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orchidman

Joined: 10 Jul 2006
Posts: 277
Location: Oklahoma City - KRCE

Posted: Thu Jan 31, 2008 1:08 pm Post subject: Alternator Circuit Breaker

Examining other builders wiring diagrams, I am finding both fuses and circuit breakers for the alternator output protection.

I am leaning to a CB but would like some input as to where to place the 60A CB.

Possible options would be forward of the firewall, or under the dash to keep the wires as short as possible, or normally positioned on the instrument panel.

_________________
Gary Blankenbiller
RV10 - # 40674
(N2GB Flying)

Tim Olson

Joined: 25 Jan 2007
Posts: 2881

Posted: Thu Jan 31, 2008 1:50 pm Post subject: Alternator Circuit Breaker

I decided on mine to forego the Circuit Breaker and do the fuse thing.

The reason is a few fold...



First, I did indeed buy a breaker at one point, but it's a pretty

fat wire you put on a 60-70A breaker, and that fat wire was stiff, and

I heard something plastic internal to the breaker crack.  This did

not leave me feeling very good.  I decided that unless you're

going to have a solid way to mount a breaker, and hold the wire

totally imobile and prevent cracking, it would not be a good idea to

use that breaker.  Also, it isn't that easy to find a good breaker

of that size, and at a good cost.



Then, you also have the big fat wire coming up to your panel or

subpanel, further into the cabin that it needs to be.  On mine,

I did mount it inside the firewall, but on the firewall, but

there is no reason that I needed to put it there.  It could have

just as easily gone in the engine compartment. I like where it

is, and it's worked out well though.



Also, on my plane, I draw in the low 40's for amps at full draw

with everything lit up and turned on, including pitot heat.  If my

60A breaker blows, I really don't think it would be a good idea for

me to re-set it in flight.  So, you may as well use a fuse, at that

point.  I work on lots of electronic things, and I don't mind

tinkering, but in the air is probably not the place.  I do carry

a spare fuse though, in my kit.



If you're really leaning towards a CB, then you may as well skip

the idea of putting it under the cowl.  If you're willing to

go under the cowl to deal with it, you shouldn't have any

objection to staying simple and cheap and going with a fuse.



As far as design goes, I was happy with my ANL fuse, because not

only was it simple to mount and hook up, but it included a nice

clear plastic case and cover.  So it's easy to see if it blows.

Of course, I haven't had the opportunity to see it blown yet.



Now, one other reason I don't care about re-setting a breaker

is because with a good backup battery system, I'd rather treat

the real unusual case of a blow B-lead breaker to be somewhat

of an emergency....and use the hour or more of battery that I

have left to get on the ground.  If that thing blows, I've got

some problems somewhere, and being on the ground is a good

plan anyway until I can figure out what caused it.



Tim Olson - RV-10 N104CD - Flying



orchidman wrote:

 	  Quote: 	
		   

 

 Examining other builders wiring diagrams, I am finding both fuses and

 circuit breakers for the alternator output protection. I am leaning

 to a CB but would like some input as to where to place the 60A CB. 

 Possible options would be forward of the firewall, or under the dash

 to keep the wires as short as possible, or normally positioned on the

 instrument panel.

 

 -------- Gary Blankenbiller RV10 - # 40674 Fuselage SB (N410GB

 reserved)

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=161652#161652

dlm46007(at)cox.net
Guest

Posted: Thu Jan 31, 2008 2:45 pm Post subject: Alternator Circuit Breaker

two 30 or 35s in parallel with a short copper bus bar between them. Easy

attach of the fat wire. 



--

P8120019.JPG

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695.38 KB

Viewed:

598 Time(s)

jesse(at)saintaviation.co
Guest

Posted: Thu Jan 31, 2008 2:46 pm Post subject: Alternator Circuit Breaker

I always put in a circuit breaker and I put it in a location that it  

can be seen if it pops, which would mean on the panel or nearby.   

Since you will likely have 8AWG wire going to and from it, it is  

important to think about routing as you plan where to put it.  That  

size wire doesn't bent too easily, so there needs to be a little  

clearance from other items in the direction that the wire leaves the  

breaker.  I as I have heard others argue in the past, when a cb pops,  

it is often unlikely that just pushing it back in will solve the  

problem, which is an argument for using fuses, but it is also nice to  

have that visual alert that something has happened rather than just  

see your voltage drop or your alternator failure light come on.



Just my $.02, which is probably worth less than 50% of that.



do not archive



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

Cell: 352-427-0285

Fax: 815-377-3694



On Jan 31, 2008, at 4:08 PM, orchidman wrote:



 	  Quote: 	
		   



 Examining other builders wiring diagrams, I am finding both fuses  

 and circuit breakers for the alternator output protection.

 I am leaning to a CB but would like some input as to where to place  

 the 60A CB.

 Possible options would be forward of the firewall, or under the dash  

 to keep the wires as short as possible, or normally positioned on  

 the instrument panel.



 --------

 Gary Blankenbiller

 RV10 - # 40674

 Fuselage SB

 (N410GB reserved)





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=161652#161652

carl.froehlich(at)cox.net
Guest

Posted: Thu Jan 31, 2008 3:39 pm Post subject: Alternator Circuit Breaker

Use a 70 amp breaker with a 60 amp alternator to avoid spurious trips.  If

the breaker does trip it means there is a serious problem, something you

might not want to troubleshoot in flight by resetting the breaker.  In my

RV-8A I mounted the breaker on the engine side of the firewall.  This kept

all the heavy wiring on the engine side of the firewall except for one

penetration to the starter solenoid.  I have a dual battery install with

separate right/left busses that support continued IFR flight without the

alternator.



Carl Froehlich

RV-8A (375 hrs)

RV-10 (wings)



--

wcurtis(at)nerv10.com
Guest

Posted: Thu Jan 31, 2008 3:45 pm Post subject: Alternator Circuit Breaker

Aircraft Spruce sells a 60-70 alternator circuit breaker (non pull-able) relatively inexpensively and is the standard of certified OEM manufacturers.  They are also less expensive than an ANL and holder.

http://www.aircraftspruce.com/catalog/elpages/6070amp.php



http://www.aircraftspruce.com/catalog/graphics/6070circuitbreak.jpg



For 60-70 AMPs the wire from the alternator only needs to be #8 AWG (or #6).  An #8AWG Tefzel wire is only 3/16" thick and easy to manage behind the panel attached to the circuit breaker.  Alternator to breaker, breaker to buss.



William

http://wcurtis.nerv10.com/

"Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."

-- Dr. Suess 



------

orchidman

Joined: 10 Jul 2006
Posts: 277
Location: Oklahoma City - KRCE

Posted: Thu Jan 31, 2008 4:01 pm Post subject: Re: Alternator Circuit Breaker

 	  Tim Olson wrote: 	
		  



First, I did indeed buy a breaker at one point, but it's a pretty

fat wire you put on a 60-70A breaker, and that fat wire was stiff, and

I heard something plastic internal to the breaker crack.  This did

not leave me feeling very good.  I decided that unless you're

going to have a solid way to mount a breaker, and hold the wire

totally mobile and prevent cracking, it would not be a good idea to

use that breaker.  Also, it isn't that easy to find a good breaker

of that size, and at a good cost. 	


I have found a source for 60 & 70 amp CBs and yes they are very pricey but no fuseses that big was one of the primary reasons I have been thinking of going the CB route.



 	  Quote: 	
		  Then, you also have the big fat wire coming up to your panel or

subpanel, further into the cabin that it needs to be.  On mine,

I did mount it inside the firewall, but on the firewall, but

there is no reason that I needed to put it there.  It could have

just as easily gone in the engine compartment. I like where it

is, and it's worked out well though. 	


Passing 'big' wires through the firewall bothers me and the fewer possible makes me feel better.  That is why I am considering possibly in front of the firewall.

 	  Quote: 	
		  Also, on my plane, I draw in the low 40's for amps at full draw

with everything lit up and turned on, including pitot heat.  If my

60A breaker blows, I really don't think it would be a good idea for

me to re-set it in flight.  So, you may as well use a fuse, at that

point.  I work on lots of electronic things, and I don't mind

tinkering, but in the air is probably not the place.  I do carry

a spare fuse though, in my kit.

...

As far as design goes, I was happy with my ANL fuse, because not

only was it simple to mount and hook up, but it included a nice

clear plastic case and cover.  So it's easy to see if it blows.

Of course, I haven't had the opportunity to see it blown yet. 	


Do you have a good source for that big an ANL fuse?  I have checked all my normal sources.

_________________
Gary Blankenbiller
RV10 - # 40674
(N2GB Flying)

wcurtis(at)nerv10.com
Guest

Posted: Thu Jan 31, 2008 4:38 pm Post subject: Alternator Circuit Breaker

If all the "heavy" wiring is on the engine side, how do you get the 60 amps from the alternator to the buss?  That's rhetorical.



I think I know what you are saying because I see a lot of builders connect the output lead of the alternator to the battery side of the starter contactor thinking they are keeping the "heavy" wires out of the cockpit.  You still need to run a "heavy" wire from the battery cable to the main buss.  So unless you buss is also forward of the firewall, you still have "heavy" wires coming into the cabin.



Having a cable from the alternator to the bus (via breaker or fuse) and then a separate cable from the battery to the buss is normal practice for certified aircraft.   Also, attaching the alternator lead to the battery side of the starter contactor MANDATES putting the alternator fuse or circuit breaker firewall forward.



William

http://wcurtis.nerv10.com/

"Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."

-- Dr. Suess 



------

seipel(at)seznam.cz
Guest

Posted: Thu Jan 31, 2008 4:47 pm Post subject: Alternator Circuit Breaker

Make sure you take a look at the data sheet for your breaker before you 

decide to upsize the number of amps too much.  For example, the 30 amp 

Tyco breaker I'm using for my backup SD-20 alternator is rated such that 

it may take up to 1 hour at 145% or 43 amps before it trips.  At 200%, 

i.e. 60 amps, it may still take up to 30 seconds to trip.  If that 

breaker trips, then my alternator is definitely overloaded and I'd sure 

want to take a look at the problem before continuing on.



PJ Seipel

RV-10 #40032



Carl Froehlich wrote:

[quote] 



 Use a 70 amp breaker with a 60 amp alternator to avoid spurious trips.  If

 the breaker does trip it means there is a serious problem, something you

 might not want to troubleshoot in flight by resetting the breaker.  In my

 RV-8A I mounted the breaker on the engine side of the firewall.  This kept

 all the heavy wiring on the engine side of the firewall except for one

 penetration to the starter solenoid.  I have a dual battery install with

 separate right/left busses that support continued IFR flight without the

 alternator.



 Carl Froehlich

 RV-8A (375 hrs)

 RV-10 (wings)



 --

apilot2(at)gmail.com
Guest

Posted: Thu Jan 31, 2008 4:52 pm Post subject: Alternator Circuit Breaker

How many REALLY need 60 amps for their panel?? Just rhetorical question. I don't see any problem using a 50-55amp 

CB on a 60 amp alternator. Alternators are normally sized so that they aren't called upon to produce more than 85 percent of their nominal rating. So using a 50 amp CB would ensure you don't exceed 85% by very much.

 

On Jan 31, 2008 5:40 PM, William Curtis <wcurtis(at)nerv10.com (wcurtis(at)nerv10.com)> wrote:

[quote] --> RV10-List message posted by: "William Curtis" <wcurtis(at)nerv10.com (wcurtis(at)nerv10.com)>

If all the "heavy" wiring is on the engine side, how do you get the 60 amps from the alternator to the buss?  That's rhetorical.

 

I think I know what you are saying because I see a lot of builders connect the output lead of the alternator to the battery side of the starter contactor thinking they are keeping the "heavy" wires out of the cockpit.  You still need to run a "heavy" wire from the battery cable to the main buss.  So unless you buss is also forward of the firewall, you still have "heavy" wires coming into the cabin.

 

Having a cable from the alternator to the bus (via breaker or fuse) and then a separate cable from the battery to the buss is normal practice for certified aircraft.   Also, attaching the alternator lead to the battery side of the starter contactor MANDATES putting the alternator fuse or circuit breaker firewall forward.

 

William

http://wcurtis.nerv10.com/

"Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."

 -- Dr. Suess



------

wcurtis(at)nerv10.com
Guest

Posted: Thu Jan 31, 2008 5:33 pm Post subject: Alternator Circuit Breaker

 	  Quote: 	
		   Passing 'big' wires through the firewall bothers me and the fewer possible makes me feel better.  That is why I am considering possibly in front of the firewall.


	


In the RV-10 with a rear mounted battery, you have to pass at least ONE "big" wire through the firewall.  Well ---correction, I don't have ANY "big" wires going throught my firewall.  I only have an 8AWG wire from the alternator going through my firewall.  Not even the main battery to starter contactor cable.  I use a thru bulkhead connector show on the attached picture.  On the firewall side is attached the starter contactor as shown.  On the cabin side is attached the main battery cable and the (smaller) battery cable to the buss.

William

http://wcurtis.nerv10.com/

"Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."

-- Dr. Suess

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carl.froehlich(at)cox.net
Guest

Posted: Thu Jan 31, 2008 5:53 pm Post subject: Alternator Circuit Breaker

You have a point if you assume a traditional power distribution scheme.

With dual electronic ignitions and an all electric panel, I opted for a more

reliable approach than that used in certified aircraft.



The issue of big wires through the firewall is really secondary.



Carl



--

orchidman

Joined: 10 Jul 2006
Posts: 277
Location: Oklahoma City - KRCE

Posted: Thu Jan 31, 2008 6:17 pm Post subject: Re: Alternator Circuit Breaker

[quote="wcurtis(at)nerv10.com"] 	  Quote: 	
		  I use a thru bulkhead connector show on the attached picture. 	


William,

Where did you source your connector?

_________________
Gary Blankenbiller
RV10 - # 40674
(N2GB Flying)

Tim Olson

Joined: 25 Jan 2007
Posts: 2881

Posted: Thu Jan 31, 2008 6:38 pm Post subject: Alternator Circuit Breaker

That's exactly my reasoning on using a 60A fuse (despite my 70A

alternator). The fact is, if I find myself drawing 60A off

my alternator, something is not right at all.  None of my

avionics or equipment can draw that much, so my battery or

wires are shorted or something.  You don't size your fuse by

the alternator, you size it to the max load you care to see

before you blow.  A 60A ANL fuse won't blow until well over

60A anyway, so if that baby blows, I sure as heck don't

want to push a reset button in flight and figure it out.

That fuse/breaker is a very big problem indicator.

Tim

PJ Seipel wrote:

[quote] 

 Make sure you take a look at the data sheet for your breaker before you 

 decide to upsize the number of amps too much.  For example, the 30 amp 

 Tyco breaker I'm using for my backup SD-20 alternator is rated such that 

 it may take up to 1 hour at 145% or 43 amps before it trips.  At 200%, 

 i.e. 60 amps, it may still take up to 30 seconds to trip.  If that 

 breaker trips, then my alternator is definitely overloaded and I'd sure 

 want to take a look at the problem before continuing on.

 PJ Seipel

 RV-10 #40032

 Carl Froehlich wrote:

> 

> <carl.froehlich(at)cox.net>

>

> Use a 70 amp breaker with a 60 amp alternator to avoid spurious 

> trips.  If

> the breaker does trip it means there is a serious problem, something you

> might not want to troubleshoot in flight by resetting the breaker.  In my

> RV-8A I mounted the breaker on the engine side of the firewall.  This 

> kept

> all the heavy wiring on the engine side of the firewall except for one

> penetration to the starter solenoid.  I have a dual battery install with

> separate right/left busses that support continued IFR flight without the

> alternator.

>

> Carl Froehlich

> RV-8A (375 hrs)

> RV-10 (wings)

>

> --

Tim Olson

Joined: 25 Jan 2007
Posts: 2881

Posted: Thu Jan 31, 2008 6:43 pm Post subject: Alternator Circuit Breaker

 	  Quote: 	
		   

 I have found a source for 60 & 70 amp CBs and yes they are very

 pricey but no fuseses that big was one of the primary reasons I have

 been thinking of going the CB route.

 


	




Just search for ANL online...they're all over in the card audio

type places.  Nice ones, too, with gold plating and good

housings.



 	  Quote: 	
		   

 Passing 'big' wires through the firewall bothers me and the fewer

 possible makes me feel better.  That is why I am considering possibly

 in front of the firewall.

 


	


Yes, but the biggest, nastiest wire in your plane is the one

going from your battery forward.  That battery can source hundreds

of amps, and it doesn't stop when the engine stops.  People forget

that of the "big wires" they're worried about, some of those

are the biggest worry.  Sooner or later you need to put that

power to the panel busses.....doesn't matter where it comes

in from.

 	  Quote: 	
		   

 Do you have a good source for that big an ANL fuse?  I have checked

 all my normal sources.

 


	


All over online.  Even Ebay.



 	  Quote: 	
		   -------- Gary Blankenbiller RV10 - # 40674 Fuselage SB (N410GB

 reserved)


	




Tim

jesse(at)saintaviation.co
Guest

Posted: Thu Jan 31, 2008 7:21 pm Post subject: Alternator Circuit Breaker

Don't forget that if you have to crank more than normal, or if  

something has drawn your battery down a little, your alternator will  

be charging your battery as well as powering everything in the plane,  

which will take you over the current that you use continuously.



However, I agree that a 60A fuse on a 70A alternator is probably no  

problem at all, and that if it blows in flight you probably won't want  

to reset it, but (just thinking out loud) is it possible that the fuse  

could blow and you not realize it, maybe thinking the alternator  

itself is bad or the field circuit has failed?  With a CB in sight  

there is no question where the failure is.



do not archive



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

Cell: 352-427-0285

Fax: 815-377-3694



On Jan 31, 2008, at 9:29 PM, Tim Olson wrote:



[quote] 



 That's exactly my reasoning on using a 60A fuse (despite my 70A

 alternator). The fact is, if I find myself drawing 60A off

 my alternator, something is not right at all.  None of my

 avionics or equipment can draw that much, so my battery or

 wires are shorted or something.  You don't size your fuse by

 the alternator, you size it to the max load you care to see

 before you blow.  A 60A ANL fuse won't blow until well over

 60A anyway, so if that baby blows, I sure as heck don't

 want to push a reset button in flight and figure it out.

 That fuse/breaker is a very big problem indicator.

 Tim

 PJ Seipel wrote:

> 

> Make sure you take a look at the data sheet for your breaker before  

> you decide to upsize the number of amps too much.  For example, the  

> 30 amp Tyco breaker I'm using for my backup SD-20 alternator is  

> rated such that it may take up to 1 hour at 145% or 43 amps before  

> it trips.  At 200%, i.e. 60 amps, it may still take up to 30  

> seconds to trip.  If that breaker trips, then my alternator is  

> definitely overloaded and I'd sure want to take a look at the  

> problem before continuing on.

> PJ Seipel

> RV-10 #40032

> Carl Froehlich wrote:

>> 

>> >

>>

>> Use a 70 amp breaker with a 60 amp alternator to avoid spurious  

>> trips.  If

>> the breaker does trip it means there is a serious problem,  

>> something you

>> might not want to troubleshoot in flight by resetting the  

>> breaker.  In my

>> RV-8A I mounted the breaker on the engine side of the firewall.   

>> This kept

>> all the heavy wiring on the engine side of the firewall except for  

>> one

>> penetration to the starter solenoid.  I have a dual battery  

>> install with

>> separate right/left busses that support continued IFR flight  

>> without the

>> alternator.

>>

>> Carl Froehlich

>> RV-8A (375 hrs)

>> RV-10 (wings)

>>

>> --

wcurtis(at)nerv10.com
Guest

Posted: Thu Jan 31, 2008 7:57 pm Post subject: Alternator Circuit Breaker

OK, that answer prompts another question that is not rhetorical.



 	  Quote: 	
		  I have a dual battery install with separate right/left busses that support continued IFR flight without the alternator.

Continued IFR without an alternator-- How is that possible?  OK, maybe possible, but prudent?
	




I used the term traditional because there are many ways to put all the wires together to achieve the same ends.  The certified aircraft to which I am referring is the all electric dual battery, dual main, dual avionics buss Cirrus SR series.  They used to have their POH on line that anyone could download which detailed the electrical system.  I can't find it on their site anymore but  I have the SR22 POH in pdf if anyone is interested.



By all accounts, the Cirrus system is very good and reliable but I don't think even Cirrus will say you can continue IFR flight without the alternator.  And the Cirrus engine is not dependant on the electrical system as your electronic ignition is.  If you have a design that is more robust than the Cirrus, I (and I'm sure other builders) would be very interested in seeing it.



I apologize in advanced for the pointed questions, however as builders, I think we sometimes design pens that work in zero-g rather than just using a pencil.



William

http://wcurtis.nerv10.com/

"Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."

-- Dr. Suess 



------

Tim Olson

Joined: 25 Jan 2007
Posts: 2881

Posted: Thu Jan 31, 2008 8:19 pm Post subject: Alternator Circuit Breaker

Even with this non-time-delay ANL, here's an info sheet

that shows some details:

http://www.aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ANL_Specs.pdf



This is on a 50A ANL:

Notice you can pull over 200A, for 1 second, and can pull 100A+ for

basically at least 100 seconds, or possibly nearly an unlimited

amount of time.  If you interpolate the graph, even the lowly 50A

ANL is likely going to stay running with no problem unless you

have some sort of hard fault.  A dead battery will draw more power

from the alternator, but you really should be running your alternator

near 100% of capacity for much time.  That's why I went with a 70A

alternator....slower turning, cooler running, and a larger margin

over the operating load.



I'm not too worried about losing the fuse and not knowing. It would

first be immediately noticeable on the voltmeter, as you won't

have a voltage anywhere NEAR 14v if you put a load on it and

don't have a working alternator, and I also have visual and

audio alerts for voltage, and can set them in the EIS for Amperage

too, since I have the hall-effect current sensor installed.

But again, with a load on a battery, your voltage will immediately

be in the 12's.....so setting a voltage alert for 13V or

even higher would give you an alert if you lost an alternator.



Tim Olson - RV-10 N104CD - Flying



Jesse Saint wrote:

[quote] 

 

 Don't forget that if you have to crank more than normal, or if something 

 has drawn your battery down a little, your alternator will be charging 

 your battery as well as powering everything in the plane, which will 

 take you over the current that you use continuously.

 

 However, I agree that a 60A fuse on a 70A alternator is probably no 

 problem at all, and that if it blows in flight you probably won't want 

 to reset it, but (just thinking out loud) is it possible that the fuse 

 could blow and you not realize it, maybe thinking the alternator itself 

 is bad or the field circuit has failed?  With a CB in sight there is no 

 question where the failure is.

 

 do not archive

 

 Jesse Saint

 Saint Aviation, Inc.

 jesse(at)saintaviation.com

 Cell: 352-427-0285

 Fax: 815-377-3694

 

 On Jan 31, 2008, at 9:29 PM, Tim Olson wrote:

 

> 

>

> That's exactly my reasoning on using a 60A fuse (despite my 70A

> alternator). The fact is, if I find myself drawing 60A off

> my alternator, something is not right at all.  None of my

> avionics or equipment can draw that much, so my battery or

> wires are shorted or something.  You don't size your fuse by

> the alternator, you size it to the max load you care to see

> before you blow.  A 60A ANL fuse won't blow until well over

> 60A anyway, so if that baby blows, I sure as heck don't

> want to push a reset button in flight and figure it out.

> That fuse/breaker is a very big problem indicator.

> Tim

> PJ Seipel wrote:

>> 

>> Make sure you take a look at the data sheet for your breaker before 

>> you decide to upsize the number of amps too much.  For example, the 

>> 30 amp Tyco breaker I'm using for my backup SD-20 alternator is rated 

>> such that it may take up to 1 hour at 145% or 43 amps before it 

>> trips.  At 200%, i.e. 60 amps, it may still take up to 30 seconds to 

>> trip.  If that breaker trips, then my alternator is definitely 

>> overloaded and I'd sure want to take a look at the problem before 

>> continuing on.

>> PJ Seipel

>> RV-10 #40032

>> Carl Froehlich wrote:

>>> 

>>> <carl.froehlich(at)cox.net>

>>>

>>> Use a 70 amp breaker with a 60 amp alternator to avoid spurious 

>>> trips.  If

>>> the breaker does trip it means there is a serious problem, something 

>>> you

>>> might not want to troubleshoot in flight by resetting the breaker.  

>>> In my

>>> RV-8A I mounted the breaker on the engine side of the firewall.  

>>> This kept

>>> all the heavy wiring on the engine side of the firewall except for one

>>> penetration to the starter solenoid.  I have a dual battery install 

>>> with

>>> separate right/left busses that support continued IFR flight without 

>>> the

>>> alternator.

>>>

>>> Carl Froehlich

>>> RV-8A (375 hrs)

>>> RV-10 (wings)

>>>

>>> --

patrick.pulis(at)seagas.c
Guest

Posted: Thu Jan 31, 2008 8:50 pm Post subject: Alternator Circuit Breaker

William, the attachment supports your comments.



I have just completed an endorsement on the Cirrus SR-20 (need to fly

something similar until the ten is completed!) and I experienced an ALT2

failure last Sunday whilst VFR, so these things do happen and from what

I have been told are common.



Patrick

#40299	VH-XPP

Adelaide, South Australia

  



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Cirrus_SR20_Minimum_Equipment_Requirements.doc

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pitts_pilot(at)bellsouth.
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Posted: Fri Feb 01, 2008 6:35 am Post subject: Alternator Circuit Breaker

Tim Olson wrote:



 	  Quote: 	
		   



 That's exactly my reasoning on using a 60A fuse (despite my 70A

 alternator). The fact is, if I find myself drawing 60A off

 my alternator, something is not right at all.  None of my

 avionics or equipment can draw that much, so my battery or

 wires are shorted or something.  You don't size your fuse by

 the alternator, you size it to the max load you care to see

 before you blow.


	


Not really true.  The size of the breaker is there to protect the wire, 

which could cause a fire if it gets a large escess of current.  The size 

of the wire is dictated by the load.  True of small wires and big ones too.

Linn

do not archive



 	  Quote: 	
		     A 60A ANL fuse won't blow until well over

 60A anyway, so if that baby blows, I sure as heck don't

 want to push a reset button in flight and figure it out.

 That fuse/breaker is a very big problem indicator.

 Tim

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