Alternator to Main Bus Mod

[ambrosesquadronca]

Can anyone think of a reason it would be bad to run a wire from the 60amp alternator circuit breaker to the main buss instead of to the starter contactor as shown in Bob's Z11 diagram? This would be a shorter wire run for my installation.

Thanks for your help.
Dave

[guccidude1]

If I understand what I think I know, the reason is by going to the starter contactor first, the battery is forward of the buss bar. The battery can dampen voltage spikes and more or less regulate the voltage . If you put the battery downstream from buss bar, the avionics suffer the voltage spikes and possible damage. Dan

[Joe]

Originally Posted by ambrosesquadronca

Can anyone think of a reason it would be bad to run a wire from the 60amp alternator circuit breaker to the main buss instead of to the starter contactor as shown in Bob's Z11 diagram? This would be a shorter wire run for my installation.

Dave,

I'm not totally clear of the location of your "60amp alternator circuit breaker" as my reference copy of Z11 uses an ANL fuse at the alternator.

But assuming the CB is located electrically at the same place (i.e. connected to the hot side of the starter contactor's feed), I can see no problem doing what you ask. Since both terminals are electrically "at the same place" you may use whichever terminal provides a shorter, easier, more robust, or whatever criterion you have for your connection.

Use of the starter contactor terminal is only a convention but a useful one as the 5/16-inch stud allows easy connection of a fat wire.

--
Joe

[Mich48041]

My name is also Joe and I agree with the other Joe. We Joes stick together.
The purpose of the 60 amp ANL fuse is to protect the wiring from excessive battery current in case the alternator shorts out. If the alternator "B" lead is connected to the main buss, then the 60 amp fuse should be located at the main buss. Engine starting current should NOT go through the 60 amp fuse.
Why are you using a 60 amp circuit breaker? A 60 amp ANL fuse is capable of carrying the full alternator output without nuisance blowing.
An alternator is self current limiting. It is not physically capable of putting out much more than than its rated capacity. If enough loads are added to the alternator output, the voltage will drop, thus preventing an increase in current much beyond the alternator capacity. Under those conditions, the alternator could overheat if not adequately cooled.
Joe Gores