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Alternator circuit breaker

I don?t follow the logic of a resettable alternator circuit breaker on the panel. The wiring from the alternator will be sized to handle all the current the alternator can make. But if the alternator was to fail a certain way, it could ask for everything the battery can deliver which is much more amps. So...put an inexpensive current limiter (large fuse) on the engine side of the firewall near the battery in-line of the wire going to the alternator. See...

https://www.amazon.com/Blue-Sea-Systems-Block-Insulating/dp/B000K2K7TW

And a fuse sized for the alternator max output that the wiring can handle, see

https://www.amazon.com/Blue-Sea-Systems-ANL-Fuses/dp/B01LBPMZ14

If this ever blows, you will not need to try to reset it. Your voltage will drop from alternator output voltage (14+ V) to battery voltage (12.5) in short order letting you know you?ve lost the alternator and go from there. If you have an engine monitor with alarm functions, set to around 13 v to let you know the alternator is offline.

Bevan
 
Bevan said:
I don?t follow the logic of a resettable alternator circuit breaker on the panel. The wiring from the alternator will be sized to handle all the current the alternator can make. But if the alternator was to fail a certain way, it could ask for everything the battery can deliver which is much more amps. So...put an inexpensive current limiter (large fuse) on the engine side of the firewall near the battery in-line of the wire going to the alternator. See...

https://www.amazon.com/Blue-Sea-Systems-Block-Insulating/dp/B000K2K7TW

And a fuse sized for the alternator max output that the wiring can handle, see

https://www.amazon.com/Blue-Sea-Systems-ANL-Fuses/dp/B01LBPMZ14

If this ever blows, you will not need to try to reset it. Your voltage will drop from alternator output voltage (14+ V) to battery voltage (12.5) in short order letting you know you?ve lost the alternator and go from there. If you have an engine monitor with alarm functions, set to around 13 v to let you know the alternator is offline.

Bevan
Click to expand...

I agree,
If your alternator CB pops, you don't want to reset it. I also have a current limiter installed on the firewall versus a CB in the cockpit. This is a simpler system that does not require another high load circuit on the cockpit side of the firewall. Keep a spare current limiter onboard and troubleshoot once you get back on the ground.
 
To the original question, the $34.50 70amp breaker is just fine - I used this breaker on three RVs.

You want a 70amp breaker to avoid nuisance trips as will happen with a 60amp breaker on a 60amp alternator. Keep in mind that a 60amp alternator is nominally rated - so it can easily exceed 60amp output if you load it up - for example a depleted battery.

I mount the breaker on the engine side of the firewall so this is not something I reset in flight. But - I still prefer using a breaker.

Carl
 
johnbright said:
60A alternator uses 60A ANL current limiter.

http://www.aeroelectric.com/articles/anl/anlvsjjs.html
Click to expand...
That depends. ANL type fuses tend to be Slow Blow, but not always. If you use a 60A Fast blow it may blown more times than you feel comfortable with. A 60A Slow Blow is a better option to prevent nuisance failures. Most alternators are capable of between 10 - 25% greater power output than rated for about 10 seconds. With fuses and circuit breakers you size them to protect the "wires" not the equipment.

:cool:
 
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