Lucio I-NLCM

Lucio I-NLCM

Active Member
Hello at all

I don't wont start a "talk show" about the ANL current limiter "NON TIME DELAY" , but I'm just looking some help to better clear my doubts about this electrical system part.
I agree about put TWO limiters on the firewall for obvious reason (one from alternator before battery and the second one before feed the main buss), but I steel need some clarification.

Before question here my stuff:
-60A alternator
-about 60A (or little less) @ full load on the panel bus
-current Shunt for SV System efis

Intention:
I would routing wire in this way:
Alt B-lead >> wire x-size* to Shunt then >> copper bar to first ANL 60A (or equivalent**) then, from here, fork to >>
> the Battery via copper bar or "x-size* wire to starter relay side

AND

> via copper bar to second ANL 60A (or equivalent**) then >> wire y-size* to the panel buss bar .

Consideration :
I read here http://www.cooperindustries.com/con.../product-datasheets-a/Bus_Ele_DS_2024_ANL.pdf
the ANL60A is rated for blow @ about 140-150A after 20 or more seconds, logarithmically less time if current rise or a short occur, so:

Assuming the Alt became crazy or due others things the current rise over 60A , the ANL doesn't melt before reach a bunch of over two time its rated 60A.

Questions :
Is it wrong think about size the "x" and "y" wire for this big amount of current ??

* Which wire size for the "x" and "y"-size wire ?
In theory that means I'd need a cables sized well over 8 or 6 AWG to avoid melt the wire before the fuse, may be a 4 or 2 AWG will be right?.... or is it academy only?

** is there any reason why don't use most popular and cheaper automotive fuse (findable in any auto part store) like this?

http://www.mta.it/en/fuses?uniq=e717c1e14b8e428d40bc78fa414a0409 look the 4th pdf from the top called "Scheda tecnica Midival" , don't worry IS IN ENGLISH, the melt curve is pretty the same as the Bussmann one (more or less seconds) why don't use those or like those ones?

Usually I prefer punch the aluminum instead think and wire electrical, so your think and suggest are pretty welcome to help me jump this big and stupid step.

Thanks in advance

Lucio
 
I can't think of a reason they would be a problem. The ANL fuses are sort of an industrial standard fuse here in the US so they are commonly available here.
 
Lucio,
The ANL 60 is a robust fuse. It and the fuse holder are well suited for FWF.
The smaller auto fuse may work fine. I like robust for this application.
Most only use one ANL.
#4 wire would be good for the 60a B-lead.
ANL to master solenoild is copper bar. Master to starter solenoid is copper bar. Starter and battery cable are #2.
qpi68y.jpg
 
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Check the chart (43-13, 11-2), I would suggest an 8 ga wire is more than adequate for the typical RV 'B' lead.
 
Thank for your input
but I'm confused yet, some say 8 some say 4 awg .... I think 2 :confused:
How can I became sure about the right size?
So in you think the automotive fuse ( with same melt curve) should be right like the anl one , just little less robust?
 
Walt is correct that the Circular 43-13 shows that a 60 amp continuous load wire size can be #8. You will also find that your 60 amp alt. will almost never run more that 20-30 amps. This means that the 60 amps would be intermittent at best. #8 will work fine. #4 that I used is heavier and more exspensive. Also a little less voltage drop.
I still like the ANL fuse and holder.
The benifit of Experimental aircraft is that we get to build it the way we want.
 
Lucio,
You can download Bob Nuckolls' book free. http://www.aeroelectric.com/Book/AEC12A_PDF.zip
The majority of home-built aircraft are wired using one of Bob Nuckolls' diagrams. His circuits have been perfected and proven over time.
I agree with others that 8 AWG is adequate for the alternator. There has been some discussion on the AeroElectric list about using a MIDI fuse (which does not cost as much) instead of an ANL. http://www.matronics.com/forums/viewtopic.php
p=405736&sid=1fbb4a358d91bc8667acf5645e6f6642
and
http://forums.matronics.com/viewtopic.php?p=391840&sid=f8f02046c66810cc18bb1782e2726292
The purpose of the alternator fuse is to protect the battery and wires from and a shorted alternator. The alternator will not produce much more than its rated current. It is self limiting.
Not to worry about alternator current melting wires. The alternator can not produce enough current to melt #8 wires. Only a short circuit will make that much current, which will blow the 60 amp fuse before wires get hot.
Do NOT use a fuse to feed the main bus! A fuse will add weight, cost, complexity, and is one more thing to go wrong. Factory-built planes do not fuse the main bus nor do any of Bob Nuckolls's diagrams. Instead double insulate the feeder where it passes through the firewall. The reason that a fuse is not needed in the main feeder is that a short circuit will clear itself when the sheet metal is burned away. Good workmanship and double insulating the main feeder at critical points will ensure that it never shorts out.
Joe Gores
 
Mich48041 said:
The reason that a fuse is not needed in the main feeder is that a short circuit will clear itself when the sheet metal is burned away. Good workmanship and double insulating the main feeder at critical points will ensure that it never shorts out.
Joe Gores
Click to expand...

Hi Joe
I can point to a case where the main feeder did not mend itself as described. Stainless firewall, glass airplane, burned to the ground during maintenance.
Just pointing out the importance of some very robust method of insulating this feed if it's not protected.

Tim
 
Fusable link instead of a mains fuse?

I installed a fuseable link on my mains to limit wire damage on a complete short. Same on my essential bus. Mine are short wire segments crimped or soldered (if not on a ridged mount) inline with the feed lines. No fuse or socket contact to corrode and cause problems.

The fuseable link may not save the wire but it should blow before the red hot wire burns up your whole harness!

I.E. What if your essential bus wires are in the same bundle going through the firewall as the mains when they melt?
 
thanks Walt; Mark;
the 43.13 is a big circular, I'll need time to study and well comply , the chapter 11 section 2 mentioned, is about "Storage Batteries" :(
But I found in the section 5 a source for cable current capacity, in fig 11-9 the 8 awg carry 38 A @ 105 ?C , far from 60A .... or I'm wrong?:confused:

thanks Mich;
I read the AeroElectric discussion about ANL-Midi , now I start to think about a conventional Bussmann ANL :)
but I'm not sure about do not protect the cable that feed the main bus :eek:
may be I'll need more learning on the text .

thanks a lot at all other guys not mentioned
 
Lucio,
Even though an alternator may be rated at 60 amps, the actual current is determined by the load. If you anticipate a continuous load of 60 amps, then go with larger wire. Unless you have pitot heat and heated seats and high current lighting, then chances are that the normal load will be less than 20 amps with occasional 10 amps more to charge the battery after starting. #8 wire is good enough for most small planes. Do not consider intermittent loads for sizing wire. Flap motors, com transmitters, landing gear do not need to be considered because they are not continuous and will not heat the wire for the short time that they are operated.
Joe Gores
 
Mich
Now everything sound better for my acknowledge ; so in this think I can disregard the mere stuff TOTAL load sum

Here the list @ max load
SV efis 3.5A (enclosed beck up battery) 5A*
Intercom 0.1A*
AP Servos 2.7A
Trim Servos 1.5A
Boost Fuel pump 4.5A (in the pattern)
Flap motor 3A
Becker Com 4A
Strob light 7A*
Nav light 6A*
Panel light 1A*
Landing light 100w 8A
TXP 3A*
Cigar power 2A*
--------------------
TOTAL about 48A

SO , considering just the continuos * load my feed need drop down at 30A or under 20A with lights off
We'll done Mich, thanks

...... The planets are aligning :)

Lucio
 
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