Dear All again. Trust you have had a good xmas and are looking forwards
to 2013.
Mr father in law and I have been trying to figure out what fried my
Narco com earth terminals. Think we found the cause but have some
questions for any avionics knowledgeables out there.
The most likely current path was battery +ve to external charging point
connection (no fuse in that wire) and across to the aerial earth (quite
possible that a metal aerial interconnector could have touched the
charging point +ve terminal as they are in close proximity). The aerial
earth is in connection with the radio case and radio/transponder tray.
The radio/transponder tray is not earthed so the current returned to the
battery via the radio earth terminal - which fried.
I will be looking closely at the siting of wires and insulation to try
and ensure no contacts can occur - but should be ensuring that such
contact will not do any damage.
You won't be surprised to see that the questions are about earths and fuses;
1. Should the metal radio/transponder tray be connected to earth?
2. I cannot find a fuse protecting the main bus bar. The master switch
works through a solenoid which connects battery direct to main bus bar.
Is it advisable to have a panel mounted 25amp circuit breaker between
battery and main bus bar? If it tripped I could then turn off selected
circuits and reset this 25amp circuit breaker and attempt to diagnose
the fault.
3. What fuse amperage would suit the requirements of an external battery
charging point? Is it best connected directly to the battery +ve terminal?
Hope the weather where you are is better than it is where I am
William Bliss
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