Where do you live and what's your climate? If you have humidity, evap's don't work. They are effective in dry climes (20% or less relative humidity). I can't comment on the cooler you linked. We've used evaps for years here in NM but our typical summers are quite dry (until the Monsoon season and then the coolers are pretty worthless). Cheers, cc
http:/groups.google.com on evaporative swamp cooler will tell you more than you ever wanted to know.
Basically, if they don't sell them at the local bigbox hardware store, you can't use them.
Evap coolers are good for 10 to 15 degrees max and only work when the relative humidity is between 0-15%. Go any higher that and you risk creating a serious mold problem for yourself and they don't cool above that level of humidity anyway.
So unless you live in the desert SW, you shouldn't be using them. Even new construction in Phoenix avoids them because a) they use a lot of water, b) the grass and resorts have bumped up the local humidity, and c) going from 110 down to 100 doesn't buy you much on the comfort scale.
-- "Tell me what I should do, Annie." "Stay. Here. Forever." - Life On Mars
I used a Master Cool Plus located on a flat roof for 8 years in the Tucson, AZ area. Worked like a charm, did not need air conditioning except during the monsoon season, mid June to Sept approx. It used very, very little water and electricity; it just had to be disconnected in the winter to prevent freezing. Big 4x4 filter was hosed down once a year;, no mold, etc. In southern parts of New Mexico, they are in use for most of the year. Las Cruces comes to mind. The picture of the unit y'all supplied probably operates on the same principle, however I have no experience with it. I doubt if it would be effective above 15% humidity, as indicated above. hth
Itt is worth noting that afaict, the ad for that one says nothing about its effectiveness depending on where one lives. It says nothing about where the ones are located that they used to get the average 12 to 20 degree drop in temperature. They might be all in New Mexico, Nevada, and Death Valley. They sure don't work in Maryland. The URL looks dishonest to me.
I live in Phoenix, and coolers are fine through about June, but once the relative humidity exceeds 20% they become lousy. Here's a table showing the best temperature you can expect from a cooler, depending on the humidity and outdoor temperature:
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Also coolers aren't necessarily cheaper to operate than newer air conditioners ( < 15 years old), and it was found that people who had combination cooler-A/C units spent more on cooling than did people who have only A/C.
A 16'x16'x8' room with R20 insulation all round and a thermal conductance of 768ft^2/R20 = 38.4 Btu/h-F would only need Q = 10x38.4 = 384 Btu/h of net cooling to lower the room temp 10 F.
If it's Ta (F) outdoors with a wa humidity ratio and 80 F indoors with wi = 0.012 pounds of water per pound of dry air (an efficient corner of the ASHRAE comfort zone), evaporating P lb/h of water while ventilating with C cfm of 0.075 lb/ft^3 outdoor air makes P = 60C0.075(0.012-wa) and
1000P = Q+(Ta-80)C. Dagget CA in August with Ta = 87.1 F and wa = 0.0077 makes P = 0.0194C and 1000P = 384+7.1C, so P = 0.61 lb/h and C = 31 cfm.
Fresh air might come from 2 vents with an 8' height difference. If 31 cfm = 16.6Asqrt(8'x(87.1-80)) (an empirical chimney formula), A = 0.25 ft^2, eg 6"x6" vents. Outdoor air with Pa = 29.921/(1+0.62198/wa) = 0.366"Hg, and Pw = 0.566"Hg indoors and 0.61 = 0.1A(Pw-Pa) (an ASHRAE pool formula) makes A = 30 ft^2, eg an 8'x8" diameter 2-sided porous shower curtain below the upper vent with a 10 watt fountain pump moving 1 gpm from a sump with a float valve up over the curtain whenever the room temp rises to 80 F.
Or maybe a 5' tall x 8" diameter nuclear bong cooler (see wiki :-)
20 PI=4*ATN(1)
30 AS=10'screen evap area (ft^2)
40 CW=2*8.33*60'water flow rate (lb/h)
50 TW(0)=70'initial water temp (F)
60 CA=665'inlet airflow (cfm)
70 FA=PI*(8/24)^2'duct free area (ft^2)
80 VA=CA/FA/88'air velocity (mph)
90 UA=2+VA/2'airfilm conductance (Btu/h-F-ft^2)
100 TA(0)=100'inlet air temp (F)
110 PA=.1*EXP(17.863-9621/(100+460))'air vapor pressure ("Hg)
120 W(0)=.62198/(29.921/PA-1)'inlet air humidity ratio
140 QTC=0:QTE=0'initialize total heatflows (Btu/h)
150 FOR S=0 TO 9'evap screen number (0 is first)
160 QC=(TW(S)-TA(S))*UA*AS'water-air convective heatflow (Btu/h)
170 QTC=QTC+QC'total convective heatflow (Btu/h)
180 PW=EXP(17.863-9621/(TW(S)+460))'water vapor pressure ("Hg)
190 PA=29.921/(1+.62198/W(S))'air vapor pressure ("Hg)
200 BOWEN=99.4*(PW-PA)/(TW(S)-TA(S))'Bowen's ratio ("Hg/F)
210 QE=QC*BOWEN'water-air evaporative heatflow (Btu/h)
220 QTE=QTE+QE'total evaporative heatflow (Btu/h)
230 W(S+1)=W(S)+QE/(60*CA*.075*1000)'hum rat leaving screen
240 TA(S+1)=TA(S)+QC/CA'exit screen air temp (F)
250 TW(S+1)=TW(S)-(QC+QE)/CW'exit screen water temp (F)
260 NEXT
270 TW(0)=TW(0)-(QTC+QTE)/CW'new water temp (F)
280 IF ABS(QTE-QTEL)>.01 THEN QTEL=QTE:GOTO 140
290 FOR S=0 TO 10
300 PRINT TW(S),TA(S)
310 NEXT S
320 PRINT QTE
I'm in Cincinnati, which can get pretty humid during the summer. But, I have central A/C. I'm just looking to cool an upper floor bedroom by about ten more degrees. I'm hoping the central A/C has dropped the humidity enough to make the air cooler effective.
Even with central AC, I really doubt that evaporative mister thing is going to do much good. I'd suggest looking at air flow from the central AC, or get a window AC.
Thank you. I missed that and it's in print the same size as the other questions.
Of course it is artfully phrased. "Best when ...below 50%". Apparently it does really really best when it is below 16 percent, but we won't discuss the area between 16 and 49! Why not say "Works best when.... below 90%"
I get confused when things get too complicated, but lets assume the AC could make the humidity in the house 15% or less. But then this swamp cooler would cool the temp further by adding humidity, which would get down to the first floor** within a day or less, and which the AC would have to work to remove.
Wouldn't this be just as bad as making spaghetti or taking a hot steamy shower in a house with AC? Don't people avoid those things? Because they add substantial costs to running the AC?
Naw, too humid. Here in the Denver area they work pretty good. Even usable when the humidity gets up to 30% as long as they are moving a lot of air. Outside temp above 90 and the air coming in will be in the low 70s. When our temperatures get near 100 the humidity may be below 10%. And here it always gets cool enough at night that only a fan is needed.
We had someone look at the air flow situation once, and from the work he said would be necessary to improve things, it sounded like it would be very expensive.
Regarding a window AC unit, I bet the other husbands out there will understand this: my wife doesn't like them because she thinks they're ugly. ;-)
(But after reading these posts about air coolers, I think I'm going to make more of an effort to change her mind.)
I live in Las Vegas, Nevada, and can give you some first hand information. Before refrigeration, all we had was swamp coolers. It was better than being outside in the heat, and at night, temperatures were good for sleeping. That said, they have lots of limitations. When it's really hot, they will cool things down, but not like refrigeration. When it's humid, they hardly feel like they work at all. They put so much humidity in the air that after a time, the house smells like one in South Louisiana. Damp and musty.
We still use swampers for a few months a year. Mostly in the spring and fall when we only want to drop the temps a little. Nothing works very well in 115 degree heat. Even a 20 degree drop leaves you at 95 inside. And swampers do not work well at all in humid weather, as we are having now in Vegas during our monsoon season. 40-60% humidity ranges.
Swampers help. But, I think that they do the best for the people who sell them, and claim that they will do all sorts of things they won't. And since the principle they work on is temperature difference created by water evaporation, some of the claims made in humid areas are laughable. Even if you get one, and it works, it won't work all the time.
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