Wire size

[Darick]

I added up the current consumption of my radio, transponder, MGL E-1, F-2, lights, etc and the total is less than 3 amps. I'm trying to determine the wire size to supply the main power buss. The plans suggest 8 ga. but that seems really big.

Also, what's the current draw for the secondary ignition? What size fuse is required?

Thanks for any help.

[Bryan Cotton]

Darick,
Here is an excellent article on picking wire size:
http://www.aeroelectric.com/articles/wiresize.pdf

When you come up with 3 amps, is that steady state or when the com radio and transponder is transmitting? I would use the latter not only to ensure sufficient ampacity but to minimize losses. I think 3 amps sounds low. My LED nav lights and landing lights all use about .7A. That is nearly 3A right there. The LED strobes average .2A but they are zero for a long time with a burst of 5A.

[wlarson861]

The plans call for an 8 ga. from the voltage regulator to the main bus, however the attachment is via "fast-on". The largest fast-on will only take a 10 ga. wire which is what I used. The 10 ga. is plenty to handle the 20 amps put out by the alternator. The link Bryan sent was my source as well. also downloaded the "aeroelectric connection" book that I used exclusively to plan my wireing.

Here is the link to the book in pdf: http://www.aeroelectric.com/Book/AEC_R12A.pdf

[jjbardell]

I agree with Bryan and Bill around the book. It was a good read, although I will be the first to admit that electrical was my biggest challenge and I struggled at first. I recommend creating a peak usage excel chart (mine is shown below) if you have not yet done so. Find your total amps to ensure your systems will all be supported at peak and no breakers will pop. And that your total peak is below the 20 alternator output.

For the secondary, I planned on 7 amps with a 10 amp breaker.

[Darick]

Thanks for the tips and suggestions...it has helped me to move on. Sometimes roadblocks pop up and u need to step back, regroup, rethink from a different perspective.

[DCASonex]

Have 10 ga. feeding my master 30 amp breaker with 40 amp in-line fuse on firewall side for short circuit protection. All my lighting, including landing and strobes are LED, and no power hungry instrumentation, so that has been quite adequate.

David A. Sonex TD, Camit 3300 with old style flywheel 17 amp alternator.