Ron Kostus said:
Just starting to acquire the various goodies for my panel. What are the advantages / disadvantages between switch/ breakers and independent switches with separate breakers other than more wiring. I see more and more new installations using just combined switch/breakers.
Thanks for your help and knowledge
Ron kostus
N567RK - reserved
Finish kit, interior
If you use all breakers, you'll probably have to run two buses. One for the in flight switchable stuff on the left side of the cockpit, and one for the rest of the stuff somewhere else. Doable, but a pain. Breakers are also about 10 times more expensive than a switch. Some people claim that switches and fuses are lighter than switchable breakers. Whatever...maybe by little bit, maybe by a lot, and maybe they're heavier in fact. It all sorta' depends on what switches you use. I can rummage around my office and hand you a switch that's much heavier than a Klixon, and vice versa. I would think that a fuse block with switches is in general lighter than switchable breakers and two bus bars.
In terms of reliability, it's not even worth talking about. The typical switch will last a long time. So will the typical switchable or Klixon style breaker. ALL of them will eventually break....some in 5 minutes, some in 50 years. Easy to predict what a bunch of 1000 switches will do. Impossible to predict what your 1 switch will do. Just expect it to happen, and design with that in mind.
I will say that a switch in-line with a switchable breaker (or any breaker really) doesn't help your SYSTEM reliability. It probably doesn't hurt it much either, but if it's not helping, why go through the expense and trouble of individual breakers when a fuse block is more reliable, simpler and cheaper. If you want to use a switch, a switch and a fuse is the way to go, in my opinion.
Whatever you choose, you'll probably end up with a reliable system, and you'll also probably have a few things break here and there over the years.
edit: I'll just add that I intend to use a hybrid of switch/fuses and switchable breakers in my own aircraft. The fuse police aren't gonna come and haul me off. Fuses for things that never need to be open (or only extrememly rarely...maybe for an annual). Fuse/Switch combination for things that get switched all the time and that I want to have convenient in flight (lights, pitot heat if I install it, etc). Switchable breakers for stuff I want to turn on and forget about for the duration of the flight (for example, the avionics bus, or "essential bus" if you're familiar with Nuckoll's book....really good book, by the way).
I'm not even going to bother explaining my reasoning since my comfort zone will likely be different than yours. I'll just offer that by far the
least effective way of creating a reliable system is by using high quality components. I would not trust my life to a so-called "mil spec" switch wired with mil spec wiring by a trained and certified technician. I would, however, trust my life to two redundant paths wired with Radio Shack wire and two cheapy Radio Shack switches wired by someone that made joints that looked okay from a foot away.
I'm not saying buy cheap components....and definately don't use Radio Shack wire...lol: cheap components break more often and will cost you more $$$ and aggravation in the long run. Top notch, gold plated, dipped in holy water components, however, do NOT have any sort of significant effect on your system reliability. If it's gotta work, you MUST have redundancy, and if you have redundancy, the "quality" of the components simply determines how often you have to replace switches to maintain the redundant circuits in working order.
