Mike Rapoport wrote:

The maximium draw of the avionics (speaker on, transmitting on both coms) is
20A, the continous draw (not transmitting) is under 15A. I realize that the
max for *continous* use is 22A with 12ga, but how much overload is
permissible for short term use (long enough for the avionics CBs to pop.

You should design the system such that the maximum load that continues for more
than a second or two is no more than 80% of the breaker capacity. This is
intended to prevent deterioration of the breaker due to frequent operation at
temperatures close to the trip point.

Design for wire is a different matter, since the heat will not cause the wire to
deteriorate until you get it very hot. The risk with wire is that an overload
will cause a fire by melting the insulation. I don't know how far you can go and
still avoid this, but it should be well above 20 amps. I know that "delayed
action" breakers in home wiring situations allow temporary surges of up to 25%
of the rated capacity.

George Patterson
The desire for safety stands against every great and noble enterprise.