So what the hell are we being sold?

[lendee]

Hi all: So I got this used chiller on e-bay and got it hooked up to my res tank . Printed on the chiller is it's water requirements 180 gph to 600 gph so I figured to use a 400 gph pump on it. To test it I used my discharge line on my bloom res & hooked it into the chiller and partially closed the input valve to the grow I use a 1055 gallon per hour res circulation pump and didn't want to exceed the max limits of chiller all went well the res chilled to set temperature and the chiller cycled fine.
I didn't want to guess at the amount of water I was supplying so having a 1 liter measuring cup I converted everything to liters and then to liters per second now I could see how many liters per second was coming from the discharge of the chiller converting low & high requirements gave 11.4 liters per min low to 37.9 liters per min high and then dividing by 60 gave 0.19 liters per second low and 0.6 liters per second high. So I expected to take from about 5 sec to 2 second to fill the 1 liter container. I was shocked when my 1055 gph pump barley obtained the low limits of the chiller I didn't know if my pump was going bad or what was going on. I had a brand new 2700 liter per hr - 712 gph pump so I hooked it up by it's self to the chiller and tested it's output. The new pump, 2700 liters per hour / 60 = 45 liters per minute divide by 60 = 0.75 liters per second, I should get a liter container filled in about 1 second. What I got was almost 5 seconds to fill a 1 liter container. Which equals 0.2 liters per second or my 2700 ltr ph pump is now a 720 ltr ph pump or 180 gph actual pumping capability.
Now I'm totally confused just what are we getting from the pump companies or what the hell am I doing wrong here other than the resistance of the chiller coil the pump has no load & when using my res circulation pump as a second test I got the same results from both pumps the actual output of each pump is about ¼ of it's advertised capability. Can anyone shed some light on this ??

 

[lushgreen]

These pump are rated with absolutely no restrictions on the outlet. Once you put a length of pipe and a chiller on it, the flow rate is greatly reduced as these fish pond pumps are not high pressure rated. Soon as you put some restriction on the outlet, impellor cavitates and flow drops off.

 

[lendee]

Thanks lushgreen: I'm real new at this just over 1 year at growing and have used a couple different systems and have settled on RDWC never checked on actual outputs of pumps until now. So here's the question what brand of pump are seasoned growers using that the output can be relied upon ?

 

[dirtybud]

I'm not using a chiller yet. But this is good food for thought.
Are Danner Mag drive pumps not suited better for this?
So I am confused. Does the chiller provide increased resistance? Which in pump terms would be a load or head pressure?
And because the water is not moving (resistance or head pressure), the pump cavitates? And head pressure drops. Right? Am I getting this correctly?
I am thinking a pump rated for 1200 gph might push through. Whats the rule, here?
I've studied fluid mechanics and thermo, but I have forgotten a bunch of that stuff.

 

[lendee]

Hi dirtybud: Your explanation is better than anything I've found out yet. I'm going to do an actual measurement of output on the 2700 lph pump I have running the chiller now and see what kind of output it's actually giving with nothing but a 1/2" hose hooked to it. I will post the results soon. I have been growing now for just over a year and have settled on rdwc. Now I want to put in-line pumps in to reduce heat in the res and have settled on Danner Mag drive pumps so I shot this issue at them asking them if I'm using the wrong type of pump or just buying junk or what ? and so far I haven't got an answer but it's only been a week or so. I use a 4000 lph pump as a circulation pump on my 47 gallon rdwc and it's timed for 10 circulations of the res per hour and now I'm not sure what I'm circulating so like you I'm going to find out.

 

[dirtybud]

Right on.
Do I understand correctly that the chiller inlet is only 1/2" dia.? That sure is small. 1/2" inlet seems like it would be a limiting factor no matter what velocity the pump is. And because the system is not pressurized (open system), you can not increase flow (can you?). You need a larger inlet on the chiller. I don't know much about chillers, but unless you are handy at modding your own stuff, you'll have to get something heavy duty.
Be great if you illustrated with pictures, because I am not sure if I am on the same page as you.
I want to make my own system (based on Alien Hydroponics). It uses 4" plumbing with uniseals. And I'll use a submersible pump in my res. taking suction from the effluent header via 1-1/2" to 2" flex line. Res to buckets will be gravity fed. I'll need a high flow inline chiller and this will be a problem for me I can see.
It would take some processing through, but seeing would help. I am sure it could work, just have to design a flow that ads pressure at the right point. I am envisioning some possibilities. Sorry, I all get are more questions for you and scatterbrained thoughts as I think about the system I want to make. I need to do some research on inlets size on the chillers, that needs to be big!

 

[lendee]

The chillers input is 3/4" & I've reduced to 1/2" which is pretty standard for what I've found out the output of the pump is not affected by connecting to chiller. I get a liter of output every 4 seconds & if you believe their specs I should be getting 3.75 liters in the same time period so basically I'm getting about 25% of the power I should be getting and this is wide open not connected to any load whats worse the pumps I have been using are testing the same way so I am doing something wrong here or I've been real lucky not to have severe problems with my circulation res formulas. Anyway I still have got no response from Danner so I'm going to try lighting a fire under them to shed some light on this. This is a picture of the chiller I'm using and the 47 gal rdwc system I'm using

 

[dirtybud]

I think you have a nice looking system. I don't think I know enough to help you on it. Sorry. If I were there to actually see it, could probably give an educated guess on what's going on. From what I see, I am surprised it's not working as you want.

I want a chiller, but I may not need one if I keep my water flow rate high (via super RDWC) and a A/C installed. I am getting a window unit for my small rooms. Maybe I can build some kind of heat exchanger that will pull off heat to an unground water loop, like a geothermal. It could be a two loop system. Ground stays 55 deg. F all year round if you get deep enough ... Free cooling.

 

[go4snypr]

I had a quick read thru the posts and the only thing i think you do not mention is the psi rating of your pumps. I have a pump that is 120 gmp but if you try and make that pump up hill it is not going to work because of head pressure. the pump works fine if it does not have to lift the water, but if it has to lift the water you need a pump that can handle the lift. My pump will not pump 4ft vertical which is only 2psi of head pressure. Every foot of water you are trying to lift is .5 psi (roughly). so if your trying to go from the res to the chiller to the top of those garbage can pots you are probably trying to lift the water higher than the pump can handle. IF you are pumping the water into the bottom, it is the same thing, it still has to meet a certain psi to push the water up. Also the size of pipe will restrict flow. You only get as much flow as your smallest fitting. Even if you up the psi a half inch pipe can only handle so much flow.(though off hand I do not know how much that is)

 

[lushgreen]

You're gonna need a bigger pump...