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Old 07-08-2012, 10:52 PM
bkthomps bkthomps is offline
Join Date: Jan 2010
Location: Destin
Posts: 1,546

Originally Posted by Danny King View Post
I can't help you with the circuit breaker problem, but I will warn you of resetting circuit breakers repeatedly! That's not a good idea! The breaker trips due to a faulty circuit. The amp load that trips it is according to the anticipated load that circuit should carry. Resetting breakers can, and has lead to a fire.
i second this, was in an aircraft with a circuit breaker that kept popping, didn't know the crew had resorted to simply resetting it before each flight and then holding it shut, they did note that it would get hot and "stick" so they assumed it was a failing CB

yeah, so smoke and fire later, that mystery was resolved, faulty wiring not a faulty CB
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Old 07-09-2012, 05:26 AM
sailvi767 sailvi767 is offline
Join Date: Sep 2010
Location: Charlotte NC
Posts: 1,324

I would add to the above posts. As a general rule you can reset a breaker once. If it pops again its telling you something. Fuel pump breakers should never be reset in flight.

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Old 07-09-2012, 06:14 AM
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Walt Walt is offline
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
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The PP alternators will draw a full 4-5 amps on the field with a heavy load or low battery (I've measured it). Using a 5 amp breaker in this circuit is marginal at best, most breakers are +/- 20% tolerance so the problem is obvious. What would I do if it were mine... assuming the wiring is of the appropriate gauge, install a 7.5 amp breaker, it will still provide the required protection and eliminate the nuisance pops.
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Last edited by Walt : 07-09-2012 at 07:18 AM.
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Old 06-14-2021, 01:22 AM
Matthias Rottcher Matthias Rottcher is offline
Join Date: Jul 2020
Location: Namibia - Africa
Posts: 1
Default Alternator circuit breaker popping

My RV7 started popping the circuit breaker every now and then, but it got progressively worse. My panel has self resetting circuit breakers and when the alternator field popped the CB it took between 10 and 60 sec to reset. Resetting the popped circuit breakers is not the answer as the CB pops for a reason.
I run a Plane Power alternator which I took out and had tested at a local electrical shop. We could find no fault, but having read up on the Plane Power alternators I chose to exchange the rectifier. We tested the alternator with the new rectifier and it was the same as before showing no different. I reinstalled the alternator into my RV and have since done 10 hours without the circuit breaker popping. I like to assume that one or more diodes on the rectifier were faulty which caused the CB to pop.
It seems to be a common problem on the Plane Power alternators that the diodes on the rectifier start to go and then the CB pops.
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Old 06-14-2021, 07:23 AM
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vlittle vlittle is offline
Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,350

This makes sense. A bad diode will cause a missing phase in the alternator output, which reduces the average voltage of the alternator.

The regulator corrects for this decline in average voltage by increasing the field current which increases the voltages of the remaining phases. The average can remain the same, but the peak voltage increases. If the peak voltage is high enough, the alternator over-voltage protection will trip the field breaker.

What kills a diode? Two things: ambient heat and current (self heating). Despite PP's instructions, aim a blast tube at the diode array (vents in the rear) and put a heat shield in between any adjacent exhaust pipe and the alternator. That helps reduce the ambient temperature.

As for self heating caused by high currents: This happens if you have a dead or discharged battery, particularly at start-up. Make sure your battery is fully charged before starting and AND NEVER JUMPSTART! Jumpstarting will still leave the battery flat and the alternator will be running at maximum output and minimal cooling for several minutes after startup. Good way to melt diodes.

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Old 06-14-2021, 07:37 AM
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Steve Melton Steve Melton is offline
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Location: Cincinnati, OH
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reset CB's on the ground only. they pop for a reason.
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