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Thread: The new cor pump versus herbie

  1. #1
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    Question The new cor pump versus herbie

    I am in the process if setting up my first sump, and looking i to the different ways of making it quiet.

    I am wanting to get the Cor 15 when it comes out. But was wondering if anyone has thought about using it, and a couple of flow sensors, to do a “reverse Herbie”.

    My understanding of the Herbie overflow method (only from reading so far), is that you use a valve to constrain the waterflow and try to achieve a full syphon in the overflow pipe.

    So i was wondering, could i put a couple of flow sensors on the overflow, and instead of restricting the overflow using a valve, crank up the cor15 and make more water flow down the pipe untill full syphon is achieved.

    The theroy sounds good on paper (if that paper is a recipt for a couple of beers), but not sure if the fusion software is able to for control a cor using data from the flow sensors, or if the idea would evem work.

    so i thought i would ask the question here to see if any of the cor testers have teied it.

  2. #2
    Frequent Contributor zombie's Avatar
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    The flow sensors won't get the feedback loop right on an overflow. The reason is that they are velocity sensors and not mass flow sensors. If full siphon is not reached but the water is moving the same speed, it will read roughly the same flowrate as full siphon.

    You might be an engineer if...You have no life and can prove it mathematically.

  3. #3
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    That would make it hard.

    Could you put the flow sensors on the emergency overflow, and configure the cor to reduce when any flow is detected down the emergency pipe? Would reduce the noise of the noise of the main overflow, but would greatly reduce the noise of my wife screaming about water on the floor.

    I suspect your going to suggest putting an optical sensor in to shut down before overflow, and i have that in place, mostly just trying to see all the neat things i can do with a apex and a small biocube (if only i get rid of the fish and coral, there would be so much more room for automation. )

  4. #4
    Frequent Contributor zombie's Avatar
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    That seems more doable.

    You might be an engineer if...You have no life and can prove it mathematically.

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    I can see several potential issues with your plan. First, you need to match the flows exactly. I don’t know how big the overflow is for your tank, but for a small tank, you may only have a gallon or two before it overflows. If you flow is mismatched by 1 cup an hour, you could have an overflow in less than a day. I don’t know what the accuracy or precision of the Neptune flow meter is, but I’d be willing to bet it isn’t that good.

    Another issue involves the degree of adjustability possible with the COR pump. Most adjustable pumps I’ve seen have 10 different flow settings. It’s likely that one setting will be significantly to low and the other significantly too high, so depending how accurate and rapid the flow readings are, you would likely see the levels oscillate significantly before the controller reacted.

    The biggest concern I have relates to safety. Herbie (and Bean Animal) overflows work because the plumbing and fluid dynamics have built in feedback mechanisms to self correct for variations in siphon flow as well as safety backups if things go out of whack. By doing what you’re proposing, you’re using flow meters and programming to take over the adjustments rather than using the intrinsic physical properties of the system, effectively changing it from a passive system to an active management system. What happens when the Apex crashes, or your programming is off, or the sensor fails?

  6. #6
    Frequent Contributor zombie's Avatar
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    The COR has fine tune adjustment of 100 steps so that is a non issue.

    If I understand his premise correctly, he has a main line that he's targeting close but under full siphon and will have an overflow with a flow meter attached that will reduce flow when/if water starts coming down it. If I am correct in this assumption, that seems pretty safe and the only issue that could arise if flow exceeds full siphon is some unwanted gurgling noises until programming senses the flow and reduces the pump intensity for a while.

    You might be an engineer if...You have no life and can prove it mathematically.

  7. #7
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    Thanks for the great info.

    Zombie is right about my plan.

    I plan to deploy a normal Herbie but with an additional flow sensor one the emergency overflow.


    I am mostly curious if i can use that flow sensor and the cor15. To “fine tune” the system.
    Now that i know the flow sensors are velocity censors, I doubt it will be effective or even possible, but i am curious to see what the data looks like.

    Not expecting much, just enjoying playing with all the options.

  8. #8
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    Yes, that’s what I was envisioning. Essentially, you’ll have 2 standpipes. One lower down that is submerged and running as a full siphon and a second one higher up. You want to adjust the COR pump flow to keep the water level in between the two pipe openings and have a sensor in the upper/dry standpipe. If the sensor detects water then you will reduce the COR speed to drop the flow/water level in the overflow. Or am I still getting it wrong and you were planning on having a small amount of flow in the upper standpipe and using the COR to adjust downward if it got to be too much?


    Even with 100 gradations, the degree of control may still be an issues. If the pump can flow 1000 gph, then a 1% change in pump speed will potentially change the flow 10 gph. Perhaps I’m thinking about this incorrectly and it’s possible to calibrate the pump to be more precise, but that would likely still be enough of a difference to cause issues. If you’re planning on keeping the upper standpipe wet, then this degree of adjustability may well be adequate.


    If your plan on keeping the upper standpipe dry, another thing I thought of is the lower standpipe breaking siphon. If you drop the flow of the COR down and the water level drops too low, then the lower pipe will entrain air and break the siphon. Depending on the pump flow, what frequently happens in this case is the pipe ‘flushes’ as air is entrained, then, because it is no longer functioning as a full siphon, the flow rate decreases and the water level in the overflow starts to increase until a siphon is re-established. At this point the flow increases again and the cycle repeats. You would need some sort of sensor lower down in the overflow to signal the pump to increase the speed. A simple float or optical sensor should work for this, but both of these would require regular maintenance to keep them clean and reliable.


    As the water level drops, the siphon standpipe will form a vortex and entrain air from the surface. If you have room in the overflow you can reduce this by putting an upside down ‘U’ on the siphon standpipe so the opening is actually facing downwards.


    The apex programming language is fairly limited, and I don’t know of a way to automatically calibrate the COR rate to the needed flow. (I.e. increase the COR flow rate, wait 1 minute and increase it again if the flow still isn’t’ adequate) Zombie is more versed in Apex programming than I am, so s/he may know of a way to do it that I don’t. From what I know you would have to define a couple of profiles, say one for low speed and one for high speed and have the Apex adjust between them based on the sensor input.


    It sounds like what you really want is a sensor in the upper standpipe to detect the presence of water, i.e. more of a digital sensor than an analog flow sensor.
    As I think about it, it could be possible to have a high and low level sensor and have pump the COR increase the flow rate when the lower sensor is uncovered and then decrease it when the upper one is covered. The water level in the overflow would be constantly fluctuating, but the Apex really doesn’t care how many times it has to adjust the flow, so it should be happy do keep adjusting it all day long.


  9. #9
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    I think you are on to something there.

    I was wanting to go with the flow sensors on the pipes, but its probebly better to go with a series of optical sensors mounted in the overflow box. Having them adjust the cor based on which ones are open or closed.

    You also bring up a great point about scale and percision. If i was running this on a huge system, i suspect the percision might be good enough, but on my little nano system of 32 gallons, I very much doubt the system could make small enough changes.

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