How About Water Misting The Condensing Unit?


  #1  
Old 06-29-02, 04:14 PM
hugbob
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How About Water Misting The Condensing Unit?

We know that water misters can drop the air temperature
about 20 degrees. Would not placing one around the
condensing unit reduce the load on the A/C unit and save
electricity? Besides the small cost of water, what would be
the downside to this approach?
hugbob
 
  #2  
Old 06-30-02, 11:54 AM
lynn comstock
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Two problems with misting the condensor

1) Water will corrode the metals of your condenser coil and box.
2) Water contains minerals, which will deposit on the coils and block the air passages over time. Removing these deposits is impossible without damaging the coil.

An air conditioning precooler (using a wetted pad) provides the evaporative cooling of the entering air without the water touching the condenser coils. They do cost money to buy and they require a lot of maintenance. I would recommend against them. They were sold a lot in Arizona back in the 70's. Most of them were abandoned within 10 years and never replaced.
 
  #3  
Old 06-30-02, 02:30 PM
hugbob
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Thank you for your reply Lynn. But when I lived in South
Florida it would rain every day and when it was not raining
the humidity was 90%, and the condensor unit never
corroded in 15 years. Do they use different materials for
outside A/C units there?
Also, we both share Colorado River water now. They sell
filters to take the minerals out now so that the misters do not
clog.
The power company here (friends of Enron) are plundering
the valley. Do you think it could do harm to run an experiment
just for the summer months?
hugbob
 
  #4  
Old 06-30-02, 03:44 PM
cmcdonell
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Let’s look at this from another angle.
With the manufactures trying everyway they can to increase efficiency to gain the upper hand. None of them have endorsed misting the condenser to lower the head pressure.
In fact some manufactures utilize a 2 speed condenser fan motor to keep the head pressure up in cooler weather.
As far as living in South Fla. The rain and humidity are not the problem, Salt is.
 
  #5  
Old 06-30-02, 05:06 PM
hugbob
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CMC.....All I observed was that condensing units do not rust
out in South Florida even though it is "waterworld". I do not
suggest this experiment for South Florida because your
temperatures are only about 85 and water will not evaporate
there (producing the cooling effect) due to the high humidity.
In the SouthWest we run temperatures of 110 (on a cool day)
and almost zero humidity. Perfect for an evaporative effect.
The manufacturers will not discuss this type of thing anymore
than Ford would talk about location of gas tanks or tires.
How about other parts of the country.........anyone?
hugbob
 
  #6  
Old 06-30-02, 06:57 PM
lynn comstock
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More on using a water mister.

An ordinary water filter will remove trash particles from the water (to protect the mister orifice) but will not remove dissolved minerals from domestic water. A Reverse Osmosis (RO) system will, but not completely. Distilled water (like rainwater) is mineral free but costly.

The worst choice would be softened water (which chemically substitutes sodium compounds for the common calcium and magnesium compounds of "hard" water). Softened water is more like seawater and is very corrosive.

High humidity is not going to corrode anything unless the temperature drops below the dewpoint and the corrodable item actually gets wet. Even then PURE water is not terribly corrosive. But if it contains dissolved sulfur dioxide or nitrous oxide (like in smog) the water will be acidic (like acid rain) and will be corrosive.
 
  #7  
Old 06-30-02, 09:47 PM
lynn comstock
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About the big, bad power companies.

In their defense:

Air conditioning imposes a huge demand on the power system in hot weather. This drives up the cost of power because their system has to be able to meet that demand or face blackouts or brownouts. The utilities have studied the waste associated with residential air conditioning because reducing this waste can cut the peak loads and the need for new power plants.

A DOE funded study by ACEEE in 1999 concluded that residential air conditioners impose a wasted extra demand on the nation's power grid of 78 gigawatts. The entire hydroelectric production of the United States (11% of the total production) just happens to be 78 gigawatts. That is an awesome waste of money and resources. It also creates unnecessary pollution. The underlying reason for the waste is equipment oversizing, poor installation practices and poor maintenance practices. The report can be ordered at: http://aceee.org/pubs/a992.htm

A critical listing of facts involving utilities:

http://www.butterflydreams.com/eac/FunEnergyFacts2.pdf
Or
http://www.butterflydreams.com/eac/FunEnergyFacts2.doc
 
  #8  
Old 06-30-02, 09:49 PM
hugbob
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Lynn.....these are not ordinary filters I am talking about. They
are a new item (check them out at Home Depot in the Misting
department) that are designed to remove the minerals that
clog the tiny misting heads. Aside from that, don't you think
an experiment would be worthwhile in a Southwest climate
to see how much electricty could be saved, if any?
hugbob
 
  #9  
Old 07-01-02, 12:13 AM
lynn comstock
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Expeiment.

I have seen the results of unfiltered water sprayed on condensers by homeowners. It helps for a while, and then the mineral buildup takes over.

If you cooled the AREA around the unit as you would a patio, the bad effects might be minimal. If the misted water completely evaporates before reaching the unit, the mineral particles would be like a fine dry dust. With the vagaries of wind, keeping water droplets from actually reaching the condenser coils is impossible to prevent.

Study the filter literature carefully. I am quite sure that DISSOLVED minerals will not be removed. If you have a really old unit, you don't have much to lose.
 
  #10  
Old 07-01-02, 12:03 PM
hugbob
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Lynn......interesting news. When I do a regular web search
for misting and a/c information I come up with nothing. But
I went to the web site you like....homeenergy.org and put
mist in their search box. I came up with an article from them
on an energy company in Palm Springs that is selling misters to
their customers and claim it can increase a/c effeciency by
40%. They claim they have a "magnetic" device to render the
minerals harmless.
Also.....how about using something like CLR to clean the coils.
I find it works like a charm on shower heads.
hugbob
 
  #11  
Old 07-01-02, 12:52 PM
lynn comstock
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“They claim they have a "magnetic" device to render the minerals harmless.”

The KEY WORD is CLAIM. I have heard the claims and do not buy the explanations. I think it is bogus. I don't see that water borne minerals passing through a magnetic field accept and hold a permanent magnetic charge. Secondly the minerals are STILL THERE. They are not collected and removed. Get a sample of treated water and evaporate or boil it away and the mineral will still be there. Are they Teflon coating it so that it won't stick? Your test will prove that as well.

“Also...how about using something like CLR to clean the coils.
I find it works like a charm on showerheads.”

These cleaners are aggressive chemicals. (Acids and Bases) Some coil cleaners use formulas like that to make the coil metals look bright and clean. So get some aluminum foil, some copper pieces, and some chalk (calcium carbonate) and soak them together in your cleaner and water mixture for a few days. Tell me what happens.
 
  #12  
Old 07-01-02, 04:16 PM
hugbob
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Lynn.....I agree with you that their claim may be overstated.
Strange, for they are the electric provider for that area.
But before we worry about getting rid of the calcium (I hope its
good for you...we drink that water) I think the first experiment
is to see if there is any energy savings from the misting. I am
willing to run a fast test on my unit.....one day with and one
day without. Would you like me to post the results here for
the readers? Most of my other appliances are gas so they
should not bias the data.
hugbob
 
  #13  
Old 07-01-02, 06:44 PM
lynn comstock
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It will work well in our climate.

The capacity and efficiency both go up. I would do it only when the temperatures are 90+. Try for area cooling and measure the actual temperature reduction of the air entering the outdoor unit. I'm sure that wind will make that a challenge to evaluate.
 
  #14  
Old 07-01-02, 11:08 PM
hugbob
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O.K.......I will report back in a couple days. 90+ would be a
cold day right now.....its been running well over 100. Don't
think I can measure the temperature drop at the condensor.
I'll just go with kwh usage both ways as that is the bottom
line anyway.
hugbob
 
  #15  
Old 07-09-02, 09:13 PM
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Commercial applications

This cooling method is very common on large commercial units but most homeowners would never do the maintaince required to keep them up

Funny how window units coils never corrode for years even though they are in water constantly ...
 
  #16  
Old 08-17-02, 05:41 PM
raylee5
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Why not use the condensate from the air conditioner? It should not have all the salts, etc. that would be in the water supply. No point on "wasting" water...

I have been searching for a discussion like this - would people seriously interested in this technique interested in putting some notes together?

For example, if you plan on using the condensate, the pressure must be increased to a level capable of becoming mist. Or else, one of the ultrasonic mist producers (think those desk fantasy fountains)... about $20 each?

Thoughts?
 
  #17  
Old 08-18-02, 07:39 AM
lynn comstock
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Room air units do something like that.

The standard way that a RAC disposes of condensate is to use a slinger ring on the outside circumference of the outdoor fan blade. The condensate is picked up and splattered on the outdoor coil to dispose of the condensate without a drain and to provide an energy benefit as well.

I have never seen this concept applied to central air conditioning packaged equipment or Split systems.
 
  #18  
Old 08-18-02, 09:41 AM
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Lightbulb Window units

The standing water is why they fill up with gunk and goop though.
They must be cleaned regularly to stay efficient or that goop will find it's way onto the condenser coil.
Most HO's aren't willing to do the cleaning required to keep a water cooled unit running properly, therefore the unit breaks down more frequently and the unit gets a bad rap.
I have seen these water cooled units commercially made and they are avalible online
 
  #19  
Old 08-18-02, 01:20 PM
rbisys
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Geetings,

Energy efficiency ALWAYS starts with the efficiency of the house.

I don't know how your home is constucted,but, I would recommend looking at radiant barrier paint for the inside and out side walls of the house. Also look into installing a radiant barrier over the attic insulation. If you have a shed roof there is a method for that too.

Doing this could reduce your a/c loads by 50% or more.
 
  #20  
Old 08-19-02, 07:21 PM
raylee5
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Simple test -

I placed a 5 gallon bucket to catch our condensate yesterday - by this morning, it was full - another 3 gallons or so was collected during the day today. We are in North Carolina, where it is obviously fairly humid, but this is somewhat encouraging for using the condensate. I also liked the idea of simply dripping the water onto the fan - saves on pumps, etc.
 
  #21  
Old 08-20-02, 10:58 AM
lynn comstock
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Most central ACs draw air through the outside coil.

The Room ACs BLOW air through the outdoor coil and water driven by the fan will carry into the coil. With a draw-through coil, fan driven water will just blow away from the coil and do no good.
 
  #22  
Old 08-20-02, 05:53 PM
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we called

those fan blades with condensate splattering capability sling rings, seen this discussion go both ways, will certianly throw your subcooling into a loop, as the unit was initially designed to work without it.
 
 

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