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Old 06-18-2018, 03:28 PM   #1
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AC freeze up

I have a 40 ft mainship trawler with a 16,000 BTU AC unit in the salon. On days in the high 80's the unit freezes up it's AIRRRRR marine unit. I set it up by the manual even have heat for 3 minute to stop it from freezing.I set the temp down to 68 degrees on very hot days is there something I'm doing wrong. Tom
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Old 06-18-2018, 03:47 PM   #2
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All my A/C's automatically go into heat mode occasionally to stop freeze up. I can feel hot air for a couple of minutes and then its back to cold.


My Mrrrrrrrrr and my Technicold both do it.
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Old 06-18-2018, 04:09 PM   #3
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AC freeze up

On your AC what temp do you set it on at very hot days. Tom
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Old 06-18-2018, 04:10 PM   #4
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A/Cs freeze up is usually due to low air flow and that is often caused by dirty filters. So first clean your filter. If freezups continue, make sure that the blower is on high. If it still freezes up then you may have a duct problem- not enough square inches of duct or a restriction somewhere.


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Old 06-18-2018, 04:19 PM   #5
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A/Cs freeze up is usually due to low air flow and that is often caused by dirty filters. So first clean your filter. If freezups continue, make sure that the blower is on high. If it still freezes up then you may have a duct problem- not enough square inches of duct or a restriction somewhere.


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Old 06-18-2018, 04:42 PM   #6
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Low air flow but more than likely low freon pressures you need to put a set of gauges on it and see what you have you could have a slow leak
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Old 06-18-2018, 06:11 PM   #7
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Modern AC units are completely sealed, no Sharader valves are on units made for some time now as a general rule. Bottom line, if you are low on refrigerant then you have a leak...that ain’t good. To prove that you have a leak is PIA. Rather than evacuating the unit, a sniffer might tell the tale. A tap valve can check as an isolation tool, but there will be a valve needed to be soldered on.
That being said, concentrate on the cheap and easy first, which is blocked air flow. Check the very thin filter, it is usually right against the intake side of rhe coils and hard to see slides up. Pull it and wash it. Home Depot sells coil cleaner in a rattle can for less than $6 as I recall. With filter out and AC running, spray the foam on the coils. Condensation will wash the foam to the pan and clean the coils, replace the filter. See if that works, then move on to duc’s as mentioned in previous post.
If this does not work, well good luck. You will have to make the decision to attempt to repair or replace. The units are almost disposable. Considering cost of hired help, many, if not most of the time it is better to bite the bullet and get a new warranted, highly efficient unit. Sure wish I had done that with my cursed Westerbeke Genset.
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Old 06-19-2018, 07:23 AM   #8
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Originally Posted by tomsboat View Post
I have a 40 ft mainship trawler with a 16,000 BTU AC unit in the salon. On days in the high 80's the unit freezes up it's AIRRRRR marine unit. I set it up by the manual even have heat for 3 minute to stop it from freezing.I set the temp down to 68 degrees on very hot days is there something I'm doing wrong. Tom

No way our saloon unit (MarineAirrrr 16K BTU) would ever get that area down to 68F if outside temps are in the high 80s.

We usually set ours for about 76-77F, partly because we find lower than that isn't necessary and partly to make the noise go away from time to time. Even then, the reversing valve causes the unit to switch to short bursts of heat occasionally...

-Chris
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Old 06-19-2018, 08:22 AM   #9
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On your AC what temp do you set it on at very hot days. Tom

A common misconception is that the lower one sets the thermostat, the more the A/C will cool. If you turn on a light switch, can you make the lights brighter by pushing harder on the switch? Your A/C thermostat is nothing more than a switch. There are no degrees of "ON". It's either ON or OFF. It will be "ON" until it reaches the setpoint, then it's "OFF"



There are non-invasive ways to check for system performance that don't involve attaching gauges. Check the air flow, as others have recommended. Most A/C problems are air side function related, get that all sorted before jumping to the conclusion that you must immediately get gauges on the system. Without the skill set to back up that choice, it can just compound the problem and obscure the solution. Once you have the gauges attached, what will you be looking for? If you're unsure, then your best option is to call in someone with experience.
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Old 06-19-2018, 09:11 AM   #10
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This below, a/c is coldest when its low on freon which then causes freeze ups.

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Low air flow but more than likely low freon pressures you need to put a set of gauges on it and see what you have you could have a slow leak
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Old 06-20-2018, 05:18 AM   #11
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I had the same problem on my 16,000 btu unit. The manual for the unit requires a specified amount of air flow for the unit to operate. The small grill below the steering wheel is not enough return air to meet the needs of the AC. We installed a grill on the second step and that fixed the problem. Also, you cannot have anything up against the AC unit nor can you have a lot of stuff in the compartment because all of that restricts air flow.
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Old 06-20-2018, 09:15 PM   #12
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Freeze up

Jugutten would love to see what the grill you installed looks like could you put it in your reply. Tom
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Old 06-21-2018, 11:42 AM   #13
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Here's the picture of the grill installation on the stair.

Jeffrey Guttenberger
2005 Mainship 400
R Time
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Old 06-21-2018, 06:26 PM   #14
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AC freeze up

Do you leave your AC on when you leave the boat for the day if you are returning the next day. If so what temperature do you set it to if the nights are in the 70s and the days high 80s. Tom
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Old 06-21-2018, 08:36 PM   #15
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I leave the temperature at 78 when I'm going to be around but if I'm gone for an extended period, I put a dehumidifier in the boat and turn off the ac.
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Old 06-22-2018, 06:29 PM   #16
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Most marine AC systems can't move the air temp more than 20F off water temp. So if you've got 90F water you'll never get colder than 70F air. And like has already been said, setting a low temp does not generate air any colder (or warmer for heat). Setting it to 68F won't get you colder air, it'll just make the system run longer trying to get there. If the water's too warm it'll never get there.

Fwiw, most heat most systems won't operate once water temp drops below 45F.

68F is likely not gonna happen with high humidity and warm water. We find 71F is about the coldest comfortable for sleep and about 74F is good for daytime in the salon. 78F when gone for a day or two, or set to the dehumidify option when gone longer.

I second the recommendation to confirm than you're getting sufficient air flow back to the system. Check that your filters or vent panels aren't clogged, and that the ducts aren't restricted (crushed, blocked, whatever). Likewise make sure the fins on the exchanger aren't clogged with dust/hair.

When's the last time the various parts were cleaned? They're likely due for it.

Also make sure the system has sufficient refrigerant pressure. Icing up can be a problem if it's low on refrigerant (which is often NOT going to be Freon anymore).

Lastly, make sure the impeller for the sea water exchanger is in good shape.
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Old 06-29-2018, 02:55 PM   #17
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Quote:
Originally Posted by Jgutten View Post
I had the same problem on my 16,000 btu unit. The manual for the unit requires a specified amount of air flow for the unit to operate. The small grill below the steering wheel is not enough return air to meet the needs of the AC. We installed a grill on the second step and that fixed the problem. Also, you cannot have anything up against the AC unit nor can you have a lot of stuff in the compartment because all of that restricts air flow.
It is very common to find marine a/c units that freeze up because they do not have adequate return air flow. Usually adding a return air grill solves the problem. BTW, it's also fairly common to not have a filter on the return... If you don't have one and/or if you add another return air grill, make provisions for an easy to clean/replace filter. This prevents dust from building up on the condenser, another reason for freeze-ups.
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Old 06-29-2018, 05:04 PM   #18
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The amount of Freon in a marine a/c is close to a pound or less. If you have a leak, it wont belong before it quits cooling all together. More likely a air flow problem to the return. Open the hatch,door to area and see if that solves the icing problem
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Old 06-29-2018, 06:06 PM   #19
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This may be starting a bit of a new thread, but what is the R-22 transition going to do to the marine AC units. Is there going to be an exemption? I would not think so. They are going away by law for household units in 2020. I am not sure what marine units use, but would think it might be R-22.
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Old 06-29-2018, 06:20 PM   #20
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Any a/c being built will have the replacement for R=22 ,R414. You are right about R-22 being replaced.No units will be made using R-22. Parts ,compressors TXV, Are still available, but will be phased out over time. R-22 is no longer made, but still can bought from current stocks, when gone that's it. Still have 60+ for my own use.
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