Wire length/size question

[er9]

im preparing to upgrade my LED lights and am starting with starboard side. going to have 13 fixtures that will draw approximately 35 watts (3ish AMPS) total if all were on at the same time.

my wire run from distribution panel to last light in v-berth will be somewhere around 40-50' one way if you factor in all the twists and turns.

when im considering wire size do i need to double that wire length number for round trip estimation? if so that would put me at 14 gauge wire for the run behind a 15 amp circuit breaker.

seems like heavy wire for an LED circuit so just want to double check my math.

[sailorboy1]

you need to use the round trip length

You don't have to use a 15amp circuit breaker just because the wire can handle that current. Nothing says that you can't use a 5amp breaker on a 15amp rated wire. But you might want to tap into the run someday and use the 15amp breaker

[TreblePlink]

Yes, if you're designing for a certain voltage drop (wire resistance) you should include up and back wire length.

#14 should be safe with a 15 amp breaker.

Another thing to consider is that a small % of your load will be fed through the entire wire length.

Folks get into trouble when although the feeder wire gauge is fine, LED small-gauge wires or the internal circuits short, and they can't handle 14 amps without emitting smoke ...

[er9]

Originally Posted by TreblePlink

Yes, if you're designing for a certain voltage drop (wire resistance) you should include up and back wire length.

#14 should be safe with a 15 amp breaker.

Another thing to consider is that a small % of your load will be fed through the entire wire length.

Folks get into trouble when although the feeder wire gauge is fine, LED small-gauge wires or the internal circuits short, and they can't handle 14 amps without emitting smoke ...

it sounds like your recomending a smaller size circuit breaker? im considering a 5amp breaker since the max load will be so light.

[TreblePlink]

Originally Posted by er9

it sounds like your recomending a smaller size circuit breaker? im considering a 5amp breaker since the max load will be so light.

From what you describe, a 5 amp would provide a better margin of safety. If you get random trips without any reason, increment up to the next size.

[Suijin]

Breakers are relatively inexpensive but on some panels you have to remove the whole connecting bar to change a breaker which can be a bit of a pain. You could probably get away with putting a 5 amp fuse in which might be easier.

[er9]

Originally Posted by Suijin

Breakers are relatively inexpensive but on some panels you have to remove the whole connecting bar to change a breaker which can be a bit of a pain. You could probably get away with putting a 5 amp fuse in which might be easier.

ok good to know i will check tonight.

[smac999]

The last light is that far away. But must current is not going that far. Only the last light. Would be tricky to actually calculate. You probably woukdn't always have all lights on at once.

That said I never use smaller then 14awg. That is certainly not big wire. That is normal wire. 16 is the smallest you're allowed to use on a boat. Which is only one size smaller.


And FYI. 3a at 95' comes up as 16awg on blue sea app.

[er9]

Originally Posted by smac999

The last light is that far away. But must current is not going that far. Only the last light. Would be tricky to actually calculate. You probably woukdn't always have all lights on at once.

That said I never use smaller then 14awg. That is certainly not big wire. That is normal wire. 16 is the smallest you're allowed to use on a boat. Which is only one size smaller.


And FYI. 3a at 95' comes up as 16awg on blue sea app.

thanks...i decided to go with the 14. i erred on the side of caution and estimated 5amp max draw. west marine had a 50% off sale this week so i ordered 200' of red and 200' of black for $80.