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Old 05-06-2009, 18:02   #1
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Installing AC

I have a 26' San Juan and I'm am going to install a small window unit inside. The unit is 14" tall and 17" wide. I have an idea of installing a wall between the cabin and the cockpit locker to place the AC in. I will only use the AC at night, and when it is being used, I will just open the cockpit locker up for venting. Worst case scenerio is having to use a small fan to add more air to the AC. After installing the AC on that side, I will need to cap off the other side so the heat from the AC wont come back in. My question is, does the aft of the boat need ventilating? Why was the boat built where its open throughout the cabin and aft hull? I wanna make sure I am figuring it right.
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Old 05-06-2009, 20:16   #2
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Quote:
My question is, does the aft of the boat need ventilating?
Only if you want it to work. Heat extracted from the cabin must be released to the outside or you end up with a hot locker and the AC unit no longer cools. It would not take very long to burn out the compressor.

You also need to be mindful of the AC power. If the wiring can not handle that much load you'll burn up from an electrical fire instead of heat. This is not such a simple solution. Fitting the AC to the hatch boards or an open hatch usually provides more cooling ability. Enclosing the back end of the AC unit adds complexities that would lead to critical failure.
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Old 05-06-2009, 20:26   #3
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I dont know if I explained it correctly. I will provide plenty of air flow to and from the AC. I do understand how the process works. I have continuely thought of this, and I feel like it will work. I will take a photo of it as I go through it. That way you can understand what I mean.
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Old 05-06-2009, 20:29   #4
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I feel like it will work. I will take a photo of it as I go through it. That way you can understand what I mean.
That would be a great idea. A lot of things are easier to see than explain. It's a lot of power and you need that part to be done properly. Just because it's a small unit does not remove the need for caution. You can post pictures to your personal gallery here on CF (it's free). We can see them and talk about them.
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Old 05-06-2009, 20:58   #5
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I have figured out the amps it will use, and it wont be that much. I am definetly going to monitor temps in all areas. I really want this to work so I can pass this on to others who would like cheaper alternatives for AC. The unit cost me 100 bucks. Materials will be around 25. Craftmenship is where it would cost. I own a contracting service company, so for me, the labor is easy.
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Old 26-06-2009, 09:50   #6
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ac in cabin

I am trying to do the exact same thing. I have a 25 ft Catalina in houston, tx. It's hot as **** here and I've put a Haier window unit between the aft berth and the cockpit locker of the boat. There is a wall there that worked quite nicely as a pseudo window opening once I cut the hole in it. However, I don't think I have the locker ventilated enough. The ac compressor comes on just long enough to barely start getting the aft part of the cabin cool, then the compressor turns off and only the fan blows. The compressor comes back on about 10 mins later with same results- off agani before it can cool the cabin down. I opened the locker while it was running and the locker is pretty large and hatch is big. You can feel all the hot air coming up from the locker hatch. I'm wondering if I should put a fan down there to try to keep it cooler. I don't think putting more holes for ventilation would help any- the hatch is pretty big. Only thing I could think of ws putting a vent down low in the cockpit so that air might circulate better. If you know what a catalina 25 cockpit locker is like, you know what I'm talking about. Only other thing I can think of is that the window unit blows the cold air into a rather confined space, which then should flow out to the rest of the cabin. I'm wondering if the thermostat is getting too cold and shuting the compressor off before the rest of the cabin can cool down. Does anyone know how hot the compressor can get before it shuts down with the safety switch? I have the thermostat set to maximum cool and it's just not working! Any advise or thoughts would be appreciated.

Thanks,
Jon in Houston
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Old 26-06-2009, 11:02   #7
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Using the overhead hatch is usually the easier route. I assume you are trying to do what you are so you can just leave it and go sailing? On the overhead hatch you just build a wood base and a box/baffle to direct the air down. build it so it seals from rain leaks. when you go sailing just leave it on the dock....... the evaporate water and hot air go directly outside.
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Old 26-06-2009, 11:27   #8
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you also need to do something with the water that comes out of the rear of the AC unit. it can be a lot of water. it sounds like the compressor would not get enough cooling air in the locker. i see folks that put an AC in the companionway and that works pretty good but is a pain to step over.
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Old 26-06-2009, 11:45   #9
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" However, I don't think I have the locker ventilated enough. "
I'd expect that. Window air conditioners usually blow up a storm on the outside, in order to throw off the hot air from the coils. They NEED to do that, the NEED generous airflow. Sticking the "outside" of the air conditioner in a cockpit locker just seems like a certain recipe for disaster unless you also cut a huge hole in the hull and force-ventilate the locker.
Sorry, but I'd suggest the only two reliable ways to use this are by hanging it in the companionway entrance, or above a deck hatch if you can get it to blow "down" into the hatch. Anything else is liable to damage the air conditoner, besides not working well. Like dragons and steam locomotives, they need to breath.
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Old 26-06-2009, 15:06   #10
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ac in locker

thanks. I'm aware of the hatch and companion way fittings, i just think they look bad. I'm going to do some tests tomorrow to see if indeed the ac is over heating and shutting off the compressor or if the thermostat is just getting too cold before the rest of the cabin. I've thought about installing some blower motors to blow outside air into the locker. If air is being forced into the locker and then out of the locker opening, that might be enought to keep the temperature down for it to operate. I've seen this done in a hunter sailboat before in a similar spot without issue. Keep in mind it's over 100 degrees here right now. That's pretty rough no matter where the little window unit it... Plus, it's only a 99 dollar ac. it won't be the end of the world if it dies.

I'll let you know what i figure out and if I have any success.
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Old 26-06-2009, 18:21   #11
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I did install the AC just as you are planning. I made a wall from 3/4 Birch ply, and matched the stain to the teak. I installed a vent at the back end of the cockpit. Also, installed a bilge blower sucking the air out of the locker threw the vent. So far no issues from 3 nights of using it. I will say, the bilge blower that I am using it very loud. Dont want to disturb the other boats. Keep the cabin cool all night. So with that being said, the biggest concern is the noise. Which, I could purchase another blower which could be quieter. And for 100 bucks, if it lasts 2 years, I will go right back to Lowes and buy another. BTW, doesnt look half bad or out of place.
But also, if you dont mind it being in the companionway, thats probaly better. More venting, the longer it will last.
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Old 26-06-2009, 22:08   #12
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Build some ductwork or a baffle.
Figure out where the cooling air goes in and then comes out of the unit.
Build some simple ductwork or baffle to direct the flow of the hot exhaust up and out of the locker. You can use thin plywood for that.
To prevent overheating of the compressor if you forget to open the locker wire in a limit switch so when the locker is closed the unit will not run.
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Old 26-06-2009, 23:32   #13
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You may want to read this recomendation by Tecumseh who is more than likely the manufacturer of the compressor in your AC unit.
http://202.56.127.90/nacg/EnggRec/EngineeringRecommendation10.PDF
It starts off with, I quote "The design engineers s objective when applying a condensing unit must be to assure that the condenser will get a full flow of unheated, unrecirculated, clean air. To accomplish this the following points must be considered"
and further on "It is imperative that the air to be supplied to the
condenser by the fan is unheated"
It talks about tunnels, baffles, bulkheads, flow divertors and sizing.

As for the temperature that a compressor's thermal protection trips it is dependent on the compressor type. I've looked for the info. I cannot seem to find it. I probably deleted it.

It must also be mentioned that when the unit is being "cooled" by hot recirculated air the unit will run 2 or more times as long.
The thermal overload is not meant to be continually tripped and reset. The starting windings in the motor will more than likely burn out due to all these hot starts.
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Old 27-06-2009, 00:37   #14
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The problem is heat dissipation and I guarantee that you will want to use it during the day when you are on board.

If you want to use a land type air con installed inside then consider a portable air con unit that comes configured already with a hose to take the very hot air from the compressor directly outside. The trouble with dumping the heat in the cockpit locker is that it will make that locker very hot (even with the hatch open)…I know…I tried!...

On SG I have a portable that I use when I am drydocked and my water cooled marine type cannot be used.

It is very economical and I plumb the condensate directly into the grey water line so that it can run day and night.



Usually the exhaust hose needs to run straight for about 24 inches before it can bend and then I run the hose out a porthole to get the heat directly off the boat.

Works well.


Cool Only Personal Air Conditioners at PortableAirShop.com
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Old 27-06-2009, 08:55   #15
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ac

Hi all:

Thanks for all the great advise. Blower motors was the way I was thinking of going as well. I can install one right above the unit to bring in air and then one higher in the locker to take out the heater air. I'm going to try it today so I'll let you all know how it went.
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