energy efficient air conditioner

Re: energy efficient air conditioner

shockman wrote: »

Before I run out and buy a window mount AC what should I know?? thinking in the hood of 6000BTU

Well, lets see, how about;

They are often loud and noisy likely the #1 complaint.

Don't even think about using the fan fold push out stuff that comes with the A/C, Buy a sheet of insulating poly styreen(?) and be sure you have at least 2" of insulation instead of the thin piece of plastic!

Mini splits tend to be much more effiecent, quiet, but of course more costly.

You can check energy star ratings and buy near the most effiecent A/C in your class, basically the most cool for the $ spent.

Know that they often have high startup requirements, so if your planning on using this with an inverter, you might expect to need 2.5 to 3x the rated wattage to start the thing.

They use a lot of wattage and unless you have a sizable system you may not be able to run them for long with out drawing your battery down.

Likely you will want a Midnite classic charge controller and the soon to be released battery module to properly charge your batteries while the A/C is running.

Most of the new designed ones use the condesation water and splash it onto the cooling fins to make them more effiecent. Them not having a drain hole is not a design flaw.

If I haven't guessed your question, please ask more a more specific one.

Re: energy efficient air conditioner

It sounds like you could run a "window Shaker" with your present system if you have a >2000 watt true sine inverter, It's a motor so a true sine will allow it to run effeicently.

shockman wrote: »

I will have about 1000 watts of panel, 760a/hr of batt. on a classic 150.

I take it this is a 12 volt system? and you have calculated your amp hours correctly, we often have people add the amperage of batteries in a string, but sounds like 4-L16 sized batteries. Your already marginal on Array to battery sizing so I would run the genny to charge the batteries at some point, but a small 500 watt unit should run over night on your battery.

Note 2; biggest problem with starting a large load on a 12 volt system is the starting surge creating a low voltage fault due to too small of wires, but if you've run a microwave from the battery your likely fine.

Note 3; If you choose to run the A/C during the day, Midnite should come out with a battery monitor module later this year that will measure the charging current across the shunt so if installed the midnite charge controller should be able to properly charge your batteries while the A/C is running, though it is likely you won't cover the A/C with your solar alone so you might skip it.

Re: energy efficient air conditioner

shockman wrote: »

It is an old 2012 Trace MSN ??? is this a problem?

On a Modified Sine Wave inverter, It's likely to run, but it's motor/compressor will run hot and have a shorter life, and the wattage used will be higher.

shockman wrote: »

Too small of wire, where??

Between the Battery and the inverter, Likely you should have 4/0 for anything over 1800 watts, unless they are very close together.

shockman wrote: »

What happens without BMM???

Bill did a great job of discribing this, I think since you have such a small array you will draw enough power for the Charge Controller to never get to Float and Likely start over each time the A/C shuts down on thermostat (Something we haven't discussed is that the 500 watt draw is only while the compressor is running and will cycle on and off)

Re: energy efficient air conditioner

shockman wrote: »

Thanks guys! great info.
The other thing I don't really understand is watts dc in/watts ac out. If I have 1000watts coming in from array and 500watts ac being used do I have 500 (less inv. inefficecies) left for charging or is there way more math to be done

Not much more than that. There are inefficiencies in the MPPT conversion, although far less than in most PWM situations. There are inefficiencies in running the inverter, and in charging the battery (power in greater than power out.)

The biggest loss of potential panel power comes when the inverter is not running (no loads) and the batteries are full (not much charging current.) In that case the potential power output of the panels remains just that, potential. This is one reason that off-gridders spend time planning when to do high energy use opportunity loads (washing machines, A/C, water heating) at times when the full output of the panels would not otherwise be used.
It is much better in terms of efficiency and wear and tear on the batteries to send power from the panels straight through the inverter to the load whenever possible rather than cycling the batteries by time shifting the loads.
Some things, like lighting, just have to shift.

Re: energy efficient air conditioner

shockman,

To your original question;

Regarding your stated desire to run a 6,000 BTU Window A/C:

We use three of them here. Two of them separately cool two different Power Rooms. In the summer, with excess power available, use the third one is allowed to run in a 550-ish SQ Ft cabin. They all are Samsung 6 KBTU models, each consumes about 530 measured AC watts at 120 VAC. These are teriffic little units with an EER of 10.7, which is fairly good, and surprisingly quiet for what they do. Bought one of these for US $100, and the following year two more for $120. Have been running one for six Summers and the other two for about four years on average.

During Summer days the cabin unit runs TRYING to kinna cool the whole cabin from about 1 PM til about 5:30 PM from excess power available when in Float. At night close the bedroom door to the rest of the cabin and cool just the small 150 SQ Ft bedroom, works great, and uses not more than 1.5 Kwh from the batteries at night because it is cycling. Do keep the fan running constantly to help the noise of the Compressor starting.

These units will start easily on my Honda EU2000isa in Eco Throttle.

Unfortunately, Samsung has no models smaller than 10 KBTU the last time I checked.

Cooling your entire cabin during the day would probably be a struggle for 6K, but if your heat load/gain is not too great, it may do OK. For my cabin, a 6K mounted in the bedroom window, with the BR door open, the afternoon temps stop rising on a full sun summer day. The temp differential twix outside and inside of those days needs to be less than 20 degrees F in oreder to stall the main cabin temp from rising.

You mentioned only a few days per year that the A/C would be essential. So, even running a small Honda EU1000 EDIT *to directly DC* charge the batteries, with a suitably large TSW Inverter might do the trick, if the A/C you select was unable to start on an EU1000 ... dunno.

There are the obvious trade offs between permitting the A/C to cycle, vs trying to get it to run constantly during the night vs EU1000 or 2000 and cooling only the BR and so on.

Am very happy with this "solution" to my cooling needs for now. Probably a Mini-Split is in the future here. Would have gotten such a system last year, but Sanyo being bought up, stalled that project.

The BMM or similar that photowhit mentioned, believe, is the MidNite battery charge current monitor, which will be able to terminate Absorb based only on the actual battery charging current.

Good Luck, Vic