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By Taukeer Ahmed Sr.HVAC Design,Estimation and Facilities Engineer - 3 months ago
It is used in secondary chilled water pumps which circulates water to AHUs, FCUs, FAHUs or other building air conditioning equipment like CCUs.
The purpose of the VFD installed on secondary chilled water pump/motor is to increase or decrease the speed of motor in order to control(increase or decrease) water flow rate. This increase or decrese in motor speed and accodingly flow rate is governed by means of pressure sensors(pressure transducers).
VFD is normally installed where we have got 2 way modulating valves on chilled water system instead of 3 way valves. In three way valve system, by pass line is available to cater the flow during no cooling load. Whereas on a two way valve, when the valve is fully or partially closes, the water pressure increase which is sensed by pressure sensors which give signal to VFD to reduce the speed of motor and flow rate is reduced and vice versa.
