AC not working well

[BRHEAUME]

Hello, all.
I have a 355 Motor Yacht. Two AC units, forward is 16,000 BTU, rear is 12,000 BTU. I find that the velocity of air out of the registers is not strong at all. The air that is coming out is cold (going to verify temp with infrared thermometer) but it just doesn't seem to have enough air pressure (similar to having the AC in your car on the lowest fan setting). Is this normal? I've checked the screens, coils (cleaned both) and can't seem to get the AC performing well. (only a 5-10 degree drop from outside temperatures in the cabin)

[bud37]

Have you checked your cold air return vents......many times they have a metal screen that gets restricted over time.

[km1125]

Are your strainers clean?

How is the water flow? At 300 gal/hr (which might be true flow with a "500GPH" pump but going through restrictions of heat exchangers), that's only about a 10 degree temperature difference from input water supply (lake temperature) to outlet temperature. When you check the indoor air temps with the IR gun, also try and get a reading of the temp of the outflowing water as well as the actual local water temp. If you're flowing 300 GPH, then every ONE degree of water temp change is about 2,400 BTU, so if you're off be just a few degrees in the water temp rise it affects the overall capacity of your HVAC systems.

[BRHEAUME]

Strainer was cleaned (did have quite a bit of growth), but didn't help once clean and back in operation. The seawater pump was next on the list to check. Good advice on the seawater temps vs. outlet of outflowing water, I'll check that. Thank you so much for the feedback.

[Midnightsun]

You probably just need to check the vents as suggested and then the unit itself as there most likely is a screen or something preventing the dust and stuff from adhering to the heat exchanger fins. Take a good look at those fins as they may be covered in dust/gunk and preventing your airflow. Careful as they are easily bent, ideally if you can get in there with a soft brush on a shop vac to clean it up.

That being said, if vents are blocked substantially and you are not getting enough air through, the unit will normally frost up on you which may be the case. Have you physically looked the units heat exchanger? The thing that looks like a radiator on a car? It may very well be all frosted up blocking your air flow.

I always clean the filter screens on my units at least once every summer as part of general things to do on board before my first beer that is.

[bud37]

Just to clarify....air return vents are in the cabin area, behind the vent grills if they open are usually metal screens that can be totally restricted, thus cutting off return air to the fan to cool and be sent back to the cabin.

Verify that first...

[BRHEAUME]

Thanks for the response. It's not frozen up, and the coils have been cleaned. It's a real head scratcher. I took the inlet screens off and cleaned well.

[bud37]

Another thing I will add.....if it is 95 degrees out, sunny and humid, and the salon cabin window bra is black it will be a hard hill to climb no matter what. These boats a not insulated and a quick check with your IR temp gun will reveal temps well over 110 degrees plus, sometimes 150 on surfaces near the windows.

Have you been thru a summer with your boat yet, is this a new issue ?

[Viper]

Make sure you don't have them set to a slow fan speed at your control panels.

[km1125]

Source of the post Make sure you don't have them set to a slow fan speed at your control panels.

This is a good point.

Which controls do you have?? On some you have to go into the settings mode to select the default or max fan speed.