Difference between revisions of "Conductor size"
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[[File:Wiresize201127.png|thumb|right|A comparison of standard mm² wire sizes and standard AWG wire sizes. AWG decreases as wire size increases, mm² increases as wire size increases.]] | [[File:Wiresize201127.png|thumb|right|A comparison of standard mm² wire sizes and standard AWG wire sizes. AWG decreases as wire size increases, mm² increases as wire size increases.]] | ||
Wires come in standard sizes depending upon the location. The proper wire size for a particular circuit depends on two important considerations: | Wires come in standard sizes depending upon the location. The proper wire size for a particular circuit depends on two important considerations: | ||
− | #The amount of current that they can safely carry given the conditions in which they will be used. | + | #The amount of current that they can safely carry given the conditions in which they will be used. The conditions of use that must be considered include: the number of wires in the [[Conduit|conduit]], the maximum ambient temperature, and the appropriate overcurrent protectiond device size. |
#The amount of voltage that will be lost under operation, which is called [[Voltage drop|voltage drop]] | #The amount of voltage that will be lost under operation, which is called [[Voltage drop|voltage drop]] | ||
The wires for an off-grid system must will be sized and selected based upon the [[Load evaluation|load evaluation]] and the [[Physical evaluation|physical evaluation]] for a particular site. This process must be done in conjunction with the sizing and selection of the [[:Category:Overcurrent protection and disconnects|overcurrent protection device]] - see [[:Category:Wire and overcurrent protection sizing and selection|Wire and overcurrent protection sizing and selection]] for more information. | The wires for an off-grid system must will be sized and selected based upon the [[Load evaluation|load evaluation]] and the [[Physical evaluation|physical evaluation]] for a particular site. This process must be done in conjunction with the sizing and selection of the [[:Category:Overcurrent protection and disconnects|overcurrent protection device]] - see [[:Category:Wire and overcurrent protection sizing and selection|Wire and overcurrent protection sizing and selection]] for more information. | ||
− | The two most common standards for wire size are American Wire Gauge (AWG) and mm². These two systems are not directly equivalent. The table below shows wire sizes in AWG and mm² with the | + | The two most common standards for wire size are American Wire Gauge (AWG) and mm². These two systems are not directly equivalent. The table below shows wire sizes in AWG and mm² with the ampacity (maximum current) rating of depending upon its temperature rating of the wire in °C. This chart assumes that there are are 1-3 copper conductors in conduit with a 30°C ambient temperature.<ref name="NEC3"> NFPA 70 - National Electrical Code 2020: Table 310.15(B)(16)</ref> These values must be adjusted for the actual conditions of use of the wire. |
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Revision as of 08:25, 1 January 2021
Wires come in standard sizes depending upon the location. The proper wire size for a particular circuit depends on two important considerations:
- The amount of current that they can safely carry given the conditions in which they will be used. The conditions of use that must be considered include: the number of wires in the conduit, the maximum ambient temperature, and the appropriate overcurrent protectiond device size.
- The amount of voltage that will be lost under operation, which is called voltage drop
The wires for an off-grid system must will be sized and selected based upon the load evaluation and the physical evaluation for a particular site. This process must be done in conjunction with the sizing and selection of the overcurrent protection device - see Wire and overcurrent protection sizing and selection for more information.
The two most common standards for wire size are American Wire Gauge (AWG) and mm². These two systems are not directly equivalent. The table below shows wire sizes in AWG and mm² with the ampacity (maximum current) rating of depending upon its temperature rating of the wire in °C. This chart assumes that there are are 1-3 copper conductors in conduit with a 30°C ambient temperature.[1] These values must be adjusted for the actual conditions of use of the wire.
60°C | 75°C | 90°C | |||
---|---|---|---|---|---|
AWG size | Area (mm²) | Metric equivalent (mm²) | Types TW, UF | Types RHW, THHW, THW, THWN, XHHW, USE, ZW | Types TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2 |
14 | 2.08 mm² | 2.5 mm² | 15 A | 20 A | 25 A |
12 | 3.31 mm² | 4 mm² | 20 A | 25 A | 30 A |
10 | 5.26 mm² | 6 mm² | 30 A | 35 A | 40 A |
8 | 8.37 mm² | 10 mm² | 40 A | 50 A | 55 A |
6 | 13.3 mm² | 16 mm² | 55 A | 65 A | 75 A |
4 | 21.2 mm² | 25 mm² | 70 A | 85 A | 95 A |
3 | 26.7 mm² | — | 85 A | 100 A | 110 A |
2 | 33.6 mm² | 35 mm² | 95 A | 115 A | 130 A |
1 | 42.4 mm² | 50 mm² | 110 A | 130 A | 150 A |
1/0 | 53.5 mm² | — | 125 A | 150 A | 170 A |
2/0 | 67.4 mm² | 70 mm² | 145 A | 175 A | 195 A |
3/0 | 85 mm² | 95 mm² | 165 A | 200 A | 225 A |
4/0 | 107 mm² | 120 mm² | 195 A | 230 A | 260 A |
Cable size
Cables are typically designed to contain all of the wires that are needed for a particular circuit. Therefore there are many different configurations of cable that vary based upon the size of the wires, the number of wires, and the color of the wires. Cables will be labeled with the size of the current carrying conductors and the quantity. For example a cable with three 12 AWG wires will be labeled "12/3". A cable with three 2.5mm² will be labeled "2.5mm²/3" or "2.5mm² three core". Equipment grounding conductors (EGCs) are generally excluded from the count of conductors and should be specified separately.
- ↑ NFPA 70 - National Electrical Code 2020: Table 310.15(B)(16)