AC not keeping up

[bud37]

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

Have you checked the intake air temp at the intake/return air vents in the cabin and compare that temp to the discharge air temp/cold air blowing vents.......there will be maybe 15 to 20 degrees difference max if all is working efficiently.

Less than 13 to 15 degrees difference means there is some problem, maybe heat exchanger, low on refrigerant etc

[Midnightsun]

Freezing up is usually an indication of poor air flow across the heat exchanger. Check to see if you have screens or filters in front of the heat exchanger and clean them, also make sure the air intake grate for the unit is not covered by pillows, a bag or whatever.

[km1125]

Think about this... if the evaporator is freezing, then there's obviously not enough hot air blowing across it to keep it from falling to freezing temperatures, and you're not getting the "cold" from the unit to the "hot" in the room.

Check ALL ducting for ANY obstructions. If you have closed off ANY registers, then open them back up. If you have ANY filters in place then check to see that they are not too restrictive (like the super-duper anti-allergen filters) and that they are clean.

If the circulation fan is set to a lower speed than "FULL", then bump it up a step or two to get the most air moving. I think on all the programmable ones now you can set a "max" and a "min" fan speed... check how yours is programmed.

Also make sure you're not "short cycling" the air. If there's a cold register too close to the return, then you might be sucking back in cold air, which is doing nothing to help you cool the room. Sometimes just redirecting the register to point away from the hvac return duct is all you have to do.

[Viper]

I assume when you say you cleaned the filters, you're also checking the filter on the evaporator, and if yours doesn't have a filter there, that you're ensuring the evaporator fins are clean too.

Is it the evaporator or the condenser that's freezing?

Is the unit running constantly, never shutting off, and maintaining 85* or is it shutting off periodically and never getting low enough as a result?

What model control panel do you have?

[cpoint]

Agreed, keeping front windows will help somewhat. But old units are just not great keeping up. Also as mentioned above, boats are not insulated well. So speaking of AC, has anyone found a quieter one for 2000 carver 356? The back one is ok, as it is under bed, and sound is insulated. but the one in main cabin is under kitchen seat, and the sound of compressor is unbearable. I am planning on replacing it, but would like to get something that would be a close to direct replacement as possible. just hookup existing power line and water lines, and hope whisper quiet. Any one replaced it yet that can recommend a unit?

[Midnightsun]

I replaced all 3 of mine with MarinAire units. Had done this on my previous boat also with the same brand. These are cold as in really cold and very quiet. Toshiba compressors which are the quietest made and arguably the best there is. I highly recommend this brand above all other common high end names out there.

Now do not get my recommendation confused as the units that came with most our boats are Marine Air and not MarinAire like I am suggesting. https://www.marinaire.com

[waybomb]

An evaporator will also freeze up with a slightly undercharge of freon. A slight undercharge will result in a lower suction pressure, thus a lower temperature of the coil. If you filters are clean, and the evaporator is freezing over, have somebody add a bit of gas.

And to the point of scroll compressors, I agree. The blower is louder than the compressor. I happen to have a Webasto unit as my front cabin ac, and it's right under the bed. The air coming from the vent is louder than the unit itself.

[Helmsman]

Qr Bbpost 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.

The bromine idea came from the AGLCA site. I have been a member there for a couple of years. I asked about the AC not producing enough cooling and this was one of the suggested solutions. Several on the site stated that they used Bromine (not regular pool chlorine) to clean “stuff” that has grown in the system. Knowing the players over there, I knew the ones offering the advice were experienced live aboards who give advice you can listen to.

I was cautioned to just put two or three in, run it some and then let the bromine work over night, then run some more. The bromine will dissolve over a few days completely. A couple of posters stated that they do it every year, though most treated once or twice and then didn’t have to anymore. Worked for me!