Aeroponic Setup, can I run 2 pumps on the same closed loop? **PICS**

[rollmydoodie]

Hi, the question is simple, can 2 water pumps be ran on the same 'closed loop'? The reason I ask is because I'm going to be building a homemade manifold using PVC pipe and EZ Clone sprayers to use on (2)-4x4 flood tables, (I want 42 sprayers per table). So a total of 84 sprayers on 2 pumps. According to my Gardener's Digest the 120 site EZ Cloner has 23 sprayers and uses a 1000 GPH pump, so that's 43 GPH per sprayer, while the 30 site uses 17 sprayers and a 450 GPH pump, or 26 GPH per sprayer. So I was thinking 30-35 GPH per sprayer should be plenty and each pump would need to output 1260-1470 GPH to accomplish what I want, and should one pump fail each sprayer would still have 15-17.5 GPH.

Instead of running each table independently and being susceptible to plant loss in the event of pump failure, I thought I'd run both pumps on a closed loop that way if one failed the other would be able to provide half the output to each table and hopefully save the day!

The benefits of the setup in the pic are;

-if I added close off valves in front and behind each reservoir I could have an extra reservoir that has been ph balanced and nuted and easily swap it out in like 5 minutes instead of tryin to drain, fill, balance and connect during my 5 minute pump off cycle, also having the pump outside the reservoir would keep res temps down and also allow for easy maintenance should it become necessary, and the strongest benefit being that if 1 pump failed the other would just pick up the slack.

In theory it seems it would work, but my only concern would be that the high output from each pump would bog the other pump down, resulting in more pump failure, but maybe this isn't the case since they are low pressure. Perhaps I could add 2 check valves, so any thought on this would be awesome as well.

Any experience/thoughts are much appreciated! Thanks

 

[fatman7574]

Hi, the question is simple, can 2 water pumps be ran on the same 'closed loop'? The reason I ask is because I'm going to be building a homemade manifold using PVC pipe and EZ Clone sprayers to use on (2)-4x4 flood tables, (I want 42 sprayers per table). So a total of 84 sprayers on 2 pumps. According to my Gardener's Digest the 120 site EZ Cloner has 23 sprayers and uses a 1000 GPH pump, so that's 43 GPH per sprayer, while the 30 site uses 17 sprayers and a 450 GPH pump, or 26 GPH per sprayer. So I was thinking 30-35 GPH per sprayer should be plenty and each pump would need to output 1260-1470 GPH to accomplish what I want, and should one pump fail each sprayer would still have 15-17.5 GPH.

Instead of running each table independently and being susceptible to plant loss in the event of pump failure, I thought I'd run both pumps on a closed loop that way if one failed the other would be able to provide half the output to each table and hopefully save the day!

The benefits of the setup in the pic are;

-if I added close off valves in front and behind each reservoir I could have an extra reservoir that has been ph balanced and nuted and easily swap it out in like 5 minutes instead of tryin to drain, fill, balance and connect during my 5 minute pump off cycle, also having the pump outside the reservoir would keep res temps down and also allow for easy maintenance should it become necessary, and the strongest benefit being that if 1 pump failed the other would just pick up the slack.

In theory it seems it would work, but my only concern would be that the high output from each pump would bog the other pump down, resulting in more pump failure, but maybe this isn't the case since they are low pressure. Perhaps I could add 2 check valves, so any thought on this would be awesome as well.

Any experience/thoughts are much appreciated! Thanks

You can buy a flow valve that would only trigger the second pump to run if the first pump fails. It is simply a valve with a paddle that sticks down into the stream of flow. The flow triggers the switch to a open poistion. If the flow lessens or stops it cloeses the relay switch sendindg power to the second pump. There are all plastic ones used by may people that use chillers on reef aqauriums or there are brass ones. The plastic ones are safer as they do not leach copper, but they are expensive. I use brass ones on my water cooled lights and plastic if the switches contact reservoir water


Plastic: http://www.aquatic-eco.com/subcategories/1463/In-Line-Flow-Switches/chiller%20flow%20switch/0

or eBay: http://cgi.ebay.com/GRID-CONTROLS-LIQUID-FLOW-SWITCH-MODEL-25_W0QQitemZ180439993755QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2a030fcd9b

http://cgi.ebay.com/Spa-Control-Sundance-spa-flow-switch-6560-860_W0QQitemZ160388743569QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2557ea0191

Brass: http://cgi.ebay.com/New-ITT-M-M-General-Purpose-Liquid-Flow-Switch-FS8-W_W0QQitemZ270503111471QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3efb3deb2f

Putting the pumps into a series would mean no real gain but double the wattage used. Using the pump feeding different parts of the loop would use less power than two pumps in a series but the two combined feeding the same loop from two different feed pipes would still use about 120 to 150 of the power of just one pump. Typical pump curve charts for magnetic drive pumps. (typiclly used in aquariums, fountains and small hydro units) show that a typical flow biased pump commonly uses less power when throttled back or when pumping against some pressure. They actually use the most power when they are experiencing nearly the least amount of resistance. The power they use is based upon the speed the motor turns. With resistance they turn at a slower speed so they use less wattage. This is not always the case but most often is the case.

 

[rollmydoodie]

Thanks for the response! The wattage used is minimal and not nearly a concern when compared to all the other environmental controlling factors plus lights ( the EcoPlus 1267 GPH pump is 90 watts and will only be ran for 4 hours a day total, 1 min on 5 off ). I still don't understand why having 2 pumps in a line rather than 1 wouldn't increase the water output from the sprayers, and you said that resistive pumping actually slows the pumps down and therefore uses less power, so wouldn't the combination of the 2 pumps make more pressure in the lines and therefore restrict each pump and force each pump to use less power?

I know a lot of things are counter-intuitive but just wanna figure this one out before I begin building, and to get the approx. 2500 GPH that I'm looking for using a flow valve would require me to buy 2 much more expensive pumps and an expensive flow valve but if it must be done, than it will.

Thats the only drawback to an aeroponic system, pump goes and left unnoticed kills a crop extremely quickly.

In addition to the question at hand, does anyone have any estimations on how long a pump can be left off before crop fatalities?

 

[fatman7574]

A pump will only put out a given amount of pressure maximum. Using tow like pumps will still only put out that same maximum. However if using just one pump supplies only a portion of the maximum rating then yes suing tow inlne can incarse the pressure. But just the same, if your getting max ratedpressure using just one pump using tow will not increase the pressure. look at itlike revolutions per minute. If the maximum rated revolution is 1000 rpm and the single pump is running at 100 rpm adding a second pump will not incraes ehe rpm's above the maximum 1000 rpm. However if using one pump the rpm is only 800 rpm then adding the second pump could push the rpm up to the maximum 1000 rpm. A third , fourth and fifth pump would still not incrase the speed above 1000 rpm. therefore you would be apying for a bunch of pumps running at 1000 rpm but the water volume and pressure would remain the same if one pump sjust fed the next pump and vice versa. If they all had sepearte feed lines yes that would incraese flow. Pressure would be more easily incraesed by reducing the manifold pipe diameter. Moving the same volume of water through a smaller area means it must run at a higher pressure. Velocity = Flow / Area

A higher velocity means a higher pressure.

If one pump supplies enough water and the second pumps is jsut to provide for the case of the first pumpnot working then the flow valve would pay off in wattage saved in a very short period of time and it would s also allow for the second pump to only run when needed therefore it will last much longer. I think I posted a few eBay plastic flow valves that were quite cheap. There are huge numbers of brass flow valves available cheaply on eBay.

 

[MoN3yb4Gs]

I've got a 4950 GPH pump, I'm not hooked up yet, but by all calculations I should be good with 100+ sprayers. I'm not too worried about pump failure. This is a good little pump. I'll probably pick up a backup if I can find a good deal, but mine does have a good warranty.

 

[rollmydoodie]

The only bad thing that I'm worried about is if a pump did go out, I would have so little time to notice the problem before all is lost.

It makes sense that the 2 pumps will help to achieve the maximum GPH as indicated on each pump. So it would be beneficial to have them inline if when the lines were combined they achieved twice as much pressure compared to individually. I will probably add a pressure gauge to measure the pressure on the lines individually and then linked to see what is truly being achieved. I'll probably end up running them on separate lines to achieve max pressure on each line, but I'll post whatever results are found and thanks for the input!