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Old 07-06-2020, 11:19 AM   #1
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12 Volt Air Conditioner

Thought I would toss this idea out there for some feedback. While we are looking at this for a Class B motorhome it could apply to our Rosborough quite well, if I can find a marine version (have sent inquiries to Dometic & Coleman). Found this truck option https://www.guchen.com/electrical-tr...owered-ac.html.


The idea started with the Class B motorhome which has dual batteries similar to our Rosborough. We travel with a dog so a 12 volt system would address (probably 3 hours max) times we may be at a restaurant, shopping, dock without shore power, at anchor, etc. If unable to find a viable 12 volt system then would likely look at an inverter system to power a small 110 volt rooftop unit. Not really interested in a generator due to the small footprint. A 12v/110v unit would be great but have not found such.


Hope I provided enough information to explain my idea for the motorhome that could also apply to the boat. Thanks in advance for your thoughts.


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Old 07-06-2020, 12:02 PM   #2
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The amount of power required to run and A/C is staggering when you start looking at running it from batteries. The system you linked to, a 12V/2400 system uses 2400 watts when running. It's likely it will not shut off much during use since it will be the hot days that you need it, so it would be drawing 200 amps continuously from your battery bank. If it did cycle 50% of the time, that's still 1.2 KW for each hour of cycled run.

There are some smaller window mount 120V A/C's that people run off inverters in the 700W range. With losses and efficiencies you would be around 800W to run one of those and if it was cycling 50% only 400W per hour but of course it would have less cooling capacity than the one you showed above. I have seen some vans that have enough solar to run a 700W unit continuously on hot sunny days.

I believe there are also some small mini-split systems in the lower Wattage range as well.

I don't know what size your boat's battery bank is or whether you have solar or what, but that would require a very large battery bank to run for long at all.

What system are you looking at for your RV? How long does the manufacturer say that it will run on our RV's battery bank?
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Old 07-06-2020, 12:43 PM   #3
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Yikes! This thing is a power hog.
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Old 07-06-2020, 12:58 PM   #4
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Running one through an inverter is going to be even more inefficient.
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Old 07-06-2020, 01:19 PM   #5
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Old 07-06-2020, 02:44 PM   #6
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Old 07-06-2020, 03:24 PM   #7
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Well, the 2,400 or 3,200 watt figures are rated cooling output, about 8,000 or 11,000 btu/hr. Air conditioners have a COP (coefficient of performance) of 2-4 meaning it produces 2 to 4 times the energy input as electric power to cooling kW out. Air conditioners move heat, they don't produce it.

Having said that, Guchen's website doesn't give power consumption figures. And to get technical data which presumable includes them you have to register with your name and email address. Any manufacturer who does that is pure crap in my book.

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Old 07-06-2020, 04:01 PM   #8
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Thanks for everyone's replies. I sent a message to Dometic directly to get better informed. It would be great to find a 12/110V unit similar to our Dometic refrigerator on the boat.



Will advise after I speak with Dometic.




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Old 07-06-2020, 04:09 PM   #9
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Well, the 2,400 or 3,200 watt figures are rated cooling output, about 8,000 or 11,000 btu/hr. Air conditioners have a COP (coefficient of performance) of 2-4 meaning it produces 2 to 4 times the energy input as electric power to cooling kW out. Air conditioners move heat, they don't produce it.

Having said that, Guchen's website doesn't give power consumption figures. And to get technical data which presumable includes them you have to register with your name and email address. Any manufacturer who does that is pure crap in my book.

David
So it's likely that the unit consumes anywhere from 600-1200 watts running, still a sizeable load to be run off batteries.
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Old 07-07-2020, 05:16 AM   #10
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Look up Red Dot , they mfg 12 or 24 v DC systems for OTR trucks.
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Old 07-07-2020, 05:38 AM   #11
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FWIW..... We have an off-grid house, and every now and then we get a nasty heat spell. This summer I decided to give a window air conditioner a try, and it actually worked quite well. It's an LG 5000 BTU unit, and power consumption when operating with the compressor on is about 450W.


I'm not a proponent of using window air conditioners on a boat, but I bring this up as an example of the actual power draw for a modest sized AC unit. With the right power system, it's quite viable. And BTW, the power consumption exactly matched the AC unit's spec sheet, so it's all pretty predictable in advance.
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Old 07-07-2020, 05:49 AM   #12
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FWIW..... We have an off-grid house, and every now and then we get a nasty heat spell. This summer I decided to give a window air conditioner a try, and it actually worked quite well. It's an LG 5000 BTU unit, and power consumption when operating with the compressor on is about 450W.
I have similar data. We have a condo in Mexico with solar and an energy monitoring system. We run AC at night in our bedroom, which has a newer inverter-technology 12k btu mini-split that is around 17 SEER, so middle ground for efficiency. Pretty healthy spike at start-up, but once running, seems to run at around 500W-600W, so inline with TT's window unit which is less efficient.

With a decent inverter and battery bank, I would think the OP could run a small AC for roughly 1-hour per 100A of FLA/AGM battery, better if LFP (maybe close to 2-hours per 100AH battery, which are small and lightweight, albeit a kings ransom to purchase).

OP - I would look forward to your updates. There are many who are looking into solutions like this.

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Old 07-07-2020, 12:06 PM   #13
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FWIW..... We have an off-grid house, and every now and then we get a nasty heat spell. This summer I decided to give a window air conditioner a try, and it actually worked quite well. It's an LG 5000 BTU unit, and power consumption when operating with the compressor on is about 450W.
That's a nice efficient unit. Does it have soft start for the compressor? What type and size of inverter are you running it off of?
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Old 07-12-2020, 07:47 AM   #14
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Found a US manufactured unit based in Arizona that manufactures 12 volt units for both truck and marine use. I am considering the HD-12L 8K BTU/h unit for the van which appears to have 4 hour run time. Will contact them on Monday to investigate further including dealer/installation services.



https://www.cruisencomfortusa.com/


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Old 07-13-2020, 11:02 AM   #15
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[QUOTE=twistedtree;897088I'm not a proponent of using window air conditioners on a boat, but I bring this up as an example of the actual power draw for a modest sized AC unit. With the right power system, it's quite viable. And BTW, the power consumption exactly matched the AC unit's spec sheet, so it's all pretty predictable in advance.[/QUOTE]\

I've always wondered why not. If you could build one into a boat to minimize sound/hide it.....why wouldn't this be a better option than water cooled? They are efficient and you could replace one 6x over than buying a dometic.
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Old 07-13-2020, 11:27 AM   #16
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They wrote an article on Panbo detailing an install of a DC air conditioner.

https://www.panbo.com/dc-air-conditi...ator-required/
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Old 07-13-2020, 12:13 PM   #17
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I have a DC system on my sailboat. The compressor is shared between two zones, one at a time may be cooled (also shared with refrigerator and freezer storage plates). In the saloon, the 5000 btu capacity has difficulty cooling it on a hot day, though it will dehumidify with some positive effect. In the smaller stateroom it works well, cooling at about 1 deg/min when running. It is even practical to run it overnight. That system is no longer made, but proves that it can be done. When running, draws about 20A at 24V, but runs at a low duty cycle once cooled down.
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Old 07-13-2020, 12:17 PM   #18
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=DavidM;896841Having said that, Guchen's website doesn't give power consumption figures. And to get technical data which presumable includes them you have to register with your name and email address. Any manufacturer who does that is pure crap in my book.

David
It does give power consumption if you click on the technical data tab. For example the 1600W capacity unit (5400 btu) uses 49A on 12V. I'd not think these units would be most efficient for a boat, where a water cooled condenser is normal and more efficient.
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Old 07-13-2020, 01:47 PM   #19
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Spoke with Chris at Cruise N Comfort in Arizona and looks like the HD-12L 8K BTU/h unit is a viable solution for the Ford Transit van with upgraded 225 amp alternator and dedicated battery. He will be sending me local dealer information so I can sit down and discuss in detail.



As for our 25' boat with pilot house enclosure, if they can identify a solution that minimizes loss of storage space through a rooftop system working from a dedicated battery independent of existing boat electrical system (50 amp alternator), I would be interested. Otherwise we have good ventilation while moving and will just retain our small window AC unit and fans for overnight use.



Appreciate everyone's input. While I have a generic understanding of HVAC, electrical and plumbing systems from my prior architectural career I am certainly not an expert in boat/vehicle systems. I will certainly be leaning on a dealer to design/install the system.


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Old 07-13-2020, 01:58 PM   #20
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I'm not a proponent of using window air conditioners on a boat, but I bring this up as an example of the actual power draw for a modest sized AC unit. With the right power system, it's quite viable. And BTW, the power consumption exactly matched the AC unit's spec sheet, so it's all pretty predictable in advance.
\

I've always wondered why not. If you could build one into a boat to minimize sound/hide it.....why wouldn't this be a better option than water cooled? They are efficient and you could replace one 6x over than buying a dometic.
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