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Old 12-08-2016, 11:18   #1
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Does anyone have experience with dc powered air conditioners

I plan to put solar panels on my boat and a large battery pack to be as eco friendly as possible. I enjoy cooling the boat with air-conditioning but hate to run the generator while anchored in a quiet spot. Does anyone have experience with dc powered air conditioners ?? I have seen ads for " marvair" and wonder if there are any positive or negative experiences. Thanks.
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Old 12-08-2016, 11:40   #2
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Does anyone have experience with dc powered air conditioners

I doubt there would be any increase in efficiency, would you believe that all or most anyway of our DC powered refrigerators are actually AC powered? The little electronic module converts DC to three phase I believe AC.

I want address plastic boats and lead acid batteries and eco friendly, cause That would make me a hypocrite


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Old 12-08-2016, 12:33   #3
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Re: Does anyone have experience with dc powered air conditioners

A company made a tiny 5000 btu DC a/c some years back. Even for that tiny amount your looking at a 100 ah load, That would take five 320 watt solar panels just just to run it during the day (with no battery charging). You would need another 4-5 solar panels to charge the batterys (10 6V batteries) to run the AC for 5 hours at night. A lot of panels and batters for 5000 BTU's.

Refrigerated cooling takes LOTS of power. A generator is the only real way to do it
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Old 12-08-2016, 13:51   #4
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Re: Does anyone have experience with dc powered air conditioners

2kw of A/C needs 2kw of solar panels. Having a battery bank is only harvesting energy outside of the time that you'r using the AC which, given that when the sun is shining, the boat gets hot, will not be of a great benefit.You need a battery bank to assist maintaining a uniform voltage as the sun does not shine perfectly all the time. The problem is that to keep the boat cool on those hot august nights, you will have to drain your battery bank and so it will come into the next day with no charge. This means that the solar panels must first recharge your batteries before they can cool the boat. I can see a neverending cycle happening here.
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Old 12-08-2016, 16:05   #5
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Re: Does anyone have experience with dc powered air conditioners

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A company made a tiny 5000 btu DC a/c some years back. Even for that tiny amount your looking at a 100 ah load, That would take five 320 watt solar panels just just to run it during the day (with no battery charging). You would need another 4-5 solar panels to charge the batterys (10 6V batteries) to run the AC for 5 hours at night. A lot of panels and batters for 5000 BTU's.

Refrigerated cooling takes LOTS of power. A generator is the only real way to do it
+ 1 on this.

I have to air condition my cabin from time to time, so I can work.

No way to "really" keep up with the 700 watt draw from the small wallmart air-con positioned right above my captains area and the laptop/monitor/wireless/ice box, vhf, and on and on, without firing up my Honda 2000.

For small sprints the 2,000 watt inverter/charger will handle it off the 2 house banks plus the solar panels but no way is there anyway that batteries can work over time. You have to remember that solar panels don't put out their full rated wattage most of the time so you don't get 100 watts from a 100 watt panel into the battery especially on a boat.
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Old 12-08-2016, 17:42   #6
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Re: Does anyone have experience with dc powered air conditioners

BTW a PSW inverter matched to your AC will allow you to look at all of the standalone room airconditioners that are quite cheap. This means that you can also use it any time that you're plugged into shore power. As a bonus, it will dehumidify the boat and can heat it too. You have to have a drain (into the bilge) and install a large waste air outlet. I cut a hole though a plastic port light and put a round inspection hatch over it. It's fairly hard for a boatie to claim eco friendly status when you consider the impact of those tonnes of resin and the motor use and the effect of converting marine environments marinas etc,etc. Guilty as charged.
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Old 13-08-2016, 02:46   #7
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Re: Does anyone have experience with dc powered air conditioners

The only DC unit I know of is by Cruise n comfort. Their efficiency figures don't look to be that great. Air con compressors are made on a massive scale by only a few global suppliers and there is little call for DC versions and AC can be pretty efficient. Domestic split units are most efficient, but really hard to fit in a boat.

Check out the Frigomar self contained unit. It's the most efficient out there for marine use. It will draw 1.5A AC at 230v. Allowing for a pump and inverter losses from out of an efficient-to-charge lithium battery you will need 10.1 KWh of battery power for 24hr use. With 5.5 hours charging you need 1,900w of panels. Maybe a bit less as it will not need to run 100%.

Then you have to fit them and I'm sure you don't have enough room and if you did, it still isn't enough as you need another say 30% of panels to charge for other consumers. Now you are also into really big batteries. Oh, and 4000btu is the Eco mode output I worked on. Barely enough to make much difference except if you hide out in a small cabin.

It could probably work at night though, for just 8 hrs - if you could fit a lot of panels.
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Old 13-08-2016, 02:51   #8
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Re: Does anyone have experience with dc powered air conditioners

You can't get something for nothing, it takes lots of electrical power to run A/C. There's no free lunch.

Unless of course, you want to turn you boat into a solar farm.
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Old 13-08-2016, 04:16   #9
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Re: Does anyone have experience with dc powered air conditioners

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The only DC unit I know of is by Cruise n comfort. Their efficiency figures don't look to be that great. Air con compressors are made on a massive scale by only a few global suppliers and there is little call for DC versions and AC can be pretty efficient. Domestic split units are most efficient, but really hard to fit in a boat.

Check out the Frigomar self contained unit. It's the most efficient out there for marine use. It will draw 1.5A AC at 230v. Allowing for a pump and inverter losses from out of an efficient-to-charge lithium battery you will need 10.1 KWh of battery power for 24hr use. With 5.5 hours charging you need 1,900w of panels. Maybe a bit less as it will not need to run 100%.

Then you have to fit them and I'm sure you don't have enough room and if you did, it still isn't enough as you need another say 30% of panels to charge for other consumers. Now you are also into really big batteries. Oh, and 4000btu is the Eco mode output I worked on. Barely enough to make much difference except if you hide out in a small cabin.

It could probably work at night though, for just 8 hrs - if you could fit a lot of panels.
I just checked again the Cruise n Comfort rated figures and they use about a quarter less power than the Frigomar, so a bit better than I first thought and seem to be the lowest power marine unit out there, but I don't know about this for sure. Information on the website is contradictory and incomplete.
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Old 13-08-2016, 10:04   #10
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Re: Does anyone have experience with dc powered air conditioners

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I plan to put solar panels on my boat and a large battery pack to be as eco friendly as possible. I enjoy cooling the boat with air-conditioning but hate to run the generator while anchored in a quiet spot. Does anyone have experience with dc powered air conditioners ?? I have seen ads for " marvair" and wonder if there are any positive or negative experiences. Thanks.
===

It will definitely work. I'm running a dorm type small fridge and a good sized household freezer with a sine wave inverter and 8 golf cart batteries. Recharge of the batteries is normally done from a large alternator when underway or with a generator. I have 800 watts of solar panels however for sunny days at anchor.
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Old 13-08-2016, 10:25   #11
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Re: Does anyone have experience with dc powered air conditioners

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I plan to put solar panels on my boat and a large battery pack to be as eco friendly as possible. I enjoy cooling the boat with air-conditioning but hate to run the generator while anchored in a quiet spot. Does anyone have experience with dc powered air conditioners ?? I have seen ads for " marvair" and wonder if there are any positive or negative experiences. Thanks.
Look up PolarProd AB. It is more like a swamp cooler but very energy efficient. Also the original price is much less expensive than a quality boat AC. As you don't want to run the generator at anchor, it may be just what you need.
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Old 13-08-2016, 11:48   #12
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Re: Does anyone have experience with dc powered air conditioners

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Look up PolarProd AB. It is more like a swamp cooler but very energy efficient. Also the original price is much less expensive than a quality boat AC. As you don't want to run the generator at anchor, it may be just what you need.
I just looked at it. The trouble is to get to the 14 deg C water temperature they refer to for cooling you have to go pretty deep in tropical water. About 250m deep, which would be quite a palaver to rig each night. Will work somewhat better in cooler waters though, say Alaska. But you don't need aircon often there. An evaporator temperature of 14 deg really doesn't do much. Air con units go MUCH cooler and will give maybe 3 times the heat absorption for the same size unit.
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Old 13-08-2016, 13:41   #13
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Re: Does anyone have experience with dc powered air conditioners

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I just looked at it. The trouble is to get to the 14 deg C water temperature they refer to for cooling you have to go pretty deep in tropical water. About 250m deep, which would be quite a palaver to rig each night. Will work somewhat better in cooler waters though, say Alaska. But you don't need aircon often there. An evaporator temperature of 14 deg really doesn't do much. Air con units go MUCH cooler and will give maybe 3 times the heat absorption for the same size unit.
I think you are comparing optimum performance to needed productive performance. 14 degrees C. means an output of 57 degrees F. If it's 90 degrees or more outside, a 75 degree output would drop temps enough to make it more enjoyable (at least I would think so). Water temp for that needs only be 65 F. Going down 10 to 15 feet below the surface would supply those numbers in many places. If you are looking at practical vs. wishful energy expenditure still thinking its a possibility. Of course, that's just my take. I am planning on putting it to the real test this following summer while I cruise the Caribbean.
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Old 13-08-2016, 13:49   #14
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Re: Does anyone have experience with dc powered air conditioners

Yes.
Have experience.

We call them fans.

Just acclimate. I can't imagine enjoying the tropics if I was always looking forward to getting back to the AC.
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Old 13-08-2016, 13:55   #15
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Re: Does anyone have experience with dc powered air conditioners

While I don't agree with the idea, look here.

https://www.indiegogo.com/projects/n...defined-home#/
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