If, after the initial ramp process, the compressor rpm´s increase dramatically, then the compressor goes off on a Fault, this may be a problem with the Inlet Guide Vanes not opening.
A good indicator of an inlet guide vane problem is if the ¨ACTUAL KW¨ of the compressor is much less than the ¨DESIRED KW¨.
The suction temperature/ pressure sensor of the compressor is upstream from the inlet guide vanes. Under the circumstances where the inlet guide vanes fail in the closed, or semi-closed position, as the compressor RPM´s are increased, there is no proper response in the suction pressure due to the fact that the refrigerant flow is greatly reduced by the inlet guide vanes.
As the compressor RPM´s are increased, the controls do not see a correct response from the suction pressure and the controls call for additional speed increase. Actual pressure at the suction of the compressor is low with minimal refrigerant flow. The result is an actual KW much lower than anticipated and, eventual entry into ¨surge¨ and a resultant Front Radial Bearing Displacement Fault.
Proper movement of the Inlet Guide Vane can be verified by observing the position of the small steel indicator ball on the exterior of the compressor in relation to Inlet Guide Vane position demonstrated on the chiller controls.