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Old 10-15-2020, 07:52 AM   #16
catalinajack
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City: Edgewater, MD
Vessel Name: Catalina Jack
Vessel Model: Defever 44
Join Date: Nov 2011
Posts: 3,585
Quote:
Originally Posted by DavidM View Post
Let me expand on my statement that reverse cycle heat pumps begin to freeze at OAT in the mid teens. First no one really measures water temps, but air temps are available on the news or on your own thermometer so that is what I used in the statement.

It isn't so much the actual water temperature although it takes temps in the 40s to freeze, because the freezing occurs inside the hull, often right at the thruhull seacock because the lower part of the bilge where that valve is located gets down to the 20s even though the cabin above is much warmer. So it takes low outside air temps combined with low water temps to allow the seacock to freeze up.

This happened on a friend's boat tied up in Oriental, NC when the OAT was 15-20. We used a hair dryer to thaw out the frozen sea cock which allowed the reverse cycle unit to come back on.

Also some reverse cycle units sense evaporator temps and shut down proactively before they freeze up.

David
David, you are making bold, absolute pronouncements that are not true for all boats, certainly not mine. The lower part of my bilge NEVER gets below freezing even when the outside temp has been in the single digits for several days. How do I know? I have lived it, three winters now going on the fourth.

As for low water temps, think about it for just a moment. Unless, one experiences water frozen to a depth of TWO feet, the water is less than the freezing point and even then the ice is 32 degrees (fresh water). My seacocks do not freeze up, the water in the bilge does not turn to ice, nor do I get any frost on any of the surfaces anywhere on the boat.

And, no one measures water temp? Really? I certainly do. It tells me when the time is approaching that the reverse cycle is going to quit. I just occasionally turn on the MFD which has a transducer in the system that quickly tells me the water temp four feet below the surface where my through hulls draw water from a sea chest.

And, my reverse cycle units DO NOT freeze with outside temps in the teens, not even in single digits. Freeze up of the units is dependent on WATER temp, not outside air temp. How do I know? Guess.

By the way, except to drain the water supply line spigot that supplies dock water and the supply line to the ice maker which is outside on the aft deck, I do not winterize the boat. If we are to be away from the boat for a week or so, I will put a ceramic heater in the engine that comes on at 40 degrees and turns off at 50 degrees. We have returned after 10 days over Christmas and New Years and never found the interior boat temp below 35 degrees never mind in the engine room that sits in a water bath of no less than 32 degrees.
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