Table E: Temperature Rating of Conductor Insulation

The Law
The Code of Federal Regulations (CFR) 183.425 Conductors

(b) Except for intermittent surges each conductor must not carry a current greater than that specified in Table E for the conductor’s gauge and temperature rating.
(c) For conductors in engine spaces, amperages must be corrected by the appropriate correction factor in note 1 of Table E.

Due to engine heat, the ambient temperature in engine spaces is usually higher than in other spaces of the boat. Wiring in and passing through engine spaces must be able to operate at these higher ambient temperatures.

The ampacity values in Table E are based on an ambient temperature of 86°F (30°C) which is considered reasonable for use on boats except in engine spaces. The correction factors in Note 1 in Table E convert the ampacities to Table E to acceptable values in an ambient temperature of 122°F (50°C). This higher temperature has been selected as satisfactory for engine spaces. Note 1 is supplied to eliminate the need for calculating the corrections to Table E. The values are already corrected.

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Table C: Conductors Sized (AWG) for 10% Voltage Drop

Use 10% voltage drop chart  for any “non-critical” applications: windlass, cabin lights, etc…

10% Voltage Drop at 12 Volts

10% Voltage Drop at 24 Volts

10% Voltage Drop at 32 Volts

ABYC Recommends…
“Conductors used for panelboard or switchboard main feeders, bilge blowers, electronic equipment, navigation lights, and other circuits where voltage drop must be kept to a minimum, shall be sized for a voltage drop not to exceed three percent. Conductors used for lighting, other than navigation lights, and other circuits where voltage drop is not critical, shall be sized for a voltage drop not to exceed 10 percent.” 11.16.1.2.7.