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Commentator

Join Date: Sep 2010
Posts: 66

### Air Conditioner Runs off Solar

08/31/2012 11:32 PM

I want to run a 5000 btu air conditioner from my solar panels and batteries and i need help trying to figure how many i need of each.

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Anonymous Poster #1
#1

### Re: air conditioner runs off Solar

08/31/2012 11:47 PM

Me two.

2
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#2

### Re: air conditioner runs off Solar

09/01/2012 12:32 AM

Well if it's a 10 seer unit we can figure it out.....that would be 500 watts divided by 120v equals 4.2 amps..(this would be RLA).4.2 amps times 5 gives us around 20 amps locked rotor....20 amps times 120v equals 2400 watts, this would be the starting requirement...Now we need to know how many hours a day you want to run this unit....? The amount of solar collectors and batteries you have will be determined by how reliable you want the system to be...ie; the more reliability you want, the more batteries you will require, hence the more solar collectors you will need....Solar pv units can be sized times two requirement.... In other words the 500 watt running requirement could be sized at 1000 watts or 5 ea 200 watt pv panels...

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#5

### Re: air conditioner runs off Solar

09/01/2012 11:09 AM

What if i just charged batteries with my 2 70 watt panels ( 5 amp that i made myself )- how many batteries - what size?

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#15

### Re: air conditioner runs off Solar

09/03/2012 3:24 AM

It doesn't matter. There isn't enough 'wallop' coming from the panels to sustain the load.

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#3

### Re: air conditioner runs off Solar

09/01/2012 4:13 AM

More than what you already have, that's for sure.

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#4

### Re: air conditioner runs off Solar

09/01/2012 8:35 AM

And don't forget that you'll need an Inverter unit to convert the DC to AC....

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#6

### Re: air conditioner runs off Solar

09/01/2012 11:36 AM

I have a 750 watt inverter

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#7

### Re: air conditioner runs off Solar

09/01/2012 12:58 PM

I doubt that will have the reserve capacity to start the AC unit. As mentioned before with most any AC units expect that it needs around 4 - 5 times it running current to get started.

If it draws around 5 amps a good 1000 watt unit with a 2000 watt peak rating should take care of it without problems.

As far as battery capacity goes find its wattage rating then figure how many hours you are going to be running it and match that to your battery voltage times their AH rating then multiply that by 2.

If it draws 500 watts and runs 10 hours between charge times then it would need a battery set that holds around (500 x 10 x 2) = 10,000 watt hours without being over drained. That would work out to you needing about nine or more 12 volt 100Ah deep cycle batteries or an equivalent to that 10 KWh watt hour capacity.

Basically if you don't already have the batteries, the proper sized inverter, and solar panels that little air conditioner is going to get very expensive real fast.

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#8

### Re: air conditioner runs off Solar

09/01/2012 5:42 PM

how many 12v 70 amp batteries will i have to charge to let it run for 2 hrs. per day? or 6v 225 ah batteries?

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#10

### Re: air conditioner runs off Solar

09/01/2012 10:22 PM

It's basic math, you can do it!

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#9

### Re: Air Conditioner Runs off Solar

09/01/2012 8:30 PM

What is the voltage of your AC unit?

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#14

### Re: Air Conditioner Runs off Solar

09/02/2012 10:08 AM

110 ac volts

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#11

### Re: Air Conditioner Runs off Solar

09/01/2012 11:23 PM

1. Where are you located? What is the expected solar insolation you can anticipate for your area? Be careful of numbers published by solar panel vendors, or others with a vested interest in the industry. If you are in the US, NOAA has a pretty good database you can use to figure out how much energy is available. Other countries probably have a similar government service that provides reasonably accurate numbers. Better, buy yourself one of the meters available on the market for something on the order of \$200-\$500 and actually measure how much power you can expect. Be sure to get a meter with a memory- spot readings don't tell you much of anything.

2. 5000 Btu is approximately 1500 Watt-hours. As others have pointed out, you will need to account for starting current as well. But, for starters, if you want to run this air conditioner for 2-1/2 hours per day, you will consume on the order of 3,750 Watts. If you are going to use batteries, rather than run the unit directly from the solar panels, then you will need to put back roughly 20% more than you take out. So, you need roughly 4500 Watts of capacity (minimum) in your solar array. Using the number from #1 above, this tells you how big your solar array needs to be.

3. Your 750 Watt inverter is about half the size you need.

4. If you want the air conditioner to run when the sun isn't producing at maximum output, you will definitely need batteries. You do not want to discharge the batteries more than 50% of capacity, or you will be replacing them frequently. You will need a minimum of 1875 AH at 12 Volts. You will need to also account for losses through the inverter and other control circuitry. You also need to plan for rainy days.

5. Don't buy cheap batteries. Cheap batteries will cost you twice as much a expensive, good quality batteries over the long haul, because you will be replacing them much more frequently. Batteries are the most critical element in the entire system.

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#12

### Re: Air Conditioner Runs off Solar

09/01/2012 11:35 PM

Call these guys http://www.solarac.com/ have them install it so you have a warranty if it does not work.

Remember the in rush to start is a drain and the amps-watts used will also depend on your ambient temperature. Heat = pressure = higher amps for the compressor to condense.

I would assume it is no less than 230 volts single phase since it is 5 ton and not many manufactures will make something that size in 115 volts as it is not efficient.

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#13

### Re: Air Conditioner Runs off Solar

09/02/2012 3:27 AM

"Its basic math, you can do it!"

Well after seeing posts 11 and 12 I stand corrected.

Good lord don't you guys have calculators or Google?

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#16

### Re: Air Conditioner Runs off Solar

09/04/2012 10:43 AM

I do not think you want to run a regular air conditioner from batteries and charge these with solar cells, . . . as the electrical system would need to be at least 5 times larger than the AC load - otherwise it will not start.

I would suggest you build your own air conditioner using thermo-electric elements. Such a system need not be oversized - as there is no starting surge. You would not need a sizeable inverter . . . you could operate the system on low voltage - such as 12 . . 24 volts that is very suitable for many solar panels.

What you need is a assembly of a number of thermo-electric elements and two fans (operating at the same voltage as your battery system). One fan would blow the cool air into your living space, . . . while the other fan would blow the warm air to the outside.

This system is not cheap - as thermo-electric elements are relatively expensive, . . . but the system is very "solid state", not requiring a compressor, . . . or periodic fills of refrigerant . . . the only moving pars are your two fans . . .

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Join Date: Sep 2010
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#17

### Re: Air Conditioner Runs off Solar

09/07/2012 12:46 PM

how about if i use a 12 or 24 v air conditioner? how many 70 watt panels or 12 volt 70 ah batteries would i need and is their a formula to use to find this out.

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