Running two chillers in series? OR... Running return pump through chiller?

Discussion in 'General Reef Discussion' started by capman, Nov 23, 2017.

  1. capman

    capman I contributed!
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    Each of my two new systems will be set up with two Arctica 1/3 HP chillers (so, four chillers total).

    Each system will have two identical, redundant return pumps (it is looking like these will be
    Iwaki MD-55RLT - 1104 GPH pumps).

    I hate running extra pumps just to pump water through chillers that aren't even running most of the time.

    So...

    What are your thoughts on the possibility of putting the two chillers in series?

    Alternatively (and this is seeming like a better idea), what are your thoughts on running the outflow from each return pump through a chiller on the way to the tanks?

    It seems that with, say, submersible pumps, running the return line through the chiller might not be the best idea (would reduce flow too much maybe), but with Iwaki pumps I'm guessing the flow reduction would not be so much of a problem.

    Thoughts?
     
  2. patent

    patent Ok Moderator
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    I would expect that running them in series would reduce the efficiency of the chillers, but if you have a pump that can handle the head pressure it would be doable. I would think putting the pump on an apex outlet where you can turn it on based on the temp would be more efficient. Only pump to the chiller when needed (though I suppose you should run it occasionally just to avoid stagnant water).

    I'm not sure I like sending the return pump's full outflow through the chiller and then to the display. Seems hard to plumb that efficiently without greatly increasing the number of elbows and thus the head pressure. But if you can get it to work.

    When I was running a chiller I used a manifold to split the Dart return pump's flow and send part through the chiller. Worked ok, but I could control how much split to the chiller, so it didn't greatly reduce what went into the display.
     
  3. DarkSky

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    Placing them in series might be a good idea if you were trying to lower temps by a significant amount, or were pushing high flow through them. Some houses with tankless water heaters have two in series, one bringing the water from 55-69 to 80-90, the other heating to desired temp. Here I don't see the usefulness.

    I think you'd be much better off doing what patent suggested, run a manifold off of your return line and put the flow through each one that way. Keep them parallel, with valves and unions before each one so you can shut one off for service while still using the second?
     
  4. marty9876

    marty9876 Banned
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    I'd run each pump directly into a chiller then back to tank. Four pumps, four chillers, each pair on separate circuits is about as redudent as one can get in a simple system.

    The GPH is well within the specs of the chillers. Head loss of the chillers and associated plumbing won't be that much and would happen anyways. Looping water through devices and then back to the sump is always the least desirable approach IMO.

    Just plumb with as large of fittings as you can. E.g. Even if they have 3/4" fittings stick with 1" for everything before and after etc. to reduce friction loss.
     
  5. OP
    capman

    capman I contributed!
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    Thanks everyone for your thoughts.


    I agree. Pretty much as soon as I wrote my original question (actually as I was writing the question) I was discarding the idea of putting the chillers in sequence.

    Indeed, I never go lower than 1" tubing for anything (and the lines from the tank overflows to the sumps will be 1.5"), if for no other reason than to reduce the likelihood of clogging.

    And it seems that a pump that can pump 27 feet high should be able to handle this (with no more than 5 or 6 feet of head pressure to deal with otherwise).
     
  6. OP
    capman

    capman I contributed!
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    So, can the inlet - outlet plate (or whatever it is called) on an Iwaki be taken off and remounted with the outflow connection going out to the side (horizontally) rather than pointing up?
     
  7. marty9876

    marty9876 Banned
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    I'd guess it could but I'd email the company to ask for sure,
     
  8. OP
    capman

    capman I contributed!
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    Rethinking things today...

    The chiller's inlets and outlets are only 5/8". As has already been pointed out above, that's surely going to inhibit flow from the the return pumps. And those narrow fittings have more risk of constriction due to growths of tube worms and whatnot inside.

    My new plan is to use the pumps supplying the ATS units to pump water through the chillers. First through the chiller, then through an ATS unit.

    On the surface of things this might sound bad (why would I want my algae in my ATS to be cold?) but with good flow rates the outflow from a chiller is only a few degrees lower than the tank temperature. I can't imagine the algae would really care all that much even if there was a 5 degree drop in temperature (or more). I've seen lush growths of Enteromorpha (the sort of algae these downflow ATS units all seem to be growing) in really shallow water right by the shore (in no more than 1 foot of water) in the Florida Keys in winter, at which times the water close to shore can drop quite a bit in temperature, and can fluctuate in temperature a lot.

    Also, the truth is, I would be surprised if these chillers even run all that much. The new building should have MUCH better temperature control than our old science building (where we don't even have central air conditioning on our floor), so the chillers are really just going to be there in case something is going wonky with the building's temperature control.

    The chillers will probably want more water flow than the ATS units, but I can have ball valves and a T-connection between the chiller and the ATS to bleed off a bit of flow to a sump if necessary.

    I'm feeling much better about this plan!
     
  9. marty9876

    marty9876 Banned
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    I have no experience with the chillers you mentioned but just on first blush, based on BRS's website, they don't look very commercial-ish at all. In fact when I saw the input sizing I really wondered why you had picked that brand. Reviews looked good/BRS seems to like them to I assume they were a popular hobbyist model. Back in my day the models below were what the cool kids were running. Either 3/4" or 1.5" models.

    I wonder how the water cooled chillers work. Might be great for keeping heat out of the classrooms.

    https://aqualogicinc.com/products/chilling/#chillers
     
  10. OP
    capman

    capman I contributed!
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    Thanks for the chiller recommendation - perhaps these would have been a better choice (and a good choice in the future).

    The main reason for using the Arctica chillers is because I already have three of these (I got good prices on two of them, and they fit really well in our limited space in our current lab) and they are relatively quiet (of course, the chillers you referenced above might be quiet enough too - I don't know).

    Dumping heat into a classroom is not an issue (we have lots of ventilation), but noise from equipment can be a huge problem. Water cooled chillers would probably be quiet though, if I understand how these work.

    And my reason for going with two smaller chillers rather than one big one is to be able to split off part of a system and run it separately if desired.
     
  11. marty9876

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    I have one of those models I linked (inline) if you looking for a cheap one to try out. I think it's a 1/3hp but I'd have to check.

    Those water cooled ones look way cool, I wonder if it's just city water dumped down the drain if one doesn't have a cooling tower.
     
  12. OP
    capman

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