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Canisters in series VS paralell

Discussion in 'General Plant Topics' started by Gerryd, Oct 25, 2008.

  1. Gerryd

    Gerryd Plant Guru Team
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    Hey all,

    I would be interested in hearing from anyone who runs inline canisters like OC or NC in series?

    Current setup:

    I have an NC 533 (30 sq ft 25 micron). Mazzei 384 venturi currently is on the secondary T leg and runs parallel with the 533.
    PanWorld PS250 pump at 1950 gph with 45' head. Not sure of the PSI rating of this pump. Have looked at their website and plenty of specs, but
    nothing that says it produces N PSI??? Anyone with this info and can share, would appreciate it!

    1" output lines all around from pump until the end loop combination back to twin 3/4 outlets.

    Pressure readings:

    1. With the venturi valve CLOSED, and the NC valve and pump outlet valve OPEN, all flow to NC, guage reads 11 PSI.

    2. With the venturi valve OPEN, same as above. Expected.

    3. I currently keep the NC at 6-7 PSI. The rest goes to the venturi.

    Option 1:

    Adding an NC model 522 which is 18sq ft but 100 micron. This would go PRIOR to the 533 as a pre-filter.

    Option 2:

    Install a bio-canister model 547 AFTER the 533.

    Now add a venturi to the equation:

    Option 3:

    Run either of the new filters PRIOR to the venturi and continue to let the 533 run on the parallel leg.

    I am more reluctant on option 3, as I do not really want to decrease pressure to the venturi. Only reason I consider it, is the two models above seem to be higher flow and will hopefully require less pressure to run. This would then affect the venturi pressure less.

    Questions:

    1. If the PSI full to the NC is 11, and then I send 6 to the NC, does this mean that I get the other 5 to the venturi? It is off a T leg at 1" and controlled by the valve just PRIOR to the NC.

    2. Based on these readings, do I have enough to do what I want?

    All thoughts are welcome.
     
  2. JDowns

    JDowns Lifetime Charter Member
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    Option 2 is what I currently run, minus the venturi.
     
  3. jeremy v

    jeremy v Guru Class Expert

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    Gerry,

    Head is the exact same thing as psi, only the units are different.

    1psi = 2.3' of head

    If your pump has a max head capacity of 45' head, that means that you can attain up to 19.5psi with your pump. That's the maximum gauge pressure you would attain right at the pump output if your output ball valve was completely closed and the pump was running.

    Have a good one, Jeremy
     
  4. Gerryd

    Gerryd Plant Guru Team
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    Jeremy,

    Thanks much, got it!

    I plan on adding a few of the Pentair lifeguard guages at various points in my next config, and the outlet of the pump was already targeted.

    So, is this an optimistic estimate, or is that rating provable?

    Reason I ask is that if my TOP PSI on the NC is only 10-12, regardless of whether the venturi valve is open or not, when the NC valve is fully open and it gets all flow, where is the other 9.5 or so?

    Here is a pic of my current split.

    1. Am I losing it due to the 3' or so between the pump outlet and the NC?
     
  5. Gerryd

    Gerryd Plant Guru Team
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    Jeremy,

    Thanks much, got it!

    I plan on adding a few of the Pentair lifeguard guages at various points in my next config, and the outlet of the pump was already targeted. They sell T with the single leg threaded where you can place these. Should not affect flow I hope.

    Pentair Aquatics (Rainbow Lifegard) 0-30 PSI Pressure Gauge Bottom Mount R172045BX, For Modular > Replacement Parts > Filters > Saltwater Aquarium Supplies

    So, is this an optimistic estimate, or is that rating provable?

    Reason I ask is that if my TOP PSI on the NC is only 10-12, regardless of whether the venturi valve is open or not, when the NC valve is fully open and it gets all flow, where is the other 9.5 or so?

    Here is a pic of my current split. The mazzei is off the single T and hidden. Loops back around and connect to the single second T just under the Y return split.

    1. Am I losing it due to the 3' or so between the pump outlet and the NC?

    2. Is it due to the NC having to go through the cartridge? I am testing with the filter up and running.

    3. Is the NC guage not sensitive enough?

    4. Or, is what I read on the NC all I really have with the current config?

    Jdowns,

    How do you like the bio canister? You still owe use a thread on your new setup!

    Thanks as always.
     
  6. JDowns

    JDowns Lifetime Charter Member
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    Gerry.

    I really like the bio unit over past setup with a canister. The 547 holds alot more bio. I took part of the bio that came with the unit out and used my already seaded bio. I never noticed a bloom, so I have to assume I didn't kill off anything during the transition.

    Only time the water isn't crystal clear is when I dump bio barley in there for the shrimp. But that cloudiness clears up in about an hour.

    A word of caution if you end up with a bio unit, and set it up backwords. Where the output of the 533 lines up with the output of the 547 and you use the input of the 547 as the new output. I used a plastic mesh sheet to keep any bio balls from plugging the output. Normal setup and this will not occur.
     
  7. jeremy v

    jeremy v Guru Class Expert

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    Gerry,

    Assuming that your pump is still capable of operating within its' original design specs you should be able to actually see that gauge pressure at the pump output when the pump is on and all the pump output lines are shut off completely so that all system flow is blocked (you are not doing that when you read 11psi at your canister). The fact that you are only reading 11psi when just the mazzei is shut off is because water is actually still flowing through your canister. That's where the other 8.5 missing psi is going, it is translated into water flow. If you have a ball valve after your canister, shut that ball valve and your canister gauge should go up to around 19.5psi instead of 11psi because then all of your system flow will be blocked so your pump will be able to achieve maximum pressure.

    I added that qualification related to your pump needing to still be within design specs, because most pumps do drop off a bit in their capabilities over time due to wear. You probably won't see that issue this soon in your pump's life, but I can't say for sure because I do remember you saying that your pump is a rebuilt one.

    Think of it like a garden hose. Your garden hose will have 40psi or so of pressure in the hose when the hand sprayer at the end is shut off, but if you open the sprayer to water the plants the water pressure in the hose drops a little bit. That difference in pressure is now turned into flow that is watering the plants.

    A pump's maximum psi rating and its' maximum flow rating are directly (and inversely) related to each other. You can only have one 100%, the other 100%, or a lesser combination of both. Your pump only operates at maximum flow when there is zero system head. Any system head reduces flow. Your pump only operates at maximum psi if you have more resistance than the pump can push through and total system flow is zero. Any system head (psi) less than the pump's max capacity becomes water flow through the system.

    For instance, if you have a gauge right at the pump output that reads 11psi, 11psi is what the pump sees. Your pump can push up to 19.5psi, so the difference between 11psi and 19.5psi is the extra pump capacity that becomes your flow rate at that head level.

    Think of it like a pickup truck. If you have a truck engine that can put 400lb ft of torque to the rear wheels, and the trailer you need to tow requires 300lb ft of torque just to get going from a stop. You will have 100lb ft of engine torque left over. That extra torque capacity will then become what is used to actually accelerate the trailer from a stop. If you had 600lb ft of engine torque instead of 400, you could accelerate the same trailer from a stop much faster because you would have extra reserve capacity. In this example, the engine torque is equivalent to your pump's max head capacity(19.5psi), the torque required to get the trailer going is your system head, and how fast you are able to accelerate while pulling the trailer (the difference between max pump capacity and system head) is equivalent to your system's flow rate.

    The key here is that any unused head capacity becomes water flow through your system, so it is not lost. That's why you want to keep the system head as low as possible in order so that the water flow through your plumbing system can be as high as possible while still using the same pump. Lowering your system head is equivalent to pulling a smaller and lighter trailer (that requires less engine torque to get going) in the above truck example. You will then be able to accelerate from a stop much faster (even with the same original engine in the truck) because you will now have more reserve capacity.

    I hope that makes sense.

    Have a good one, Jeremy

    P.S.- EXTRA NOTE- If pump flow and head are inversely proportional to each other shouldn't pump flow curves be linear instead of being an arc like they usually are? Yes, and that's because pump motors themselves do operate more efficiently when operating somewhere in the middle zone of their flow curves. For instance, at the exact middle point in the pump flow curve, many pumps can have 50% of their maximum possible head resistance and still be able to flow 65% of their maximum flow. That extra 15% above expected flow is real, and it is a mechanical efficiency gain from the pump itself, not a loophole in fluid dynamics.
     
  8. Gerryd

    Gerryd Plant Guru Team
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    Jeremy,

    Well I DID just so happen to have a throttle valve AFTER the NC, so with this valve and the valve prior to the venturi, SHUT, I got about 19-20 PSI on the NC guage. Seals started to leak, so did it quickly....

    So, I get most of what you said, but think I may need a bit more help....

    Assumptions

    1. My pump can pump 19 PSI at it's outlet.
    2. The NC gets 6 of that PSI via the main T leg.
    3. This leaves 13 PSI that is diverted to the venturi valve via the single T outlet.

    Questions

    1. If there were a guage after the venturi valve and PRIOR to the venturi, would it read 13 PSI if the venturi valve were fully open?
    2. If so, if I then split this 13 PSI between the venturi and another canister, and gave the canister 6 PSI, would this mean the venturi guage would now read 7 PSI?

    I ask, as I think my venturi is simply getting too much pressure and is causing cavitation within the venturi and coming out as air bubbles and 'mist'.

    I thought the 384 was rated at around 5 PSI??? If so, and am giving it 13 PSI if the above is true, that is more than 2x it's need. I read a lot of threads, and don't think many venturis are getting this much........at least that seems to be the case, but not many PSI ratings in the posts.....lol

    Just trying to figure it out.

    I will be installing these guages as soon as they arrive, so will let you know what they read currently. it will be nice to see what the ratings really are.... I can switch things around too with flex hose, while I look for the best combo. May take a bit, but will be worth it to get the best config.

    Just trying to plan how I want to do the final config with flex and hard PVC, unions, etc and what components will go where.........I want to put this plumbing thing to rest and get some new fish!

    I love the new closed loop config. Glad I dumped the sump......

    thanks as always...........
     
  9. ntino

    ntino Guru Class Expert

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    Gerryd,

    System PSI should be the same when you run things in parallel. So, your mazzei is getting whatever your OC is getting - around 6 or 7 psi you said.
    Now Mazzei work on a difference of pressures, in other words, its important that there are not restrictions after the mazzei - so if your PSI before mazzei is 6 psi, and after its 1 or 0 you would get around 5 psi on the mazzei, which is what you need.
    I dont see why you dont like the fact that there is a fine mist? it should come out as a fine mist AFAIK - not big bubbles that you can see well, but fine bubbles as that you see when looking close.
    hope that made sense...
     
  10. jeremy v

    jeremy v Guru Class Expert

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    Gerry,

    Perfect, that's exactly what you should have under that situation. That is your maximum head capacity. Notice though that when the gauge read 19-20psi you were getting absolutely no flow through the system. Look at your pump's flow chart and notice that when the pump is at 19.5psi or above the flow level is zero. You have to start dropping from that 19.5psi level before you can actually begin flowing water through the plumbing system and the farther you drop from 19.5psi the more water you will flow.

    Assumption 1 is completely right but when the pump sees 19.5psi or greater resistance to flow the total system flow level is zero, assumption 2 is correct, and assumption 3 is what is throwing you off. The 19.5psi of possible pressure from the pump is not like having $19.50. You don't spend $6 here and then $13 there until all the money is used up. Any of that $19.50 you don't spend becomes water flow through the system, which is what you want. You want the pump to have as little resistance as possible so that you can flow as much water through the system as possible for good tank circulation and filtration.

    If the venturi valve right before the venturi was fully open the gauge would read the exact same pressure as your canister gauge (they would both read around 5-6psi most likely). This is key, and notice how the two numbers don't add up to 19.5psi.

    If flow levels are kept low enough so that plumbing friction losses are negligible, the pressure in a pipe will remain the same everywhere in that pipe no matter how many times it splits, etc. all the way until it goes through a component like a partially closed ball valve, mazzei, canister, etc. That means that (with the ball valve before the mazzei fully open) the gauges in your system will most likely read ~5-6psi on the input side of the mazzei, ~5-6psi on the input side of the canister, and ~5-6psi at the output of the pump for your setup. Your total system head will also only be 5-6psi. All of that pump capacity (19.5psi possible- 5-6psi at pump output) and energy that would have been spent just creating pressure is now spent flowing water instead. You will be flowing a lot of water with that setup.

    Now, if you started closing the ball valve on the input side of the mazzei the gauge pressure at the pump output and at the canister input will both go up and will both always show the exact same psi in comparison to each other since there is no added restriction to flow between those two points in the system. The pressure shown on the gauge at the input of the mazzei will go down, because some pressure will now be lost through the restriction of the ball valve itself before getting to the gauge. If you had a gauge on the input side of the mazzei intake ball valve, that gauge would also always read the same pressure as your pump output and your canister input gauges.

    If you made three parallel legs, one for a canister, a second leg for another canister, and a third leg for the mazzei your input pressure to all three of the elements would be exactly the same for all the legs if all the input ball valves were fully open. In that case your pump output pressure would most likely be something like 3-4psi for each of the three legs and also 3-4psi right at your pump output, so your pump would be flowing the amount of water it flows at 3-4psi x 2.3 = feet of head on your pump flow curve. Notice that adding a third leg would make it so that your pump is now seeing less total resistance and will be flowing more total water. That's what running things in parallel does, it drops total system resistance and in turn increases total system flow.

    Most venturis and mazzei's for aeration purposes operate most efficiently at around 3psi of pressure drop across the mazzei. If your intake ball valve for the mazzei is fully open and your canister intake gauge is reading 6psi that means that right now you have 6psi of pressure at the input to the mazzei, not 13psi. You just want to set the pressure at whatever level gets you the mist fineness you want without cavitating the tank water when the CO2 is off. You might not be able to ever get that though, because the actual design of the mazzei itself plays into that significantly and that can't be changed by adjusting flow levels. By the time the cavitation stops the flow might be too low to get you the mist you desire when the CO2 is on, so there are trade-offs and that's why there are so many different model of mazzei's with only slightly different specs from each other. Very small changes make big differences in operational performance for stuff like that.

    That's good to hear, it does simplify everything a lot to remove the sump and I am sure you are saving a lot of CO2 now which is a nice side benefit.

    Have a good one, Jeremy
     
  11. Gerryd

    Gerryd Plant Guru Team
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    Ntino,

    I am getting mist with the c02 off.. otherwise, yes I do want the mist...

    The venturi works fine, but I get bubbles and such when the c02 is off. If I fully close the venturi valve, they disappear so when the co2 is on, it is mixed with this other and is harder to adjust my venturi, based on visual clues..........

    Ntino and Jeremy,

    I think I get it. Just to make sure. True paralell all the components are the same PSI.

    1. The pump ball valve is fully open.
    2. The venturi ball valve is fully open.
    3. I am restricting the ball valve PRIOR to the NC so that it reads 6-7 PSI.
    4. When this valve is fully open, the NC reads 11 PSI.

    So, I am causing the 6-7 PSI, I really have 'more' don't I?

    So, if I had 3 parallel legs, one to the NC 533, one to the NC bio, and one to the mazzei, and all ball valves PRIOR to these components were fully open, I would be getting 11 PSI at all 3?

    Not sure how you got to approx 3-4 PSI at each.

    I am almost there, please bear with me.

    Really appreciate the help. Will save me time to know what the PSI would be so I don't have to put it together just to find out.
     
  12. jeremy v

    jeremy v Guru Class Expert

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    Gerry,

    I didn't know that you were restricting the flow before the canister, I thought you were running full flow to the canister. I must have missed that tidbit, sorry about that.

    Yes, you would really have whatever the canister gauge reads when the canister intake ball valve is completely open.

    No. Since you will now have additional paths for the water to flow (in comparison to what you have now) you will have less water taking each path. It is easier for the canister filter to flow a smaller volume of water, so the resistance of the canister will drop. I don't know exactly how much, but with three parallel legs, all three legs will have the same gauge pressure at their inputs if their input ball valves are completely open and the gauge readings will be less than 11psi, probably something like 6-7psi. That is just a guess though, since the drop will be unique to your exact system and components.

    That was only because I didn't know you were restricting water flow into your canister when you had the 6psi reading, I thought that was the full flow reading.
    With that being the case, in a three leg parallel setup your gauges would all read a little higher than 3-4psi, but how much higher would be unique to your setup.

    Have a good one, Jeremy
     
  13. Gerryd

    Gerryd Plant Guru Team
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    Jeremy,

    Thanks as always. I got it now.............

    I see a lot of guages in my near future to map this out and see what I would really get. I would love to see 5-7 at each of the 3 legs.......

    So.......11 PSI at the mazzei seems like a lot, assuming that is in fact what the venturi is getting. There is nothing after the mazzei and it connects via a second T with the NC output......

    This may explain the issues I have when no c02 is entering the venturi...Too much pressure. I see an e-mail or call to Mazzei in the near future........

    Thanks again to all.
     
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