Swamp Cooler Conversion to 12 volt DC

5 Posts
May 6, 2009 12:33 pm
Swamp Cooler Conversion to 12 volt DC

I have a Swamp Cooler that I would like to power with Solar. It has a 115 volt, Approx 8-9 amp, 600-700 watt motor. Would it be better to try to convert the whole thing to DC power or use an inverter off of my battery ? I am trying to make a good working cooler with little or no cost, and spend very little on PV Panels.

Thanks Chris
351 Posts
May 7, 2009 10:52 am
Re: Swamp Cooler Conversion to 12 volt DC

Do you want the same performance that you are currently getting ?
You have a 700 watt motor. If you go with less than that, it will cut down on the air flow. That will mean less cooling.
How many hours a day do you run the thing ?
If you run it 4-5 hours, you are going to need about 700 watts of panels (not counting losses).  If you pay 4.50 a watt for panels, you are looking at about $3150 in solar panels. 

Whether you use an inverter or go straight 12V, the 700 watts would be 60 amps on the 12V side (without inefficiencies or losses.)
5 Posts
May 7, 2009 05:40 pm
Re: Swamp Cooler Conversion to 12 volt DC

Check out this link. This is similar to what I was thinking about doing, except a 12 volt motor for the existing fan. Their system, with this type of Fan(12 Volt Auto \Radiator Fan) makes about 2500cfm using less than 10amps, just wondering what a I could find out about electric motors. They are using 100 watts on a Tracker. I could afford 100 watts already fabricated or make my own PV Panels.
Thanks for the advice about the inverter

351 Posts
May 8, 2009 11:16 am
Re: Swamp Cooler Conversion to 12 volt DC

I don't believe anything on youtube.

I also don't know how you can expect 100 watts to do the work of 700 watts.
My suggestion would be that you do not do anything in your conversion that would make it difficult to revert to the original configuration.

In fact, if I were attempting it, I would build a test cooler first. I would buy some smaller evap pads and mount them in a box with a fountain pump. Mount the fan and duct it into one room. See how it works. Power the thing with a battery or 12V power supply.

If you were to modify your original cooler with the radiator fan, I would guess that you would only get about 10% (or less) of the current cooling capacity.
5 Posts
May 8, 2009 11:55 am
Re: Swamp Cooler Conversion to 12 volt DC

Thanks for the advice. I am gonna try a mock up DC cooler with 55gallon plastic barrel and see what hapens.
May 8, 2009 04:03 pm
Re: Swamp Cooler Conversion to 12 volt DC

Can't help you with which way is better or best or even inexpensive. To me thats all a matter of opinion and like the Guru says, "Opinions are like belly buttons. Everybody has one."
(The U.S. government made the choice to bail out Wall Street to the tune of 700 billion tax payers dollars. I would of let it crash. Americans survived the first stock market crash, we could have survived another. I think too many people in our government were just too sk-sk-sk-skeerd of losing their own personal investments and thats why they voted "yes" the second time around. In order to "buy" some time. But thats just my opinion. It was Katie Couric that made the statement "Congress has failed to pass the bail out bill." after the first vote made was "no." Thats her opinion. Obviously she had a lot to lose.)

Anyway here are some places where materials for building such things as a "swamp" cooler are available.


I've seen "firsthand" those type of coolers used in large hog house operations pulling cool water from deep wells. A cool creek might be a good source too. Of course they work best in areas were relative humidity is low, like 40%.

Browse around the FarmTek store though. You might find something thats more to your liking.

I do not know, maybe some stuff you might find interesting.
5 Posts
May 8, 2009 05:45 pm
Re: Swamp Cooler Conversion to 12 volt DC

Thank You for the advice.
I am learning more each day. I hope to put together a 12 volt cooling system with fairly inexpensive parts, maybe with components that are used on boats or RVs. The DC fan motor seems to be the biggest obstacle. Are there any very effecient fans/ fan motors(capable of spining a metal wheel)that could blow around 4500cfm that would use very little amperage (maybe 10 amps or so?)The Radiator Fans for Cars seem to be a great alternative, but would need to modify the cooler housing and remove the old wheel. I have a Bilge Pump that  uses 1.5 amps at 12 volts and it pumps 450 gpm(gallons per minute)I am hoping to construct a system including pv panel for about $500 that would cool approx 1200 sqft.
351 Posts
May 8, 2009 10:53 pm
Re: Swamp Cooler Conversion to 12 volt DC

Lets try it a different way.
You have what is approximately a 3/4 hp electric motor.
If you reduce it to 1/20 hp, it will not do the work.
You need a 3/4 hp motor, regardless of voltage.

Here is a 12v dc motor (3/4 hp) that would come close to replacing your AC motor.
I am not sure whether the rpm is a good match or not.
But note the power draw, 58 amps.

No matter how you try to get around it, you are going to need a motor that pulls 60 amps plus or minus at 12V.  Or you are significantly reducing the cooling capacity.

Do not get too hung up on CFM numbers. You can have 2 fans that move about the same amount of free air, but one will drop out quicker when you expect it to pull a partial pressure. CFM numbers are often about as accurate as EPA mileage numbers used to be.

By the way, you better go read your bilge pump again. If your amps are correct, it is a 450 gph (gallons per hour) pump.  That would make it about 7.5 gpm. And that rating is at 3 feet of water or something under 1.5 psi.  Put more back pressure on it, and the numbers fall off rapidly.
5 Posts
May 9, 2009 01:28 am
Re: Swamp Cooler Conversion to 12 volt DC

Thanks Ken
That helps a bunch
May 9, 2009 06:47 am
Re: Swamp Cooler Conversion to 12 volt DC

I was having a few cold beers with and, got to talking about "swamp" coolers with a friend of mine and these were some of her ideas.





As you might have guessed, shes a race fan. No pun intended. I've been trying to get her interested in this - http://www.nedra.com/ - with minimal results. I joked around with her saying, "You just like the smell of burnt nitrogen and hot rubber better than hydrogen and hot rubber." She came back with, "How do you know its not just the hot rubber that turns me on?" I guess you had to be there.

Doing it all for under 500 bucks... Thats the real trick isn't it? Those links she provided take you to all new, brand name auto racing stuff, but I bet a lot of it could be salvaged from an auto "junkyard." If desired.
26 Posts
May 24, 2009 02:29 pm
Re: Swamp Cooler Conversion to 12 volt DC

My 'default' is always to go 12v dc on this type of thing. I tried to pump water once with a 110 v jet pump (admittedly inefficient at any power source) and found my batteries failing with the first round of garden irrigation. Back to 12 volts. Surplus Center (https://www.surpluscenter.com/home.asp ) always has a selection of dc motors to choose from...

Jim Sluyter
May 31, 2009 06:58 am
Re: Swamp Cooler Conversion to 12 volt DC

Here is an idea to "kick around" since we are on the subject of cooling homes via alternative means.
In particular, in the above file on the bottom of page 2
"market opportunities," "absorption AC" and, "off grid homes."

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