I have been asked to do this MOD? 3

[SteveOOO]

I have been asked to do this MOD, I am not 100% certain this is a good idea.

Here is my mail registering my concern:

For me it is not possible to do what you have proposed by shunting 2 individual current sources together. As you have 2 different 5 amp current sources which is IT= I1 + I2 (Kirchhoff’s first law states for any junction in an electrical circuit, the sum of currents flowing into that junction is equal to the sum of currents flowing out of that junction) which therefore equals 10 amps and the wires are only 22 AWG not rated to safely carry 10 amps under fault conditions.

Cheers

Steve


Here is the reply i received, and the answer has totally confused me!

Steve,
The failure mode of a diode is shortcut (non rev. blocking) or open circuit. In the case of the Annunciations are powered by BUS1 OR BUS2 thru 2 diodes, there is no effect following diode failures (single or combined) and wire are always protected by CBs.

I know that this kind of design is not common, you are right in this way but there is not technical and no safety issue.

Have a nice week-end

Xavier

Any constructive criticism either way welcomed

 

[itsmoked]

His answer does not address your valid concern.
Protect the 22AWG with an appropriate fuse or breaker as shown:

Keith Cress
kcress -

http://www.flaminsystems.com

 

[zeusfaber]

Agree with IRStuff. Classic example of focussing on the first failure location and mode that comes to mind and failing to recognise that there might be others.

A.

 

[Sparweb]

This is a double-post (also posted with responses in Aircraft Eng forum), but the concern you express, Steve, is warranted and collecting information about this quickly is understandable.

More, and more detailed responses already provided on the other thread.

http://www.sparweb.ca