a/c trips breaker -- sometimes - SailNet Community
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a/c trips breaker -- sometimes

Odd behavior from old Lunaire Marine model LPSC-16HL:

This old beauty still works, both heating and cooling. Itís 20+ years old. However, when I first turn on the cooling, the main panel circuit breaker (brand new, 30 amps) opens in about two seconds. During that time the ammeter reads about 40 amps and the voltage at the main panel drops to around 50v. (the air conditioner is supposed to draw about 15 amps.) After going through this cycle around ten times, it continues to run, the current reads about 18 amps, and the voltage drops from around 120 to around 100. (no other load is connected through all of this.) It runs fine, indefinitely, after that.

The heating option also works fine. The thermostatic control also appears to work. The rheostat (?) thatís supposed to control the fan speed does not work, but thatís not a problem.

Any thoughts? Wire too thin? What tests should I make?
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Re: a/c trips breaker -- sometimes

Often, these units have a start capacitor on them to help with soft starting. If yours is bad, the full locked rotor amperage on startup could be tripping the breaker.

Just googled - it has a start cap in it: http://trojanboat.com/wp-content/upl...-AC-wiring.pdf . Try starting there. If it is easy to replace, then replace it (they are inexpensive); otherwise search how to test a capacitor. Be careful to short the terminals first before touching them.

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Re: a/c trips breaker -- sometimes

I agree, it looks like your compressor is having trouble starting. The capacitor is what gives a single phase motor it's starting torque. First step is to replace the existing capacitor. They are cheap and generic. Brand doesn't matter, as long as it is the same microfarad (mfd) rating.

If that doesn't work you can try adding a Hard Start Kit. They give old compressors a little extra starting torque.

Both items should be available at any HVAC supply house.

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Re: a/c trips breaker -- sometimes

If you're not qualified or able, have someone go through the complete shore power supply from the dock all the way down to the receptacles I can almost guarantee you're going to find problems,

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Re: a/c trips breaker -- sometimes

Thanks -- a lot. I see a start capacitor on the wiring diagram -- says "with 15k, 2 w bleeder resistor" (if i'm reading it correctly). I'll have a look at it today or more likely tomorrow, and follow your advice from there. I can also get some guidance from a pro marine electrician, easily enough. If I can find it, I hope it has the parameters on it so that I can get the correct replacement, or maybe I can find it in the manual. Appreciate the help -- your suggestion makes a lot of sense.
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Re: a/c trips breaker -- sometimes

I've thought of that too, and even figured out how to test it. But I'll look into the possibility of a faulty start capacitor first, as I think it's more likely.

Many thanks for your help.
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Re: a/c trips breaker -- sometimes

Please take a picture of the compressor capacitor and wiring compartment of the air conditioner, I can take it from there,

the start capacitor is showing in dotted lines which means it's an added accessory. if you have it so we need to determine if it's there, it probably isn't,

Start up amperage is very very high for a split second but you should not be getting voltage drop

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Last edited by deniseO30; 5 Days Ago at 02:38 PM.
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Re: a/c trips breaker -- sometimes

Quote:
Originally Posted by SchockT View Post
I agree, it looks like your compressor is having trouble starting. The capacitor is what gives a single phase motor it's starting torque. First step is to replace the existing capacitor. They are cheap and generic. Brand doesn't matter, as long as it is the same microfarad (mfd) rating.

If that doesn't work you can try adding a Hard Start Kit. They give old compressors a little extra starting torque.

Both items should be available at any HVAC supply house.

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I agree, but also ensure that in addition to the micro farad rating is that you have the same or exceed the voltage rating, i.e. if you had an 100 mfd rated at 75V you could replace it safely with a 100 mfd 150V capacitor but not a 100mfd 50V capacitor. Exceeding the rated voltage on a capacitor is quite explosive and depending on where you are when it happens can result in shrapnel injury. I would also avoid those sold by Chinese merchants, go with a good brand Rubycon, Nichicon, Panasonic, Vishay, you may pay more but they will stay in spec and last. If you are curious just google first and second tier capacitors.
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Re: a/c trips breaker -- sometimes

You have a wiring problem if the voltage drops from 120 to 100 volts when it is running. lower volts means higher amps through the wiring. looks like a corrosion problem in the wiring.

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Re: a/c trips breaker -- sometimes

it seems to be human nature to dive into the major things and go for the major repairs, rather than taking the time to check all the little things. ALL wiring connections, terminals, connectors, are suspect on something that's 20 plus years old!

Shore power plugs and receptacles are notorious for being bad even when they look good!

Brass terminals will turn green!

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Last edited by deniseO30; 4 Days Ago at 03:56 PM.
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