How to choose the proper circuit breaker

[fgayford]

Hi guys.
Even though my background is in electronics I have never applied it to an aircraft.
I have room for only 6 circuit breakers. Aircraft quality, the kind that pop out when overloaded.
How do I select the proper value?
If I had room in my panel I would need 8, one for each toggle circuit.
So I thought I would put the fuel pump and transfer pump on one breaker and the EIS and GPS on another.
One person suggested that I look at the steady current draw of the device and then go to the next size up of circuit breaker.Does that sound right? But if there is a start up surge that is higher than the steady current draw shouldn't I go up a little higher than one size up?
Thanks
Fred

[blaswichk]

Hi Fred, how much extra (next size) is always an opinion. I spent many years in the old school electronics lab too, and our general rule was to double the breaker for the steady state load. Sometimes we would consider only half again the steady state current. My plane has a slew of switches, and one 20 amp breaker feeding everything, and another 20 amp that is the electric prop protection. Just know that the 503 alternator only can supply only 165 watts, or about 13.2 amps at 12.5 volts dc.

kb

[fgayford]

Hi Kess
Thats good advice. The double size seems a good guess. In some places I have read that the wire size should dictate the breaker size. You want the breaker to go off before the wire melts. It said your not trying to save the equipment you are trying to prevent fires. My plane came with a 15 and a 10 amp breaker for the whole plane.
Thanks Again.
Fred