I'm not convinced of the utility of Circuit Breakers for flight critical systems.  I would put each of my fuel pumps, the EFIs and what have you on dedicated circuits, each protected with a HEAVY fuse.  My objective is not to protect my fuel pump in case of a surge.  It's a flight critical component, so I'm going to allow it to go while it can.  The fuse is waaaay heavier than the pump (or whatever) draws, and is meant to protect the wire going to the mechanism rather than the mechanism itself.  I do not regard fuel pumps as delicate items, so I don't intend to protect them from transient surges and the like.  I will ride it 'till it drops, and the fuse will blow shortly before the wire melts.

Delicate avionics I might very well protect with CBs.  These might need to be protected from transient surges/voltage spikes (from whence I cannot say since I have OV protection on my alternator) and the like.

Heavy duty, robust components like fuel pumps need no such coddling IMO ... Jim S.


WALTER B KERR wrote:

John Slade wrote:

 

My understanding is that the pumps, at least the ones I'm using (or at least WAS using when I used to be able to fly this #@#$ing thing, long ago), are designed to run continuously. I have one Walbro Inline fuel pump-GSL393 (from Tracy) and one Walbro Inline fuel pump-GSL394 from Lightning Motorsports. Both have metal screw in connectors which fit AN adapters. They're fused at 20 amps.

 

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OK, I'll stir the pot some more. I am not an electrical engineer, but I do understand the power of redunancy!

 

I will take two separately fused circuits over 1 circuit breaker every day of the week. If there is a short in my one device or in the power supply lines, I do not wish to be starting a fire by resetting circuit breakers while looking for a glider port. I know there are rotary powered airplanes out there that depend on one circuit breaker for the entire electrical engine power source that have many, many more hours of rotary time than me, but I sleep better have two parallel circuits bringing electrical power to my fused engine buss and then reduntant pumps on entirely separate fused circuits. My pumps are both checked during run up and both on during T/O and landing.

 

Bernie