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Closed Loop Pumping systems

Solomon_2
Solomon_2 Member Posts: 1
in THE MAIN WALL
I have a closed loop system that has the pump and xtank on the ground floor and circulates water 30 ft high before returning. My expansion tank is located on the suction side of the pump and I have set my fill pressure to give me an additional 5 psig at the high point in the system (set at 18 psig). I understand that the xtank is the point of no pressure change and it is also my understanding that if this tank is at the suction side of the pump that this will be my lowest pressure point in the system. So once I fill my system entirely and get all the air out I should be reading 18 psig at the pump suction and pump discharge (prior to turning on the pump) and should be reading 5 psig at the high point in the system. Now I turn on my pump (TDH 20 psig) which takes my discharge to 38 psig. Shouldn't the high point of my system now be higher than the suction side of my pump?

Another question; if my suction pressure is above my saturation pressure at the highest water temperature in the system I should not flash any water. Any confirmation or insight is appreciated.

Comments

  • Big Ed
    Big Ed Member Posts: 1,117
    Point of no pressure change......

    ......is the pipe that connect the expansion to the system. This is where you connect your PRV. 12 # is needed for a 30' rise . Water could still flash into steam under higher pressure , it just takes higher temperature.....
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,611
    The pump's pressure

    gets added to (or subtracted from) the static pressure of the system. The pump's pressure diminishes as the water flows through the closed-loop circuit. In this case, the pressure at the top floor will be greater than 5 psi when the pump is running. The pressure at the point where the tank connects to the circuit will be constant. So whatever it is when the pump is off will be what it is when the pump is on. The pump will have its highest pressure at its discharge and it's lowest at its suction, and all in relation to the tank's location.

    If the net positive suction head available is greater than the net positive suction head required then the water will not flash.
    Retired and loving it.
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