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Schooner Captain
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Discussion Starter #1 (Edited)
I have up-sized my raw water pump for my AC...
It went from blowing not very cold air, to iceing up. I have cleaned the evaporator coil, but it still freezes up. Has anyone done an upgrade on the fan to increase air flow? I feel like the AC has more capacity then the fan will allow for.

S/V Union Pacific : Cool it!

Its a marvair 16K unit.
 

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Old as Dirt!
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I have up-sized my raw water pump for my AC...
It went from blowing not very cold air, to iceing up. I have cleaned the condenser, but it still freezes up. Has anyone done an upgrade on the fan to increase air flow? I feel like the AC has more capacity then the fan will allow for.

S/V Union Pacific : Cool it!

Its a marvair 16K unit.
Icing is a symptom of insufficient Freon not inadequate air flow. Given your comments on the thread dealing with Marine Pricing, I'm sure you can invent something yourself but if not, contact a knowledgeable marine AC technician who may be able to find and repair the leak and recharge your system and get you another year or two out of it before you replace it.
 

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Schooner Captain
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Discussion Starter #3
Icing is a symptom of insufficient Freon not inadequate air flow. Given your comments on the thread dealing with Marine Pricing, I'm sure you can invent something yourself but if not, contact a knowledgeable marine AC technician who may be able to find and repair the leak and recharge your system and get you another year or two out of it before you replace it.
So if my condenser is too cold, its low on freon?
 

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FWIW The AC unit has a high and low pressure sensor and cut off.
Think PV=NRT and remember how "frosty" a CO2 Cartridge/CO2 Fire Extinguisher/Compressed Gas "Air Horn", or simply a Compressed Air Dust Blaster for your computer keyboard get when the pressure is released/blown off. The same thing is happening in your air handler...Low "Freon" or whatever passes for Freon in your particular system. BTDT...Got the T-Shirt.

Hey, don't take my word for it if you prefer. Google "Don Kollman", the Guru of marine AC/Refrigeration, and ask him. If you're lucky, he might respond. Or not. "Are you feeling lucky...?"

FWIW...
 

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Is it your condenser or your evaporator that is freezing up?

Evaporator freeze up may be a symptom of low on refrigerant but not always. When a system is low on refrigerant the evaporator pressure will be lower than normal, and that lower pressure can correspond to a temperature below freezing, but only if there is still enough refrigerant in the system for liquid to be present in the evaporator before boiling off. Often when that is the case the frost will form at the bottom of the coil, or in bands across the coil.

Having said that, most of the time when a system is low on refrigerant it does not freeze up because there is not enough refrigerating effect with the remaining refrigerant to get the coil that cold.

If the coil is freezing evenly over the entire coil face, you may be dealing with a different problem. For example, you say you upsized your raw water pump. On refrigeration systems the head pressure and the suction pressure are related. If the condenser is cooling too much it will cause low head pressure, which in turn causes low suction pressure. Low suction pressure means low evaporator temperature which can result in a frozen coil. When it comes to condensers too much cooling is not a good thing.

Poor air flow will also result in a frozen coil. things like a dirty evaporator, dirty fan wheel, or restricted ducts would be the main culprits.

Then of course there is the #1 cause of air conditioner freeze up: under sizing/setting the thermostat too low. Air conditioners need off cycle time. If they run all day without cycling off because either they cant keep up with the load, or you are setting the temperature lower than it is capable of achieving, they WILL freeze up.

What is the temperature of the supply air before it starts to freeze? What is the ambient air temp? How cold is the suction line going back to the compressor? How cold is the liquid line feeding the evaporator?

I am curious, looking at your pictures it looks like the unit is enclosed in a locker of some kind. How does the unit get return air? In order for any a/c unit to work correctly it needs to recirculate the air in the conditioned space. For every cubic foot of air you blow into the cabin you should be sucking the same amount of air back to the unit. If you are drawing air from another space, cooling it, then dumping it into the cabin the A/C will never keep up.
 

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Discussion Starter #8 (Edited)
I had thought of a dirty fan wheel. I may take it off an inspect.
The unit draws air thru a vented door. 12" x 12". The air comes from the forward bedroom.
The unit does run about 22 hours a day. I believe the rear unit is undersized. The boat came with a 16K and a 6 or 8K rear unit. I believe this may be undersized. I am seeking out a second 16K to mount aft, adding 8-10K should solve the issue of running all day.
This is most likely my issue, thou airflow may be a second factor.

evaporator coil is icing up.
not the watercooled portion, but the air cooled portion
 
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