It is not true that:
a) For speed controlling of compressor we can use a variable frequency drive with speed controlled according to the cooling load
b) In the case of steam driven compressors, a pressure sensing device, located in the chilled water outlet may be used
c) Suction throttling is accomplished by a butterfly damper installed at the inlet to a centrifugal compressor
d) Suction throttling application is not economical because the input power to the compressor does not decrease by the same amount of capacity
e) Pneumatic vane operators are used on centrifugal compressors
Answer: B