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Balancing water systems

Brad White_9
Brad White_9 Member Posts: 2,440
Can you get me a model number for the pump?

I would put more stock in the circuit setters than any valve mounted what might be too close to the discharge of any pump. Seven diameters minimum is still prone to bounce and unreliable readings when at a pump.

Can you furnish me with a list in series of the devices and rough estimate of pipe and fittings? Evaporator PD, control valve PD's/Cv's?

As mentioned earlier is there a DP or other bypass? If not set high enough and bypassing around the pump, there she goes.

Unless you have 3-way valves or this is a variable-primary flow set-up, I have to assume you have a DP Bypass valve somewhere. Where is that and across what does it flow? (Pump discharge to suction? Chiller outlet to pump suction? Those kinds of things.) Diagramming this in my mind would help.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,329


    Ok. I need some help from the experts. I am having a few issues with balancing water or maybe not really a balancing problem but how to determine if the water flow is correct.

    We have a chiller installed by another company that has flow problems on the evaporator (chiller barrell) side. At factory start-up Carrier said the water flow was low. The original contractor was called back to install a new pump and motor (base mounted). The problems continued and we were called in to troubleshoot.

    The 100 ton chiller would like 250gpm and the Taco Pump installed is rated 300gpm at 60 ft. All the piping is 4" and appears ok. We have checked the obvious, closed valves, circuit setters, we have removed and cleaned all
    strainers and have removed the end bells on the chiller and punched and cleaned the tubes.

    If we take the differential pressure across the chiller barrell (as Carrier did) we show a flow of 200 gpm for this chiller using the chart provided with the chiller which is the correct chart (double checked). We have measured this with a diff. flow meter (B&G) which reads ft. of head directly and by using pressure gages and subtracting the pressure and converting to ft. of head.We get about the same #.

    Each air handler (there are two) has a B & G circuit setter. (The two ahu's are the only load) If we measure the flow at the ahu and total them we get approx 180 gpm. This diff. 200-180 dosent bother me much and could be attributed to circuit setter location etc. At least theysomewhat jive.

    Now the problem. The Taco pump has a Taco triple duty valve mounted at it's discharge. If we measure the flow there and use the correct chart it shows the flow is 400gpm and is almost off the circuit setter chart-4" circuit setter (Ithink). The pump is running very near it's 60'ft of head rating.

    I have tried to get a pump curve from the local Taco Rep who always seams(unfortunatly) to be uncooprative. They sold the pump to the original contractor--who probably dosen't wan't us on the job.

    I also have another job that is acting in a similar way.

    Are triple duty valve mounted close to the pump accurate for flow measurement??

    I tend to beleive the pressure drop as shown across the chiller barel.

    Which flow would you believe?? and how to approach this???

    I gotta get a pump curve.

    Thanks in advance for the help.

    ED
  • Brad White_53
    Brad White_53 Member Posts: 7
    Ed

    Running off to my train soon but I will take a crack at this later. In the meantime look for any bypassed flow between the pump and the evaporator. Short shot, more later..

    Brad
  • Empire_2
    Empire_2 Member Posts: 2,343
    EBEBRATT

    FIrst off,...Taco-HVAC.com has a large selection of pumps and the specs you are looking for. 2nd,... I dont have a problem with the TDV on the discharge and I think you have to slow that flow down to your desired flow rate. If each AH needs 50 ton, the Circuit setters should be adjusted accordingly...about 120 GPM. My question, sounds like your loop pump is pumping over your required GPM for thew loop but that is why you have the CS on the discharge line. Can you throttle it down?

    Mike T.
  • John White
    John White Member Posts: 120


    Where might you be located?? Just curious.
    John White
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,329


    John we are located in Western, Ma. Job is also in Western Mass.

    ED
  • Brad White_53
    Brad White_53 Member Posts: 7
    bump

    Not that you are working the weekend, Ed. Just keeping current and interested. Love solving these kinds of things :)
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