a/c breaker keeps tripping

[Dieseldude]

Originally Posted by Mauruuru

My pump is driven from the A/C breaker and is controlled by the A/C controller. I had a problem with my compressor and the temperature limit switch would trip and then the system shut down. Of course the water pump would turn off too. Is the pump magnetically coupled impeller? If not is it leaking along the shaft onto the motor housing? If so time for a replacement with a magnetically coupled impeller (totally sealed pump).
Are there other things going on like high temp/low pressure switches shutting down the system? A typicall AC circuit breaker will carry 1.5 times rated current forever, and 2X for hours to days before tripping on overload. Because the time/current characteristics are logarithmic it will take a real motor/pump problem to trip the breaker on load alone.

I've had a similar problem. The compressor would shut down. But the sea water pump was independent of the system controls. Problem was that the sea water pump had been shut off. Without sea water cooling, the compressor shut itself off on excess head pressure. There should be a pressure switch somewhere in the compressor discharge. Restarting the sea water pump and resetting the pressure switch solved the problem. If discharge pressure becomes excessive, it will shut off the compressor. This can be caused by poor sea water coolant flow. The pump could be defective, or the pipe work or condenser tubes could be choked off with marine growth. Excessive charge of refrigerant could cause this, but you had not mentioned if any refrigerant had been added. Do you have a tube and shell type cooler? These are not hard to clean with a rifle style brush once you remove the end covers. But sometimes clearance to maneuver the brush is an issue. They should have anodes that ought to be checked too.


Before opening up any equipment, can you look at the sea water discharge? Does it look normal? But since this is a new to you boat, it could be hard to tell. Does the pump have a pressure gauge, and do you know its normal reading? A choked discharge path will cause excessive pressure. If there is a suction gauge, this can be helpful to check for any suction obstruction. But you need to know what is normal.



A magnetically coupled pump would be a rare item. Magnetic coupling arrangements are quite expensive, compared to conventional shaft with mechanical seal or gland. So I would not expect to find one aboard most cruising boats. If you remove any shrouding or covering from the pump and motor, you should be able to see what type of coupling you have. Spider type shaft couplings for direct drive equipment are quite common. If the shaft seal is leaking, you would know by finding water under the pump.

[Bowdrie]

Have installed a few and serviced a few dozen.
Mag drive pumps are not rare at all, they are quite common for marine AC systems, in fact just about every system that Marinaire sells features them, they are also common for refrigeration use.
https://www.marinaire.com/category-s/25.htm

The condensers on many of the AC units of the sizes most used for pleasure boat application are generally produced by Packless Industries.
https://packless.com/products/conden...ls/shape/helix

You should not have to prime a system, the majority of the pumps are centrifugal and need to be mounted under the waterline or a check valve needs to be used so they hold prime.
Below waterline mounting without a check valve is better, it allows the water to back-drain from the condenser so that the condenser doesn't have standing water in it during the off cycles, (particularly when not used for days/weeks/months at a time).
Yes, this requires a seacock on the pump inlet that you will close when not needed.
Avoid long/convoluted hose runs.

[piloto]

Originally Posted by Lepke

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.

Two words (or is it three?) clamp-on meter

[Sailorman4009]

I had the same problem. The freshwater pumps that came with the system were oil filled to prevent water intrusion and as old as the original installation. This oil leached up the electrical cable and dried out the interior of the motor causing it to over heat and blow the breaker. I replaced the freshwater pump motor and everything ran smoothly. If that doesn't work look to the starter capacitor on the compressor or even the compressor itself.

[Cheechako]

As mentioned multiple times, it's unusual for a breaker like used on most boats to fail and break fast and early. So try that first.
They are not expensive.

I had built in AC that I tried to run on the hard by recirculating water. It didnt work as the water heated up fast and it would throw the AC breaker when it did.
SO step 2 after the breaker would be to check for adequate cooling from the pump.

[BelizeRumRunner]

It could also be the fan motor. The motor can get sticky and be hard to spin. You might be able to remove the duct work from where it attaches to the fan and move the fins with your hand to see how easily or hard it is to turn. This was an issue I had. I replaced the squirrel cage fan and it worked fine. To see if it is the breaker itself put an amp meter on the positive side of the wiring when it is on for that brief time and see if it draws more than the breaker rating. If you put the meter clamp around the positive and negative wires they cancel each other out and dont give a correct amp draw. Just test one leg.

[bstreep]

Wow. Lots of advice here! One more to add: If you have a March or similar mag pump that's designed to work both submerged and dry, and you are running it dry, it might be the problem. Those pumps have tiny tubing on them that routes cooling water to the motor on the pump. Those passages can and do become clogged, causing the pump to overheat, stall, and quit pumping. It might be enough to throw a breaker, as it is a stalled motor. This, of course, will cause your compressor to kickoff due to a lack of cooling water.

P.S. I do have an HVAC certification, but I'm not in the business. Just so I can legally do my own HVAC and refrigeration work, and buy stuff.