Originally Posted by mikefossl
I'm thinking that the 18 gauge wire on the float switch would be covered by one of the exceptions (as long as the 'pigtail' is less then 30 inches). In any case, the exceptions do indicate that yes there is a place for 18 gauge wire on a boat
(my instrument panel is full of them)
Excerpted from A
220.127.116.11 Conductors shall be at least 16 AWG.
1. 18 AWG conductors may be used if included with other conductors in a sheath and do not extend more than 30 inches (760mm) outside the sheath.
2. 18 AWG conductors may be used as internal wiring on panelboards.
3. Conductors that are totally inside an equipment
4. Conductors on circuits of less than 50 volts having a current flow of less than one amp in communication systems, electronic navigation equipment
and electronic circuits.
5. Pigtails less than seven inches (178 mm) used as wiring on panelboards.
18.104.22.168 Voltage Drop - 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.
2. If the ampacity as specified in E- 22.214.171.124 exceeds the ampacities in TABLE IX and TABLE X, the conductor size necessary to keep voltage drop below the maximum permitted level may be calculated by means of the following formula:
CM = (K x I x L) ÷ E
CM = Circular mil area of conductor.
K = 10.75 (constant representing the resistivity of copper)
I = Load current in amperes
L = Length of conductor from the positive power source connection to the electrical
device and back to the negative power source connection, measured in feet.
E = Maximum allowable voltage drop at load in volts (e.g., for a three percent voltage drop at nominal 12V, E= 0.03 x 12 = 0.36; for a 10 percent voltage drop at nominal 12V, E = 1.2).
See also ➥ "Ohm's Law & Boats"