Help with circuit breakers

  I am ready to order my circuit breakers for my panel. I see spruce has two kinds, the Tyco, that you can't pull and the Klixon 7277. The Tycos seem to be a little cheaper. I guess I could go with fuses but I want breakers.What would you all recommend? 

 Next, what amp should I get for these?

Nav

Strobe

Avionics Master

Comm (Val Com 760)

Transponder

Flap Motor

Cigarette Plug

Engine- EIS

Landing Light

Fuel Pump- if I use one.

Spare

Maybe some of these can be ran together off one breaker? 

Any help with this would be greatly appreciated!  Thanks! 

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Permalink Reply by David Josephson on July 2, 2015 at 7:32pm

The breakers are to protect the wiring, so they are sized according to AC 43.13-1B (search for that on the web and you'll get the current version from the FAA.) See Section 4 for choosing wire and breaker size, there is more detail later on in the AC to figure voltage drop, etc. Use a breaker rating at least 1.5x the current draw of the device, and wire size to match.  You don't need an avionics master breaker, and you don't really need an avionics master switch either unless you are concerned about fragile switches in your radios.

I prefer the 7277 type breakers. While you don't want to use them every day as switches, if there is some reason you want to disconnect a circuit you can. I wouldn't piggyback any of the circuits you mention on the same breaker.

Permalink Reply by Steven Ward on July 2, 2015 at 10:48pm

Thank yo David for the help!

Permalink Reply by Kurt Satter on July 4, 2015 at 8:56am

Thanks also.  Yesterday I started researching the same two series of breakers via a local (N. Texas) source.  I too like the 7277's because of the smaller foot-print for my smaller 701 panel. 

Permalink Reply by David Josephson on July 4, 2015 at 1:28pm

Often you can find the 7274 mil-spec version, qualified to MS 26574 (now obsolete, replaced by SAE-AS26574.) The current Klixon (Sensata) 7277 is said to be identical to the mil spec version but for looser test tolerances.  They have been made by several companies and being the MS version gives you some assurance that they're made right. FAA and general wisdom recommend never using breakers as switches to turn loads on and off, however they are rated for 5,000 manual activation cycles and there are plenty of aircraft that use them in the startup sequence. I'd have no reservation about using them wherever they would be actuated once per flight. This comment does not necessarily apply to other circuit breaker/switches that might not have the same test conditions, although there is a mil spec toggle switch/breaker from Airpax that's fine too.

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