On Wednesday, June 20, 2018 at 7:56:31 AM UTC-7, OHM Ω http://aviation.derosaweb.net wrote:
QT,

All breakers suffer a voltage drop of some amount (see more below). Therefore some pilots like fuses as they have no voltage drop at all. I went away from fuses as they don't give me a positive indication of a trip, are difficult to fix in (soaring) flight, and are fragile.

Breaker voltage drop - As you probably know current is passed inside of breakers through a tiny "heater" (for want of a better phrase). The more current, the hotter the "heater" gets, until finally things get too hot and the heat trips a bi-metallic strip, and the current flow is interrupted. This "heater" can be thought of as a resistor. Small value breakers have a high value resistance and thus they drop a high voltage across them. For a 1A Tyco W31 breaker this is 0.6v! Ouch! A 5A breaker only drops 0.15v, 10A = 0.1v, 15A = 0.09v, etc. That is why I only recommend 5A breakers and above to be used. These are maximum voltage drop values so I am still holding with choosing breakers over fuses. See the specs at See https://www.alliedelec.com/m/d/6526f...72ec951f9f.pdf.

PS - I had stated before that ONLY switch/breakers like the Tyco W31 may be used as a switch. I said that pull-type breakers should NEVER be used as a switch. I just found out that the pull-type Tyco W23 breaker is rated to be used as a switch! Huzzah! But I digress.

- John OHM Ω

Glass fuses also suffer a voltage drop - how do you think they work? They are simply a resistive element that heats beyond the melting point above the label current. In fact a Bussman 1A AGX fuse has a resistance as much as 0..15 ohms, or a 1.5V drop. See http://www.cooperindustries.com/cont...AGX_Series.pdf

In addition, fuses are mounted in holders, and the ones used by many German glider manufacturers have at least 5 extra sliding connections in them: Faston to holder, holder to fuse, fuse to holder cap, holder cap to holder, Faston back to circuit - 5 more opportunities for voltage drop or failure. I've found them to age poorly and become quite unreliable. If you are going to breakers, I'd pick the Klixon 7277/7274 series, these are more compact and made for aircraft use.