Jim Weir wrote in message . ..
(Dan Thomas)
shared these priceless pearls of wisdom:


- The 4522 bulb is a 250 watt bulb at 13 volts.

Read the original post. The poster said it was a 4552, not a 4522. The 4552 is
a 250 watt bulb at 28 volts.



That translates into
-19.23 amps. As the charging system comes into play the voltage rises
-to 14 volts, and assuming that the resistance of the bulb doesn't
-change much, the current flow rises to 20.71 amps. The breaker will
-pop after a bit, especially if it's old. It's a Cessna engineering
-screwup.

Hardly. The aircraft would never have been certified with a breaker running
that close to limits.


- We have a 172 with the same system. We had to increase the breaker
-to 25 amps (and go to #10 wire to satisfy AC43.13 requirements for
-current flow) to eliminate nuisance tripping.

Well, ONE of you is wrong. Either the original poster made a typo or you made
an incorrect interpretation. Tell me, though, just for grins, what year and/or
model 172 had this "engineering screwup" so that I can go back through the TCDS
and parts list to see where the screwup really is.

1972 172L. All breakers and bulbs were as per parts manual.

Dan