A.C. Freezing up..Why?

Pat

.
Jun 7, 2004
1,250
Oday 272LE Ninnescah Yacht Club, Wichita, Ks.
The 12,000 btu Mermaid AC in our O'Day 272 freezes up and ceases to cool the boat....did it
twice this week....when it does this it ceases to cool anything and we were close to 100 degrees
every day this weekend....I then have to put a fan in front of the grill and it eventually thaws and
runs properly again, until or it refreezes and we repeat the exercise. When we arrived at the boat on Friday afternoon it was 102 in the cabin. It promptly cooled down to around 82 degrees and then continued to cool to around 70 for sleeping. Saturday and today it froze up again....I can get an AC fellow to the boat, but just wondered what could be the cause of ice build-up on the fins/grills? Thanks for your thoughts, Patrick
 
Jan 8, 2015
360
MacGregor 26S, Goman Express 30 Kerr Reservoir
Your unit is low on refrigerant. The coolant operates as a saturated system. Thus the temperature is dependent on the pressure. When the coolant gets low, the pressure drops, thus the temperature follows. When it gets low enough that the temperature is below 32 degrees, ice starts forming on the evaporator coils.
 
Feb 20, 2011
7,990
Island Packet 35 Tucson, AZ/San Carlos, MX
From the manual:
5. Evaporator Freezing:
a) Supply air vents closed or insufficient number of vents. Open and/or add additional
vents.
b) Fan not running or intermittent.
c) Return air blocked. Clean air filter and/or remove any blockage.
d) Thermostat set too low and is not allowing unit to cycle and remove icing. Set
thermostat at a higher setting.
e.) Thermostat improperly located in a position not giving “true” cabin temperature.
Examples would be in a sunny spot near glass, or near the hatch. Relocate thermostat.
f) Low freon due to leak. Unit will require professional service.
 
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Mar 31, 2013
234
O'day 23 Pa
removing 30 degrees likely won't let the unit cycle either.
Get the gas checked first, then try running it slightly warmer so you see the system cycle on/off a little more often, see if it freezes then.
 
Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
I did some shipboard large satellite antenna installations inside radomes some years back. The radomes had AC units in them. One of the AC units started to freeze up to the point it stopped working. At first we thought it was faulty but them the HVAC guy on the ship said the cause was the hot air port was too close to the intake port. Normally not a problem with good circulation, however, the ports were a few inches above the ship's deck. A pressure system formed and prevented cool air from entering the intake port. Thus the AC was cycling the hot air.

Just another thought about this issue.
 
Nov 6, 2006
9,884
Hunter 34 Mandeville Louisiana
Question is.. is the freezing up a new thing or has it always done that? All previous notes are good.. if it always has done that.. could be low on refrigerant .. if it just started that: look to air flow, like dirty filter, blocked vents, blocked return, dirty cooling fins.. and last low refrigerant..
 

Pat

.
Jun 7, 2004
1,250
Oday 272LE Ninnescah Yacht Club, Wichita, Ks.
Thank you to everyone above....we arrived at the lake late Friday afternoon....when I turned on the Mermaid
circuit breaker, the unit came on and indicated the temperature in the boat was 102 degrees...I turned on the unit at the circuit breaker to run the ac and it had the temperature down to around 80 or 78 in about an hour....it ran fine all night w/ no issues....we decided to go sail on Saturday morning and observe the regatta then came back to the slip.....I plugged in the shorepower and turned on the Mermaid and it froze up before it could really lower the temperature much below ninty...then checked the compressor and it was frozen up....so I turned the vornado fan on and directed the flow to the compressor and melted the ice into the pan...we repeated this several more times, but it never really cooled the boat down although with the hatches open, it was comfortable to sleep...Sunday was
very hot and the race was cancelled due to very light winds so we dicided to go home.....end of story...this weekend is not the first time the above has taken place....maybe I should find a local dude that can check the level of the refrigerant. Our club is very near several towns that should have an AC repairman. Thanks for any further
replies or thoughts based on the above.....Patrick in paradise.....
 
May 23, 2016
217
O'Day 1984 23 Island Park, NY
If there's no obvious change in airflow like a sorry filter suspect the freon low... Current draw is a good confirmation of this... If current draw while running is low compressor isn't working as hard due to low freon... Sounds like it's continuing to leak
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
Both of our parents have had the same experience in their homes this season and it was low refrigerant. Is it possible that blocking off too many registers will cause this too? Or is the low airflow only on the supply end?
 

Pat

.
Jun 7, 2004
1,250
Oday 272LE Ninnescah Yacht Club, Wichita, Ks.
hello again Justin, can I buy the refrigerant and put in myself? Or shall I wait until I see you walking down the slip....looking for someone to help..........I about died yesterday putting our boat away in the heat.....but we recovered quickly as the afternoon wore on.....Pat
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
Sorry Pat, I'm not an HVAC guy nor do I play one on TV. I have to think someone in the club knows this stuff and could charge it. I don't know what your system uses but it's probably one that requires a license to buy. I wonder if yours could be upgraded to newer cheaper gas? We ran ours almost all day yesterday. It was too dead to attempt to go out. Saturday was wonderful. We took a couple out that had never been sailing. She is ready to sign up for classes!
 

Pat

.
Jun 7, 2004
1,250
Oday 272LE Ninnescah Yacht Club, Wichita, Ks.
Yes, we had great sailing Saturday.....I've got a bunch of friends at Professional Engineering and one of their
mechanical people can help me.....I don't think the actual issue is the gas as it's done this many times over the last
5 or 6 years.....then it will just work fine for a day like saturday and then not work on Sat. night.....did not really try to run it on Sunday as we were in and out packing to go home.......I'll let you know what I find out...Patrick
 

Pat

.
Jun 7, 2004
1,250
Oday 272LE Ninnescah Yacht Club, Wichita, Ks.
Boy, I will tell you, the value of information available on this site is simply incredible. I know almost nothing about mechanical issues like this AC, but I do know it has done this periodically ever since we installed this unit about 6 years ago.....then on other days it is just fine....One more bit of information is that we installed an in-line
duct fan on the main 8 inch trunk line out of the compressor...this at the suggestion of the then current president of Mermaid...It makes a huge difference powering up the system.....unfortunately, I used flexible duct for the other
ducts...and the runs are fairly long so there is increased resistance in all the duct-work once the air get's away from the main compressor.....problem is many times it just works like a champ....the AC is under the v-berth insert, while the thermostat and controls are in the main salon shall we say..all the hatches in the boat have shades, except the thick plexiglass companion way hatches and two overhead non-opening ceiling hatches...The Mermaid thermostat offers a world of various settings, etc., but I usually just hit the 'automatic' button and all is well..but not
this last 102 degree afternoon...I appreciate everyones help...One last bit of info: the AC usually runs issue free every night just putting out a constant stream of cold air and seems to shut off periodically as it attains my temp. settings...that said, it almost never freezes up at night....there you have it...more than you wanted to know...Patrick
 
Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
Hate to say it but last night we had a fire in the wood stove. Feel bad for you with triple digits.

All U Get
 
May 24, 2004
7,129
CC 30 South Florida
Two causes, low on refrigerant or obstructed air flow. Dirty filters or coils will do it. Had an instance where the air intake grill in one boat was prone to be inadvertedly blocked by item being placed in front of it.
 

Pat

.
Jun 7, 2004
1,250
Oday 272LE Ninnescah Yacht Club, Wichita, Ks.
A fire in the woodshed sounds fun...spent many a weekend @ Killington back in the 70's when I lived in Newport,
RI...beautiful country...evidently the Mermaid rep...pay's attention to Sailboat Owners.com as they replied offering their help yesterday...hopefully, they may retain an AC fellow to charge the Freon...will get that out of the way
first...also a new filter, etc...Thank you again for everyone's advice.....Patrick in Wichita....104 today....
 

Pat

.
Jun 7, 2004
1,250
Oday 272LE Ninnescah Yacht Club, Wichita, Ks.
I'm going to call them this morning.....I have a fellow sailor who has an O'day 28 and he can check the Freon this
weekend. I've found the refrigerant in my old Mermaid literature, i.e. R22, but he needs to know the baseline
pressure numbers, both high and low, and those numbers mean nothing to me...thankfully, they do to him...
the odd deal that continues to nag me is sometimes this unit just works great...such as last Friday, when it took the temperature in the cabin down to 72 on a 102 degree day, then a day later, it just freezes up....what could be the
variable? Could the variable be the in-line fan that was installed to power up the whole system....? could it be a
blanket up against the grille in the v-berth..could it be closing the duct at the grille...that would allow air to just sit
in the duct which is a waste? could it be sun shining thru the ceiling hatch? Why does it work great sometimes and almost not at all at other times, i.e. like last Saturday evening? Patrick