Is there an energy efficient a/c unit in existence?

[Mike]

We've seen folks on here talk about what they've done to add to their heating needs,
like those quiet oil filled heaters some use, and just good old dogs and blankets.
I was wondering if anyone has ever seen any energy efficient (something that could be
run off coach batteries, not requiring shore power or generator use) portable a/c units?
It seems to me that even something that could help cool and dry the air inside the confined
space in a conversion van might exist, and I'd be interested in hearing others thoughts
or even experiences or what you may have tried.

I googled this. and found someone selling an insulated board that fits inside a Coleman ice
chest, with a small fan in it that can run off a 12V DC power source.
http://www.kooleraire.com/Product%20Information.htm
Not exactly what I had in mind, but inventive, none the less.

[VernM]

I wondered the same sort of thing out loud on another forum one time, Mike, and got an answer from an engineering teacher in one of the Provinces. My question was why is there not an absorbtion air conditioner unit if there can be absorbtion refrigerators. He said he couldn't think of a real good reason other than efficiency. I guess someone is going to have to try the idea with a broken refrigerator and see if you can't come up with a propane A/c.

[Mike]

I did a bit of googling and emailing, and already got a reply back from a company that can add
small 12,000-14,000 btu systems to truck cabs. They're called Arctic Breeze, and do this
for truckers, so they don't have to run their diesels all day/night to cool the cab/sleeper.
This is the reply I got when I asked about a battery powered A/C system for my Roadtrek.
The down side of such a system is price.
Hi Mike,

We would recommend using our split system with dual evaporators. The condenser would mount under the truck with a power fan. The compressor box would have to be mounted inside the van someplace. It measures 16.25” x 15.25” x 10.25”. The two evaporators each measure 9.5” x 9.5” x 11”. This will provide you with approximately 12000-14000 BTU of cooling. List price for this system is $5520.00. Two group 31 AGM batteries will give you between 3-5 hours of run time depending on what else is drawing power. The group 27 batteries could be less that that.

This was from their authorized retailer/installer in Ingersoll, Ontario.
The other thing I noted was do you really need that many btus of cooling in a conversion van?
I might find 1/3 of that more than sufficient to cool and dry the air, at night, even just for a few hours.

[VernM]

Look at it this way, Mike. You could do away with the refrigerator and freezer. But you'd need to wear your winter gear while in the van?

[Mike]

I know. How do the truckers who do install these systems drive with frozen fingers?
Not to mention having to run their defrosters constantly

[Mike]

Wonder if this unit might work?
http://www.bestbuy.com/site/Danby+-+7%2 ... Id=9172922
It's about $300 and might be small enough that I could power it off the coach batteries.
Specs say it draws 8 amps or less, and I've got 2 Deka AGM Group 27 8A27 batteries.
I believe the draw down time in minutes for one of these batteries, is 640 at 8 amps.
So, I think I've got enough power to do/try this, but I need a good DC to AC inverter that can
handle the 8 amps continuous. I don't think my little 100W or 150W inverters will do it.
Any suggestions or recommended inverters I should look at? How/where would I connect
a higher capacity inverter into my electrical system?

[g1g]

Originally Posted by Mike

Wonder if this unit might work?
http://www.bestbuy.com/site/Danby+-+7%2 ... Id=9172922
It's about $300 and might be small enough that I could power it off the coach batteries.
Specs say it draws 8 amps or less, and I've got 2 Deka AGM Group 27 8A27 batteries.
I believe the draw down time in minutes for one of these batteries, is 640 at 8 amps.
So, I think I've got enough power to do/try this, but I need a good DC to AC inverter that can
handle the 8 amps continuous. I don't think my little 100W or 150W inverters will do it.
Any suggestions or recommended inverters I should look at? How/where would I connect
a higher capacity inverter into my electrical system?

Keep in mind that the 8 amps is for 120 volts and when you are using the inverter you will be drawing something like 80 amps at 12 V out of the battery to get the 8A 120V plus the power it takes to power the inverter. I think everyone forgets that one factor when converting amps, I know I made that mistake several times.
A 1000 continous or better 1200-1500w continous inverter would be needed. I believe most inverters are rated on the spike so a 2000w spike would equal a 1000w continous one. Also since a motor is being powered you should have a true sine wave inverter to match the rotation as othewise it would not run full speed and possibly cause problems like freeze up.
As for connecting to the battery you should put it very close so there is a very short length of very heavy cable. I would have to look up sizes to say exactly how heavy, but keep in mind you can never get a cable to big. If the distance is long or cable is to small there would be a voltage drop at the inverter and possibly burn it up. I learned that the hard way.

[Mike]

Hmmmmm, sounds like a major rethink is in order.
Considering what you've said, how long would I be able to run this setup, assuming it will be cycling on/off,
overnight. Could I get 6-8 hours out of it before my batteries are depleted?

Opinion?

[VernM]

It'll draw 960 watts continuous (at 100-percent efficiency) at full duty, Mike and perhaps twice that much at compressor start. Plus, with any compressor type air conditioner unit -- with any air conditioner -- there is the matter of water accumulation to vent overboard somehow from the heat exchanger.

A modified sine wave inverter will run electric motors with adequate performance. I'd wager you couild run that unit on my Powerworks 1,000 watt converter. And it is hooked to the battery from about two feet away with Number 6 wire and a seriously big disaster fuse.

But, keep hunting.

[Mike]

So, that does not compute?
Searching, searching, searching.....

[g1g]

OK Mike, I tried searching for your battery and couldn't find exactly what you have. Looking at other group 27 batteries some had a reserve capacity from less than an hour to almost 2 hours. Now your inverter will also require so many volts until it shuts down and as it has been said do not drain you battery more than half way. Without knowing all the facts and taking measurements I really don't know but my guess is that it would be less than 30 minutes because as the inverter draws a large amount of power and I think there will be a voltage drop to the point that the inverter will turn off, however after it is off for a short period of time I think the battery will recover a bit but not for long. Also the electronic calculations would be at 100% effeciency and no voltage drop then I'm not sure where cut off voltage is and at what power so like I said I would just guess at the 30 minute mark at the most.

[VernM]

Mike, you might also want to go back to the site of that "7000 BTU" air conditioner unit and read some of the buyer comments. Lots of reasons to look elsewhere.

[Mike]

I'm already looking for alternatives.
Wife says just don't go anywhere hot and we'll be OK.
Here, I thought I was the pragmatist.

[VernM]

All is relative.

From my friend in Fairbanks; "My driveway pad is covered with ice about an inch thick, which will probably freeze for the winter after Wednesday, then I will have to live with it until spring. So much for life in the Wilderness............"

[Mike]

When life gives you a driveway covered in ice, make sno-cones.
Happy Thanksgiving Vern.
And a safe holiday weekend to all on the forum, wherever you're from,
or whatever you're celebrating.