Strange A/C performance

P

PatSea

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I was running the Marine Air A/C model 12 on my 32' express cruiser this week on a very hot day where the temperature reached 92. The A/C had run for about 7 hours straight and brought the cabin temperature down to about 75, which I consider good performance considering the water temp is at least 80. After running about 7 hours straight the compressor and water pump shut off but the fan was still running. I noticed the red protective device on the unit had tripped. The compressor was quite hot, but then it always is hot after running for a long time.
I reset the button on the protective device, let it cool down for about 30 minutes, then it ran fine for the next two days. Do I have a problem or is this explainable by the very high temperatures? BTW, the protective device has tripped occasionally over the years, but only when the A/C was restarting. I never had it trip out while running.
 
To be honest I think the system was functioning normally. The trip is there to protect the compressor and I think it did it's job.
 
check the water flow to make sure it's strong enough. as water temp goes up in summer, everything runs hotter.

that said, are you sure the red "device" is overheat protection? on all the compressors i've seen, the heat protection is built in the compressor and self resets. where is it located? if on a gas line, it's not a thermal device but gas pressure. high means not enough water flow.
 
I forgot to mention in my original post that I checked the filter and it was clean. I also had a real good water flow. I was just wondering if maybe the protective device was going bad and tripped when it should not trip. BTW, what does the protective device measure? How does it work?
 
Pascal, the device sits on top of the unit and has a small tube (I assume with refrigerant) running into it. It also has wiring running from it to the unit control box. So I'm assuming it is measuring pressure, not temperature. It has a small reset button on the side that must be reset manually when it trips.
 
sounds like a manual high pressure switch. That woudl mean the pressure was too high, likely due to not enough water flow or incorrect charge.

i'd leave it alone for now to see if it was a one time glitch, otherwise have an AC guy check pressures.
 
I had a unit like that and it always tripped when the water flow was impeded.

YMMV.
 
You may have had a piece of gunk block your inlet and when it tripped and shut down the gunk floated away .

You really have to respect the power of gunk :)
 
You guys may have hit on the answer. There was an unusual amount of eel grass and other debris floating around the marina this week. I only looked at the water stream after the unit restarted.
 
If you have good water flow and your compressor is running very hot all the time you could be low on Freon. The incoming Freon line should be cold right up to the compressor as I recall. In fact right where it attaches to the compressor it should be cool. If not, your Freon charge is more than likely low.
 
Capt. Bill, the freon line was very cold in the 3 or 4" leading into the top of the compressor. Also, I'm getting at least 20 degree differential between the marina water temp and the cooling air temp which I believe is about all that can be expected from this type A/C system. Bottom line, I don't think it's a compressor/refrigerant problem.
 
Red button is a high pressure switch . Low water flow , is usual culprit . Low freon is not an issue here .

Examine the strainer and flush the liines with water is a great start

Rob
 
Red button is a high pressure switch . Low water flow , is usual culprit . Low freon is not an issue here .

Examine the strainer and flush the liines with water is a great start

20 degree temp difference is between the space temp and the air discharge out of the ac unit ! A 20 degrees temp differential is excellent

Rob
 
Thanks for all your replies!! I'm concluding that the most likely explaination is a temporary water blockage. I will check the strainer when I return to the boat.
Robski, your comment about the temperature difference being measured between the space (cabin?) temp and the cool air discharge temp is interesting! I can see how the cabin air temp plays a role as it is the air drawn across the evap. However, it seems the water temp that the boat sets in also is a factor in the A/C performance as this water is drawn thru the unit. Maybe one needs to consider both of these to determine the A/C system performance. I was considering only the water temp.
 
Water temp is most def a factor ! Warmer the water the more load on the equipment . The 20 degree number u spoke of is the ideal temp drop pertaining to the air temp with in the cabin .

Rob
 
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