A method of controlling capacity in a compressor comprising: calculating an output capacity parameter with a control program; measuring at least one system operating parameter; comparing the at least one measured system operating parameter to corresponding predetermined threshold values for the system operating parameter to determine whether the at least one measured system operating parameter is within a limiting region or an override region corresponding to the at least one measured system operating parameter; adjusting the output capacity parameter in response to a determination that the at least one measured system operating parameter is within the limiting region or the override region; wherein said adjusting the output capacity parameter in response to a determination that the at least one measured system operating parameter is within the limiting region or the override region includes: limiting the output capacity parameter to a predetermined amount of increase in response to the at least one measured system operating parameter being in the limiting region; and setting the output capacity parameter to a predetermined amount of decrease in response to the at least one measured system operating parameter being in the override region; calculating a minimum variable speed drive frequency for the compressor to avoid surge conditions; comparing the calculated minimum variable speed drive frequency to a variable speed drive frequency based on the output capacity parameter; modifying the output capacity parameter in response to the minimum variable speed drive frequency being greater than the variable speed drive frequency based on the output capacity parameter; and applying the output capacity parameter to the compressor to adjust the output capacity of the compressor. calculating an output capacity parameter with a control program; measuring at least one system operating parameter; comparing the at least one measured system operating parameter to corresponding predetermined threshold values for the system operating parameter to determine whether the at least one measured system operating parameter is within a limiting region or an override region corresponding to the at least one measured system operating parameter; adjusting the output capacity parameter in response to a determination that the at least one measured system operating parameter is within the limiting region or the override region; wherein said adjusting the output capacity parameter in response to a determination that the at least one measured system operating parameter is within the limiting region or the override region includes: limiting the output capacity parameter to a predetermined amount of increase in response to the at least one measured system operating parameter being in the limiting region; and setting the output capacity parameter to a predetermined amount of decrease in response to the at least one measured system operating parameter being in the override region; calculating a minimum variable speed drive frequency for the compressor to avoid surge conditions; comparing the calculated minimum variable speed drive frequency to a variable speed drive frequency based on the output capacity parameter; modifying the output capacity parameter in response to the minimum variable speed drive frequency being greater than the variable speed drive frequency based on the output capacity parameter; and applying the output capacity parameter to the compressor to adjust the output capacity of the compressor.