Romex is the brand name of a nonmetallic nm sheathed electrical cable made by southwire company, llc of carrollton, georgia. Romex 122 nmwg wire type nm b cable is designed specifically for use in residential and commercial wiring of branch circuits. Type nm b nonmetallic sheathed cable is commonly used for residential wiring of luminaries, devices and appliances. Type nmb nonmetallicsheathed cable grounded border. A great tool to help electricians, engineers and contractors answer the question, what. C conductor temperature rating, as specified in the nec. Wire sizing and overcurrent protection home owners network. With those modules, the user can evaluate the magnetic flux density at any point on or above the ground of an underground cable installation, determine the positive and zero sequence impedances and admittances for all the cables. Jan 03, 2008 where more than two nm cables containing two or more current carrying conductors are bundled together and pass through wood framing that is to be fire or draftstopped using thermal insulation or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with table 310. Bare copper conductors common items in stock qi thhnthwn2, copper, 600 v common items in stock qi thhnthwn2, aluminum, 600 v common items in stock tffntwen 600 v copper fixture. Nonmetallic sheathed nmb cable is used in normally dry installations in residential wiring, as branch circuits for outlets, lighting and other residential.
C ampacity column of table 31016, provided the derated ampacity did not exceed the ampacity for a 60. Southwire 63946822 14 awg romex simpull 3 conductor 50. Southwire company romex simpull copper nonmetallic. Ampacity for circuit size types seu and ser cables. The primary purpose of the ampacity calculations was to detennine a minimum conductor size and cable system configuration based on the design requirements provided by xcel energy. That was made simple in 1984 as the construction of nm cable was changed to require all conductors in nm cable to be 90. Even though the wires within nmb cable are thhn wire and have insulation rated for 90 degrees c, many versions of the code, including 2011 nec section 33480, limit ampacity of nonmetalic cables such as nmb to no more than that permitted with an insulation rated for 60 degrees c probably due to heat retention by the thick outer pvc jacket. The 90c 194f rating shall be permitted to be used for ampacity adjustment and correction calculations, provided the final derated ampacity does not exceed that of a. Ampacities are based on the 2017 nec and do not reflect any temperature correction or ampacity adjustments that may be required. The ground wire is wrapped with fireretardant paper and laid parallel between the insulated. Type nm b ampacity limitation shall be in accordance with the 60. Southwires romex simpull type nmb nonmetallicsheathed cable may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90 deg c with ampacity limited to that for 60 deg c conductors as specified in the 2011 national electrical code. Southwire company romex simpull copper nonmetallic building wire assortment excludes bythefoot items. The 90c 194f rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed.
I see above references to permission to use up old stock of nm labeled cable. Actual ampacity rating romex simpull type nmb in a. Thermal effects of residentialinstalled type nmb cable nema. This table will apply to almost all branch circuit and feeder wires in modern residential electrical systems. Conduit fill is the percent of area inside the conduit taken up by the cable s. Nonmetallic sheathed nmb cable is used in dry applications, as branch circuits for outlets, lighting and other residential loads. Learn the principles of ampacity, temperature ratings and derating factors. Romex is for indoor use only and the ufb cables can go outdoors and even directly underground without conduit. Infornation derived from manufacturers spec sheetsthe cable is installed. Understanding the nehermcgrath calculation and the ampacity of. Even though the wires within nm b cable are thhn wire and have insulation rated for 90 degrees c, many versions of the code, including 2011 nec section 33480, limit ampacity of nonmetalic cables such as nm b to no more than that permitted with an insulation rated for 60 degrees c probably due to heat retention by the thick outer pvc jacket. Romex nmb cable indoor electrical wire wesbell electronics. The software examines cable temperature and ampacity in performing analysis of existing systems.
Ampacities of insulated conductors rated up to and including 2000 volts. These values are based on allowable ampacities of insulated conductors rated up to and including 2000 volts, not more than three currentcarrying conductors in a raceway, cable, or earth, singleinsulated conductor in free air, and an ambient air temperature of 30c 86f. Nmb is rated at 600 volts and although it is rated at a conductor temperature of 90c dry, its ampacity is. Nm cables in bored holes electrical codes forum icc. In this installation, the cable must end at the junction box and conductors that are listed for wet locations, such as thhw, must be. The ampacity shall be in accordance with the 60c 140f conductor temperature rating. The accuracy of the calculation provides increased confidence in the design, upgrading, and analysis projects. Southwire romex brand simpull nmb nonmetallicsheathed cable may be used for both exposed and. Voltage rating for nm b cable is 600 volts meets or exceeds ul standard 83, ul standard 719, federal specification aa59544, and requirements of the national electrical code made in the usa white jacket 3 conductor design 14 awg 19 mils insulation and jacket thickness 74 lb per per lb 15 allowable ampacity 307 mil. Using pirr, i compute the cable has a cross section of 0. The allowable ampacity shall not exceed that of a 60c 140f rated conductor. The ampacity of types nm, nmc, and nms cable shall be determined in accordance with 310.
Nmb is rated at 600 volts and although it is rated at a conductor temperature of 90c dry, its ampacity is limited to 60c according to the nec 2008 and nec 2011. But the nm equation and the nec assume that a conductor and surrounding thermal. I have had many inspectors pass the nmb cable, now one has failed a. Intended for use in accordance with the national electrical code. The accuracy of the software provides increased confidence when upgrading power cable installations and designing new ones. The user inputs basic parameters cable type, insulation type, voltage rating and conductor area. It may be fished through masonry or tile walls, where not exposed or subject to. Conductor ampacity calculation part seven electrical knowhow. We sell the south wire brand romex wire and ufb cable. The newer nmb cable has a 3mil pvc jacket, colored. Nov 19, 2018 the newer nm b cable has a 3mil pvc jacket, colored. Transition from type nm to nmb wiring 2015 update madison wisconsin presently uses the 2011 nec code in which i see 334.
Provides quick and easy results for the conduit fill percent, per nec guidelines. The cable ampacity analysis software applies to cables in above ground trays, conduits, and air drop. Southwire notes that they vigorously monitor and protect the use of the romex brand. Multiple nmb cables through a 2 emt conduit nec 2002. Home resources calculators conduit fill calculator. The results show the nehermcgrath calculations and cymcap software outputs. The aeic cable specifications are builtin to the program. Cable ampacity power system software and arc flash hazard. The calculation determines the proper cable sizes to carry specified loads in designing new systems and upgrading power cable installations. Installation above ground and in dry locations only. In addition to tester101s excellent answer on when nmb can be run through conduit, there is a section in the nec which indirectly prohibits running nmb through conduit in specific scenarios. Although conductors with a temperature rating of 90c can be installed, the ampacity must not exceed the 75c ampacity. The cymcap software is dedicated to the calculation of ampacity and temperature rise calculations for power cable installations. Cable ampacity software cable sizing software cable derating.
Nm b cable may be run in air voids of masonry block or. Usamp prime software models all types of underground power cables pipetype, extruded, and solid paper. Finding the original rca value is easier than it looks. Conductor ampacity calculation part four electrical. Its applications are outlined in nec 2008 and nec 2011 article 334.
Nm cable romex ampacity and overcurrent protection 1. While this is common legal boilerplate language for many products, with southwire and romex it is more of critical concern since. Nm cable is often referred to by the trade name romex. Nmb is rated at 600 volts and although it is rated at a conductor temperature of 90. Southwires romex simpull type nm b nonmetallicsheathed cable may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90 deg c with ampacity limited to that for 60 deg c conductors as specified in the 2011 national electrical code. Pvcjacketed cable with two, three or fourcircuit conductors and an equipment grounding conductor. The nec standard does not provide cable ampacity derating due to bottom cover or correction of the cable ampacity multiplying factors due. Voltage rating for nmb cable is 600 volts meets or exceeds ul standard 83, ul standard 719, federal specification aa59544, and requirements of the national electrical code made in the usa white jacket 3 conductor design 14 awg.
Because the 63 cable has a neutral conductor which will be used in the circuit the voltage will be expressed as 120240 volts. Southwire 28828255 12 awg romex simpull 2 conductor 250. I have had many inspectors pass the nm b cable, now one has failed a. Southwire romex brand simpull nmb nonmetallicsheathed cable may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90c with ampacity limited to that for 60c conductors as specified in the 2011 national electrical code. Romex 122 nmwg wire type nmb cable is designed specifically for use in residential and commercial wiring of branch circuits. Cable ampacity power system software and arc flash. Nm b cable is primarily used in residential wiring as branch circuits for outlets, switches, and other loads.
Cable ampacity software cable sizing software cable. Home products our products lie in the walls of your home, in the transmission lines that power our neighborhoods, in the places we work, schools where we learn and the hospitals that keep us well. An exception to 33630b was added to the 1996 nec to allow derating of type nm cable from the 90. Type nm b is rated 600volt for both exposed and concealed work in normally dry locations. Conductor ampacity calculation part four electrical knowhow. What is the rating of 4446 ser aluminum for wire size to 100 amp subpanel electrical diy. Twoconductor constructions have the insulated conductors laid parallel. Understanding the nehermcgrath calculation and the ampacity. Before the 1996 edition, derating from the 90c column was not allowed. Type nmb nonmetallic sheathed cable is commonly used for residential wiring of luminaries, devices and appliances. They come in 2 and 3 conductor in awg sizes 14, 12 and 10. Used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90 deg c with ampacity limited to that for 60 deg c conductors as specified in the national electrical code.
Table 1 says that i can only fill this cable to 40% if i have over 2 conductors. Using your example of 63 cable with a ground, the l1 and l2 conductors have the capacity of 55 amps each, and this amperage capacity is not added together for a total circuit capacity. Where more than two nm cables containing two or more current carrying conductors are bundled together and pass through wood framing that is to be fire or draftstopped using thermal insulation or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with table 310. This dissertation addresses underground electric power cable ampacity and. Cable design form to scale input of cable designs is facilitated by a cable expert system.
Southwire 63948422 50 103 with ground romex brand simpull. C ampacity column for derating ampacity for ambient temperature and bundlinglack of maintaining spacing and nm became nmb in 1984. Understanding the nehermcgrath calculation and the. The ampacity of an 8 awg conductor in the 75c column is 50a. Its used for indoor and outdoor electrical wiring applications. As a cable ampacity analysis application, etap engineering software determines the cable current capability based on ieee, iec, icea, nec nfpa, bs, and. Cme type nmb, nonmetallic sheathed cable, pvcnylon. Pvc polyvinyl chloride jacket and pvc insulated, nylon jacketed conductors with ground wg. It may be fished through masonry or tile walls, where not exposed or subject to excessive moisture or dampness. Nonmetallic sheathed nmb cable is used in normally dry installations in residential wiring, as branch circuits for outlets, lighting and other residential loads. Calculate conductor ampacity with temperature correction you wiring a home solar photovoltaic pv system page 2 table 310 15 b 3 a adjustment factors for more than three power quality in the age of leds part 3 by guy holt. Southwire is one of the worlds leading manufacturers of wire and cable, tools, components and assembled solutions. Transition from type nm to nmb wiring inspectionnews. For a quick approximation of the derated ampacity add this calculated thermal ohm feet value to the rca value used in the nm original calculation and recalculate the ampacity.
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