Originally Posted by jliltd
The GDL 82 STC installation instructions for certified aircraft state that they must both be connected to the same circuit breaker, with their own individual ring terminals. I think the FAA wants to make sure one is never on without the other. And I think the individual ring terminal mandate is for reliability of some sort. I am aware of some experimental installations who use the switched power output of the transponder to power the GDL 82. Seems to work fine.
Ok so let's suppose I want to connect both to the same breaker.
I have a GTX 327 Transponder
I am an electronics neophyte so I need some assistance:
The circuit diagram for the GTX 327 shows a 3 amp breaker.
The documentation does not specify a current draw but says that the max power is 22 watts. So I calculated the max current this way:
GTX 327 amps = watts/volts = 22.0/14 = 1.57 amps
The documentation for the GDL 82 says it draws 0.45 amps at 14 volts.
To total current draw of the two devices is:
1.57 + 0.45 = 2.02 amps
So one would think I could use a 3 amp breaker for the combined units.
AC43.13 Table 11.3 shows that for 22AWG wire I need a 5 amp breaker.
The GDL 82 circuit diagram says I need a 5 amp breaker
(power line is 22awg I believe)
The GTX 327 circuit diagram says I need only a 3 amp breaker.
So I'm thinking I need to use a 5 amp breaker for the combined units. It's way over the 120% max current draw requirements in the documentation. I'm concerned that a problem would draw much more current than necessary before the breaker trips
Is the 5 amp breaker the correct breaker size to use for the combined units?