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.

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.

try with a mister nozzle? something on the order of 1/2 gpm or less?

Haha!

Fixed.

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....

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.

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.

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.

wait... isn't this the same thing newer window AC units are achieving with the lack of drainage holes and allowing condensate to pool up and be splashed/sprayed all over? I have 2 units that both have this design. They become slime mold factories quickly and have to be washed often. The larger unit (8000btu) become so annoying i just drilled a hole and no it just leaks condensate into a bucket...requiring far less cleaning..but probably also increasing energy usage.

the 8k unit i'm working on has some kind of thermostatic drain valve in the outdoor half.

Haven't seen that happen here. Its hot and humid here with the highs 100+ mist days so the condensate doesn't hang around to slime up. Window units typically run 24/7 here as well so there is always agitation and airflow.

I have a 2 ton window unit in the shop which is way way undersized and it stays very clean. Its also out of the weather as its covered by a large roof.


What the OP wants to do is not use water directly on the coils but to use it in a swamp cooler style to precool the incoming air.

Maybe its all the bugs-spiders build webs/mosquitoes--that get into the inside of the AC unit. Probably just fuel for the slime molds. I would spray out thick snot like chunks of slime after a week or 10 days of straight running. I've been cooling the house with this one unit..so it would run nonstop most of the summer. Now i added another small unit to another room for during the real hot stuff. Just looking my 8000btu pulls about 730 watts on low with an outside temp in the upper 80Fs with dews in the upper 60Fs..so plenty of moisture in the air. Very very wet spring/summer.

I really don't want to spray my condenser.
The water here is incredibly hard. It maxes out the water test strips I have.

lots of water in your rock, eh?

RO is probably the only way to get water that won't foul it. I'm sure they use cooling towers down in NM - what do they do to keep the fouling at bay?

What is the humidity there in the summer? Spraying with cold water will work anywhere but using the swamp cooler method to precool the incoming air wont be very successful with humidity over something like 25%.

I will never understand why they sell swamp coolers here as the humidity never lets them be effective here....


Looking at your numbers thats a drop of 5 amps and a decrease in vent temp which could be computed into even lower amp draw for comparison sake. Just doing some rough numbers in my head even if you were to spray the coils with water the energy savings would be more than worth it and end up in an actual lesser usage of water when you factor in the water needed to produce electricity.
A better use would be to use condensate water as it is much cleaner and essentially free in a way. Here we produce well over 5 gallons a day but you would need a tank and a pump.

But the issues of direct water on the coils like mentioned can be mitigated. However the other issue would be the runoff which over time would soak the ground around the condenser if not routed to the yard away from the unit.

Been reading a little here and there on the subject and found references to an old condenser that was like what the OP is wanting to do. It was basically a condenser coil with a swamp cooler wrapped around it. Sounds like it worked but had issues with rusting out.


Now I have planted a couple mister heads about 3' from the condenser. I'm using a couple of drip irrigation spikes that have screw in heads. The mister nossles have the same thread so... They spray straight up. I am funning the water through a big commercial water filter from a wendys remodel. Its a triple filter with an ice machine clarifier that removes the vast majority of the minerals.
I wouldn't usually do this on my own unit that is only a couple years old but its been quite hot here. It was 119* the last two days and its 115* right now in the back yard.... Its 95* by 9am some mornings and still 100* by 10pm. So anything that might help keep the house a little cooler...

I have noticed a slight drop in amps even though my sprayers are further away but the water is being drawn towards the unit. Most is evaporating on its way to the unit cooling the air. Its only 1-2 amps but its a benefit and it does shut off for a few minutes here and there. However I have had to close off a bedroom which makes a marked difference on hot days. I only plan to run this from about noon till 9pm while its the hottest and until the extreme heat passes.

Will see how it goes. Oh and here is a link to my weather station. I just went out and checked it with a second thermometer and they are both reading the same, unfortunately my exterior temp is correct... https://www.wunderground.com/persona...d?ID=KTXAZLE23

I also let the water tun for a bit to see what the cold water temp was... The "cold" water temp rose to 88* after I let it run a few minutes...

Oh and also luckily we changed our electric plan last year. So last month was only about $155 where as on the old plan it would have been well into the 200s. Oh I cant wait till we move...