BAPI Recommended Wire Lengths for Various Power Loads – Application Note

When an electric current flows through a wire there is a drop in voltage due to the resistance of the wire.  The voltage drop is found from Ohm’s Law: E=IR, or Voltage Drop = Wire Resistance x Amps of Current.

The wire length recommendations below represent a 10% voltage drop in a 24 VAC or VDC circuit for various wire gauges and maximum currents. The voltage drop is linear, therefore cutting the wire length in half would result in a 5% voltage drop rather than a 10% voltage drop. The currents in the two tables represent the various models of power supplies and voltage converters available from BAPI.

Wire length recommendations in Table 1 are based on a wire temperature of 70 ºF.  If the wire is run in a portion of the building where temperatures can increase to 140 ºF, such as an unventilated attic, then decrease the recommended wire length by 5%, as shown in Table 2.

The minimum wire gauge is determined by the maximum worst-case load. When in doubt, use the next larger size wire.  All wiring must comply with the National Electric Code (NEC) and local codes.

Wire Lengths App Note Table 1
Table 1: Recommended wire lengths at 70 ºF and below (10% maximum drop in voltage)
Wire Lengths App Note Table 2
Table 2: Recommended wire lengths above 70 ºF (10% maximum drop in voltage)

If you have any additional questions about wire lengths, please contact your BAPI representative.

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