Keep your Swamp Cooler from becoming a Swamp Thing

Swamp coolers collect and breed all kinds of bacteria and mold in the water. As the cooler operates, these organisms can travel into your home and cause a variety of health problems. Chemicals can be added to the water to kill bacteria, mold and algae, but can be difficult to maintain.

It's be a proven fact that Bacteria, Molds and Algae can be killed by introducing copper and zinc ions into the water. Silver works very well to, but may be difficult for the home owner to construct a proper electrode.

All that is needed is to connect a suitable electrode of these metals to a DC power supply. The following shows how I made a simple ion generator.

For the emitting electrode I used a brass pipe found in a hardware store. Most brass material is composed of 60 % copper and 40% zinc.

For the DC power supply, only a milliamp (1/1000 th of an amp) is required. I used a 2 watt 62K resistor in series with an 1N4005 diode and connected it to a line cord for plugging into the 120 AC outlet that powers the swamp cooler pump. Heat shrink tubing covers the assembly. The diode forms a half wave rectifier and the resistor limits the short circuit current to about a milliamp. Ions are generated on the positive half of the line frequency and travel off the electrode as bursts of ions at 60 hertz.

The resistor value determines how many ions are generated. It operates like the principle of electroplating, but in reverse. We are "unplating" the zinc and copper from the brass pipe.

Step 1 Build the DC power supply

You will need a 1N4005 diode and a 62k ohm 2 watt resistor to make a pulsing DC power supply

Comments

[botronics]

Copper does kill bacteria. Its being used in ICU wards to combat bacteria.

http://af.reuters.com/article/commoditiesNews/idAFN1E7600JD20110701

[gsxr123007]

$8.53 at home depot

DIAL Zinc Evaporative Cooler Anode
Model # 5157 Store SKU # 341842
Write The First Review
$8.53 /EA-Each

[gnalleweg]

So, has this worked? You mentioned you would check back to see if the green stuff was gone....
Is the fishy smell gone?

[stienman]

"It's be a proven fact that Bacteria, Molds and Algae can be killed by introducing copper and zinc ions into the water. Silver works very well to, but may be difficult for the home owner to construct a proper electrode."

While I don't doubt it, I would like to see relevant links that back this claim up.

Also, I consider this to be a very dangerous project. Let's say that you have grounded the entire swamp cooler and it's working well. Then one day the ground becomes broken, or high resistance. Suddenly your swamp cooler is at 120V potential. Not only that, but your water pipes are likely to be energized. Yes, they will provide an inefficient return path to ground, but at points along the water supply you may touch a faucet and feel a shock. The low current may seem to prevent fatalities or injuries, but those components are not rated for AC safety use - they could fail shorted (lightning, large motors starting, AC line spikes, etc).

Even if everything works perfectly, let's think about the path you're forcing your current through:

Start at the AC transformer outside the home. Go to the breaker box, through house wiring to outlet and then to your circuit. At this point everything is low resistance and appropiate. Now the current goes to the electrode and into the water. The water has impurities in it, so it conducts a small amount of electricity - but to where exactly? You haven't defined in this instructable exactly how the current goes to ground. You specify that the swamp cooler must be grounded, but how does the water touch that ground? Will it work exactly the same way in every model of swamp cooler in use today?

Assume it goes through the plumbing. Now you've electrified all of the plumbing in your house. Then it flows to ground through either the dirt outside your home and then to a ground rod at the utility transformer or one outside your home, or through a ground clamp on the plumbing pipe leading to the breaker box. This is a poor return path, and at times it will rise to a 120VAC potential. Further, if you experience a huge line spike (regardless of whether your circuit fails or not) while you are touching a faucet or perhaps showering the incident may in fact be fatal. Further, this constant ground current may cause problems with grounding rods and plumbing scaling, to the detriment of the house's grounding system.

If we assume it goes through the swamp cooler's grounding system (maybe the pool of water touches the grounded metal) then you've electrified the swamp cooler. The ground then goes back to the electrical box then to the utility transformer. The current has a very poor path not only through the water (which is intended) but then has to go through the scale, muck, and slime that covers the metal in the cooler. The grounding screw in the cooler may be covered in oxides and provide a poor return path. The entire ground circuit from that outlet back to the breaker box is now electrified. Under the most ideal circumstances the resistance is low enough that the swamp cooler is only a few volts above "real" ground. House wiring is far from ideal. Not only is the swamp cooler likely to be at a dangerous potential, but any electrical item grounded in the same circuit is going to share that potential, and will also be several volts, dozens, of volts, over a hundred volts, and under bad conditions thousands of volts above ground potential.

I could go on, but the upshot is that this project should be torn down and re-developed. At minimum the project should be isolated, and a neutral electrode (not ground) should be placed near the hot electrode in the pool so the current follows a "correct" path. Isolation could be easily and cheaply accomplished with two back-to-back transformers if you don't have access to a real isolation transformer. A fuse and perhaps an MOV or two would add more security in case the transformer windings short, or the components fail. You should use a diode and resistor that will fail open under most common power problems (although the MOV and transformers will signifcantly protect the rest of the circuit, and clean up the AC a bit). I'd also consider using a constant current supply, rather than just a resistor.

Personally, I'd consider using a wall wart to provide the DC power - it'll have the isolation required, convert AC to DC for you, etc. You only need a few volts to get the electrode to dissolve in water. Since you're drawing less than a milliamp, a 9volt battery would last a month (625mAH/0.9mA/24H = 28 days).

Please don't encourage others to do what you've done. A disclaimer isn't appropiate here - this is design cannot be safely done even by an expert without huge changes. A disclamer is only appropiate where the design and execution are sound, but the workmanship requires special care or expertise. You may also want to touch on the buildup of hydrogen and oxygen gas. Keep it covered in the winter but forget to turn off the power and properly drain or evaporate the pool? oops...

[Uthman]

I'm with stienman; just use an ac => dc converter as opposed to using 'hot' 120vac. when i was reading through this instructable, i couldnt understand why you would plug it in directly into the wall

[James (pseudo-geek)]

you just wasted some 20-30 minutes of your life to point out something that can be fixed by simply dropping a ground like into the reservoir, AND you didnt provide a solution. I'm gonig to flag your comment for being antagonistic and pointless.

[stienman]

1. Dropping a ground into the reservoir isn't going to resolve the root problem.
2. I did provide a solution - the second to last paragraph suggested a wall wart or even a battery. The power source should be completely isolated from the 120 VAC line.
3. I hope that I didn't waste 20-30 minutes for this - my expectation is that my comment will help people understand that this design is fundamentally UNSAFE, and I hope that others will choose to implement something safer, such as I suggested. If this stops even one other person from dropping a non-isolated AC line into a swamp cooler then my time will not have been wasted.
4. I'm sorry if my phrasing suggests an antagonistic tone, that is certainly not my intention. But I must emphasize how unsafe this design is.

Lastly, I provided a design analysis. My comment is essentially the information I would have provided if this design was dropped in front of me at work and I was expected to critique it as an electrical engineer. Notice that I am not attacking the person. Notice also that I am providing substantial commentary - I didn't waltz in here and say, "Wow, this design is terribly unsafe, it could kill someone," and leave it at that. I carefully described why this design was unsafe, showed a few ways that it could prove dangerous to the occupants of the house, and then provided a suggestion that would lead to a better solution.

I'm sorry my comment was not helpful for you, but I do hope others have benefited or learned from it.

-Adam

[James (pseudo-geek)]

sweet! I just got you to waste another 15 minutes of your life! lol I'm just messing with you. I see you did provide a solution, I dont think it will work permanently, but it is a solution. if you drop a ground like in the water, the electricity will take the path of least resistance down the line and into the ground, rather than risking it going into the water pipes, etc. I would think. I'm not a pro.

[Madrias357]

Which thereby electrifies everything connected to ground. Not the wisest idea to do, because ground, as he stated, goes either to a grounding rod or to your water pipes. As also mentioned, there's a 120 volt supply possibility in the water. There may be a chance that the components on the board don't fail and they work as intended, but last I checked, heatshrink isn't exactly waterproof. Another thing that I don't like is putting 120 volts AC into water that I'm using to keep cool. Something about being shocked by Line power 3 times before has told me that mixing any electricity with a conductive liquid is not the wisest idea. A good solution mentioned would be to use a wall wart type transformer to do the job instead of Line power.

[vatosupreme]

Cool Idea! always looking for new swamp cooler hacks to add to mine. http://www.instructables.com/id/EYQ6NYU6U7EQ6T23AZ/ In terms of safety, what about putting a gfi in line ? wouldn't that take care of any possible problems mentioned by stienman?

[mabelallbright]

i have figured it out per my neighbor..now i am adding a purge pump that lets old water out every 8 hours thus eliminating mold!

[vatosupreme]

that helps but is not foolproof. The bromine is the best.

[botronics]

Its a pretty much standard thing to let a little water out when it is running. This will keep down the mineral buildup from evaporation. A hose connects to the recirculation pump with a valve. I let out about a gallon per hour. Total purging, that's a great idea.

[Mr. Smart Kid]

a gfi might trip

[botronics]

The UL requirement for a GFI to trip is 5 milliamp of leakage current. My device is only a milliamp.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/gfi.html

[ANDY!]

You should see my A/C I made. Look up ANDY! and there's a pic with a Cooling fan on a wooden box. Author is ANDY! himself!

[botronics]

If you are really concerned about shock a GFI can be used. But really, 1/1000 amp is so little. I held on the electrode and dipped my finger in the water. I had to run current through the very tip of my finger just to feel a tingle. A resistor is just about the most reliable electronic component around. Once it is installed, no one will be touching it. a extra ground pad added to the water would insure a ground path, but that would prevent the pan from recieving the protection as an "impressed current cathode" See wikipedi about cathode protection. And about hydrogen production, so little hydrogen is produced that the water alone will absorb hydrogen and there is always ventilation, even with a cover on. I ran the device for a week using a 5k, 5 watt resistor to see what happens to the electrode. Current around 12 milliamps (12 times normal). A blue coating of what I suspect is Copper Hydroxide (mixed with zinc hydroxide) formed on the brass and on the bottom of the cooler. Copper hydroxide has a very low solubility, but copper is present. The bioslime that was there before is changing shape and seems to be dieing off. I now reduced the current to 1/1000 amp I checked on the internet about copper hydroxide and found it is being used as a fungicide. Sounds good to me. Zinc and copper chips are being added to roofing shingles to decompose and form compounds for stopping mold and algae growths. The principle is sound.

[mabelallbright]

i have a problem with the moldy swamp cooler. i went out of town and when i returned smeltl a sour then checked to see the pads had dark mold. so i throw out the pads, but my concern is the black and pinkish mold in there. now i will drain the cooler to rid it of this. i have read of your invention and planned to implement it...but the fellow that wrote about how unsafe it is. i was wondering about using food grade hydrogen peroxide in the water? would this cure the whole business?

[botronics]

Peroxide would break down real fast. If you are concerned with the part about plugging into 120 vac, just use a DC wall wort for the power source. Its isolated and low voltage and should not pose a shock hazard.

[Cobra152004]

I would like to try this project. I have two "Class 2 transformer" wall wart/worts available: One putting out 4.5V at 600 mA and another putting out 12V at 1800mA. I could also use a battery, but am unsure of voltage required. I know that Positive goes to brass and negative goes to the water reservoir somehow, but how should I go about limiting current to 1 mA? I don't want to overdo it. I don't know how to calculate a resistor to use due to not knowing how much voltage the resistor needs to drop.

Also, have you noticed any damage to plants due to the water coming out of your cooler with copper and zinc ions in it. I don't know if I need to dispose of the released water in a special way or not. I have heard that steel wool will grab excess copper ions, so could try it in a bucket under the overflow pipe if necessary.

My main problem is calculating the proper resistor to use for 1mA of current. Thanks for posting this project. It is very interesting. I hope it can help my sometimes fishy evaporative cooler.

[botronics]

The calculation of current through the resistor is an Ohms Law thing. Current equals voltage divided by resistance in ohms. The other factor we don't know is the additional resistance of the water path. If you use a 12k resistor with a 12 volt power supply and the resistor shorted to ground through the water path, you would have 1 milliampere. You could get an inexpensive ohmmeter and measure the current or the voltage across the resistor. I got one(digital too!) from Fry's for 5 bucks. For starts try a 10k resistor.

As far as hurting the plants, copper is actually a required nutrient. I made a bubble lift hydroponic setup for a bell pepper plant. I used bare copper wire in the tubing to allow me to make a stiff bend and hoping the copper would stop algae growth. The plant did fine and the algae just continued to grow. With such low current, the copper ion production is also low. Copper ions quickly form low solubility compounds such as copper hydroxides in the soil, unless your soil is acidic.

[Cobra152004]

The resistance of the water path appears to be what I was missing.  I have an older digital multimeter, but it doesn't seem to be sensitive enough to detect current in series with the 10k .25 watt resistor or resistance through the water.  It detects 16.29-16.47 volts from the "12 volt 700 mA" power supply unloaded and 14.22-14.25 volts across the 10k resistor, indicating a current around 1.42 mA.  (I miscopied the transformer's max mA earlier.)

I have a 1/2" X 6" brass pipe sitting on large a plastic coffee can lid one one side of the pump and several inches of 10 AWG stranded copper wire on the other side to act as a cathode.  I hope ions will get pulled into the pump and circulated.  I couldn't think of a good place to ground the cooler pan, since it's still in good shape.  The paint doesn't appear to conduct well.

Everything appears to be working as intended.  All components appear to be cool.  Is the quarter watt resistor strong enough tolerate the load?  Do you think ~1.43 mA is too much current?  The pan holds close to ten gallons, but I don't have a purge pump or bleed off system.  My soil is basic, so I'm glad to hear about the low solubility copper compounds.  Thanks for all of the help.

[botronics]

Calculating power is easy. Its simply volts times current. So 1.43 milliamps times 14.25 volts is 20.3 milliwatts. I always run a resistor at halve its rating or less. In this case 125 milliwatts for a 1/4 watt resistor. So your good to go. The low current should be more than enough. The ions will quickly form low solubility compounds in the water too. Anymore would just be in excess. Try it in a cup of water (not one for drinking later, use a disposable cup) with a lower value of resistor and you can see a pale green precipitate form. This is copper hydroxide. Add vinegar and the precipitate will turn to soluble copper acetate ,which is toxic, so dispose carefully.

[Cobra152004]

I'm glad to hear about sufficient power dissipation and current.  After having the ion generator running for about a week in the same water with no circulation (due to cooler weather and lack of A/C use), a precipitate has formed under the brass pipe.  It's good to know that the water will only hold needed ions.  The precipitate appears to be pale green.  I didn't test its texture, but copper hydroxide definitely makes sense.  I appreciate the update.

[botronics]

I found a patent for a device that releases copper ions to kill mold and bacteria using a current flow of a few milliamps like what we are doing.
http://www.freepatentsonline.com/y2004/0026264.html

[vatosupreme]

You should clean it with bleach. In our coolers we put bromine tablets (like from a hot tub) in ours and it seems to work very well it got rid of the fish smell in about 30 minutes. (but is smells a little like the chemical) good luck

[botronics]

The device is still running and the electrode is very slowing eroding away. The biofilm is gone. I think it's working. the only way to tell is to culture the bacterial and fungi and do some kind of count. I will consider using a low voltage system to generate the current to make the device safe of electric shock.

[Mz3FRS]

Any noticable change in your biofilm or your electrode since it's been running for close to a month now?

[botronics]

The biofilm is shrinking and loosing shape, not so fluffly as before. Particles of the zinc and copper compounds (hydroxides, I suppose) are sticking to them. Now that it is winter, I drained and shut down the system. The electrode (brass pipe) was dissolving away and has a green patina.

[botronics]

Here is the patent number for a device (Bonaire) you install in your cooler to make zinc ions. My device will also generate these zinc ions, in addition making copper ions to help stop mold and bacteria. 6,609,386 B1 Go to: www.uspto.gov Do a simple search, interesting reading

[spinach_dip]

BTW, is this your idea? I can google up nothing closer than something that looks like the zincs that are attached as sacrifical anodes on boats. They also seem to have some chemical blocks and such. Your solution seems pretty inexpensive and clever. How long has it been in use? Is it working out OK?

[botronics]

Another good way to make the compounds is to simply bolt together one of those zinc sacrifical anodes (got one at Mcmaster-carr) with a piece of copper. The whole affair forms a "shorted battery" and starts to corrode the zinc into the water. No external power needed! I placed it in cooling tower at work. It's been running a month, and will need to wait longer to form an opinion. I use the water to cool high current power supplies and can't add chemicals (increases conductivity).

[botronics]

There are several devices out in the market that do the same thing. You might check this patent number; 5,603,843 and these links; http://www.copper.org/innovations/2000/01/cleansup.html
http://en.wikipedia.org/wiki/Cathodic_protection
http://www.thinkzincanode.com/bustims.cfm

[spinach_dip]

Yea, but this instructable isn't like a plan to build a low-buck copy of an existing product, no one makes something like this for sale. Although I would dang sure want to unplug it before use, I could see something like this used in a hot tub or pools too.

[botronics]

I really believe the danger is quite minimal, but this gives me a good excess to make another one. Perhaps use one that uses a solar garden light as a power source. Heck, I've been finding other uses for those lights. See my " Solar Night Light" project, another instructable.
http://www.instructables.com/id/EWKMPVTF7FERIE2I8J/

[spinach_dip]

You should probably point out that you are drawing current from the hot lead and returning it through the grounded swamp cooler. It took a little head scratching to figure out the complete circuit. Although this violates common electrical practice, a quick google search found that the trip point for GFI is 5 mA of leakage current, and you have less than a fifth of that.

[botronics]

That is true, I hadn't considered that. I just made a model that uses a 5 watt, 5k ohm resistor that generates more ions running at higher current. I don't have a GFI on the cooler, so that's not a problem, unless I get a shock. I have such a device with the high current running at work for a industrial sized cooler.

[spinach_dip]

Well maybe my comment was premature, as it seems you are still tweaking this instructable. I mentioned the GFI and the 5 mA threshold merely because that's where the GFI trips. Underwriter Laboratories has decided that leakage current under 5 mA is safe. A GFI way up there would probably be a bad idea, as you might need to frequently reset it. Sometimes they can be a bit flaky.

[Beanwaur]

wouldnt it work better if you used 4 diodes to create a steady dc supply?

[botronics]

Since so little current is needed, extra diodes would be a waste, increase parts that can fail, size of device, cost. All that is needed is a few ppm of copper and zinc into the water. You still make ions if its pulsed or steady.