In Chilled water system (Closed Circuit) VFD system used to save energy.i am having a doubt that when system load attained by pass system will open( assuming by pass inside the pump room) and pump speed will go down , only specified amount of water will flow through the pump.

My question is is by pass installed at index run, pump will run at low speed @ pr drop equal to index run?

If pump runs with index run required pressure drop, is there any saving in electrical energy?

Purpose of VFD will be satisfied if by pass at index run?

I request please clarify i will be thankfull