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Old 29-05-2022, 04:17   #1
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a/c breaker keeps tripping

I have a Marine Air Systems A/C aboard an older boat that is new to me. Experimenting with it, I find that I can get the pump primed and it will pump fine for about 10 minutes or so, after which time it trips the breaker and shuts off.

Any ideas on what might be going on? Thanks in advance.
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Old 29-05-2022, 04:30   #2
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Re: a/c breaker keeps tripping

bad breaker
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Old 29-05-2022, 04:44   #3
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Re: a/c breaker keeps tripping

assuming the system was working previously. In oorder to trip a breaker you need to draw above it limits. Since is after 10 minutes I would check the wiring to make sure is not oxidated. this add resistance and increase current consumption. I would check with another breaker same current . If this dont work your pump is going dead soon.

another thing if you can check the pump consumption (make sure pump is not clog) with an AC meter and check against the spec. Normally if is not corrosion is the equipment pulling more to stay operational.
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Old 29-05-2022, 04:44   #4
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Re: a/c breaker keeps tripping

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Originally Posted by sneuman View Post
I have a Marine Air Systems A/C aboard an older boat that is new to me. Experimenting with it, I find that I can get the pump primed and it will pump fine for about 10 minutes or so, after which time it trips the breaker and shuts off.

Any ideas on what might be going on? Thanks in advance.
Not a lot of information to go on there, for example, do you know if it EVER worked properly? There is a detail that is important.

You mention needing to "prime the pump." I assume you mean the seawater cooling pump. In a proper installation, this should never be needed. The pump should be below water level, and there should be no high points in the plumbing between the seacock and the pump. Even if it is not the cause of the blown breaker, a pump that losses prime will be an ongoing source of frustration with the system.

If the pump losses prime, or otherwise stops, the compressor _should_ shut down on its internal high pressure switch, but if that switch is faulty, or if the breaker and/or wiring is marginally sized the breaker might trip as the compresser power draw goes up.

It is also possible that the cooling circuit is clogged with debris or biogrowth.

It's a bit of a reach, but with no details onthe system, it's hard to say...
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Old 29-05-2022, 05:57   #5
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Re: a/c breaker keeps tripping

Is the breaker thatís popping only for the pump, or the whole AC?

If itís for the whole mess, whatís the water flow look like?
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Old 29-05-2022, 08:47   #6
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Re: a/c breaker keeps tripping

Water flow is good when it's working and I checked for debris in the strainer and found none. I don't know much about the boat prior to me, but assume the A/C was working previously.
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Old 29-05-2022, 17:44   #7
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Re: a/c breaker keeps tripping

The pump may be a different brand than Marine Air. You should determine where the excess amperage is from, the pump or the ac. Marine Air has some of the best customer service in the marine industry. The phone number should be in your owner's manual. Call them. You'll be impressed.
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Old 29-05-2022, 17:49   #8
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Re: a/c breaker keeps tripping

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bad breaker
Guess you want a more exoctic reason to chase
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Old 29-05-2022, 19:29   #9
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Re: a/c breaker keeps tripping

had this once; lots and lots of looking.
turned out to be not enough cooling water and tripping off on compressor overheat.
put a bucket under cooling water output and get some real numbers; gpm or whatever your ac needs
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Old 29-05-2022, 23:25   #10
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Re: a/c breaker keeps tripping

Breakers that appear to trip for no reason is usually a bad breaker. Switch with another breaker and see if it still trips. Check the amp draw.
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Old 30-05-2022, 04:06   #11
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Re: a/c breaker keeps tripping

In my experience, it’s the compressor that causes surges in power draw when it first goes on. In many systems, there’s a delay between turning on the overall AC system (seawater circuit) and the time the thermostat first causes the compressor to engage. We have two compressors onboard. They kick in and off according to separate thermostats but when they both coincidentally kick in at the same time, that sometimes trips the shore power circuit breaker.

Try to see if the circuit breaks coincidentally to your compressor turning on.
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Old 30-05-2022, 05:10   #12
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Re: a/c breaker keeps tripping

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Try to see if the circuit breaks coincidentally to your compressor turning on.
If it's not a bad breaker you likely have a voltage drop in the wiring feeding the unit: wire gauge to small, loose or corroded connections, etc..

AC motors are designed to run at a constant RPM determined by the frequency (50 or 60 cycle depending on the country). If the voltage is low from voltage drop in the circuit, an AC motor will draw more amps to maintain the fixed RPM. Too many amps = tripping breaker and/or an overheated motor.

One other possibility from past overheating is cooked motor windings leading to an internal short in the compressor motor. I don't know about the serviceability of your particular AC system, but the really bad news is if the motor is cooked you may end up having to replace the whole unit.
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Old 30-05-2022, 05:19   #13
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Re: a/c breaker keeps tripping

I should add that since this is AC wiring, if you are not an experienced electrician, please hire someone who is before you hurt yourself or have an electrical fire.
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Old 30-05-2022, 05:29   #14
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Re: a/c breaker keeps tripping

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bad breaker
3rd5sm
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Old 30-05-2022, 09:14   #15
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Re: a/c breaker keeps tripping

How are you 'priming the pump'? Make sure your seacock is open all the way and check that your raw water filter is clear. (You DO have a filter, right?) One year our A/C pulled a lot of pine straw into the hose. Cleared the filter, but that did not help much. Took the hose off and it looked like a playdoh machine extruding the pine straw that was still stuck in it. After that it worked fine.
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