Chiller Flow Rate/Energy Consumption Question

Discussion in 'General Reef Topics' started by ReefSparky, Aug 10, 2009.

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  1. ReefSparky

    ReefSparky Super Moderator

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    My chiller paperwork recommends the flow rate through it to be between 480-2,400 GPH. I'm currently running about 600 GPH through the chiller using a submersible CA3000 powerhead. I'm considering upgrading to a larger, external main return pump that would put about 1,200 GPH through the chiller.

    When I purchased the chiller, I employed the powerhead scenario because I had it already; and my main return wasn't strong enough to T off of. Now; the PH is in the sump, running in closed-loop fashion from sump, to chiller, back to sump. As a result, I have an extra heat-producing, submersible pump running in my system. And I'm not a great fan of powerheads for use as pumps, as they are prone to clogging, which would cause even more heat.

    If I simply upgraded to a stronger external return pump and ditched the powerhead, would it be money well spent? For sake of example assume the new external pump would consume the same amount of electricity as the current scenario (pump plus the powerhead).

    To sum it up--I would get rid of the powerhead, and replace it with a single inline pump that would:
    a) not add heat to the water,
    b) consume no more electricity than the current scenario, and
    c) would nearly double the flow rate through the chiller.

    From what I understand, a slower flow through the chiller results in longer dwell/contact time and hence speed up the chilling process. What I'm not sure of, is whether it is more taxing to the chiller. So in a nutshell--my intent is to minimize energy consumption, and maximize chiller lifespan.


    Here are my questions:

    Should I expect the chiller to now run more, or less?
    Would it simply run a bit longer each session, but less time overall? (more efficiently?)
    Would it be a "wash?"
    Would it not make a frag of a difference?
     
    Last edited: Aug 10, 2009
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  3. Otty

    Otty Giant Squid

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    I would run the chiller in the middle of the flow rate they recommend. External pump is the way to go for many reasons. You will get more gph for less wattage then having a hole bunch of PH's. Plus you can size one for a manifold and prepare for future expansions.
     
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  4. ReefSparky

    ReefSparky Super Moderator

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    Thanks, Otty. That's pretty much what I'm planning on doing. Right about in the middle at about 1,200 GPH or so.

    I'm still wondering if I should expect any difference in the percentage of time the chiller runs. Right now, it's running about 35% of the time (when halides are on).
     
  5. dufresne

    dufresne Feather Duster

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    Love this kind of posts - to the point, with all the info needed, asking specific question/s... there's a lot to be learned that way ;)
     
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  6. steve wright

    steve wright Super Moderator

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    opinion

    I dont believe the % of time will be affected by much it at all

    the size of the chiller in relation to volume of water dictates the efficiency ( run time needed to achieve target)

    I believe that despite the contact time being shorter, it will still remain well within the units limits , thus temp of water leaving unit may be a little warmer (have slightly less heat molecules removed) but as the water travels through it more often in any fixed period of time, a balance will be achieved

    I think you on off times may be closer together than they are at present - but I think it will be more like (example) on for 10, off for 10, on for 10 etc - rather than on for 20, off for 20

    Id be interested to know factually so Im sure if you go for it you will help all of us with chillers and keep us informed

    Steve
     
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  7. PackLeader

    PackLeader Giant Squid

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    Let me ask you this: since you are running just the power head, where is the chiller located?
     
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  9. Powerman

    Powerman Giant Squid

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    It isn't a matter of contact time. The refrigerant in the chiller is capable of absorbing 4000 btus an hour (the rating of your chiller). The amount of heat needed to raise one pound of water one degree. There being 8 pound per gallon.

    So for the sake of making it easy..... 1000 gph is 8000 pounds an hour. So you can cool down 8000 pounds a half of a degree in an hour, or you can cool 4000 pound one degree in one hour. The chiller works the same. In your 100 gallon system, you only have 800 pounds of water. At 4000 btu/hr, you can cool your tank 5 degrees in one hour. Since you are well within limits of the cooler, you should not see it run any more or less. Does that make sense?

    Now having said that, there is no problem running a flow rate in the middle of the range. Seems like a good place to be for me.

    As far as external or internal.... you have too much heat in the Summer, but do you have enough in the Winter. If temps run the same for you year round.... then there is no reason to run a chiller to cool your internal pump. A double wammy electricity wise. But if you need a heater to maintain temps while your halides are off.... the larger part of 24 hours.... then all that heat of the external is lost to the air, and you wioll need to run a heater. Pick which ever one is best energy wise.
     
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  10. Robman

    Robman Great White Shark

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    Damn Sparky, You bought the same chiller I have--That thing is a beast!!! It carries my 150 easily. You'll never have to worry about heat with that thing. You had mentioned tee-ing off your return pump. I just sent the return pump through the chiller and into the tank..works great. no xtra pumps and still has plenty of flow. Chiller sits to the left of my cabinet.

    [​IMG]
     
  11. ReefSparky

    ReefSparky Super Moderator

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    I love 'em too. I love this place
    :)

    Thanks, Steve. I think you're right. I tend to overthink things. So you're saying the amount of time it runs should even itself out, but should be the same, in general. I guess in any scenario, the only difference will be the small variation insofar as how balance is achieved.

    The chiller is located about 5' to the right side of the tank, 12" off the wall it's against to the rear. The powerhead is in the sump directly below where water enters from tank. The outlet of chiller back into sump, is on the opposite side of the sump, directly adjacent to the area where water exits sump to the return pump. I attempted to avoid recirculating cold water through the chiller.

    Thanks, Powerman. You've explained this to me countless times, and you're probably wondering how many more times it'll take before it sinks in. I think I have it now. :) You and Steve said the exact same thing, I suppose--with you taking a more explanatory bent. I always appreciate your time and effort attempting to help me understand.

    Thanks, Robman. You must be utilizing quite the beast of a return pump. What pump is it?
     
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  12. Powerman

    Powerman Giant Squid

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    I'm responsible for about 2 MMBTUs an hour. You walk me through wiring my light, least I can do is help you with some heat exchange.;)

    All your ratings of course are subject to ambient temp and the ability to reject that heat to the surroundings, but you are well with in range. I was not going to put all my return flow through my chiller. My max flow is 790, but I think my chiller will be too restrictive to get the amount of flow I want to the tank. So I will tee off. But you have the capacity to put it through.

    I don't see the need to supply it with max flow. Too much water moving, too much electricity. There is no need to just pump water. But you can get a pump to give you the flow you want through your chiller and account for head and get that to the tank and you will be cool. (pun intended);D