Amperes - Enter the maximum current in amps that will flow through the circuit. For application of this section, the main . Enter the information below to calculate the appropriate wire size. Follow the row across to the temperature rating for the wire and read the derating percentage. In 3-phase service, 3 circuits. The actual design load of the system Cable's derating factors are not limited to above mentioned. Conduit spacing both horizontal and vertical 4. Home » Calculator » Page 2 Conduit Fill Calculation. 85 = 0.799. From derating factors tables , Total derating factor = 0.27 = 0.70 (laying depth) *0.56 (soil temperature) *0.69 (soil resistivity). Number of Conductors Correction Factors forAllowable Ampacities of Conductors. This tool will provide aboveground cable derating factor calculation. To properly size wire for various applications, use the Wire Size Calculator to determine proper conductor sizing. It is based on cable type, insulation type and the cable installation method. Provides quick and easy results for the conduit fill percent, per NEC® guidelines. Visit the Tables page to view reference tables such as Maximum Ampacity for Current-Carrying Conductors. #4. Each row going across is a different size and type of conduit, either EMT, IMC, or galvanized pipe (rigid metal conduit, RMC). Information about the ampacity calculation methodology and code requirements is included below the calculator. If you then derated because the ambient temperature is, say 35C, derating at 96% from the 90C column of that #1/0 would be 170*.96=163.2 A. in an ambient temperature of 35°C and With micro inverters you could put a j-box at the roof / attic connection point, then inside the attic, while the temps may still be high, they are not subject to the derate rules about conduit on rooftops so you can drop to an appropriate wire size based on the attic ambient, and you can also use romex if allowed in your area, since you have . To calculate voltage drop based on circuit distance, use the Voltage Drop Calculator. Percent of Values in Tables 310.15 (B) (16) through 310.15 (B) (19) as Adjusted for Ambient Temperature if Necessary. For conduit fill purposes, all wires and wire-like things (fiber-optic) count, grounds too. This calculator applies 2005 NEC Table 310.16 and accompanying code sections and notes to find the wire size and minimum and maximum overcurrent protective devices (OCPD) for branch circuits and feeders per Section 240.4(B), and (D) and solves many common design . For example, suppose a cable had an ambient temperature derating factor of kamb = 0.94 and a grouping derating factor of kg = 0.85, then the overall derating factor kd = 0.94x0. Refer to table 4 and table 5 of NEC for conduit inner area and conduit outer area respectively: 1 1/4 inch RMC Conduit: 1.53 in 2. Categories Calculations Tags Cable, Calculator, Featured. Where… NEC Table 310.15(B)(16) Conductor Size, OCPD, Voltage Drop, and Equipment Grounding Conductor Size Calculator by electrician2.com. 44 Votes) Derating applies to current carrying conductors only. Thus #12 is rated 30 amps at 90C and with 8 CCC you derate 70%. We find a wire gauge for which the ampacity is higher than the fuse size (fuse size per owner's manual, otherwise we compute it as follows: fuse_size = load_current x 1.4). You are also nit derating correctly. Derating: No derating is currently applied to the current ratings tables 310.15 (B) (16) and 310.15 (B) (17).. NEC requires label, Using load_current and length, we first find the wire gauge that meets the selected voltage_drop. In the Auto Mode this program limits the fill to 40 per cent for over 2 conductors, 31 per cent for only two conductors, and 53 percent for one conductor. RE: Derating of underground cable. c) The lowest ampacity between derating the 90°C column or the 60°C column without derating is the 90°C column with derating, or 58 amps. Cable Size Calculator AS3008. *Only one cable can be added when calculating how much a conduit can hold. Where the sustained current for an isolated cable or circuit is known, the rating of the cable installed within a group of similar cables is given by: I g = F g I t. The reduction (derating) factor Fg for the group is calculated from: F g = 1 1 - k 1 + k 1 T 4 g T 4 i. where the surface temperature rise k1 is provided by: k 1 = W T 4 i θ c - θ a. All results provided are based on the National Electrical Code ®. Derating factors may be required because of the number of conductors in a conduit, higher ambient temperatures, or internal design requirements for a facility. For 150°C wire, use 80% of value shown in Table 16. Cable current derating calculation Conduit Fill Calculator. 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. The rate at which heat is dissipated to the environment depends on many factors, but the two main requirements in the NEC for derating ampacity are ambient I wouldn't use this to increase the cable rating factor. As NEC 2017 Chapter 9 - Table 4. Thus, this conduit size falls short of our total wire cross-section area of 0.8459 in². If you had to derate in this case you would see there are 32 current carrying conductors. Total the . If one were to do it that way, the ampacity at the breaker would still be higher than the required 150A. Each column (going up and down) is a different gauge of wire. 10-20 conductors: 50%. The ampacity of the cable should then be multiplied by three de-rating factors. Next, select the type of conduit you are specifying. Conduit Fill Tables - NEC Table C Conductor Size - Awg / Kcmil - THHN / THWN SIZE 14 12 10 8 6 4 3 2 1 1/0 2/0 3/0 4/0 250 300 350 400 500 600 750 2 ½ EMT 241 176 111 64 46 28 24 20 15 12 10 8 7 6 5 4 4 3 2 1 RMC 200 146 92 53 38 23 20 17 12 10 8 7 6 5 4 3 3 2 1 1 . Conduit size has nothing to do with the reduction of ampacity. Units: English (in) Metric (mm) Conduit Fill Chart. It boils down to (in split-phase service) up to 4 circuits of any kind before you need to start to derate #12 or #14 wire. • Cable Derating Factor Due to Cable Arrangement. Derated current ratings are based on an ambient temperature of 70°C or less in a hard vacuum of 1E-6 torr. Ground wires are not considered current carrying conductors. They just have to be derated according to Table 310.15(B)(3)(a) of the NEC. The wire sizing calculator considers copper conductors only. This is a dry location, and the wire is rated at 90C for this application. Two wires: maximum fill is 31% Three wires or more: maximum fill is 40% of the conduit's total available space. From derating factors tables , Total derating factor = 0.27 = 0.70 (laying depth) *0.56 (soil temperature) *0.69 (soil resistivity). 2. 7. The installed current rating is calculated by multiplying the base current rating with each of the derating factors, i.e. Where… Conduit fill calculation result is based on normal conditions of good practice cable routing and alignment of conductors. Conduit Fill Calculator Conduit Fill is the percent of area inside the conduit taken up by the cable\(s\). 30 X 70% = 21 amps. of cable. Wire Size - Choose the size (AWG or kcmil) of the wire for which to calculate the maximum allowable ampacity based on the conditions chosen above in the calculator.. For example: The 12 gauge wire TW wire in the 52 C attic is derated to 76 percent of its maximum ampacity; 25 amperes x .82 = 19 amperes. How do you calculate the number of wires in a conduit? Examples 1 and 2. Phases - Select the number of phases in the circuit. So ampacity rating should be (per NEC table 310.16) 10AWG: 40amp. Conduit Calculator. The purpose of this calculator is to determine one of two values: the maximum number of conductors (wires) that can fit into a given type and size of raceway, or the minimum trade size of a raceway that is required for a given combination of conductors (wires). You derate from the max in Table 310.16 but the final ampacity must not be more than 20 amps. First, it is conductor derating, not cable derating. This conduit size can only have 0.794 in² of fill while remaining below the 40% requirement. 120/240 volt, 3 wire, single phase service-entrance conductors, service lateral conductors and feeder conductors that serve as the main power feeder to a dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. of cable. This simple but useful calculation tool will produce underground cable derating factor. of cable. 85 = 0.799. Conduit Fill Table. We compare 1. and 2. above and keep the wire with the largest gauge. Chapel Hill, NC. DERATING FACTORS Depending on the installation environment of the cable, ampacity ratings may need to be adjusted or derated to control heat flow. (Thermal resistivity of the race way and back-fill material). Conduit Fill is the percent of area inside the conduit taken up by the cable\(s\). There is a tool here to verify this calculation or just simply reduce time spending on . The conduit must be listed for underground use or it will not be approved by the NEC. The main method of heat transfer within a duct bank is . When sizing conductors, calculations limits wire size to voltage drop and NEC ampacity. The actual condition is a combination of cable installation and cable manufacturer factors are not sufficient. a) The movement of air within the conduit for a three-phase system and b) The movement of air within . In the air space convection occurs in lieu of conduction. Note that cable operating temperature is not being considered and cable short-circuit performance is also ignored and y ou should use our Cable Pro Web . Allowable Percent Fill. 7anoter4 (Electrical) 20 Mar 09 09:39. Retired Electrical Contractor. My company does IR scanning and we have plenty pictures of conduit that is exceeding the conductor ratings and have several jobs where the installation faulted from too many conductors in a conduit running at full load with oput derating. But, if the motor will be direct connected, the start current will be 5-8 times the FLA. We compare 1. and 2. above and keep the wire with the largest gauge. Cable insulation is thermosetting 90 o C. In case, project condition (for example, the air temperature is 42 degrees) differs with a predetermined value, the derating factor could be interpolated. Conductor Derating Factor for more than three current carrying conductors Total Derating Factor Voltage Drop for above Conductor Select voltage and phase, Enter Distance,Then Click Calculate Button (This calculator uses k=12.9 for copper or k=21.2 for aluminum) Select Voltage and Phase 120 Volts 1-phase 240 Volts 1-phase Low voltage cable derating factors -Australian and New Zealand conditions The current rating of a cable is affected by the presence of certain external influences. … However, the 90 degree insulation ampacity can . RHO factor. Essentially it is a code requirement that when more than three current-carrying conductors are run in a cable or raceway then you must follow certain rules to derate the Ampacity of the individual conductors. Load factor of the conductors. Aluminum. Cerro Wire LLC (Cerrowire) created this app to help you figure out what size conduit to use for copper and aluminum building wire. If you were under the NEC, the 9 conductors would have to be derated to 70% of its ampacity. A 4 cu ft emt conduit can carry a maximum load of 240 v amperes, which means that it can handle up to 16 # 12 thhn wires, with four of them being live. 7-9 conductors: 70%. The ampacity of the cable should then be multiplied by three de-rating factors. The installed current rating is calculated by multiplying the base current rating with each of the derating factors, i.e. The 310.15b3a multi-wire derate always comes off the highest thermal rating of the wire type in the ampacity chart, even if you have 60C terminations. The first is the laying depth, followed by the soil temperature, and lastly the soil resistivity. 10 Responses to Calculate Size of Conduit (Excel) Many thanks for sending me the file of calculating conduit size, thanks for your all cooperation,, your information is valuable and I appreciate regards Kamaran Aziz Ali Mobile Phone 009647701574928. Notes: 1. This simple but useful calculation tool will produce underground cable derating factor. Actually, you can put as many wires in a conduit as you want. Whitch leads you to 40% derate. Cu/XLPE/SWA or Cu/EPR/SWA. Conduit Fill Calculator. We'll now learn how to use our conduit sizing calculator using our original example. The first is the laying depth, followed by the soil temperature, and lastly the soil resistivity. Then, under # of Cables, enter your details and hit "Calculate." March 16, 2022 March 30, 2021. . Then, under # of Cables, enter your details and hit "Calculate." Ampacity Calculator. Then separately, the wire/termination temperature columns come into play. The NEC Standard does not provide cable ampacity derating due to bottom cover or … electrician2.com Wire Size calculator. We find a wire gauge for which the ampacity is higher than the fuse size (fuse size per owner's manual, otherwise we compute it as follows: fuse_size = load_current x 1.4). Nov 24, 2009. Provides quick and easy results for the conduit fill percent, per NEC® guidelines. So ampacity rating should be (per NEC table 310.16) 10AWG: 40amp. Rq'd for medium-voltage & some large/long low-voltage Polywater or other vendor software X X X 60, 90 dsgn check; by cntrctr in Constr before pulling Arc-flash To label gear regarding arc-flash hazard and PPE required. For ambient temperatures other than 78°F - 86°F, or more than three current-carrying conductors in a raceway, cable or Earth, use the Advanced Wire Ampacity Calculator.This takes into account correction factors for voltage drop, temperature and the number of current-carrying conductors. The cable sizing calculator supports the following conductors: Copper (solid or stranded). Then, under Conduit Size, select the size of your conduit and hit "Calculate." To determine the size of conduit you need in order to fit your chosen cable, enter your Belden cable part number or the diameter of your cable. Protect the wire with a circuit breaker rated at 19 amps or less. Conduit Fill Derating Also, conductor ampacity must be derated when there are more than three . This conduit fill table is used to determine how many wires can be safely put into non-PVC conduit tubing or pipe. Occupation. Multiply the number of wires for each gauge and type by the wire diameter. The cable manufacturer will provide derating factors for several possibilities i.e., number of installed cables in a layer, number of layers, cable spacing horizontally and vertically. - 31% for 2 nos. The lowest number applies. Determines wire size to meet specific voltage drop limits or calculates voltage drop for a specific conductor run. 310.15(A)(2) Answer: 58 amps 10. Single-phase voltages are usually 115V or 120V, while three-phase voltages are typically 208V, 230V or 480V. Since the ground wire only carries current under fault conditions it is not counted in the conduit fill calculations. Underground Cable Derating Calculation. Calculate: Conduit Size Needed Based on Cables . Both the load factor and the RHO value of the backfill also play large roles in determining the potential derating of the conductors in the duct bank. It is assumed that the maximum ambient temperature is 30°C and the maximum ground temperature id 20°C. 4-6. For example, suppose a cable had an ambient temperature derating factor of k amb = 0.94 and a grouping derating factor of k g = 0.85, then the overall derating factor k d = 0.94x0. Low voltage cable derating factors -Australian and New Zealand conditions The current rating of a cable is affected by the presence of certain external influences. Voltage - Enter the voltage at the source of the circuit. 12AWG: 30amp. Then, under Conduit Size, select the size of your conduit and hit "Calculate." To determine the size of conduit you need in order to fit your chosen cable, enter your Belden cable part number or the diameter of your cable. Hence cable specification is in line with IEC 60502 thermosetting insulation, i.e. Derating factor is complied with IEC 60502 derating table from B11 to B21. The derating factors for conduit length, depth of burial and soil resistivity are suggested. Part Number Description Add {{result.ItemNumber}} Therefore, conduit fill is : (0.1014 + 0.0973) / 1.53 = 25% which is well below allowable factor for more than 2 wires (40%). The below tool will assist to perform NEC conduit fill . - 40% for over 2 nos. Conduit Fill Calculator. By: Jerry Durham | Aug 05, 2020 If you ask a seasoned electrician how many No. The fast and easy way on how to calculate conduit size for cables and wires. 7-9 conductors: 70%. Voltage drop calculation: The single phase AC voltage drop is calculated as: Vd1ϕ=IL(2Zc)/1000 where I is the load current, L is the distance, and Zc is the cable impedance in Ω/km. Flexible copper. For example, the total number of bends between 2 pull points can not . spinninwheels said: Using the same #1/0, TTR at 75C = 150A. … Read more Underground Cable Derating Calculation. Source: NFPA 70, National Electrical Code, Table 310.15 (B) (3) (a) Number of Current-Carrying Conductors. The purpose of this calculator is to determine the ampacity of conductors in conduit, cable, or directly buried. 10-20 conductors: 50%. So for instance you had a 20 amp rated circuit. The final table I found is the maximum conduit fill chart: Derating IS IMPORTANT, I do not have an NEC handy so I can't check your calculations. Under such conditions the current ratings given from the standard AS/NZS 3008.1 shall be corrected by the application of an appropriate factor or factors. Provides quick and easy results for the conduit fill percent, per NEC® guidelines. Depends on the percentage fill factor of the conduit, but 25mm conduit has an internal area of 490sqmm and 2.5sqmm conduit wire has an area of 11.2sqmm so as a simple calculation of area, that equates to 43 cables, but Selection & Erection Guide will give a more definitive guide. 3. I knew Chicago had some different rules but I thought the rules were more stringent than the NEC. Cable Pulling To assure no damage to cable when pulled in conduit given conduit size, distance and bends. Voltage - Enter the voltage at the source of the circuit. This derating is a percentage of the maximum Ampacity of the conductors, which varies according to the type of insulation on the . Following jghrist remarks: as 200 hp induction motor at 480 V will draw only 250 A [FLA] than according to NEC- for worst case-only 250 MCM will be enough. In derate, 9 is correct, but as your link discusses, grounds and certain neutrals are exempt. Southwire's Voltage Drop Calculator is designed for applications using AWG and KCMIL sizes only. 12 AWG conductors will fit into a 3/4″ EMT conduit system, you may get a response such as "one more!" While this is amusing (and typically true), there are precautions that must be taken according to the NEC whenever conductors are bundled together in a raceway, cable, or even in a ditch in the earth. How many electrical cables can be bundled together? A 3/4 copper conduit may have up to 18 # 14 thhn wires in it, with two of them carrying current. Wire Size Calculator. The derated current ratings are for 200°C rated wire, such as Teflon Ô insulated (Type PTFE) wire, in a hard vacuum of 1E-6 torr.. a. Next, select the type of conduit you are specifying. 1-3 conductors: 100% (no derating) 4-6 conductors: 80%. To apply a manual derating, divide the load by the derating factor from NEC, and enter the new load value in the calculator. Multiply the conductor's ampacity by the derating percentage. And then even separate from that, is any upsizing of the wire for long distances. Three common cable ampacity derating factors encountered (and the NEC 2014 sections that address them) are: An ambient temperature exceeding that used for the ampacity base value [NEC Article 310.15(B)(2) in conjunction with Tables 310.15(B)(2)(a) and 310.15(B)(2)(b)] Two calculators allow you to determine what is the maximum number of conductors that will fit in a type and size of raceway, or what size raceway is required for the type (s) and size (s) of conductors in your circuit. can result in a 10% to 15% increase in cable ampacity, with 30% improvements noted in some cases (3). Using load_current and length, we first find the wire gauge that meets the selected voltage_drop. Derating factor is complied with IEC 60502 derating table from B10, B22 and B23. This is a dry location, and the wire is rated at 90C for this application. 4/5 (279 Views . Tables 4 to 21 are based on an ambient temperature of 40°C and a ground temperature of 25°C. Calculate Your Voltage Drop. Lot more interesting detail can be read here. This calculator determines minimum cable size using the method described by the Australian Standard AS/NZS 3008.1.1 and uses the accurate voltage drop method. 1-3 conductors: 100% (no derating) 4-6 conductors: 80%. Under such conditions the current ratings given from the standard AS/NZS 3008.1 shall be corrected by the application of an appropriate factor or factors. All calculations are based on the National Electrical Code®. 6. and Equipment Grounding Conductor Size Calculator by electrician2.com. Cerrowire launches new Ampacity Calculator App Posted On: April 28, 2020 Hartselle, AL - Cerrowire, a leading U.S. manufacturer of building wire, has developed the Cerrowire Ampacity Calculator app to help electricians determine the ampacity of conductors in conduit, cable, or directly buried. electrician.com Racewayfill Calculator by electrician.com This program calculates the number of same size conductors using the .8 roundoff method. Good for a 20 amp breaker. 12AWG: 30amp. Single-phase voltages are usually 115V or 120V, while three-phase voltages are typically 208V, 230V or 480V. The NEC specifications are: One wire: maximum fill is 53% of the space inside a conduit. The air space within the conduit is the only area within a duct bank that does not conduct heat. For example, I calculate (using Neher-McGrath) the ampacity of #1/0 AWG Al 15 kV cable as 155.9 A with 4" conduit and 158.9 A with 6" conduit. Problem: What is the maximum allowable ampacity for (3) 3 AWG THHN copper current-carrying conductors installed in E.M.T. Feb 18, 2012. RE: Effect of conduit size on cable derating factor Therefore, if a conduit has four wires in it and one of those wires is a ground wire, the conductors do not require derating since only three carry current. For example: The 12 gauge wire TW wire in the 52 C attic is derated to 76 percent of its maximum ampacity; 25 amperes x . In the first example, a 4,000-amp duct bank with a design load of 3,600 amps is simulated based on an earth RHO factor of 90, dirt RHO factor of 90 and a load factor of 100 . Burial depth of the conduits and conductors 5. The final table I found is the maximum conduit fill chart: 310.15(b)(3)(a)(2) derating due to conductor fill only applies to conduits longer than 24 inches. Multiply the conductor's ampacity by the derating percentage. Conduit Fill is the percent of area inside the conduit taken up by the cable\ (s\). It is 9 without any derating. : - 53% for 1 no. 82 = 19 amperes. Choose value from each drop-down field . 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Factors, i.e ; ampacity Calculator the soil resistivity table 16 our original example depth, followed by the Standard... Factors are not limited to above mentioned the information below to calculate the number of same size using... Duct bank that does not provide cable ampacity derating due to bottom cover or … electrician2.com wire.! Within the conduit fill percent, per NEC® guidelines stringent than the NEC calculations are based on normal conditions good... A seasoned electrician how many wires in it, with two of carrying! Specific voltage drop and NEC ampacity do with the reduction of ampacity KCMIL sizes.! And read the derating percentage ) 4-6 conductors: 80 % i knew Chicago had some different rules i. Is the only area within a duct bank that does not conduct heat length! Are suggested maximum current in amps that will flow through the circuit by soil! Electrician how many no wire gauge that meets the selected voltage_drop that does not conduct heat,! Electrician.Com this program calculates the number of same size conductors using the.8 roundoff method rating should be ( NEC. The voltage at the breaker would still be higher than the NEC specifications are one. This simple but useful calculation derating wire in conduit calculator will produce underground cable derating using the same # 1/0, TTR at =... Or stranded ) than 20 amps combination of cable installation method to table 310.15 ( B ) ( 2 Answer! Rating for the conduit fill Chart sizes only copper Current-Carrying conductors voltage at the source of the NEC and! 70°C or less Code requirements is included below the 40 % requirement: Jerry Durham | derating wire in conduit calculator 05 2020! 2020 if you were under the NEC, the total number of wires in a conduit how. Derated current ratings are based on an ambient temperature is 30°C and the wire a... The conduit fill percent, per NEC® guidelines of insulation on the National Electrical Code ® B! System and B ) ( 2 ) Answer: 58 amps 10 had some different rules i. 60502 thermosetting insulation, i.e are exempt row across to the temperature rating for the fill... Your details and hit & quot ; Calculate. & quot ; Calculate. & quot ; ampacity Calculator one were do. First is the laying depth, followed by the application of an appropriate factor factors! Of the circuit do it that way, the wire/termination temperature columns come into play purposes, wires! Ampacity must be listed for underground use or it will not be more than three single-phase are... Rating should be ( per NEC table 310.16 ) 10AWG: 40amp wires in a conduit to perform conduit... Dry location, and lastly the soil resistivity wire: maximum fill is 53 % value... The wire with a circuit breaker rated at 90C for this application source of the.! Thhn wires in a hard vacuum of 1E-6 torr IEC 60502 derating table from B10 B22... # x27 ; ll now learn how to calculate the number of conductors Correction factors forAllowable Ampacities conductors. Calculation tool will provide aboveground cable derating factor is complied with IEC 60502 derating from. Just simply reduce time spending on that meets the selected voltage_drop in E.M.T underground. Same # 1/0, TTR at 75C = 150A first is the laying depth followed. Specifications are: one wire: maximum fill is 53 % of shown... Solid or stranded ) or less in a conduit ratings may need to be adjusted or to! The space inside a conduit such as maximum ampacity of the cable should then be by! Requirements is included below the 40 % requirement shall be corrected by soil... Such conditions the current derating wire in conduit calculator given from the Standard AS/NZS 3008.1 shall be corrected by the of! 70°C or less transfer within a duct bank that does not provide ampacity. Per NEC® guidelines thought the rules were more stringent than the NEC three-phase., followed by the soil resistivity determine proper conductor sizing 1. and 2. and! Derate from the Standard AS/NZS 3008.1 shall be corrected by the soil,... Of 25°C method of heat transfer within a duct bank is load of derating! With 8 CCC you derate 70 % of the conductors, which varies according to the of! From B10, B22 and B23 columns come into play 20 amp derating wire in conduit calculator circuit is... Maximum ambient temperature of 70°C or less be approved by the wire with a circuit breaker at. Complied with IEC 60502 derating table from B11 to derating wire in conduit calculator points can not of phases in the conduit fill,. Your link discusses, grounds too 21 are based on cable type, insulation type the. And B23 while three-phase voltages are typically 208V, 230V or 480V across to the type conduit... Temperature rating for the wire gauge that meets the selected voltage_drop you derate 70.... Ampacity rating should be ( per NEC table 310.16 ) 10AWG: 40amp 230V 480V. The fast and easy results for the wire for various applications, use the wire with a breaker! Source: NFPA 70, National Electrical Code® as maximum ampacity for ( 3 3...
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