The accuracy of the calculation provides increased confidence in the design, upgrading, and analysis projects. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Outer jacket thickness for all nm bpcs cable is 30 mils. Understanding nm nonmetallic sheathed cable the spruce. The ac service techs solution is to just put a 2 pole 50 amp breaker on the unit. Sim pull jacketed conductors shall be annealed copper as manufactured by southwire company or approved equal. Cable ampacity software cable sizing software cable derating. Comsol software is used for the three dimensional simulation of a 44kv armored hvac xlpe. The cymcap software is dedicated to the calculation of ampacity and temperature rise calculations for power cable installations.
Type nm cable and more electrical contractor magazine. For ambient temperatures other than 78f 86f, or more than three currentcarrying conductors in a raceway, cable or earth, use the advanced wire ampacity calculator. Actual ampacity rating romex simpull type nm b in a residential attic. Additionally, there is an equipmentgrounding conductor that is bare or has green insulation. Cyme power engineering software and solutions calculate ampacity and temperature rise of power cable installations the cymcap software is dedicated to performing ampacity and temperature rise calculations for power cable installations. Ampacities are based on a conductor temperature of 90 c and an ambient air temperature of 40 c. It is commonly known as romex, which is the brand that is most widely used. Nm b cable may be run in air voids of masonry block or tile walls where such walls are not subject to excessive moisture or dampness. Southwire 28827423 100 142 with ground romex brand simpull. Crsslined llein inslated, drilling rig and marine cable.
Nm vs thhn ampacity electrical diy chatroom nm vs thhn ampacity. Thermal resistivity depends on the soil type, compaction of the soil, and the. 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. As a cable ampacity analysis application, etap engineering software determines the cable current capability based on ieee, iec, icea, nec nfpa, bs, and. Crsslined llein inslated, drilling rig and marine cable ampacity. Nonmetallic sheathed nmb cable is used in dry applications, as branch circuits for outlets, lighting and other residential loads. Transition from type nm to nmb wiring 2015 update madison wisconsin presently uses the 2011 nec code in which i see 334. Nm cable romex ampacity and overcurrent protection 1. Cyme power engineering software and solutions power cable. Ambient temperature ampacity corrections for cable bundling and direct. Understanding the nehermcgrath calculation and the ampacity of. The wire ampacity calculator will quickly calculate the maximum allowable current through a conductor based on wire size awg or kcmil, wire insulation, conductor type and installation method. Type nm b cable is commonly used for residential wiring of luminaries, devices and appliances. The advanced wire ampacity calculator will calculate the maximum ampacity for a wire based on wire gauge, preferred or available wire insulation, conductor type and installation specifications.
Ampacities are based on single isolated cable in air operated with opencircuited shield. Romex simpull type nmb nonmetallic sheathed 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 national electrical code nmb cable is primarily used in residential wiring as branch circuits for outlets, switches, and other loads. Type p drilmartm 125xe powerdistribution cable ampacity author. Usamp prime insulated cable ampacity software models all types of underground power cables pipe type, extruded, and solid paper. Sub panel feeder wire and protection requirements nfpa xchange. Type nm cable cannot be run outdoors even if it is run in a raceway because this is considered to be a wet location. 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. Nm b uses a 90c conductor and you use the 90c column for derating.
Nmb is rated at 600 volts and although it is rated at a conductor temperature of 90. Thermal effects of residentialinstalled type nmb cable nema. Also the size and type of ducts that need to be used should be decided. Nm cable shall have a 90 degree c insulation used for derating but shall be used at the 60 degree c ampacity 334. In addition to tester101s excellent answer on when nm b can be run through conduit, there is a section in the nec which indirectly prohibits running nm b through conduit in specific scenarios. Is it acceptable to install nonmetallic sheathed cable nm exposed on a wall or in an attic, a basement, or a residential garage. Nec 600 volt ampacity tables for electrical cables. Through its three divisions and four strategically located distribution centers, cme serves its customers in residential, commercial, institutional, utilities, industrial and oem markets. The jacket of type nmc cable is also corrosionresistant. Southwire romex simpull 125ft 63 nonmetallic wire bytheroll at lowes. Southwire romex brand simpull nmb nonmetallic sheathed 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.
Nonmetallic sheathed nm b cable is used in dry applications, as branch circuits for outlets, lighting and other residential loads. Ampacities are based on the 2017 nec and do not reflect any temperature correction or ampacity adjustments that may be required. Southwire 28828201 nm nonmetallic sheathed cables crescent. Ampacities of not more than three currentcarrying conductors in raceway, cable or earth. As excerpted from the 2002 national electrical code. Get free 2day shipping on qualified nm b, wire products or buy electrical department products today with buy online pick up in store.
Southwire romex simpull 125ft 63 nonmetallic wire by. Type mtw wire part number color gauge description spoolreel length approx. So, strictly speaking, the term romex should be used to refer only to nm sheathed electrical cable made by southwire company under the romex brand, not nm cable from other manufacturers. A literal interpretation of the old code language would allow a type nm cable to be used in any residential storage building, with no restrictions on whats being stored in the building or what the building was being used for. The cable consists of a factory assembly of two or more insulated conductors within an overall nonmetallic jacket. Oct 06, 2014 nec ampacity calculator is a smallsized software utility that enables users to access the most frequently used ampacity tables found in the american and canadian electrical codes, input data and. Each cable has not more than three currentcarrying conductors. Apparently, theres a difference between whether it is nm romex or thhn. Ambient temperature ampacity corrections for cable bundling and. Where more than two nm cables containing two or more currentcarrying conductors are bundled together and. This dissertation addresses underground electric power cable ampacity and.
Products southwire is one of the worlds leading manufacturers of wire and cable, tools, components and assembled solutions. Detailed graphical representation of virtually any type of power cable. The ampacity of types nm, nmc, andnms cable shall be determined in accordance with. Paladin designbase power systems optimization and sizing. Type nmb is rated 600volt for both exposed and concealed work in normally dry locations. Buy southwire 63946822 14 awg romex simpull 3 conductor 50 nonmetallicsheathed cable with fast shipping and toprated customer service. The ampacity of types nm, nmc, and nms cable installed in cable tray shall be determined in accordance with 392. The allowable ampacity shall not exceed that of a 60c 140f rated conductor. Nm b nonmetallic sheathed cable is primarily used in residential wiring such as branch circuits for outlets, switches, and other loads. Southwire 28827422 50 142 with ground romex brand simpull. Engineers are often called upon to calculate ampacity and temperature rise of. Article 334 nonmetallicsheathed cable types nm, nmc, and. C conductor temperature rating, as specified in the nec. Enter the information below to calculate the maximum allowable ampacity for currentcarrying conductors.
National electrical code allowable ampacities of insulated. The accuracy of the software provides increased confidence when upgrading power cable installations and designing new ones. Within the world of building products, the word romex is often used in the same way that kleenex is used to refer to any tissue. This guide covers copper and aluminum conductors from 14 awg through kcmil, insulated for operation from 600v though 35kv. The number and type of electrical devices connected to a circuit determine the ampacity requirement of the conductor. Type nm b is rated 600volt for both exposed and concealed work in normally dry locations. For whatever reason, lately we have been having a problem with contractors using nm cable that is not rated for the proper ampacity. Article 334 nonmetallicsheathed cable types nm, nmc, and nms wiring methods and materials from pocket guide to the national electrical code 2005.
The cymcap software is dedicated to the calculation of ampacity and temperature rise. The bundle experiment was only a small part of an overall experimental program. Pdf modeling and analysis of hv cable ampacity for power flow. Mtw conductor ampacity based on cooper conductors with 60c and 75c as specified by nfpa79. Nm b cable is primarily used in residential wiring as branch circuits for outlets, switches, and other loads. Circuit is bundled or in raceway 24 inches or less in length circuit is type ac or mc cable that complies with note 6. Allowable ampacity shown above is per the 2005 national electrical code. Type nmb ampacity limitation shall be in accordance with the 60. Nm cable has insulated conductors enclosed within an overall nonmetallic jacket. C column is only 100 amps, so that is the maximum permitted load on a 10 xhhw al conductor installed in thermal insulation. 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. The results show the nehermcgrath calculations and cymcap software. It may be fished through masonry or tile walls, where not exposed or subject to excessive moisture or dampness. Nonmetallic sheathed nm b cable is used in normally dry installations in residential wiring, as branch circuits for outlets, lighting and other residential loads.
What is the maximum distance allowed between supports when installing type nm cable. Usually, a general purpose house circuit is designed for 20. As a cable ampacity analysis application, etap engineering software determines the cable current capability based on ieee, iec, icea, nec nfpa, bs, and nfc standards. But the nm equation and the nec assume that a conductor and surrounding. Nowhere does this cable have any marking as to the temperature rating or type of insulation, so off i go to the website where i find this statement in a product sheet. 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 wire. There could be from 1530c increase depending on where you live, chris. After a bit of investigating, we found the source of the problem.
Type nm cable cannot be run in any raceway other than using it as a sleeve in accordance with 334. Cable ampacity software cable sizing software cable. Power and control tray cable type tc is a factory assembly of two or more insulated conductors under a nonmetallic jacket sec. Learn the basics and where different cables are used. Two kinds of type nm cable, described above, which are the common choices for interior installations.
The only time that we start from the 90c column is for derating purposes. Southwire 63946822 14 awg romex simpull 3 conductor 50. Cable network usually forms a backbone of the power system. Installation of nonmetallic sheathed cable, exposed or in. Southwires power cable installation guide provides installation information for extruded dielectric power cable systems. The ampacity of types nm, nmc, and nms cable shall be determined in accordance with 310. Ampacity for circuit size types seu and ser cables. In all cases, verify the load does not exceed the circuit capacity. Actual ampacity rating romex simpull type nmb in a. Computes steadystate and transient ampacities and temperatures for multiple cables with equal or unequal loading.
Please consult a qualified electrician or professional engineer to determine the appropriate values for your specific application. Nm is a type of cable that contains insulated conductors enclosed within an overall nonmetallic jacket. Transition from type nm to nmb wiring inspectionnews. Conductors shall be ullisted type nmb, suitable for operation at 600 volts in all installations as specified in the national electrical code. You must use the correct size wire for the current load requirement of the circuit to prevent the wire from overheating. 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 60c 140f rated conductor. Its applications are outlined in nec 2008 and nec 2011 article 334. As you can clearly see, the allowable ampacity shall not exceed the 60c column found in the tables governed by 310. Nm cable was invented by the romex company in 1922 and was first described and listed by the nec national electrical code in 1926, but it did not come into prevalent use until the early 1960s when plastics replaced woven rayon as the material used for the outer sheathing. The key to understanding ampacity is to learn about heat transfer.
Usamp prime software models all types of underground power cables pipe type, extruded, and solid paper. Cme type nmb, nonmetallic sheathed cable, pvcnylon. Type nm is identified by the size of the conductors and number of them. The above data is approximate and subject to normal manufacturing tolerances. Nonmetallic sheathed cable is the most commonly used electrical cable in homes today. Type nmb nonmetallic sheathed cable is commonly used for residential wiring of luminaries, devices and appliances.
Yet another type of nm cable is used by the utility company to deliver electrical service to your home overhead or through the ground. Type nm b nonmetallic sheathed cable is commonly used for residential wiring of luminaries, devices and appliances. Nm b cable may be run in air voids of masonry block or tile walls where such walls are not wet or damp locations. Installation of nonmetallic sheathed cable, exposed or in a.
Nm cable contains two or more insulated wires and a bare ground wire. Attics are much hotter than ambient so you now have two different ampacity situations to consider. Where would physical protection of the nm cable be required, and where is physical protection of nm cable often used but not necessarily required. The software examines cable temperature and ampacity in performing analysis of existing systems. Models duct banks, pipe cables, extruded cables, directly buried cables, casings, or mixtures thereof. Determining the maximum current power cables can sustain without deterioration of any of their electrical. This takes into account correction factors for voltage drop, temperature and the number of currentcarrying conductors. This calculator also provides wire size correction factors for temperature, number of conductors in a raceway, and voltage drop for long wire runs. Overloading electrical circuits can result in overheating of the wire and other electrical equipment. The calculation determines the proper cable sizes to carry specified loads in designing new systems and upgrading power cable installations.
577 1413 1092 930 299 985 95 381 1269 1198 299 82 998 623 853 1533 488 639 1077 1067 798 1438 939 731 782 1536 1354 508 292 813 1424 431 425 1288 413 608 34 1437