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  1. #1

    Airpax Circuit Breakers – How do they go bad?

    Anyone know why circuit breakers go bad? I have found about 3 of the Airpax 12 volt breakers on my 1976 43DC have gone bad. I put a new load on one and maybe it works for a few minutes, then it appears the voltage drop goes thru the roof, but they don’t trip. If I reset, they still don’t work, but maybe leak just enough to make you think the problem is elsewhere – you get a 12.7 volt reading at terminal, but try drawing some juice off it (like a 2 amp motor) and watch it go to 8 volts. This has happened on three spares I used and was a real bitch to trace the first time it happened. Now it’s the first thing I check and it’s always been the problem.

    Curious - what happens internally that make these breakers go bad?

  2. #2

    Re: Airpax Circuit Breakers – How do they go bad?

    The breaker starts to go bad the first time it is tripped. There is a heating type element inside that starts to loose its elasticity when it gets hot. After numerous trips the element takes a permanent set and will not reset. They are not intended to be a current limiter switch as such. They are a safety device to prevent overloads on the wiring. After the first few trips the unit will start tripping at lower and lower levels until it no longer will reset.

    BILL

  3. #3

    Re: Airpax Circuit Breakers – How do they go bad?

    Just to stay on track, the Airpax breakers used on Hatteras boats are magnetic breakers not thermal.

    Pete

  4. #4

    Re: Airpax Circuit Breakers – How do they go bad?

    Interesting - I thought all circuit breakers were of thermal design. For anyone following, here is a short and nifty explanation of how both types work - http://www.bcae1.com/cirbrakr.htm.

    I turn everything off at electrical panel when I leave the boat with exception of bilge pumps and battery charger. Am I adding allot of wear and tear to AirPax magnetic circuit breakers by doing this? Looks like magnetic design would be no problem (and I guess why Hatteras used them). I turn all appliances off first so I don't arc internally on breaker. Maybe previous owner left appliances on and shut off and on from electrical panel that caused arcing in breakers and caused oxidization of internal electrical contactors. After installing new bilge pumps, deck lights, inverters, etc over past year – I moved breakers around to fit need, so possible these 3 bad ones were once heavily used. New breakers solved the problem immediately.

  5. Re: Airpax Circuit Breakers – How do they go bad?

    The issue with all breakers (including magnetic) over time becomes contact erosion if they are opened under load.

    Avoid doing that!
    http://www.denninger.net - Home page with blog links and more
    http://market-ticker.org - The Market Ticker

  6. #6

    Re: Airpax Circuit Breakers – How do they go bad?

    Will do. Because the 'bad' breakers don't trip and can leak full voltage with no load on them, I thought worth posting as a good place to start when troubleshooting. First thing I do when something replaced that was not working acts eradicately is take the positive off load end of breaker and piggy back it on breaker I know is good. You can then order a new one and possibly leave positive piggy backed on other breaker pending you don't need both loads at same time. Wish there was a cheaper replacement for Airpax that fit exising opening cleanly.

  7. #7

    Re: Airpax Circuit Breakers – How do they go bad?

    I have always been told that it is a bad idea to use breakers as ON/OFF switches on a regular basis. Cheap switches can be inserted and used for that purpose.

    Have other people been turning things off every week using the breakers? How do they hold up?

    I also find it frustrating that you can't turn off power to the DC panel (Ships Service) without cutting power to the bilge pumps. In my old boat, the bilge pumps were all on circuits separate from the main DC panel so you could just switch off the whole panel via a disconnect. That way you don't have to be flipping breakers all the time. Hatteras must not have liked this arrangement for some reason.
    Last edited by fissioneng; 07-14-2009 at 04:27 PM.
    Looking for another boat...not a Hatt

  8. #8

    Re: Airpax Circuit Breakers – How do they go bad?

    Quote Originally Posted by Pete View Post
    Just to stay on track, the Airpax breakers used on Hatteras boats are magnetic breakers not thermal.

    Pete

    How do they work?

    BILL

  9. #9

    Re: Airpax Circuit Breakers – How do they go bad?

    I've addressed this tripping breaker problem quite successfully. If I encounter a breaker that's tripping I simply replace it with a much larger breaker. For instance if Hat fitted the circuit with a 10A breaker and it's tripping I simply replace the 10A with a 50A and it never trips again. I'd like to elaborate on this method further but I've got to go because I smell something burning.

    Brian

  10. #10

    Re: Airpax Circuit Breakers – How do they go bad?

    "I'd like to elaborate on this method further but I've got to go because I smell something burning."


    Good one!
    Mike P
    San Miguel de Allende, Mexico; Kent Island MD; San Antonio TX
    1980 53MY "Brigadoon"

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