Results 1 to 6 of 6
  1. #1
    Join Date
    Aug 2011
    Location
    vietnam
    Posts
    39
    Rep Power
    0

    pump on return piping



    hello,
    For heating system, distribution(secondary) pump locate on return pipe is pretty popular but for chilled water system, i hadn't rarely (mostly never) seen secondary pump, which located on return pipe in primary/secondary. Please help me clarify about this difference and their advantage/disadvantage.
    Thanks



  2. #2
    Join Date
    Feb 2012
    Location
    Bolivia
    Posts
    270
    Rep Power
    7

    Re: pump on return piping

    It is not popular, in heating you place them on cooler water so you can maximize NPSH.

    In refrigeration water temperature is lower but you have the largest pressure drops usually at the HE so it is better to place them upriver not to produce cavitation inside the HE under any operating condition and the HE can absorb the pump heat so you get colder water for the process.
    Well, did anybody ever dream of calling Aramis a coward? No, certainly not!

  3. #3
    Join Date
    Aug 2011
    Location
    vietnam
    Posts
    39
    Rep Power
    0

    Re: pump on return piping

    Thanks for the comments. Here is my general schematic. For chilled water loop (from chiller to manifold) continuous line is supply, dash is return. Distributed Pump (4.2) on return along with flow meter (FM-2).
    schematic.png
    Please give me some advices ?

  4. #4
    Join Date
    Feb 2007
    Location
    UK
    Posts
    2,479
    Rep Power
    38

    Re: pump on return piping

    Most pumps will operate with a much higher discharge pressure than suction pressure. One example of this is inline condensate pumps, typically these will be able to suck ~1m but be able to discharge up to a 30m head.

    It therefore make sense to let pumps suck from a header and discharge towards the system and it's control valves.

    But...
    When it comes to hot water you get another factor to consider, heat.
    The higher temperature the pump is rated at the more it will cost to buy.
    It therefore makes sense to put heating pumps at the point in the system where the fluid is at it's coldest.



    .

  5. #5
    Join Date
    Dec 2010
    Location
    Toronto, Canada
    Age
    54
    Posts
    1,492
    Rep Power
    17

    Re: pump on return piping

    Quote Originally Posted by The Viking View Post
    Most pumps will operate with a much higher discharge pressure than suction pressure. One example of this is inline condensate pumps, typically these will be able to suck ~1m but be able to discharge up to a 30m head.

    It therefore make sense to let pumps suck from a header and discharge towards the system and it's control valves.

    But...
    When it comes to hot water you get another factor to consider, heat.
    The higher temperature the pump is rated at the more it will cost to buy.
    It therefore makes sense to put heating pumps at the point in the system where the fluid is at it's coldest.



    .
    That is old school thinking from back when seals were not very good. Now all the pumps are rated to 110C minimum and many of them higher than that so I would say that unless you have to operate close to the limits in temperature or on the curve, keep the pump on the supply to the load. Remember to keep your expansion tank on the suction side to keep the suction pressure stable.

  6. #6
    Join Date
    Feb 2012
    Location
    Bolivia
    Posts
    270
    Rep Power
    7

    Re: pump on return piping

    Unless your runs are extremely long or have high pressure drop, I don’t see the need for the extra pump.

    If that pump does not work on variable speed you may overflow the tanks in the wrong direction.

    The flow meter would be better placed at the suction of the chiller pumps provided you have slack NPSH-wise.

    Why do you need this pump for?
    Well, did anybody ever dream of calling Aramis a coward? No, certainly not!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •