Marine air frozen

B BARKER

Active Member
Apr 20, 2014
233
TENNESSEE RIVER- CLIFTON,TN
Boat Info
1974 CENTURY ARABIAN 454 CRUSADER MARINE V-DRIVE.. ALSO 1987 SEA RAY 390 EXPRESS CRUISER..
Engines
454 MERCRUISER 340 INBOARDS
Went to my boat and my front marine air is frozen,no water going through the cooling line, the rear one is pumping fine. My concern right now is can it thaw out and leak water in the boat if the pump is not running, will water bypass the impeller or not...
 
It won't "thaw out and leak", but if something bursts from freeze damage, then that could of course leak into the boat. Are both air systems fed by the same seacock on your boat? If not, close the front seacock. If the same seacock feeds both, you may want to turn the system off and close the seacock until you get it unfrozen.

Are you sure it's frozen and not just plugged with sediment/crap?
 
They are both fed from the same source I'm almost certain it is frozen up the rear one works fine and the front one worked a few days ago we have had some extremely cold weather...
 
If you can work on unfreezing it now, you can probably just let the rear one keep blasting away. If not, you may want to close the seacock, remove the hose, drain the system and pump some AF through from the hull fitting. If you have access, you could also remove the front hose and plug it securely - at least then you could keep the rear one working and if something is burst in the front system, it won't leak anymore water into the boat than what is in the line. Essentially, remove the front unit from the circuit. I suppose there's really any number of things you can do - depending on your timeframe for working on it and such.

It's kinda strange that the front one froze up - if it was running, that's enough to keep it from freezing. You only need a small trickle to keep pipes from freezing up - usually, as long as water is flowing through the pipes it will not freeze.
 
The unit runs it just isn't getting warm and is not circulating water through it..
 
The unit runs it just isn't getting warm and is not circulating water through it..

That's interesting..... I'm pretty sure the units shut completely down when there's no water.

I would try doing a factory reset and see if the unit comes back alive.

And just for fun please check to make sure the "heat" function is selected. This past year there was a few on here that had air units just blowing air and then they realized that Heat and /or AC was not selected.

Lets hope it's that easy.

If you don't know how to do a factory reset please post a picture of your HVAC controls and someone should be able to assist.
 
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It's not going to leak water into the boat unless the hose is broken (split from freezing) or something of that nature.

I have seen the discharge line freeze up while the unit was cycled off. I remember a boat here on LKN that the line froze and either broke or came loos from the through hull - whatever happened, the pump kept running and filled the boat with water. Like your home heatpump but with water, in heating mode the water being discharged is much colder than the water coming in.
 
I have had my unit freeze up when I ran it for heat the day I was winterizing systems a couple years ago. Water temps would have been just above freezing, maybe 38 degrees that day (it was really cold that day and air temps were below freezing).

Keep in mind that when in heat mode, it is transferring cold to the water discharge so it is possible to freeze those lines. For me nothing got damaged, but I did have to thaw out the coils before I could finish winterizing the AC unit. (I used a hair dryer on the coils and it took a bit of time). I don't run the heat in really cold water any more.
 
He is on the Tennessee River and they are having record lows.

This isn't an A/C problem; water just cannot get out of the thru hull. When you don't have water flow, the A/C unit shuts down because it triggers (opens) a high pressure switch on the compressor head, not because of flow. The boat is obviously cold enough inside that the high pressure switch isn't tripping.

The a/c pump housing is plastic so he is in danger of flooding the boat unless the bilge temps stay above freezing.

B Barker….check your pm's…..I saw and responded to yours this morning.
 
Thanks everyone i'm headed to the boat for a long weekend and will get on top of things...it's suppose to thaw out Sunday...
 
I had this happen on my boat last year when I went to winterize. The hvac tech that came to fix it switched the unit to ac and put the temp sensor in his hand to warm it so the thermostat would trigger the unit to turn on. This thawed the system.
 
Here is my advice.... listen to the wise owl...

=Mr. Webster
 
Ok here's the deal, cranked up both marine air's the rear one got warm and water was flowing fine, good stream, the front one heated up warm with about half the stream as the rear. after about 15 minutes the water flow started slowing down to the front unit and finally quit, turned it off about 2 hours and then turned it back on same thing ran ok for a while then quit pumping water ????
 
Ok here's the deal, cranked up both marine air's the rear one got warm and water was flowing fine, good stream, the front one heated up warm with about half the stream as the rear. after about 15 minutes the water flow started slowing down to the front unit and finally quit, turned it off about 2 hours and then turned it back on same thing ran ok for a while then quit pumping water ????

Are you sure they are getting water from the same source/pump?

I've only owned boats with one HVAC unit so I'm just guessing here.
 
Yea there's a T in the line that comes off the pump and goes opposite directions...
 
Wonder if the one unit is just sensing water colder then it can work with. I'm actually surprised how well mine is heating my boat tonight with a nice thin layer of ice around the docks.

From Cruise Air Manual:

In heat mode, the opposite is true. As the seawater temperature gets colder, there is less heat available and heating performance drops. Full heating capacity is available in water temperatures as low as 55°F (13°C), but drops to about 50% capacity in 40°F (4.4°C) water. Below this, the refrigerant pressure can be so low that the unit will not produce heat, (or may shut down on low-pressure fault, if this option is installed).
 
Turned up the portable heaters and warmed everything up and front unit started working again but gradually started freezing up again. I think water temperature is just too cold, it's starting to try to freeze over in the harbor. I checked all my cooling lines and I don't appear to have any leaks I think I lucked out this time. The warm air is back now so every things good. Thanks to everyone for all your suggestions and help. B.B.
 
Out of curiosity is the unit itself freezing up or the thru hull? If it’s the unit itself it may be low on coolant.
 
And also thanks to the wise owl for answering my pm....
 

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