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How many fuses needed???

Mike D

Well Known Member
Seems like a simple question, but proving not to be.
How many fuses are needed in a full IFR dual screen system?

I'm on my 3rd panel on the -6A, and every re do added more fuses. Now I'm planning the -10 electrical. I'm at the point I need to start mounting the fuse block and don't want to get caught short on fuses. :)

Btw, I am set on fuses not VP or breakers.
Fuse block is being mounted to the wall where my left knee would be.

I am thinking I will go with the Cooper Bussmann 15712 or the 15401
You can have up to 32 fuses on these. The 15401 adds relays to the block.

The advantage to the 15712 is it can have a low profile cover if only using fuses.
The advantage to the 15401 is the addition of relays, but it has a tall cover.

Both can use Cooper's circuit breakers in the blade type fuse holder. This adds the advantage of going with a few breakers in the same fuse block. But this drives a higher cover.

Would I need more than 32 fuses?
Relays might be nice for switching on the 2nd buss or to use micro switches on the panel. They were not needed in my -6a's system, but might be nice in the -10

http://www.cooperindustries.com/content/public/en/bussmann/transportation/products/power_distribution/fuse_panels/series_15710_rearterminalatcfusepanel.html

http://www.cooperindustries.com/content/public/en/bussmann/transportation/products/power_distribution/power_distribution_modules/series_15400_rfrmrear-fedfuserelaymodule.html
 
Seems like a simple question, but proving not to be.
How many fuses are needed in a full IFR dual screen system?

I'm on my 3rd panel on the -6A, and every re do added more fuses. Now fuse block and don't want to get caught short on fuses. :)

Btw, I am set on fuses not VP or breakers.
Fuse block is being mounted to the wall where my left knee would be.

I am thinking I will go with the Cooper Bussmann 15712 or the 15401
You can have up to 32 fuses on these. The 15401 adds relays to the block.
I'm planning the -10 electrical. I'm at the point I need to start mounting the
The advantage to the 15712 is it can have a low profile cover if only using fuses.
The advantage to the 15401 is the addition of relays, but it has a tall cover.

Both can use Cooper's circuit breakers in the blade type fuse holder. This adds the advantage of going with a few breakers in the same fuse block. But this drives a higher cover.

Would I need more than 32 fuses?
Relays might be nice for switching on the 2nd buss or to use micro switches on the panel. They were not needed in my -6a's system, but might be nice in the -10

http://www.cooperindustries.com/content/public/en/bussmann/transportation/products/power_distribution/fuse_panels/series_15710_rearterminalatcfusepanel.html

http://www.cooperindustries.com/content/public/en/bussmann/transportation/products/power_distribution/power_distribution_modules/series_15400_rfrmrear-fedfuserelaymodule.html

Since the output contacts/connections are not changeable, the 16 g minimum wire size might need a creative work around for typical RV wire sizes.

fuseholder2text.jpg
 
How many? Totally depends on how many circuits you decide to put in the plane. The snarky answer is "one more than you have room for" - and that is about the way it usually turns out, in my experience. Do you have electronic ignition? Dual or single source? Add one to four fuses. How many landing/taxi/Nav/strobe/Interior lights? going to have a little light in the baggage area? USB outlets? electronic heater valve control? All add circuit protection.

You really have to do your own circuit design for the airplane the way you want it, then see how many circuits fall out of that. Then add 30%.
 
VP-X :)

I used the VP-X, it has 32 breakers.
I used all of them, with one connected to a fuse box for 5 more circuits.
So in all I had 36 circuits in my RV-10. 3 screen G3X w/IFR, 3 power outlets, and 2 lighting circuits, defrost fans, insturment lights, etc.
 
FWIW, a fairly typical VFR install required 12 slots on the airframe bus, and 8 or 9 on the avionics bus.

As Paul says, "one more than you have". I recently added an airframe power subpanel so I could have a slot for the variable cowl exit servo, and power for experimental devices like temp probes, previously cobbled in.

Stein has these panels up to 12 slots, and B&C has 16's and 20's.

BTW, I could not get my original Plane Power alternator to play nice with a 5 amp field fuse; I suspect an infrequent transient crowbar event. I put the field on a 5-amp breaker to make it slow-trip, which eliminated the issue.

 
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Thanks Gil. That is something I had not considered with these fuse blocks. I like the rear terminations because they look clean, but I also like the fast on's the fuse blocks I have in the -6a. Makes it easier to rearrange wires. :)

So true that I always need one more. :)

Thanks Paul, I completly forgot about the overhead lighting.
Still working on the circuit design but there are so many unknowns as buying avionics is still aways out.

So, taking Bill's answer of 36 and adding Paul's 30-percent.... I get 46 to 47.
I'll plan on that for my spacing requirement numbers.

Any thoughts on using relays? Cars have a lot of them but haven't needed them in the plane's electrical just yet.
 
The version with the 10 relays in the middle has a completely different connection method and takes sealed automotive pins. The wire sizes are more applicable to our wiring -

Wire Size: Accepts #12-22 AWG wire sizes
Terminals: Delphi Packard 280 Series Metri-Pack? sealed/tang style
terminals


DSCN2301_zpsbcbf0162.jpg
 
sold on fuses?

I have fuses in my RV7a but followed the factory instructions and installed breakers for my efii electronic ignition and efii bus manager components including alternator output and alternator field. Like you I've encountered the nearly universal enthusiasm for breakers over fuses with some skepticism but I'm not sufficiently versed to defend either choice. I wonder why you are so certain about your choice of fuses over breakers.

As for relays, I have four between the my infinity stick grip and my ray allen roll and trim servos. This reconciles the disparity between the minimum operational current for the trim motor and than the maximum tolerable current of the stick grip switch wires.

I hope this latter comment helps your plans and justifies the moment you might take to detail your certain confidence with fuses v. breakers.

thanks in advance

jeff H
N377CP, KWVI
 
Here is what I did in my 3rd panel redo on my -6a. (22 fuses used+ some spares)

cPRHFc.jpg


version 1.0 had the 10-fuse block on the sub panel. But this was moved to the new location in version 2.0 for easier access and to make room for the EFIS.

I have a terminal strip on the sub panel with the screw type attachment as shown by wjb. But I hate dropping the screws so I won't repeat this mistake in the -10.

I like the location. By my left knee. I like that they are auto fuses and fast on connectors. I like the low profile of this block.
But it just does not look clean like I want. This is why I am looking into the Eaton/Cooper fuse blocks. They can hide all the wires behind the fuse block.

Well, off to continue the electrical layout. :)
 
I'm looking at using fuses, too, rather than breakers or VP-X equivalent.

These blocks look promising and it connects with screws with ring terminals rather than a special crimp-on connector for the fuse terminal. Lots of sizes and configuration options

http://www.ceautoelectricsupply.com/fuseholders.html

Different fuse location, but this ANL fuseholder sold at the link above looks useful.

Too late for me to change, but I think it work work better than the totally open holders -

ANLFuseHolder_sm.jpg
 
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