# Evap coolers

Any idea how much a "pad" and "pump" would cost....big thing on the roof. I was told \$150 for the pad and \$139 for the pump HD has pumps for under \$40 and pads under \$40
Terry
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Big thing on the roof? Geeeez....you have to have more information than that, since if you have a MAsterCool unit, with the larger 12 inch pad, \$150 would be cheap. Depending on the model, 139 could be high, or cheap as hell for the pump.
You didnt give enough information...
Home Depot has AC units for \$77 too, that does not mean that you can put one in to replace a \$10,000 8 ton unit either. And I KNOW that HD does not have the MC2 unit pads for under \$40....more like \$120...so, if that price was installed, then why are you bitching?
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Where do you live? NREL says the average May air temp in Phoenix is 78.8 F with a 0.0045 humidity ratio, so Pa = 29.921/(1+0.62198/w) = 0.215 "Hg...
The average daily min temp is 63.9 F, so the average night temp is about (78.8+63.9)/2 = 71.4. The average day temp is about 78.8+(78.8-71.4) = 86.2. At night, the wet bulb temp Tw (R) = 9621/(22.47-ln(71.4+460+100(0.215)-Tw) = 9621/(22.47-ln(553-Tw)). Plugging in Tw = 520 on the right makes Tw = 507 on the left. Plugging in 507 on the right makes 516, then 510, 514, 511.5, 513.3, and 512 R, ie 512-460 = 52 F.
You might water an 8' tall x 28" indoor column of 8 vertical 2-liter bottles inside 26 radial layers of 8 2-liter bottles at night using a \$15 thermostat and a \$10 10 watt fountain pump and a float valve to keep the bottom pan full, and turn on a \$12 window box fan with a humidistat to move outdoor air through the house when the indoor RH is greater than 50%.
The 216 bottles would have about 1000 Btu/F of thermal capacitance and about 264 ft^2 of surface with about 1.5x264 = 400 Btu/h-F of thermal conductance to room air. They might build up an interesting mineral encrustation over time and increase their wet surface. You might add some salts or color (bluing and coal?) to the pan water to help. And a few lights inside, for drama.
If the outdoor temp were 86.2 F for 12 hours, a 200 Btu/h-F 80 F house would need (86.4-80)200 = 1280 Btu/h or 15.4K Btu/day of cooling. Bottles at 80-1280/400 = 76.8 F at dusk and 76.8-15.4K/1000 = 61.4 F at dawn would average 69.1 F, so Pw = e^(17.863-9621/(460+69.1)) = 0.726 "Hg. If they cool 15.4K Btu in H hours, H100x400(0.726-0.215) = 15.4K, using an ASHRAE pool formula, so they need to be sprinkled for H = 0.75 hours per night.
Herbach and Rademan (800) 848-8001 http://www.herbach.com sell a nice solid brass \$4.95 Navy surplus humidistat, their item number TM89HVC5203, with a 20-80% range, a 3-6% differential, and a 7.5A 125V switch that can be wired to open or close on humidity rise.
Nick
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Join solar guru Steve Baer and PE Drew Gillett and PhD Rich Komp and me for an all-day workshop on solar house heating and natural cooling strategies ("HVAC Nonsense") on July 9 in Portland, OR--see page 25 of http://www.ases.org/conferences/2004_call_for_papers/SOLAR2004_prelim_program.pdf
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Terry Cano wrote:

The \$150 and \$139 figure sounds to me almost like an installed price.
Depends on the size. Seems to me I got a pump from them for about \$20. I always keep a spare around. The price of the pads depends on what type you want to use. The Aspen pads are the cheapest. I like the honeycomb paper pads or synthetic fibre. With them I think you get more area for evaporation.
Doing a little search I see there are lots of sites about maintenance:
http://www.kennspenns.com/cooling/cooler~maintenance.html
Be sure to install a small bleed line to keep the water from getting saturated with minerals.
http://hem.dis.anl.gov/eehem/96/960511.html
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Terry Cano wrote:

Four pads at around \$10 a piece sounds about right. The pumps are cheap little gizzies that should cost less than \$20. The small pumps suitable for 30" square evaporative coolers run around \$15. I agree with another responder \$150 for pads and \$139 for the pump has to include labor to install. But that sounds high since you can buy a complete unit for less than that. Anyway installation is simple, so there is no reason to hire it done, unless you can't or don't want to climb up on the roof. \$50 for labor would be reasonable since this isn't anything technical (equivalent to mowing the lawn).
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The labor cost was seperate \$190 The \$139 and \$150 parts only... I did check around and the Master Cooler Pads big thick things (not Aspen) go for around \$150..... pumps I found are a lot cheaper....suspecting I've been ripped
Terry

roof.
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You may find the expensive pads don't work any better and maybe not as well as thicker pads, but hopefully they would last much longer. \$140 buys a good irrigation pump, so yes, you were probably ripped off. The labor cost is also high, unless your cooler was a complete mess that required major fixing including soldering holes, painting, replacement of fan bearing, new water hose and float, and a lap dance or a one hour trip to Vegas.
Terry Cano wrote:

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