I installed a 16,500 BTU Mermaid Air Conditioning Unit with reverse cycle under the settee berth at the nav station. I have only run the unit for a few hours and I did run it with the locker wide open for an hour. Later I closed the settee compartment up, but I am not sure that I may still have a potential freeze up problem or not. My question is what are the conditions and the preventitive measures against freezing up of the coils? My dock buddies were trying to tell me that this is a common problem on any boat. Their suggestions were to insulate the compartment that the unit sits in very heavily because it is thought that when the unit draws air from the compartment itself that is what causes the freeze up. In my installation the return air is 14x10 and the unit is mounted flush with the return air grill, so very little air is drawn from the settee compartment itself. Any suggestions? Is freeze up of the coils going to be a problem or a once in a while thing? I can always run the unit in reverse cycle for a few minutes to clear it, but that's a hassle.
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Wayne Estabrooks
Possible reasons for freezup
It must be A/C week! There are several post related to A/C installations in 340's. I am just completing the installation of a Mermaid 16500 btu reverse cycle heat & cool which I am installing myself on my 340. FYI, the causes of freezing up of the evaporator can be, not enough duct outlets, restricted air flow, ambient air temperature already too low, or thermostat set too low and the unit is not cycling normally. Also low freon can cause this and the only reason the freon might be low is that there is a leak. If this is the case, the unit would have to be removed for professional service. Mermaid cautions about the handling of the unit it is fragile and do not lift it by the refrigerant lines as they can be damaged and cause leaks. I have a 4 inch outlet in the V berth, a 4 inch outlet in the aft cabin, and a 6 inch duct to a 12 X 8 inch supply grille in the main cabin and a 12 X 18 inch return grille. Try running it with the thermostat set at 78F or so. Don't try to turn the boat into a meat locker at 60 degrees. Hope it is something simple. Good luck with your 340. BTW, the Mermaid staff are very helpful and responsive. They followed up my calls immediately and gave me advice freely. Their web site link is below. I chose the Mermaid unit because it appears to be high quality construction. Wayne s/v Wind Drift h340
It must be A/C week! There are several post related to A/C installations in 340's. I am just completing the installation of a Mermaid 16500 btu reverse cycle heat & cool which I am installing myself on my 340. FYI, the causes of freezing up of the evaporator can be, not enough duct outlets, restricted air flow, ambient air temperature already too low, or thermostat set too low and the unit is not cycling normally. Also low freon can cause this and the only reason the freon might be low is that there is a leak. If this is the case, the unit would have to be removed for professional service. Mermaid cautions about the handling of the unit it is fragile and do not lift it by the refrigerant lines as they can be damaged and cause leaks. I have a 4 inch outlet in the V berth, a 4 inch outlet in the aft cabin, and a 6 inch duct to a 12 X 8 inch supply grille in the main cabin and a 12 X 18 inch return grille. Try running it with the thermostat set at 78F or so. Don't try to turn the boat into a meat locker at 60 degrees. Hope it is something simple. Good luck with your 340. BTW, the Mermaid staff are very helpful and responsive. They followed up my calls immediately and gave me advice freely. Their web site link is below. I chose the Mermaid unit because it appears to be high quality construction. Wayne s/v Wind Drift h340
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John K Kudera
I agree with Wayne
I have a 12,000 unit in our H 34 installed last year, insufficent air flow is the reason for many ills, since you just installed the unit, make sure there are no restrictions in any duct,re check any place the duct turns, as the turn itself restricts flow, and there may be a kink or two.(the duct should be pulled tight) for best flow. Hope you get the problem resolved, the Mermaid units and the customer service are excellent. Our unit was a bit noisy, a friend installed his unit this spring, as a noise reducer, he installed a piece of pick-up bed liner under the unit that worked so well for him, I did the same, the difference is amasing!
I have a 12,000 unit in our H 34 installed last year, insufficent air flow is the reason for many ills, since you just installed the unit, make sure there are no restrictions in any duct,re check any place the duct turns, as the turn itself restricts flow, and there may be a kink or two.(the duct should be pulled tight) for best flow. Hope you get the problem resolved, the Mermaid units and the customer service are excellent. Our unit was a bit noisy, a friend installed his unit this spring, as a noise reducer, he installed a piece of pick-up bed liner under the unit that worked so well for him, I did the same, the difference is amasing!
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Tim Bowers
Other Ideas
Locker open or locker closed should have little effect on weather the unit freezes up or not. I have a factory installed CruisAir unit, but I believe that the units are all basically the same. They have a water cooled condenser, and the evaporator is at the air inlet. From there the cooled air goes through the fan box to the plenium and is distributed to the individual air outlets. If there air no air leaks on the discharge side that would allow the air to "short circuit" back to the evaporator, having the compartment open or closed makes no difference. When the compartment is closed the the air is drawn out of the cabin through the grill that has a filter installed in it to trap dust and dirt before it gets to the evaporator. Is the filter grill clear? Another possible cause of icing up, was the boat closed up? Having the hatches and companionway open will allow humid air to enter the boat. Airconditioners work by cooling the air AND removing humidity (perhaps the most important part). Allowing humid air to continually enter the boat will restrict the airflow across the evaporator by condensing water on it faster than it can drain away. As airflow decreases so will the evaporator temperature, it can quickly get below freezing and cause the unit to start to ice up, allowing more humid outside air to enter the boat will allow the evaporator to completely freeze in a short period of time. Close the boat up, set the thermostat around 75-78 degrees and run the unit. If you have sufficent airflow through the unit, it should bring the temperature down to the theromstat setting rather quickly and shut down. If the unit continues to run after the set point is reached, the problem could be the thermostat. If the unit ices up quickly or a portion of the evaporator ices, I would have the charge in the unit checked. Hope this helps. Tim Bowers s/v Moonlight Bay
Locker open or locker closed should have little effect on weather the unit freezes up or not. I have a factory installed CruisAir unit, but I believe that the units are all basically the same. They have a water cooled condenser, and the evaporator is at the air inlet. From there the cooled air goes through the fan box to the plenium and is distributed to the individual air outlets. If there air no air leaks on the discharge side that would allow the air to "short circuit" back to the evaporator, having the compartment open or closed makes no difference. When the compartment is closed the the air is drawn out of the cabin through the grill that has a filter installed in it to trap dust and dirt before it gets to the evaporator. Is the filter grill clear? Another possible cause of icing up, was the boat closed up? Having the hatches and companionway open will allow humid air to enter the boat. Airconditioners work by cooling the air AND removing humidity (perhaps the most important part). Allowing humid air to continually enter the boat will restrict the airflow across the evaporator by condensing water on it faster than it can drain away. As airflow decreases so will the evaporator temperature, it can quickly get below freezing and cause the unit to start to ice up, allowing more humid outside air to enter the boat will allow the evaporator to completely freeze in a short period of time. Close the boat up, set the thermostat around 75-78 degrees and run the unit. If you have sufficent airflow through the unit, it should bring the temperature down to the theromstat setting rather quickly and shut down. If the unit continues to run after the set point is reached, the problem could be the thermostat. If the unit ices up quickly or a portion of the evaporator ices, I would have the charge in the unit checked. Hope this helps. Tim Bowers s/v Moonlight Bay
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Jay Meyer
A/C on a 340.
I have the same unit on my 340. The key to not icing up has been stated in the previous replies, I just wanted to convey that this is normal. I often block the main cabin vent AFTER the boat is cooled down to pump more air into the aft cabin. You must make sure the forward and aft air vents are open fully (mine are adjustable from knob in middle). The second point is you must close up the boat. I have left the companionway open and have noticed that the unit will ice fairly quickly on a humid day. One trick we use is to place our companion way canvas over the opening when the boards are not installed, makes going below easy with two snaps. Enjoy you’re A/C! Jay
I have the same unit on my 340. The key to not icing up has been stated in the previous replies, I just wanted to convey that this is normal. I often block the main cabin vent AFTER the boat is cooled down to pump more air into the aft cabin. You must make sure the forward and aft air vents are open fully (mine are adjustable from knob in middle). The second point is you must close up the boat. I have left the companionway open and have noticed that the unit will ice fairly quickly on a humid day. One trick we use is to place our companion way canvas over the opening when the boards are not installed, makes going below easy with two snaps. Enjoy you’re A/C! Jay
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Bryce
A/C freeze up
I have the same unit in the salon on my 410 and all the solutions outlined in previous replys. In the setup functions on my unit there is an option to have the freeze up detected (does this by monitoring the cooling rate). The amount of time the reverse cycle comes on can be set from 1 to 3 minutes. I set mine to 1 minute seems to work fine. Bryce
I have the same unit in the salon on my 410 and all the solutions outlined in previous replys. In the setup functions on my unit there is an option to have the freeze up detected (does this by monitoring the cooling rate). The amount of time the reverse cycle comes on can be set from 1 to 3 minutes. I set mine to 1 minute seems to work fine. Bryce
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