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60A Buss fuse attached to baffling?

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Tim_Lewis(at)msm.umr.edu
Guest

Posted: Sun Sep 02, 2007 8:08 am Post subject: 60A Buss fuse attached to baffling?

I'm considering protecting my alternator wiring with a Buss 60 Amp 

current limiter (B&C, C903-1 base with C905-60 fuse).  Does anybody know 

if those devices can take the heat/vibration associated with being 

mounted on the baffling, right near the alternator?  That location would 

provide fuse protection to almost the entire length of alternator 

wiring, but is in a high heat/vibration environment.



Thanks,



Tim Lewis



-- 

Tim Lewis -- HEF (Manassas, VA)

RV-6A N47TD -- 900 hrs

RV-10 #40059 under construction

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Bob McC

Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON

Posted: Sun Sep 02, 2007 9:41 am Post subject: 60A Buss fuse attached to baffling?

Tim;



The source of energy which puts the alternator "B" lead at risk is the

battery. Therefore this fuse goes at the battery end of the wire not the

alternator end. The alternator is not capable of delivering much greater

than it's rated current, whereas if the alternator shorts the battery can

deliver several hundred amps into the fault.



Bob McC

---

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_________________
Bob McC
Falco #908
(just starting)

bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Tue Sep 04, 2007 1:59 am Post subject: 60A Buss fuse attached to baffling?

9/4/2007

Hello George, You wrote: "I think you have it backwards, you are trying to 

protect the battery."

I was under the impression that fuses and circuit breakers were primarily 

intended to protect the wiring between some source of electrical supply and 

a recipient device on that circuit.

The idea being that a short somewhere along that wiring could generate heat, 

smoke, and possibly fire. The protective device (usually heat activated) 

would open up in the case of excess electron flow because of the short and 

prevent the generation of a dangerous amount of heat and the resultant smoke 

and potential fire.

It has been written earlier that the huge amount of unwanted amps that could 

flow in the alternator B lead in case of a short would be coming from the 

battery and not the alternator. So in that sense maybe one is trying to 

protect the battery from depleting itself as well as protecting the B lead 

wiring in order to avoid smoke and fire.

Perhaps it is a semantic thing -- Bob Nuckolls would you care to comment? 

Thanks.

'OC' Says: "The best investment we can make is the effort to gather and 

understand knowledge."

PS: One may also speculate on just what wiring constitutes the B lead. Let's 

say that you have an adequate sized wire that goes from the B lead terminal 

on the back of the alternator through an appropriately large fuse to the 

input terminal of the starter contactor or relay. Also connected to that 

starter contactor input terminal is a very large sized unfused wire, say AWG 

2, going to the battery plus terminal some distance away.

What portion of the total enroute wiring connection between the alternator B 

terminal and the battery plus terminal is considered the B lead?

----------------- RESPONDING TO -------------

Time: 05:44:16 AM PST US

From: <gmcjetpilot(at)yahoo.com>

Subject: Re: 60A Buss fuse attached to baffling? No

Tim:

  I think you have it backwards, you are trying to protect the battery.

I would not put it on the shaking rattling Lycoming. It may take it

but your do add fatigue to anything vibrating, although based in

the above, its a moot point, protect the battery and put the 60 amp

fuse on the firewall. George

  >From: Tim Lewis <Tim_Lewis(at)msm.umr.edu>

 	  Quote: 	
		  Subject: 60A Buss fuse attached to baffling?

Does anybody know

if those devices can take the heat/vibration associated with being

mounted on the baffling, right near the alternator?  That location

 >would

 	  Quote: 	
		  provide fuse protection to almost the entire length of alternator

wiring, but is in a high heat/vibration environment.

Thanks, Tim Lewis

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nuckollsr(at)cox.net
Guest

Posted: Fri Sep 07, 2007 10:09 am Post subject: 60A Buss fuse attached to baffling?

At 05:57 AM 9/4/2007 -0400, you wrote:



 	  Quote: 	
		  



9/4/2007



Hello George, You wrote: "I think you have it backwards, you are trying to 

protect the battery."



I was under the impression that fuses and circuit breakers were primarily 

intended to protect the wiring between some source of electrical supply 

and a recipient device on that circuit.



The idea being that a short somewhere along that wiring could generate 

heat, smoke, and possibly fire. The protective device (usually heat 

activated) would open up in the case of excess electron flow because of 

the short and prevent the generation of a dangerous amount of heat and the 

resultant smoke and potential fire.



It has been written earlier that the huge amount of unwanted amps that 

could flow in the alternator B lead in case of a short would be coming 

from the battery and not the alternator. So in that sense maybe one is 

trying to protect the battery from depleting itself as well as protecting 

the B lead wiring in order to avoid smoke and fire.



Perhaps it is a semantic thing -- Bob Nuckolls would you care to comment? 

Thanks.


	


    The thing being protected is mostly the alternator itself. The fault

    that opens the b-lead fuse is (1) shorted b-lead (rare) or (2) shorted

    diodes in alternator (also rare but more probable than shorted wire).

    The energy that will cause damage is going to come from the battery

    in terms of many hundreds of amps . . . hence, there's a notion that the

    b-lead fuse should be located as close as possible to the battery. I

    suggest right next to the starter contactor and b-lead shunt (if used).



    If not fused and the diodes short, it will take out stator wires

    causing much smoke and a much higher repair bill. Also, if the battery

    is soggy [of course, nobody who reads this list goes flying with a

    soggy battery], then a hard short could take the battery down too

    and make the whole panel go dark. Under the best scenario, a well

    maintained battery supplies 1000+ amps for milliseconds necessary

    to open the fuse and repairs are a relatively simple maintenance

    event.



    Bob . . .

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