High Pressure Mist Cooling Systems

az1324

Senior Member
I want to install a high pressure mist cooling system in my backyard. I have done a little looking around and it seems like the good pumps are around $1500-$2000+. These pumps generate 1000psi at 0.5-3 gpm.

My thought is... why can't i use an electric pressure washer that I can get for < $200 that is rated at 1300psi and 1.3 gpm?

The other thing they say about these systems is that you should choose the pump so that it is at or above 90% utilization all the time. This means a multi-zone system would require a separate pump matched to each zone. That doesn't sound optimal, especially for my wallet.

The larger, more expensive pumps seem to have built in self-regulation for this. Maybe they operate more like a compressor and have a small storage tank on which pressure is monitored so the pump only runs when it has to. I think they might have said something about variable speed. Anyway, sounds expensive.

The question is do pressure washers have this feature? Probably not (at least the cheap ones) as they are designed for a specific constant flow rate. If they don't then the same 90% utilization rule would probably apply.

Now there are a lot of replacement pumps for pressure washers available and these are probably the same parts (or close to) those used for these "misting pumps". They are either direct drive or belt driven. So another option is to buy one and hook it up to a variable speed electric motor with control electronics such that depending on which zone was active the pump would operate at a different speed or perhaps have a pressure sensor and a feedback loop to adjust its speed to achieve the desired pressure at any flow rate. I don't really know anything about hydraulic systems.

Anyway, hope you guys have some ideas.
 

DavidL

Senior Member
I suspect the real difference is that of MTBF (Mean Time Between Failure) or, how long it will last. A Power washer isn't intended for many hours of use. I also suspect that a power washer pump / motor will be louder in use, though I haven't heard the misting pumps.
The power washer will also have to cycle on /off very regularily to maintain constant pressure. Anothe thing they aren't designed to do.
 

The Pod

Active Member
How much better is a $2000 system going to be vs. something LIKE THIS? I bought a single misting head on a copper tube from a fair for $10 last summer which just hooks to my garden hose and it seems to do just fine covering a 12'x12' area of the patio. Are you looking to cool your entire yard with this?

The Pod
 

az1324

Senior Member
Well the difference is one is a misting system and one is a fogging system. The water atomized at 1000psi is going to flash evaporate, meaning nothing is going to get wet. With the mist at ~80psi line pressure, the droplets are much larger and take longer to evaporate, meaning you will feel the water.

And yes I am going to put the system on multiple patios plus around the pool and sundeck area.

It can drop the temp of the area it covers up to 30 degrees.
 

Chakara

Active Member
Yep and the difference is very noticable. Out in the San Diego area these are common. I saw them there and tried something like what The Pod linked (home built, but same jist). The pro (read high pressure) systems are far superior. Cost kept me from pursuing it more, beside then new house faces west so the back yard is shaded now....
 

jay

Active Member
az1324 said:
I want to install a high pressure mist cooling system in my backyard. I have done a little looking around and it seems like the good pumps are around $1500-$2000+. These pumps generate 1000psi at 0.5-3 gpm.

My thought is... why can't i use an electric pressure washer that I can get for < $200 that is rated at 1300psi and 1.3 gpm?

The other thing they say about these systems is that you should choose the pump so that it is at or above 90% utilization all the time. This means a multi-zone system would require a separate pump matched to each zone. That doesn't sound optimal, especially for my wallet.

The larger, more expensive pumps seem to have built in self-regulation for this. Maybe they operate more like a compressor and have a small storage tank on which pressure is monitored so the pump only runs when it has to. I think they might have said something about variable speed. Anyway, sounds expensive.

The question is do pressure washers have this feature? Probably not (at least the cheap ones) as they are designed for a specific constant flow rate. If they don't then the same 90% utilization rule would probably apply.

Now there are a lot of replacement pumps for pressure washers available and these are probably the same parts (or close to) those used for these "misting pumps". They are either direct drive or belt driven. So another option is to buy one and hook it up to a variable speed electric motor with control electronics such that depending on which zone was active the pump would operate at a different speed or perhaps have a pressure sensor and a feedback loop to adjust its speed to achieve the desired pressure at any flow rate. I don't really know anything about hydraulic systems.

Anyway, hope you guys have some ideas.
I'm curious as to where you are. These things work great in low humidity environments (have family in SanDiego using them) but not in high ones - well, so far as my experience shows. I have homes in PA and SC which are very humid in the summer. I've tried simple systems but the water doesn't evaporate. It just gets you wet (but cool :D )
 

az1324

Senior Member
Phoenix, AZ

Looking at this photo
psi4_1.jpg

there is a loopback from the output to the input which I'm assuming will push the water back into the supply line if the output is overpressurzed. There is also some kind of pressure sensor that is connected to the motor control electronics that either shuts it off at a critical pressure or feeds back the pressure in realtime to adjust motor speed accordingly. Other than that it seems like a pretty simple system.

EDIT: The thing on the left might be the input with a solenoid valve and the hose at the bottom could be the output line. That would make the top mounted device an unloader (or pressure relief valve) with feedback loop. Makes more sense now. No thermal relief valve or dynamic motor control then.
 

az1324

Senior Member
So I figured out that if I want to have a variable speed system I will have to get a drive control and a 3 phase motor which will run about $300-$400. Then the pump is $200. The rest of the parts should come in around $100-$200. So that puts me at $600-$800 and still well under the price I have seen for a non-variable output pump.

The other option is to use smaller pumps for each zone. Each pump will run up to 10 nozzles @ 800 psi and they seem to be priced around $300. So 3 of these would probably run as many nozzles as 1 large pump but be slightly more expensive. Then I could individually control zones and not have to worry about building the speed control system. It would probably be more electrically efficient too.

Finding a lot of good info on snowguns.com.
 

elcano

Active Member
Skibum said:
You have 3 phase power at your home?
Not a problem. If you really need 3-phase in your house you can buy or build a Rotary Phase Converter. They are very cheap if you buy surplus parts. There are several articles on how to make them. Here are just two:

http://home.att.net/~waterfront-woods/Arti...seconverter.htm

http://www.metalwebnews.com/howto/phase-co...-converter.html

If you add an automation controller and a few rated relays you can make it turn on without human intervention. ;)
 
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