Marine Air Systems Tripping Breaker

[Stasis]

I have two older three-dial Marine Air Systems AC units on my boat, sharing the same water pump. One of the two units is tripping the breaker, the other is functioning fine. So far it has only been during the peak heat of the afternoon however it has only done it for a couple of days so I am not sure if the high heat is causing it.

After turning the unit on, the compressor seems to run for about 30 seconds and I get cool air coming out. The amperage is at 17.5 while the plate indicated 16 amps peak for cooling. After around 30 seconds I hear the compressor shut off, draw goes to 2.5 amps. Then after about 10 seconds I hear a click in the unit somewhere and the amps spike to around 47 and trips the breaker. I am pretty mechanically and electrically inclined but do not have much experience with AC. Anybody have any suggestions or troubleshooting steps to avoid replacing the compressor/entire unit?

[a64pilot]

Has refrigerant been added recently?

[Stasis]

Originally Posted by a64pilot

Has refrigerant been added recently?

Nope, boat has been in our possession for about 5 years and hasn’t ever had any added during that time.

[Thumbs Up]

A lack of or clogged cooling water system will cause the high pressure switch to disengage. The compressor is unable to restart after only 10 seconds thus trips the breaker. I am no expert on AC systems but Google says to check your cooling water system for low flow, a bad pump, or clogged strainer. The condition is called short cycling and can also be caused by a faulty thermostat.

[a64pilot]

What it sounds like is happening is that the compressor is being short cycled, meaning it’s off and of course stops at a compression stroke, plus there is high pressure in the line, and then it attempts to start again, but as it’s a locked rotor it pulls an excessive amperage and the breaker does it’s job.
Normally a compressor has a timer and won’t allow it to be restarted so quickly, given a couple of minutes and the pressure bleeds off through the expansion valve of course.

If it had been over serviced, that’s one reason it could be acting like it is.

If I had to guess, it has a clogged expansion valve and it has a high pressure switch, but that’s a guess.

Normally a compressor starts, then several seconds later you heat a whoosh as the valve changes over from heat to cool, but the compressor never stops.
Perhaps the reversing valve is stuck or is sticking? Maybe give it a percussion adjustment with a wrench, sometimes that will free a stuck valve. What do you have to lose?

You could also try installing a hard start capacitor, cause what your describing is called a hard start. Hard start caps are cheap and easy to install, what they do is give the compressor a hard kick to get it going through the locked rotor.
https://georgebrazilhvac.com/blog/wh...hard-start-kit

[Stasis]

Originally Posted by a64pilot

What it sounds like is happening is that the compressor is being short cycled, meaning it’s off and of course stops at a compression stroke, plus there is high pressure in the line, and then it attempts to start again, but as it’s a locked rotor it pulls an excessive amperage and the breaker does it’s job.
Normally a compressor has a timer and won’t allow it to be restarted so quickly, given a couple of minutes and the pressure bleeds off through the expansion valve of course.

If it had been over serviced, that’s one reason it could be acting like it is.

If I had to guess, it has a clogged expansion valve and it has a high pressure switch, but that’s a guess.

Normally a compressor starts, then several seconds later you heat a whoosh as the valve changes over from heat to cool, but the compressor never stops.
Perhaps the reversing valve is stuck or is sticking? Maybe give it a percussion adjustment with a wrench, sometimes that will free a stuck valve. What do you have to lose?

You could also try installing a hard start capacitor, cause what your describing is called a hard start. Hard start caps are cheap and easy to install, what they do is give the compressor a hard kick to get it going through the locked rotor.
https://georgebrazilhvac.com/blog/wh...hard-start-kit

Suggestion on how to identify and locate the valve?

[Stasis]

Originally Posted by Thumbs Up

A lack of or clogged cooling water system will cause the high pressure switch to disengage. The compressor is unable to restart after only 10 seconds thus trips the breaker. I am no expert on AC systems but Google says to check your cooling water system for low flow, a bad pump, or clogged strainer. The condition is called short cycling and can also be caused by a faulty thermostat.

I guess the water supply could be clogged however two units use the same water supply and pump, and I have a good flow coming out of the discharge fitting so I thought that was unlikely.

[Cpt Mark]

Call the manufacturer. I found them very friendly and helpful

[GuerrillaCamper]

Just because you have "good" water flow out of the system does not mean you are clog free. I went through this exact problem about 2 months ago. Two Marine-Air units on a common circulator pump. Downstairs unit was initially cycling or shutting down. A small oscillating fan placed directly in front of the unit's intake helped for a while but then... the dreaded high pressure fault.

I replaced the pump...
I cleaned all of the zebra mussels from the raw water strainer...
I reamed the through-hull
All to no avail.

Then I bought a small plumbers' snake and cleaned ALL of the lines to and fro, re-primed the pump, and fired them up.

Success!!
Both units have been running perfectly ever since (and I have a spare circulation pump, to boot).

[Coolerking]

It is super easy to just have someone (you) place your hands on the condenser tubing, the actual part that the seawater flows through and then ask the unit to cool...if it's not getting water flow, you will know very quickly.
In fact the water should be running through it in the opposite direction that the refrigerant does, so if its hot as hell at the far side then you know you have an issue.
Of course if you have 2 units and one works perfect, then you have an example of the temps you should have at various locations on the unit.

[Stasis]

I was wanting to try cleaning the coil as it never has been. Everything seems to be riveting, I don't see any easy way to access the coil without completely removing it. Am I missing something?

[Coolerking]

Take a picture and post it up, but it goes something like this, close thru hull, loosen hose clamps on seawater hoses, remove hoses and attach flush kit.
Flush it out with barnacle buster for about 10 minutes, rinse well immediately with clean water (salt or fresh).
Hook hoses back up, tighten hose clamps, open thru hull, bleed/flood pump head, run unit.
Easy.
You could have bad compressor start components too, but that's a whole new ballgame.

[Stasis]

Originally Posted by Coolerking

Take a picture and post it up, but it goes something like this, close thru hull, loosen hose clamps on seawater hoses, remove hoses and attach flush kit.
Flush it out with barnacle buster for about 10 minutes, rinse well immediately with clean water (salt or fresh).
Hook hoses back up, tighten hose clamps, open thru hull, bleed/flood pump head, run unit.
Easy.
You could have bad compressor start components too, but that's a whole new ballgame.

Thanks much for the instructions, I will likely do this as well but I meant the exterior from the airflow. A neighbor mentioned that he gained a considerable amount of cooling performance by cleaning the dust and gunk built up on the exterior. However my coil has a cover over it which is all rivetted on.