How to determine fuse size.

AVEO led nav and strobe in one unit. Spec sheet says current on nav .35 amps,strobe is .54 amp (2.7 A peak)..Power on nav is4.2 W and strobe is. 6.5 W (32.5 W peak.)...In the 43.13 book says 50 feet 18 awg and thats what i have. My question is what size fuse should I figure for nav light circuit and strobe circuit. Do I add up total length of all 3 wire runs? According to 43.13 I used 18 awg and comes in under 50. The 3 strobes are to flash at same time.

Thanks guys
Ron in Oregon5

Everything you say is correct except for adding up all the lengths to become one. They are all parallel runs so the longest run is all you would need to calculate for, as you will be splitting the circuit and going three ways under the seat pan someplace.

I used a number 18 awg for strength, even thought technically the wire could be smaller.

That being said, the fuse protects the wire. You could fuse the number 18 awg higher, but in this case you shouldn't need more than 5 amps. I would fuse it at that.

my two...

CJ

Thanks Captain John. Understand. 5 amp it is. Much appreciated.

Ron in Oregon RV9A

Power and fuses are usually based upon average power or current. A pulsed load will draw more more during the active pulse interval. If the peak pulse is short enough then a fuse can live through a higher load than its rating. The equipment manufacturers take this into consideration when providing suggested fuse ratings.

I have the same set-up. 1A for the strobes, 3A for the navs. Strobes are intermittent, navs continuous, so using the 43-13 charts as appropriate that's what was called out for my wiring runs. Don't recall the gauge, probably 18.

3 years, no problems. And they're both on all the time.

Ray and Joe thanks. Always a learning process with input like yours. Helps to understand the 4313 book and charts. 1amp crossed my mind as I tried to figure out the peak values in the intermittent current flow.

The Ron in Oregon RV9A