f)(1), Table 250-122, 250-66,250-24(b)(1),

SOURCE:  Charlie Trout

QUESTION: Can a receptacle be installed in a wet bar countertop?

ANSWER:  No. For the 1999 NEC a new sentence was added to Section 210-8(a)(7) to prohibit the installation of receptacles in a face up position in wet bar countertops. This provision was already in place for kitchen countertops [210-52(c)(5)] and bathroom countertops [(210-52(d)].

SECTION:  210-6(a)(7), 210-52(c)(5), 210-52(d)

SOURCE:  Charlie Trout

QUESTION:  Is GFCI protection required for outdoor receptacles that feed snow-melting equipment?

ANSWER:  For dwelling units (Section 210-8(a)(3)Exception), receptacles that are not readily accessible and are supplied by a dedicated branch circuit for electric snow-melting equipment shall be permitted to be installed in accordance with the applicable provisions of Article 426. For other than dwelling units, a new exception to 210-8(b)(2) has been added for the 1999 NEC, which is identical for the requirement for dwelling units. Section 426-28 of the 1999 NEC has been changed to require ground-fault protection of snow-melting equipment. Previously the wording specified that the protection was for the branch circuit.  An interesting note here is to check Sections, 550-8(g) and 552-41(d) which require that, an outdoor receptacle for pipe heating must be ground-fault circuit-interrupter protected.

SECTION:  210-8(a)(3), 210-8(b)(2), 426-28, 550-8(g), 552-41

SOURCE:  Charlie Trout

QUESTION:  What constitutes a habitable room?

ANSWER:  Although "habitable room" is not defined in the NEC, Section 210-70(a)(1) does give guidelines such as "in every habitable room and bathroom" which clearly shows that Panel 2 does not consider a bathroom a habitable room. Section 210-70(a)(2) and (3) show locations in addition to habitable rooms. A habitable room would probably be more appropriately defined in a building code.

SECTION:  210-70(a)(1)(2)(3)

SOURCE:  Charlie Trout

QUESTION:  My customer wants his refrigerator on a separate circuit. Does this have to be another 20 ampere small appliance circuit with a 1500 VA load computation?

ANSWER:  No. Section 210-52(b)(1) Exception No. 2 permits an individual branch circuit rated 15 amperes or greater to supply refrigeration equipment in a dwelling unit. A new exception has been added to Section 220-16(a)which permits this individual branch circuit to be excluded from the load calculation.

SECTION:  210-52(b)(1), 220-16(a)

SOURCE:  Charlie Trout

RELATED PRODUCT:  1999 NEC Changes Video

NECA Comment:  "1999 National Electrical Code Changes video"
This 60-minute video training course combines expert commentary, outstanding graphics, and footage of actual installation situations to bring new 1999 Code requirements to life right before your eyes, and provide the information contractors need to apply the NEC correctly on the job. Contact the NECA Order Desk at (301)215-4504 Tel, (301) 215-4504 fax, or sgw@necanet.org and request Index No. 5016V. The price on NECA's code change video has just been DROPPED to $79.  (NECA-member and quantity discounts are also available)

QUESTION:  What is the reason for the ubiquitous "standard" residential 120/240 volt, 3-wire service conduit sizing: 1-1/4" for 100A and 2" for 200A?

ANSWER:  If someone is still using those sizes as a "standard," then they are probably using a 1968 Code book. Either that, or they never had a Code book and are just doing what they have always done for years.   However, just because we are able to read the National Electrical Code and know that 2-#4 THWN CU and 1-#8 THWN CU conductors will fit in a 3/4" conduit and that Table 310-15 (b)(6) permits those sizes for 100A service entrance conductors to a dwelling unit (served with 120//240-volt, single-phase, 3-wire) doesn't mean that that is the way to go.
Always keep in mind Section 90-1(b), which very neatly tells us that "the code contains provisions that are considered necessary for safety." It goes on to say that even though you have an installation that is essentially free from hazard, it is "not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use." Electrical design is not limited to the scope of the National Electrical Code.

SECTION:  310-15(b)(6), 90-1(b)

SOURCE:  Charlie Trout

RELATED PRODUCT:  1999 National Electrical Code Tables

NECA Comment:  "1999 National Electrical Code Tables"
NECA's most popular technical publication is a "must" for contractors, electricians, inspectors, and everyone else who uses the Code daily in their work. 1999 NEC Tablesputs the information you use every day - conductor properties, raceway dimensions and capacities, motor code letters and overcurrent device settings, plus much more - in a compact package that's handier to use in the field than the complete 650-page Code book. Tables are photographically reproduced from the 1999 NEC, to insure accuracy. Contact the NECA Order Desk at (301)215-4504 Tel, (301) 215-4504 fax, or sgw@necanet.org and request  Index No. 5036 $7.50  (NECA-member and quantity discounts are available)

QUESTION:
I have an island counter-space.  The dimensions are 48" x 30".  The countertop is flat.  The overhang is 6" on all sides.  How many and where should I install the receptacle outlets?

ANSWER:
Only one receptacle is required by Section 210-52(c)(5).  Since the countertop does not have an overhang that extends more than 6" beyond its support base you are permitted to install the receptacle not more than 12" below the countertop [210-52(c)(5) Exception Part (b)].  This exception was revised for the 1999 NEC and the words "where acceptable to the authority having jurisdiction" were deleted to eliminate different interpretations by AHJ's in different jurisdictions.

SECTION: 210-52(c)(2),   210-52(c)(5)

SOURCE: Charlie Trout

RELATED PRODUCT: NECA 400-1998

NECA COMMENT: NECA 400-1998, "Recommended Practice for Installing and Maintaining Switchboards"This publication describes installation and maintenance practices for deadfront distribution switchboards rated 600 volts or less.   It also covers periodic routine maintenance procedures for switchboards, and special procedures to be used after adverse circumstances such as a short-circuit, ground-fault, or immersion in water.  Contact the NECA Order Desk at (301)215-4504 tel, (301) 215-4504 fax, or sgw@necanet.org and request Index No. NECA 400 $25 (NECA-member and quantity discounts are available)

BROOKE STAUFFER Director, Codes and Standards National Electrical Contractors Association (NECA)<mailto: brooke@necanet.org>