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Old 06-22-18, 05:08 PM   #1
oil pan 4
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Default evaporative cooling for A/C condenser test with garden hose study

The scope is to determine if evaporative cooling can boost home A/C efficiency.
Instruments used:
Flir i7 thermal imager
Fluke325 amp clamp

Control over Observations:
Gave the A/C unit a 10 minute warm up time to stabilize.
105F out side temperature
81F inside
52F discharge temperature on closest duct to air handler.
12.5 to 12.7 amps going to A/C unit.

Test procedure:
Have wife spray condenser with hose while I observe instrument readings. I gave it a 5 minute cool down rinse with the hose on it before I took readings.

The readings were:
105F outside
80F inside
48F cold air Discharge
8.3 to 8.5 amp system draw.

I checked it again 20 minutes after the water was off it and it was back up to nearly 13 amps.
You know A-B-A testing like on ecomodder.

Spraying cold water on the unit significantly reduced amp draw.
Now constantly spraying tap water on the condenser is bad for the coils over time and wastes a ton of water.
But I do have a whole home swamp cooler that I'm not using.
That could reproduce most of the gains from putting water right on the coils.
The temperature of the discharge air didn't change much because the system likely has a mechanical thermal expansion valve.


Last edited by oil pan 4; 07-02-18 at 11:51 PM..
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Old 06-22-18, 05:21 PM   #2
oil pan 4
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Can one of the mods fix my title?
It said "evaporative cooling for A/C condenser test with garden hose study"
Then I put my phone in my pocket.
It could have been a lot worse.
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Old 06-29-18, 03:35 PM   #3
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try with a mister nozzle? something on the order of 1/2 gpm or less?
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Old 06-29-18, 03:36 PM   #4
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Quote:
Originally Posted by oil pan 4 View Post
Can one of the mods fix my title?
It said "evaporative cooling for A/C condenser test with garden hose study"
Then I put my phone in my pocket.
It could have been a lot worse.
Haha!

Fixed.
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Old 07-02-18, 06:51 PM   #5
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interesting. I will be very interested in the data you come up with.

I was outside earlier thinking about your post and washing the dust and plant fur off the condenser... There is a definite change in load when the coils have water flowing over them. Not checking with amp meter but its obvious just by the sound of the compressor. Course it was around 110* when I did that while outside cooking on the grill. At that temp it probably makes a major difference in amp draw.

Condensers do huff and puff allot harder when its that hot. And the air out of the condenser is extremely hot....
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Old 07-03-18, 01:43 AM   #6
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I've tried spraying my condenser down(it had been running for over an hour already) with a hose once before and came inside and noticed my discharge temperature actually went up until the water evaporated. It wasn't what I expected so I did it again on a different occasion but with less water and the result was similar. The amp draw went down but it didn't seem to be cooling as well, I assume because the pressure going to the evaporator wasn't high enough for the refrigeration cycle or something.

My system uses a fixed orifice, an standard A coil, fixed airflow, and a reciprocating Bristol compressor.
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Old 07-03-18, 10:49 AM   #7
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Quote:
Originally Posted by MN Renovator View Post
I've tried spraying my condenser down(it had been running for over an hour already) with a hose once before and came inside and noticed my discharge temperature actually went up until the water evaporated. It wasn't what I expected so I did it again on a different occasion but with less water and the result was similar. The amp draw went down but it didn't seem to be cooling as well, I assume because the pressure going to the evaporator wasn't high enough for the refrigeration cycle or something.

My system uses a fixed orifice, an standard A coil, fixed airflow, and a reciprocating Bristol compressor.

Whats happening is the high side pressure is dropping because its being cooled. Then on a fixed orifice system the amount of liquid being forced through it drops. At the same time liquid is starting to accumulate in the condenser coils. Hence less cooling due to less liquid refrigerant going into the evap coil.

Now on a system with an expansion valve the valve will self meter and it isn't an issue. That said TXVs arent the fastest to react. They do lag some to keep the system stable.

So that said any additional cooling on a condenser on a fixed orifice system will not have a benefit. Its also why on cooler days the ac runs longer to cool as it cant build the high side pressure as easily. A system with a TXV "should" see an improvement but i would like to see some real data to back it up as it seems that no entities are interested in that testing.

IMO anything that results in better cooling and lower pressures and lower amp draw is a good thing to try. The high pressures are still taking their toll on evap coils on brands like rheem/rudd in the effect of leaks... I like their very quiet condenser fans and compressors but their evap coils leak like a sieve.



On a similar area... In cars with fixed orifice tubes.... There used to be allot of problems with cooling going away temporarily then coming back. What was happening was when the car is traveling at a steady speed or accelerating it works fine. But as soon as you would just lift on the gas the cooling would go away.
The airflow over the condenser would drop as would the cfm of the compressor and then the pressure in the condenser would quickly raise. Then the liquid in the condenser was quickly forced through the orifice tube into the evap flooding it. So now you have an evap coil that isnt working as well and you have a condenser that is having a hard time trying to rebuild the liquid in the bottom.
Many things like electric fans and different metering devices finally remedied the issue then 134 came out and the problems were multiplied until they finally worked out those issues. IE serpentine and headered condensers and higher cfm compressors.
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Old 07-03-18, 07:56 PM   #8
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There is a product on the market that does this already. The names of the products are mist-n-save, cool-n-save, and mistbox. Pretty much all of them boast a 30 percent performance boost. They all State in the instructions that you have to tweak the rig to your unique condenser and climate. Fwiw, the manufacturers don't include the things on prefab units not because of the corrosion concern, but because of the few gallons a day of water usage. Because no water usage is good water usage.
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Old 07-03-18, 11:37 PM   #9
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Quote:
Originally Posted by jeff5may View Post
There is a product on the market that does this already. The names of the products are mist-n-save, cool-n-save, and mistbox. Pretty much all of them boast a 30 percent performance boost. They all State in the instructions that you have to tweak the rig to your unique condenser and climate. Fwiw, the manufacturers don't include the things on prefab units not because of the corrosion concern, but because of the few gallons a day of water usage. Because no water usage is good water usage.

Yeah but i wouldn't trust their testing though.

As to water usage... Remember to produce electricity it requires the use and loss of water. Around half a gallon(average lost to evaporation) per KWH. So now double that because roughly half of the electricity produced is lost in transmission. Now those of you with power derived form hydroelectric dams already have way cheaper than us and I wouldn't be as worried about the elec usage besides those are also areas with mild summers(most anyway).

So that would have to be brought into the equation as well if you are worried about water usage. And even at that if it took more water than is used in electricity production the impact of using more water is quite a bit less than the impact of creating more electricity.


No mater what Id like to see what some real world not trying to sell a product testing would show. The issues with corrosion and mineral buildup are a costly problem to deal with so personally I wouldn't be likely to do it on anything but an old unit.
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Old 07-05-18, 07:33 PM   #10
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Well the corrosion issue is easily nullified by the fact that window units bathe their own condenser in the moisture drained from indoors. Yes, it's pretty pure water, but the drain pans in window units tend to rust out way before the condenser assembly. Using a small filter on the supply line feeding the mister would eliminate that concern. Also, the misters are pointed away from the condenser coil to maximize evaporative cooling effect on the intake air. If installed correctly, the heat exchanger should be exposed to mostly moist humid air. Only occasional direct spraying might happen during strong wind gusts.


Last edited by jeff5may; 07-05-18 at 08:11 PM..
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