AC not keeping up

[audcarver]

New owner of 1994 320 Voyager. Equipped with Marine Air System 16K to run on shore power. Boat had been sitting on the hard until July 3rd. Marine air appeared to work initially and cooled the boat to 77 degrees according to digital display when outside temp was 91. Today it is struggling to maintain 85 with outside temp of 91. Owners manual for the AC was not with the boat. Any and all guidance is very much appreciated.

[bud37]

Welcome to the forum.....one thing about boats, they are not insulated......if the sky is clear, sun beating down and humid, the air will have a hard time keeping up for sure.

Get an IR temp gun and shoot different areas, the side where the sun is on, the front window in the salon area....it will amaze you how hot those areas are....then check the discharge air temp at the vents.
Did ours today , vent temp was 61 and the readout temp would only get to 78....was 90 here and humid. Our boat does not have the big front window in the salon. and there was a sea breeze.

Check your return air vents for filter screens that may be blocked etc.

[g36]

Keeping the front window covered will help for sure also the water temp will effect your ac . The warmer the water you will find it will not cool near as well

[km1125]

Measure the water temp where the A/C unit is exiting the boat. If it's appreciably warmer then the actual water temperature the boat is in then you need to find out why. Perhaps the strainer is getting just a bit clogged slowing down the flow. Just a few gallons a minute difference can be the difference between the unit running "great" and "so-so".

[Helmsman]

I had the same problem two years ago. I put 3 or 4 1” bromine tablets (chlorine used mainly in hot tubs) in the AC strainer and ran it for 15 minutes. Then, I let it sit for a day or two while away from the boat. Immediately felt a big difference and has worked well since. A hot July and warm water is an issue though I still can get it down to the mid 70’s inside.

[audcarver]

Thanks everyone for your assistance. I did check the water temperature as suggested. Intake water 86, exhaust 91. I do not take that as a major difference. Please advise if you think differently. Exhaust water flow is strong. I would like a little more info about the use of bromine. I am currently leaving the AC on when away from boat on with a set-point of 85 to remove moisture and lower the strain on refrigerator. Again, thank.

[km1125]

See if you can measure how much water is flowing per minute. Just hang a bucket and count how many seconds to fill it, then do the math to get gal/min.

If you measured 5 degrees difference and your pump is flowing 3 gal/min and there's a 5 degree temperature difference, that's 7,200 BTU. At 5 gal/min it would be 12,000 BTU. At a 5 degree difference, you'd have to flow nearly 6.5 gal/min to get to 16,000 BTU. Most 16K BTU units spec a 400 gal/hr (6.6 gal/min) flow, which would be about a 5 degree temperature difference.

If there's a buildup insulating the pipes inside the heat exchanger, then the bromine or some other flush may help restore the efficiency of the heat exchanger. Each 1 degree difference in the output water temperature (at 400 gal/hr) is roughly equivalent to 3,200 BTU.

Also, make sure you're not sucking in too much hot humid air from outside through leaky door or window seals. You're somewhat limited because your engine compartment is (and needs to be) open to outside airflow, but if that air is leaking into the cabin it puts an additional load on the cabin HVAC.

[audcarver]

I will check water flow in a few days when back on the boat. Thanks for the detailed information.

[Wsullivan71]

I have the same units (2) in my 2001 404 and am experiencing the same problem here in hot, humid, Florida. The units are fine at night but struggle to keep up during the day. I cleaned out the strainer and the air intake filters and it helped a lot. But now after having them running for 4 days the rear unit’s condenser keeps freezing up. I bought a fan to try and keep the coils dry but it’s still freezing up over time.

[audcarver]

I have cleaned the filter. Will clean strainer when back on the boat. Thanks.