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Abraham

Well Known Member
I have the Aero Electric book. I seem to reference the book depending on what area I need knowledge on. One thing that I did not see in the book so far, is how to determine the size of the circuit breaker required for a certain circuit. Can anyone give some insight on how I could determine what size breaker to use on a specific circuit? Or provide me a reference in his book on where to look.

thanks in advance
 
The basics will be: Determine the total amount of amperage the circuit will feed, then provide for a percentage above that to allow for a margin of safety above whatever that total amperage would be. Simplistic approach that I am sure can be expounded upon by more expert advisors. They may provide more specific details (the devil is always in the details isn't it?).

One caveat in addition to the circuit breaker size is the size of wiring feeding the circuit. Whatever amperage is being drawn by the circuit must have the appropriate size wiring for that load. That is another discussion as equally important.
 
Your reference for wiring and circuit breaker or fuse selection is AC43.13 which is (or should be) a mandatory document for all builders of aircraft.

There are actually only two or three pages that you will use for your wiring selection, but I don't have it with me right now. You can download it, try Google.
 
Most things you install will provide the information needed but, as vlittle said, you can use the generic recommendations too.
 
OP Drawings

If you are building a simple electrical system the Van's OP drawings will give you a place to start for CB and wire sizes. Of course, once you vary from the Van's design you're on your own.
 
John Tierney said:
If you are building a simple electrical system the Van's OP drawings will give you a place to start for CB and wire sizes. Of course, once you vary from the Van's design you're on your own.
Click to expand...

Don't tell anyone but I am not building an RV.....

How can I see the RV drawings for reference.?
 
Important!

The circuit breaker is there to protect your wire from glowing red and starting a fire, not to protect your equipment. The breaker should be sized to match your wire, not your equipment. It is okay to use a big wire, a suitable breaker and not use all of the AMPs it will carry.
Determine the maximum AMPs for a given circuit, use the size wire that will carry that load, + your safety factor and then use a CB that will protect that wire.

http://www.aeroelectric.com/articles/wiresize.pdf
 
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Update:

AC43.13 Change 1
page 11-13 for breaker/fuse sizes.
pages 11-30 and 11-31 for wire size vs load and length selection.

You choose the wire size based on load and length first, then you select the breaker size. It is acceptable to use a smaller breaker, as its only purpose is to protect the wire.

If a load needs a fuse to protect it, it is likely a non-aircraft part (or a Garmin Aera!). In this case, a separate fuse as close to the load as possible is acceptable, as specified by the manufacturer. In general, this is shoddy design and to be avoided as much as possible. All of the avionics widgets that I designed either did not require overcurrent protection or had internal fuses to prevent smoke.
 
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