fuses v circuit breakers

[tonyjohnson]

Not to rehash what may be an old topic, but I could use some help in the final design of my electrical system. I will be using fuses instead of circuit breakers for most electrical items but I am wondering if there are some items so essential that they should be on circuit breakers.

For those of you who are using fuses, are there any items that you chose to use a circuit breaker instead? Are there some items that you used fuses for that in retrospect you wish you had used a circuit breaker for? GPS, flap motor etc.?

[n468ac]

The only fuse we used is the 'keep alive' for the radio and dynon ... and we are switching it over to a circuit breaker! If you just jump start the plane it blows every time.

[dan]

Originally Posted by n468ac

The only fuse we used is the 'keep alive' for the radio and dynon ... and we are switching it over to a circuit breaker! If you just jump start the plane it blows every time.

??? Jump start the plane?

I used fuses on literally everything with the exception of the alternator field. Absolutely no issues or regrets in almost 1000 hours. I have never had to look at my fuses let alone change one. Nuckolls/AeroElectric Z-11 for the most part. B&C externally regulated alternator.

Build your system correctly and it won't matter what you use.

I should also mention that adding new items (autopilot, XM radio, Garmin 396, etc.) has been at worst trivial, since all I had to do was wire to another fuse terminal on the block. With breakers, I swear I hear builders talking about "piggybacking" on other breakers all the time when they add doodads. The fuse blocks are truly convenient in the context of upgrades. Fuses are cheaper, lighter...where's the down side?!

[Jekyll]

I fused all except the alternator and trim. Why, fuses: cheaper, easier, lighter and less complex. Fewer possible failure modes. Alternator has CB's for the DC master power and voltage warning light because that's the way the PlanePower drawing showed and I didn't feel like altering that. I went with a 60 amp schottky in lieu of a 60 amp CB or ANL for the main feed. I put a CB in the trim circuit so I could shut off power in the event of a run-away. I considered one for the flaps but in the end, I went with a fuse.

Fuses do provide for easier growth as stated by Dan. Just add the wire to the block and insert the new fuse. Couldn't be easier.

Jekyll

[Jconard]

Don't the rules of night flight require a set of spare fuses, within reach of the pilot, and the ability to change those in flight?

Most RV's that use fuses seem to put them in places where they cannot be replaced in flight.

[dan]

It says absolutely nothing about the ability to change fuses in flight. 91.205 merely says that the spare fuses themselves must be accessible to the pilot in flight:

91.205(c)(6) One spare set of fuses, or three spare fuses of each kind required, that are accessible to the pilot in flight.

[N916K]

Originally Posted by Jconard

Most RV's that use fuses seem to put them in places where they cannot be replaced in flight.

Actually it's quite easy to place the fuse block in a place that is easy to reach during flight. Mine is on a plate that pivots down in front of the passenger.

I couple of months ago I had a over voltage situation that popped a fuse. The breaker on the panel should have popped but as it turns out the breakers don't always pop at their rated current, like the fuses do. I was in the rain at 1500 feet AGL and was able to replace the fuse by myself. Before I get slammed for replacing an over voltage fuse in flight, the regulator had be going up and down in voltage and it just got too close to the OV limit. I had a pretty good idea that replacing the fuse would have been just fine, and it was.

[n468ac]

Originally Posted by dan

??? Jump start the plane?

Yes, we've used those jump start power packs ... just clamp the postive cable to the master / starter bus bar.

[jlfernan]

Without it becoming a commercial for a particular company, I would prefer to get all my stuff in one place. Who would you all recommend that carries most of the materials needed to wire my plane?

[Yukon]

Can somebody explain why Van's, Cessna, Piper, Boeing, Douglas and Lockheed etc. uses circuit breakers, but they aren't good enough for me???

John