Leave AC on when not there?

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jefndeb

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Joined
Jun 11, 2018
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Location
US
Vessel Name
Indigo Star
Vessel Make
2006 Mainship 400
I was just wondering what most people set their Air Conditioning system to when away from the boat for a week or so??

It was recommended to set at 85F and another guy said to put in humidity mode.

The boat is on Hilton Head and it gets hot every day till about Oct...

Thanks for suggestions and comments.

Jeff
 
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I set my A/C in my Florida condo to 80 deg F when we are not there in the summer.

I don't know what humidity the "humidity mode" controls to on marine A/Cs and I kind of doubt it has a humidity sensor that it controls to.

So setting it to about 80 should work fine.

David
 
I leave one of mine on set to somewhere around 76-78 when away from the boat in hot, humid weather.
 
I use Moisture mode. Here is the description from Marine Airrr Elite control panel.

Moisture Mode
While in the On Mode, press the Mode Button until the Moisture Mode LED is illuminated. Every four hours, the fan is started and air circulated for thirty minutes. During this time the air temperature is sampled and entered into memory. The cooling cycle is started and continues until the temperature is lowered 2°F (1.1°C). The compressor is allowed a maximum of one hour running time to reach the desired temperature. Four hours after the tempera- ture is satisfied, or the compressor times out, the cycle will be repeated.

The boat may get to 90 degrees, but it is always dry.
 
I set a Peltier effect dehumidifier to run all the time draining into the galley sink. No marine a/c left on because I worry about some casualty to the water supply like the plastic end of a march pump or a loose hose fitting ot God knows what sinking the boat. I once had a hatch top air-to-air unit I did not mind leaving on, and the current boat has a rooftop unit in its hardtop which I could use, but the return for the electric bill would not be worth it since the little dehumidifier does s good job.
 
I left mine in humidity/moisture mode when I left it from mid March to early May unattended in Ft Myers FL. I was very concerned about the strainers because they would clog pretty quickly under normal usage in those warm protected waters. Temps were 80s and 90s.

The boat had no mold or moisture when I returned, and strainers had moderate accumulation. That might help you gauge.
 
I leave the AC set to 85 deg in the summer but.....

If I leave for a week or two, I set it to dehumdify mode so the strainers don't get clogged. Water temp down here in Ft. Myers is 90 deg so stuff grows in the water easily. If I'm around the boat......

I clean the strainers every 3-5 days and fill them up with Bromide pool tablets. I've been doing that for years and it keeps growth out of the lines.

If I don't set the AC to 85 deg., the interior temperature of the boat will go to 125-135 deg in the afternoon and I think that's too hot.
 
During the summer, I leave one unit set at 80 to keep the boat dry and the temperature from getting excessive. The rest of the time I have a 2,000 square foot capable dehumidifier with a humidistat set at 50% relative humidity, that sits on the galley counter and drains into the sink. Both do a great job of keeping the boat humidity low to avoid mold and other types of growth.

Ted
 
If we didn't leave ours on, we would have a mildew explosion with our high humidity down here. Luckily, our marina charges a flat fee for electricity, so it doesn't matter.

We run a dehumidifier, too, that was built into the boat from the factory.
 
OK, a dehumidifier sounds like a good plan, can I get a few recommendations of what type or size?
 
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I put a household dehumidifier in the salon of my boat. Unit cost about 200bucks. Has a hose connected so it piddles into the aircon sump. Uses about 3.5A when running. Boat gets hot as heck in the daytime, but heat decreases RH so unit does not run during the day. Comes on at night. Boat stays nice and dry. I leave the AC units off. Power bill on my shop/dock meter went up about 10bucks a month. When I left the AC's on to control humidity, power bill was up about 50-100bucks a month. And they would come on mostly mid day what humidity was not an issue fighting the solar heat. The dehum is the cat's meow.
 
Use humidity mode. That’s what it’s for.
 
I leave mine on. I would rather pay a little extra in electricity than bake the inside of my boat. And as far as wearing out the equipment, if it is going to fail, I would rather have it fail at the dock than away from it.
 
i use 30 quart dehumidifier. just be sure your wife doesn't put the drain stopper in. yes that was a disaster . i think i'm going to connect my forward ac unit to my monitoring system so i can turn it on before i start my 3 to 4 hour drive to the boat. should make the first entry much better .
 
It is sometimes inconvenient to place a portable dehumidifier in a location where it will self drain. For a few more bucks you can find one with a built in pump that will pump the condensate uphill into a sink or overboard.

I solved the problem by building a whole house dehumidifier into the AC ductwork. It can be run on batteries an anchor.
 
30-35 pint dehumidifier drained directly into the sink is great, no pumps to worry about. I am at the boat frequently enough to empty the tank on the unit but if away for any length, hook it up to a hose make sure to weigh the other side so it doesn't pop out of the sink and let it do it's thing. If temp is the concern then run the AC unit. Have a boat neighbor stop by and check on it for you say every week or every other week.
 
I did not want to run any of my 3 dometic turbo DTU air conditioners while the boat sat for a long time in the Florida heat/humidity. I bought a relatively inexpensive ($350 USD I think) Haier two hose portable air conditioner.... It has no water accumulating ability.. the water vents outside with the hot air that blows from the Haier. No need to run a cooling water pump like my dometics use... so all thru hulls can be closed....
 
jefndeb said:
I was just wondering what most people set their Air Conditioning system to when away from the boat for a week or so??
Jeff
Click to expand...

Like others have indicated, we use a dehumidifier from Home Depot draining into one of the sinks. Why run a $2K marine AC when you can run a $300 dehumidifier that also cools the air a bit? A couple of fans on a timer help circulate the conditioned air around the boat and it's three cabins.

Sanderling's asking price has been reduced to $75K!
 
All my recent boats have a humidity mode, I use this on all four AC units and it seems to work perfect.
 
At first I thought this was about ACV.
Don’t ever think about AC up here.

But if it’s similar I leave the Wabasto heater on for many hours while not aboard the boat. Once it starts (and now it always does) it never stops unless it runs out of fuel. But I assume that as I’m quite sure it’s not run out of fuel.
 
Don't run AC-- too many variables that can turn into expensive repairs, water damage. Run a dehu set beside or in the kitchen sink and drain hose into other sink if you have one to go straight from sink drain to overboard (do not let drain through disposal side if you have one as it is unnecessary rusting potential for disposal). I agree inside of boat gets warm.

I also have as a back up, a portable AC (on wheels) that I keep as spare in the event boat AC's dont work. I can run it instead of dehu. It has an exhaust hose (4") that I hook up to the dryer vent (after taking the dryer vent hose off) to exhaust the hot air outside and not have to leave a door or window open. IT seems to generate very little condensate but the little that it does goes through a hose downhill to a nearby sink.
 
RLKramer said:
Don't run AC-- too many variables that can turn into expensive repairs, water damage. Run a dehu set beside or in the kitchen sink and drain hose into other sink if you have one to go straight from sink drain to overboard (do not let drain through disposal side if you have one as it is unnecessary rusting potential for disposal). I agree inside of boat gets warm.

I also have as a back up, a portable AC (on wheels) that I keep as spare in the event boat AC's dont work. I can run it instead of dehu. It has an exhaust hose (4") that I hook up to the dryer vent (after taking the dryer vent hose off) to exhaust the hot air outside and not have to leave a door or window open. IT seems to generate very little condensate but the little that it does goes through a hose downhill to a nearby sink.
Click to expand...

We don't run our marine, sea water cooled air, when the boat is unattended. We have a 1200 BTU portable, two hose unit, that we use for that.

I'm with you. When I leave my boat unattended, I like all of the sea cocks to be closed and marina fresh water supply off. Done like that, I've got only one likely chance of water intrusion failure: the PSS shaft seals.
 
While it may be rare, a boating friend of ours just went through the process of replacing BOTH of their AC units after leaving them both on while they were away from the boat for several days. It was in the Fort Myers area. I guess both strainers got clogged well enough that no water was circulating. It can and does happen.
 
AZ2Loop said:
While it may be rare, a boating friend of ours just went through the process of replacing BOTH of their AC units after leaving them both on while they were away from the boat for several days. It was in the Fort Myers area. I guess both strainers got clogged well enough that no water was circulating. It can and does happen.
Click to expand...

I believe most modern ones shut down now with no damage if the water stops.

Mine do, it happens a lot.
 
AZ2Loop said:
While it may be rare, a boating friend of ours just went through the process of replacing BOTH of their AC units after leaving them both on while they were away from the boat for several days. It was in the Fort Myers area. I guess both strainers got clogged well enough that no water was circulating. It can and does happen.
Click to expand...
That seems very odd. I've never seen a water cooled AC unit that didn't have a high pressure shutdown circuit on the feon loop. The lack of sufficient raw water makes the freon pressure rise. Everyone I've ever seen has a manual reset to prevent them from recycling. Something fishy there.

Ted
 
We only see our boat once or twice a month. We leave 2 of the 3 ac units set to 90 during the summer. It seems to be working well because it’s always bone dry in the boat. We figure 90 is high enough that the ac units will start kicking on early afternoon, cycle for a few hours then done for the night.

We did have the inlets clog once but the compressors just tripped. So the fans would still kick on but no air conditioning was happening. That was the worst thing that we had happen.
 
O C Diver said:
That seems very odd. I've never seen a water cooled AC unit that didn't have a high pressure shutdown circuit on the feon loop. The lack of sufficient raw water makes the freon pressure rise. Everyone I've ever seen has a manual reset to prevent them from recycling. Something fishy there.

Ted
Click to expand...
I'll see what else I can learn about it the next time I talk to them. They were in a marina in Fort Myers area. Not sure if they just failed to shut down somehow or what happened, but they said they had to replace BOTH of their AC units. If I talk to them (and I likely will) I'll try to get the full story. I know he was not happy about it! Owner is actually pretty mechanical, I think, too, so I be he will know exactly how it occurred.

You guys are on to something with it being fishy, too, because the boat is a LOT newer than ours. I think his is about a 2004 or so, Carver. Year is approximate, but that's pretty close. In any case, it's new enough that your points (OC and psneeld) are valid. I'll what else I can learn. The owner has decent mechanical knowledge as I recall, too, so I bet he will be able to tell me exactly how it happened.
 
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AZ2Loop said:
I'll see what else I can learn about it the next time I talk to them. They were in a marina in Fort Myers area. Not sure if they just failed to shut down somehow or what happened, but they said they had to replace BOTH of their AC units. If I talk to them (and I likely will) I'll try to get the full story. I know he was not happy about it! Owner is actually pretty mechanical, I think, too, so I be he will know exactly how it occurred.

You guys are on to something with it being fishy, too, because the boat is a LOT newer than ours. I think his is about a 2004 or so, Carver. Year is approximate, but that's pretty close. In any case, it's new enough that your points (OC and psneeld) are valid. I'll what else I can learn. The owner has decent mechanical knowledge as I recall, too, so I bet he will be able to tell me exactly how it happened.
Click to expand...

It seems very odd that 2 units would fail that way. Wondering if the tech figured he could turn 2 fairly simple restarts into 2 new unit and installation sales.

Ted
 
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