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Old 06-21-2016, 01:10 PM   #1
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Breaker ratings

I have an older but unused Airpax breaker labeled "F.L. Amps-40" and "Trip amps-50."

Which of these ratings should I be paying attention to for correct sizing? This is for a davit that seems to have done well with a 50-amp breaker for many years. I'm replacing it because it was damaged.

Thanks in advance.
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Old 06-21-2016, 01:45 PM   #2
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The breaker protects only the wiring, not the powered device.
What gauge is the wire?
http://forums.mikeholt.com/showthread.php?t=125173
Difference may be motor current versus resistive current . FLA is full load amps.

Your breaker is likely a 40 amp breaker.
The 50 amp is instantaneous trip.
A breaker can run at it's rating, when amps go over that, it will eventually trip off.
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Old 06-21-2016, 03:25 PM   #3
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Thanks, I understand that it protects the wire (which I believe is #6). I just need to know whether I have a 40 or 50-amp breaker.
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Old 06-21-2016, 06:35 PM   #4
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Wire Sizes and Fuses
6 gauge wire good up to 80 amps.
So a 50 amp breaker is ok. I would probably go to 50 amp breaker. The motor may occasionally draw more than its rated power. And the motor might also has an internal thermal breaker.

Does the motor have a plate telling you any info?
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Old 06-21-2016, 08:12 PM   #5
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Quote:
Originally Posted by angus99 View Post
Thanks, I understand that it protects the wire (which I believe is #6). I just need to know whether I have a 40 or 50-amp breaker.
You have a 40 amp breaker. It's normal for a breaker to hold until about 20% over its rating (common for fuses too). Manufacturers even publish "trip charts" which document how long it will take a fuse or breaker to trip depending on level of overload. All common fuses and breakers I've ever researched are roughly in that 20% above range, after that, time to blow all depends on the extent of the
Overload.

Ken
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Old 06-21-2016, 09:19 PM   #6
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Appreciate the info. I'll be at the boat tomorrow and will verify the wire size and amp draw of the motor.
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Old 06-22-2016, 11:44 AM   #7
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Be aware that the "amp draw" of your motor as stated on the motor plate is most likely the draw while the motor is running. The initial start-up current draw can be significantly higher. For example, I had a problem with my garage door opener 15 amp breaker going off occasionally. The "draw" was stated as only 3.5 amps. Turned out start-up draw could be as high as 18 amps. Solved the problem with a slow-blow hiogh magnetic 15 amp breaker. Now multiple doors operate simultaneously just fine.
In your situation I would definitely replace with another 50amp breaker (not the 40amp) or even higher, no matter what the motor plate indicates.
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Old 06-22-2016, 12:11 PM   #8
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All breakers have trip characteristics that can be expressed on a curve. Likely your breaker can run continuously at 40a, trip in xxx seconds at 45a, and trips quickly ?? at 50a. Without the curve, can't really tell.

But you should be ok to install it and try it. If it does not trip, you should be good to go.
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Old 06-23-2016, 01:46 PM   #9
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Sounds like a plan. Thanks, Ski and all.
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