12 Volt Air Conditioner

[Leonard Atkins]

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-truck-air-conditioner/dc-powered-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.


Leonard

 

[sbman]

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?

 

[Crusty Chief]

Yikes! This thing is a power hog.

 

[caltexflanc]

Running one through an inverter is going to be even more inefficient.

 

[Rossland]

BoatRx

 

[Olebird]

https://www.amazon.com/Compact-Refr...e+air+conditioner+12vdc&qid=1594064598&sr=8-1

 

[DavidM]

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

 

[Leonard Atkins]

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.




Leonard

 

[sbman]

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.

 

[FF]

Look up Red Dot , they mfg 12 or 24 v DC systems for OTR trucks.

 

[twistedtree]

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.

 

[mvweebles]

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.

Peter

 

[sbman]

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?

 

[Leonard Atkins]

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/


Leonard

 

[Enyar]

\

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.

 

[stevemitchell]

BoatRx

They wrote an article on Panbo detailing an install of a DC air conditioner.

DC Air Conditioning - Comfort on the water, no generator required

 

[DDW]

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.

 

[DDW]

=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.

 

[Leonard Atkins]

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.


Leonard

 

[Enyar]

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.

 

[Olebird]

If these people would produce a unit with a water sourced condenser, a 24 or 48 vdc compressor and a dedicated Lithium-Ion battery pack, might make sense. The individual parts are available on line -- might be a business opportunity for an entrepreneur.


https://tinyurl.com/ycz8hjrb

 

[Maritina.J]

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

Hi David, I have downloaded a PDF file about Guchen's air conditioner, and in the file there is the power consumption info. It shows the power of a 2400W 12V air conditioner is 600W - 860W. I am also considering installaing one of these 3 models onmy boats, any suggestions?

 

[GoneDiving]

As a general comment, I've found the more specialised and low volume the product, the lower the efficiency. It would be hard to find more bang for your buck and battery capacity than a modern AC inverter mini split system. As a reference my home aircon is rated as 8kw cooling capacity but barely draws 1kw a few minutes after startup. It easily cools half my house. My boat based unit works equally as well.

Much smaller versions are available, they are cheap and reliable, and can be maintained by nearly any electrician. I'm sure the system efficiency would out weigh any inverter losses.

For a permanent or high use system a 24 or 48v house bank would be a benefit but that's a whole other debate.

Good luck!

 

[zcxvv]

You can buy batteries, but they will weight really a lot.

 

[FF]

At times the boat can be cooled with out air conditioning.

IF the water the boat is floating in is cool , the hull below the WL will be cool.

Simple floor vents will allow the denser bilge cool air to push out the warm air in the cabin if a vent is provided to let the air out.

IF the hull and deck are cooled with the wash down pump as soon as sunset , one can enjoy the temperature difference .

 

[Mako]

Concur with @GD's comments. Having lived in the world of the mini-splits and portable diesel powered cell towers (the Middle East) I agree that today's digital inverter mini-splits are fantastic solutions, as long as you can fit the outdoor condenser unit and perhaps camouflage it with some stainless grating or such. The most efficient are the 230v/50hz units and the Chinese lead the way (Sapphire series are pushing SEER 27 if I recall).

I also checked into the telecom mini-splits which are 48vDC powered, to try to eliminate the inverter losses and point of failure. However they are hopelessly inefficient - not the way to go at all.

The only units which appear to be more efficient are the marine DC aircons (5kbtu-12kbtu). Incredible low energy use. However you're paying about 3-5 times what the mini-splits would be, and I don't like wasting money needlessly with the marine industry.

Edit - just did a quick search and it appears that products are advancing nicely. Now I see 12kbtu mini split units of 48vDC only drawing 500 watts- price tag of $2500 is double what a domestic unit costs but still half what the water cooled marine units are. So sleeping at night, 50% duty cycle so 250 watts/hr, say 2 kwhr of power gets you through the night. That’s opening up a whole new world of possibilities, even with FLA batteries.

 

[rwidman]

The voltage is not really important, it's the amount of power required to air condition a boat that's important.

If you look at production boats, you will find that they are nearly all equipped with 120 volt AC units and only operate on shore power or a genset. It's not practical to run an air conditioner from batteries unless you fill the bilge with batteries. Even then, you would need a way to recharge the batteries for the next use.

 

[DDW]

The problem with the small mini-splits is they don't put any effort at all into making the compressor cabinet any smaller. That makes are really huge wart on your boat that must be quite visible. The stuff inside isn't near that volume - wish they would package it appropriately. If they did they would upend the RV air con market which is huge compared to boats.

 

[TheAtomicDog]

Not sure if this was already linked in this thread but it is on point:

 

[Mako]

@DDW, those condenser cabinets are just ugly sheet metal boxes. This could be an opportunity to grab some stainless steel sheet and sections and weld/rivet a small new cabinet that blends in better.