Wie viele Leiter passen in ein Rohr
Bei mehr als zwei Leitern im Rohr sind nach NEC Chapter 9 höchstens 40 % des Innenquerschnitts belegt. Die Zahlen gelten für Kupferleiter mit Normisolierung.
| Leiter | 1/2" (16 mm) | 3/4" (20 mm) | 1" (25 mm) | 1 1/4" (32 mm) | 1 1/2" (40 mm) | 2" (50 mm) | 2 1/2" (63 mm) | 3" (78 mm) | 4" (103 mm) |
|---|---|---|---|---|---|---|---|---|---|
| 14 AWG (6.3 mm²) | 12 | 21 | 34 | 59 | 81 | 124 | 191 | 282 | 489 |
| 12 AWG (11.7 mm²) | 6 | 11 | 18 | 31 | 43 | 66 | 103 | 152 | 263 |
| 10 AWG (21.2 mm²) | 3 | 6 | 10 | 17 | 24 | 36 | 56 | 83 | 145 |
| 8 AWG (33.6 mm²) | 2 | 4 | 6 | 11 | 15 | 23 | 35 | 52 | 91 |
| 6 AWG (53.2 mm²) | 1 | 2 | 4 | 7 | 9 | 14 | 22 | 33 | 57 |
Welcher Querschnitt für Ihre Last nötig ist, zeigt der Kabelquerschnitt-Rechner; wie viel Spannung dabei verloren geht, die Spannungsfall-Tabelle.
Worked Example: 1/2-Inch Conduit with 14 AWG Conductors
To determine the maximum number of current-carrying conductors that fit in a half-inch rigid metal conduit, you must first identify the internal cross-sectional area of the conduit and the area of a single conductor. According to standard NEC Chapter 9 Table 4, a 1/2-inch EMT or RMC has an internal area of approximately 0.314 square inches. For 14 AWG THHN wire, which is commonly used in residential and commercial branch circuits, Chapter 9 Table 5 provides a single conductor area of 0.0020 square inches. The National Electrical Code mandates a 40 percent fill limit for more than two conductors in a raceway. Therefore, you calculate the allowable fill area by multiplying the total conduit area by 0.40. In this specific case, 0.314 multiplied by 0.40 equals 0.1256 square inches of usable space. Next, divide this allowable area by the area of one 14 AWG conductor. Dividing 0.1256 by 0.0020 yields 62.8. Since you cannot install a fraction of a wire, you round down to the nearest whole number. This calculation confirms that you can safely install 62 conductors of 14 AWG THHN in a half-inch conduit while remaining compliant with the 40 percent fill rule.- Mistake One: Ignoring Insulation Type. Many installers assume all wires have the same thickness. However, THHN wire is thinner than older NM-B or XHHW cables. Using the area for a thicker insulation type when calculating for THHN will result in underutilizing the conduit, while using the wrong table value for THHN when installing thicker wire will lead to dangerous overfilling. Always verify the specific insulation code from Chapter 9 Table 5 before performing any math.
- Mistake Two: Rounding Up Instead of Down. A common arithmetic error occurs when the division result is not a whole number. If your calculation results in 62.8, rounding up to 63 violates the code because it exceeds the 40 percent limit. The NEC requires you to always round down to ensure the physical volume of the conductors does not exceed the permitted percentage. This strict downward rounding prevents overheating and makes future wire pulling feasible without damaging the insulation.
Related calculators
Calculators that go with this one:
- Wire Gauge Chart — AWG wire gauge chart with cross-section in mm² and current-carrying capacity for copper conductors at 60 °C
- Transformer kva calculator — Calculate the required kVA rating of a transformer from load voltage and current, with a loading factor for sa
- Transformer sizing calculator — Find the transformer kVA you need from the connected load in kW and power factor, or from the current and volt
- Voltage drop calculator — Calculate voltage drop in volts and percent for copper or aluminum wire, in AWG/kcmil or mm², for 120 V, 240 V
- Solar panel angle calculator — Find the optimal tilt angle for your solar panels based on latitude and season
- Energy consumption calculator — Estimate the annual energy consumption and electricity cost of any appliance or device