Curcuit Breaker Question

hammer408 · #1 02-21-2007, 10:46 AM

I'm ready to start wiring my 9A and I see there are several types of Circuit Breakers on the market: push-pull, toggle/breaker combination( which seems to save a lot of space); regular(pop-up)........and they all vary in costs.

Does anyone have any recommendations or experiences as to what type is better?

Henry
N918HB reserved
Pittsburgh, Pa.

fmarino1976 · #2 02-21-2007, 11:08 AM

I work on completions on Bell Helicopters. We use the push-pull type for almost everything. I recommend the Klixon ones. The klixon toggle type are also very reliable, you could use this type as a switch for the equipment without any trouble. Potter & Brumfield makes some toggle breakers that are ok. They are not as good as the klixon ones but they are cheaper.

fmarino1976 · #3 02-21-2007, 11:10 AM

I wouldn't use the pull-push type breakers to turn things on and off on a regulat basis as that will wear them out prematurely.

jcoloccia · #4 02-21-2007, 11:31 AM

Doesn't matter as long as you have a quality breaker (i.e. P&B or Klixon).

I haven't noticed in practice that the push-pull Klixon's wear out any more than a "switch" style when used as a switch. Statistically it might but for the few that we use it probably doesn't matter. It's not uncommon practice, by the way, to use Klixon's as switches in military applications.

The only thing that's a pain with switch/breakers is making a second bus on the pilot's side of the plane.

I'll also mention that there's no law that says all the breakers have to be the same, or that you can't mix and match breakers with fuses. So if you wanted to, you could do something like:

Small fuse block and switches for things like lights, strobes etc. The available switch configurations allows you to do some pretty slick switching here.

Regular breakers for things like avionics.

Push/Pull breakers for things like alernator field, flap and trim motor etc. Stuff that should never go off but that you may want the option of yanking off if it runs away.

So you can optimize for whatever functionality/complexity/weight/$$$ you want to drive to

alpinelakespilot2000 · #5 02-21-2007, 12:02 PM

Quote:

Originally Posted by jcoloccia

Regular breakers for things like avionics.

Push/Pull breakers for things like alernator field, flap and trim motor etc. Stuff that should never go off but that you may want the option of yanking off if it runs away.

So you can optimize for whatever functionality/complexity/weight/$$$ you want to drive to

I agree with your mix-and-match philosophy, John. Just curious, why do you seem to prefer breakers (as opposed to fuses) for avionics? I've been planning to use fuses for everything except those things I'm concerned about running away (flaps, boost pump, and autopilot). Definitely NOT trying to re-ignite that almost-silly "fuses vs. breakers" thread from a couple months ago, but am at the stage where I need to decide myself right now. Thanks.

jcoloccia · #6 02-21-2007, 12:30 PM

Quote:

Originally Posted by alpinelakespilot2000

I agree with your mix-and-match philosophy, John. Just curious, why do you seem to prefer breakers (as opposed to fuses) for avionics? I've been planning to use fuses for everything except those things I'm concerned about running away (flaps, boost pump, and autopilot). Definitely NOT trying to re-ignite that almost-silly "fuses vs. breakers" thread from a couple months ago, but am at the stage where I need to decide myself right now. Thanks.

I don't prefer breakers. I also didn't want to re-ignite that almost-silly "fuses vs. breakers" thing as well so I thought I'd make sure everything was well represented.

I'll use fuses for darn near everything. There might be a spattering of a couple of push/pull breakers for the alternator field and maybe one or two other things as I come across them.

For example, I'll probably just use a push/pull breaker as my "avionics master" and just leave it in all the time. That gives me the option of switching it off later if something in the panel starts acting up during engine start. I can always go back and add a bat handle switch if I can't fix the problem, and the push/pull breaker buys me some time to fiddle. The only place I'll use a breaker is places where I want it on 99% of the time but reserve the right to shut it off manually (just as you said).

This is just my personal philosophy although it's based on years of observing what fails and what doesn't. Breaker and switch failures aren't too uncommon. The old glass style fuse holders were pretty junky too as they age. The blade fuses holders, on the other hand, just seem to always work.

alpinelakespilot2000 · #7 02-21-2007, 12:46 PM

Thanks John. Your approach makes a lot of sense it seems.

N941WR · #8 02-21-2007, 01:32 PM

Quote:

Originally Posted by jcoloccia

Push/Pull breakers for things like alernator field, flap and trim motor etc. Stuff that should never go off but that you may want the option of yanking off if it runs away.

So you can optimize for whatever functionality/complexity/weight/$$$ you want to drive to

Ditto for me. Only I elected to use push/pull breakers for everything that didn't get a breaker/switch.

My thinking on this was simple; when I start flying, who knows what kind of problems I'll run into, even though everything has tested out on the ground. This will allow me to pull a breaker and isolate my equipment since each and every piece of equipment is on its own breaker. The only exception is the two Dynon "keep alive" circuits, they share one breaker.

The cost difference between the two types of breakers is negligible and they don't take up any more room, nor are they more difficult to install.

BTW, it is not my intention to start trouble shooting electrical problems during my first flight hours. However, if I get a bad hum or screetch in my headsets, it would be nice to turn things off, when the time is right.

(Also, not wishing to re-start the breaker vs. fuse debate or the "when is the proper time to debug system issue?" debate.)