proper chilled water pump sizing

[duvy]

When a system requires a GPM flow rate to supply system AHUs is there a percentage increase needed to over come pipe resistance? If system GPM is 172 needed to AHUs, should the pump chosen be rated at 172GPM or increased by a certain percentage say 25%,215 GPM to insure enough GPM for the chilled water system.

 

[trashcanman]

Negative. The pump should be sized for the calculated flow rate and calculated head loss. Select the pump in the middle of the pump curve, so that you will have some "wriggle room" in case your calculations are off or the operating conditions change (additional load). Flow friction increases by Q^1.85, so you do not increase flow to overcome friction. You increase Hp instead.