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Topic: Ampacity

	Power cable - Wikipedia, the free encyclopedia
		The ampacity (current-carrying capacity) of any given cable is the maximum amount of current a cable can constantly carry without jeopardizing the integrity of the insulating/sheathing materials due to excess heat dissipation.
		The ampacity for a cable is thus based on conductor composition, insulator composition, conductor size, ambient temperature, and environmental conditions adjacent to the cable.
		The overall ampacity of the insulated conductors in a bundle of more than 3 must be derated, whether in a raceway or cable.
	en.wikipedia.org /wiki/Power_cable (1205 words)

	Mine Safety and Health Administration (MSHA) - Compliance Information - Program Information Bulletin - P03-13: Trailing ...
		Ampacity derating factors are included in the ICEA tables for cables layered on a cable reel.
		The ICEA ampacity table derating factors are based on continuous current flow through the cable, not the ON/ OFF duty cycle of typical mining equipment using a cable reel.
		This magnitude of ampacity derating would require, for example, that a 1/0 AWG trailing cable be replaced with a 500 MCM size cable when 4 layers are used on the reel.
	www.msha.gov /regs/complian/PIB/2003/pib03-13.htm (862 words)

	Electrical - Busbar
		Ampacities were calculated using a nominal conductivity of 99% IACS and should also be applicable to other coppers with the same electrical conductivity.
		Ampacity Calculations - Accurate emissivity is essential because it is used to calculate the heat dissipated by radiation, a factor in the general equation for ampacity:
		Ampacity may be raised by increasing heat dissipation through the use of convection cooling or surface treatments.
	www.copper.org /applications/busbar/homepage.html (553 words)

	September-October 2001: Overcurrent Protection for Conductors
		Section 310-15(b)(2) requires an ampacity correction factor when the number of current-carrying conductors in a raceway or cable exceeds three or where single conductors or multiconductor cables are stacked or bundled together without maintaining spacing in distances longer than 610 mm (24 in.).
		Where the overcurrent protective device for the conductor exceeds 800 amperes, the ampacity of the conductors is required to be equal to or greater than the rating of the overcurrent device as defined in Section 240-6.
		Make sure that (1) the conductor has enough ampacity for the load to be served, and (2) the next standard size device still properly protects the conductor after adjustment factors have been applied to it (see photo 3).
	www.iaei.org /subscriber/magazine/01_e/johnston.htm (1913 words)

	Electrical capacity or size: How to estimate the electrical service ampacity and service voltage entering a building by ...
		If you are unable to determine the wire ampacity because there is no view, or because its dimension is not one with which you are familiar, say so.
		Markings in or on the panel box about ampacity indicate what current limiting device (such as a fuse) size could or should be installed, not what fuse or breaker size is actually present.
		Inspectors attempting to determine (or estimate) the ampacity of the electrical service at a building should report their determination.
	www.inspect-ny.com /electric/ElecAmps.htm (6576 words)

	Underground Cable Ampacities and the NEC Code
		In the 1987 Code ampacity tables, the configurations in NEC Figure 310-1 were utilized and ampacities calculated in accordance with Neher-McGrath.
		Thus, the ampacity of the installation is determined by the current which causes the hottest cable to run at rated temperature.
		Finally, to properly distinguish ampacities for the various cables in various positions and perhaps various sizes, it is necessary to construct and solve a set of simultaneous equations for each case to be considered, with the number of equations equal to the number of cable positions.
	www.calcware.com /cwnec2.htm (937 words)

	Calculations of a Conductor's Ampacity
		Therefore the total adjusted ampacity of that 8 awg copper conductor as described in its installation design is now a 7 amp rated ampacity for an 8 awg copper conductor.
		This 7 amps of ampacity of this 8 awg copper conductor would then be considered the true adjusted ampacity rating of that 8 awg copper conductor.
		If you are required to calculate an ampacity de-ration calculation for either ambient temperature or more than 3 current carrying conductors in a raceway, you may start your calculation by using the ampacity rating found in NEC Table 310.16 column for 90 degree C if the conductor’s insulation is originally rated for 90 degrees.
	www.selfhelpandmore.com /homewiringusa/2002/definitions/ampacity (2230 words)

	NFPA :: Publications :: necdigest :: necdigest Magazine :: necdigest® archives :: Winter 2003 :: Ask the Experts
		Determining conductor ampacity is accomplished via one of the two methods specified in 310.15.
		Additionally, although the NEC permits determination of conductor ampacity through calculation, it is also necessary to coordinate the conductor ampacity with respect to the temperature ratings of the terminals that conductors connect to.
		The most commonly used method for determining conductor ampacity is to use the allowable ampacity tables contained in Article 310. Of these tables, the one most often used is Table 310.16.
	www.nfpa.org /displayContent.asp?categoryID=559 (2008 words)

	Code Guide
		The state inspector is requiring me to size the protective device using 80A because he is derating the feeder to 80% of its maximum ampacity.
		When the neutral is counted as the fourth conductor, an adjustment factor of 80% must be applied to the ampacity as required by 310-15(b)(2)(a).
		Thus, the conductor ampacity would have to be increased in order to permit the use of a 100A overcurrent device.
	ceenews.com /mag/electric_code_guide_13 (665 words)

	Cable ampacity library linking - Topic Powered by eve community
		The cable ampacity value within the cable properties window should be dependent upon the ambient temperature setting.
		Therefore, when the ambient temperature is adjusted, the cable ampacity values should be scaled by the ampacity correction factor settings for the different ambient temperatures.
		The only way the ampacity value changes is if you manually click the Rated Temperature dropdown bar (within cable properties window), select a different temperature, click the 'tab' button, then click the actual temperature value that you want, and finally click the 'tab' button again.
	forums.edsa.com /groupee/forums/a/tpc/f/4966038832/m/9811071841 (681 words)

	Forced Cooling Eliminates Distribution Bottleneck
		SCL found that the ampacity of the crossing 115-kV cable was limited in the region where it passed 18 inches (46 cm) below the 13-kV duct banks.
		Before-and-after ampacities are hard to compare exactly, but the gain seems to be 40% of the original design rating.
		Ampacity is then obtained empirically, not based on assumed material properties, mathematical modeling or worst-case air and soil temperatures.
	tdworld.com /mag/power_forced_cooling_eliminates (1867 words)

	Calculations of a Conductor's Ampacity
		When counting current carrying conductors you do not need to count equipment grounding conductors in your de-ration of ampacity due to the number of conductors in a raceway at all, they are not current carrying conductors.
		When counting current carrying conductors you do not need to count in your de-ration of the ampacity of a conductor, any white neutral conductors, that are carrying only the unbalanced load of two hot conductors of the same two pole circuit and installed in the same raceway.
		You must use the worst scenario in the ampacity rating of that conductor after comparing the de-rated ampacity you found after your calculation to the ampacity found in the column that 110-14 required, if smaller than #1 = 60 degree column or #1 or larger = 75 degree column.
	www.selfhelpandmore.com /homewiringusa/1999/definitions/ampacity (924 words)

	CYME International - Software, Cable Ampacity Calculation
		The Multiple Duct Banks module (MDB) is the extension to CYMCAP designed to determine the steady state ampacity of cables installed in several neighboring duct banks and/or backfills with different thermal resistivity.
		The module computes the values of T4 (the external to the cable thermal resistance) using finite elements and then the ampacity (or operating temperature) of the cable system is obtained using the IEC standardized solution method.
		the sum of the ampacities for all circuits, is minimized.
	www.cyme.com /software/cymcap (710 words)

	March-April 2000: Wire Temperature Ratings and Terminations
		Although a 90°C conductor is being used, ampacity must be chosen from the 75°C column because the circuit breaker termination is rated at 75°C. Based on the table, a 1/0 copper conductor is acceptable.
		Conductors with higher temperature ratings, provided the ampacity is determined based on the 60°C ampacity of the conductor (see Figure 4).
		By beginning the derating process at the ampacity of the conductor based on the higher insulation value, you may not be required to upsize the conductor to compensate for the derating.
	www.iaei.org /subscriber/magazine/00_b/pauley.htm (2108 words)

	NEC Rules - Conductor Sizing
		The ampacity of a conductor is it’s current rating in amperes that it can carry continuously, after applying conductor ampacity reduction factors for conductor bundling and ambient temperature.
		In addition, the 1996 clarified in Section 110-14(c), that the ampacity reduction of THHN (90°C) conductor is based on the conductors ampacity as listed in the 90°C column of Table 310-16 and not on the terminal temperature rating.
		The No. 4 THHN which is rated 76 amperes after ampacity correction is properly protected by a 70 ampere overcurrent protection device in compliance with the general requirements of Section 240-3.
	www.mikeholt.com /news/archive/html/master/conductor.htm (1138 words)

	IEEE CAP Paper (Site not responding. Last check: 2007-11-01)
		The expert system provides hourly values of line ampacity up to seven days in advance and is used for the operation, planning, and design of transmission and distribution lines at all voltages.
		The program is an economical line ampacity system that does not require the installation of additional transmission line hardware, conductor temperature sensors, meteorological sensors or telecommunication system, and is easily implemented in all geographic regions.
		The power line ampacity system lends itself very well to object-oriented design where power lines, meteorological stations, conductors, analytical models and the system for the manipulation and display of data are objects.
	users.aol.com /akdeb/cap95.html (2671 words)

	ETAP Cable Systems (Site not responding. Last check: 2007-11-01)
		ETAP calculates cable ampacity based on NEC and ICEA P.54-440 methods for U/G duct banks, U/G direct buried, A/G cable trays, A/G conduits, and air drops.
		For duct banks, specify the number of rows, columns, ambient temperature, and soil thermals resistivity, ETAP calculates the derated ampacity based on the hottest location not exceeding the maximum operating temperature.
		Cable ampacity and sizing are included in the ETAP Base Package.
	www.etap.com /cablesystems.htm (300 words)

	Duquesne Light > Customer Service > Connecting Service > Electric Service Installation Rules > (Site not responding. Last check: 2007-11-01)
		All service equipment, consisting of circuit breakers or switches and fuses, shall be located at a readily accessible place near the point where the service-entrance conductors enter the building.
		Commercial and industrial service-entrance conductors and equipment shall have a minimum ampacity of 100 amperes and meet the available fault current interrupting requirements.
		The actual service ampacity shall be determined by the installed electrical loads and the requirements of the National Electrical Code.
	www.duquesnelight.com /customerservice/newcustomers/electricserviceinstallationrules/esir27.cfm (210 words)

	PDC_offices
		Evaluating existing cable systems, “ampacity audits,” is becoming more common as utilities find increasing need to improve the power transfer on existing cable systems.
		Since the earth portion of the cable thermal circuit is so important — and so variable — we team with Geotherm, Inc., the world’s foremost firm for soil thermal analysis, to accurately characterize the native soil and the trench backfill.
		An ampacity audit is intended to carefully determine the actual ampacity of an existing cable system.
	www.pdc-cables.com /pdc_m_am.html (517 words)

	Ampacity
		Conductors between motor and controller shall have an ampacity not less than 125 % of the motor full load current based on the 75°C table.
		The ampacities determined are considered the absolute minimum, NEC and NFPA do not have adjustments for 105º C. In reviewing the tables for various lower temperature ranges (if such a table even existed), the overall gain for this may be only several percent.
		When sizing a power cable, the maximum current of either device must be used, and in the case of electronic control device, the design tolerance of current specification must be added in.
	www.motionvillage.com /training/handbook/cabling/ampacity.html (471 words)

	Fundamentals of Electricity (Site not responding. Last check: 2007-11-01)
		Ampacity is a function of the cross-section area (or diameter) of the Wire and its material type.
		Larger diameter Wires have larger cross-section areas and can safely carry more electrical current without "overheating." The maximum Ampacity for different types of Wires is reported in the Electrical Codes used throughout the industry.
		These Tables are based on the size of the Wire and the particular "Insulation type" for the particular Wire.
	www.study-center.com /femp/content/demo/basics/bwa.htm (103 words)

	ampacity tables for wire gauge - Project Management Issues - BBS - BobVila.com
		I said the restriction was for either circuit (1440 va).
		The requirement to rate luminaires as demand loads is elsewhere as is the requirements for wire gauges used in circuits based on ampacity as well as other tables for derating, temperature, etc.
		from my previous post: "cross reference the ampacity tables, etc. for 18 and 16 AWG and the answer becomes clear regards to a combination circuit with luminaires not being allowed to be 20 amps.".
	www.bobvila.com /BBS/ampacity_tables_for_wire_gauge-Project_Management_Issues-1-T21.html (296 words)

	Okonite Ampacity Tables: Triplexed Conductors in Air
		The ampacities are for a single, loaded cable in still air.
		In a group of loaded cables in close proximity in air, exposed or enclosed, follow the correction method shown on the ampacity correction factors page.
		For ambient temperatures other than indicated, also use correction factors shown on the ampacity correction factors page.
	www.okonite.com /engineering/triplexed-conductor-air.html (98 words)

	Ampacity Chart for Copper Bus Bar
		Knowing required ampacity, determine possible busbar dimensions from the table.
		Example: Assume that required ampacity is 185 amps at 30 °C rise.
		This is confirmed by Table 1 which lists the ampacity of 1/6 x 1 in.
	www.stormcopper.com /design/Ampacity-Quick-Chart.htm (92 words)

	KEMA - Ampacity of underground power cables
		The current loading is improved by load monitoring and use of measurement of actual temperature of the cable sheath, by hot spot investigation and by improvement of the thermal soil properties.
		Additionally, the emission of magnetic fields at the soil surface may influence the ampacity of underground power cables, but since reductions in magnetic field strength result in a reduction in circuit ampacity, a balanced approach must be applied.
		Determination of the actual thermal resistivity of the soil is very important since the thermal characteristics of the surrounding soil and the laying depth of the cable circuit can alter the circuit ampacity by more than 50%.
	www.kema.com /high_and_medium_voltage/high_and_medium_voltage_components/cable_technology/Ampacity (487 words)

	Conductor ampacity - Chapter 12: THE PHYSICS OF CONDUCTORS AND INSULATORS - Volume I - DC (Site not responding. Last check: 2007-11-01)
		Though the melting point of copper theoretically imposes a limit on wire ampacity, the materials commonly employed for insulating conductors melt at temperatures far below the melting point copper, and so practical ampacity ratings are based on the thermal limits of the insulation.
		These ampacity ratings are given for copper conductors in "free air" (maximum typical air circulation), as opposed to wires placed in conduit or wire trays.
		Skinny wires have a lower allowable current ("ampacity") than fat wires, due to their greater resistance per unit length, and consequently greater heat generation per unit current.
	www.allaboutcircuits.com /vol_1/chpt_12/3.html (843 words)

	When Can I Use 90°C Conductor Ampacity for Feeders?
		This means that conductor ampacity, when required to be adjusted, is based on the conductor insulation temperature rating in accordance with Table 310.16.
		For example, the ampacity of each 12 THHN is 30A, based on the values listed in the 90°*C column of Table 310.16.
		However, an 8 THHN insulated conductor has a 90°C ampacity* of 50A, but 8 AWG cannot be used for this circuit because the conductor's operating temperature at full load ampacity (50A) will be near 90°C, which is well in excess of the 60°C terminal rating.
	www.mikeholt.com /mojonewsarchive/NEC-HTML/HTML/When-Can-I-Use-90-Degree-C-Conductor-Ampacity-for-Feeders~20040914.php (712 words)

	Buss Bar Ampacities - Ampacity Tables
		The Buss Bar ampacity tables presented here are for rectangular Buss Bars of Copper Alloy 11000 whose surface condition is similar to that of busses at typical installations.
		Ampacities of Copper Alloy 11000 Buss Bars - Ampacities in this table are for buss bars having an emissivity of 0.4.
		This was observed on samples exposed for 60 days in an industrial environment, and it is probably identical to that of buss bars in service.
	www.stormcopper.com /design/Buss-Bar-Ampacities.htm (232 words)

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