Refrigerant system with multi-speed scroll compressor and economizer circuit

A scroll compressor comprising:

• a scroll compressor housing;
• a compressor pump unit mounted within said housing, said compressor pump unit including an orbiting scroll and a non-orbiting scroll, each of said orbiting and non-orbiting scrolls having a base and a generally spiral wrap extending from said base, said wraps interfitting to define compression chambers;
• a motor for driving said compressor, said motor being operable at multiple distinct speeds;
• an economizer injection port for injecting a refrigerant from an economizer circuit back into said compression chambers, said economizer injection port extending into said housing, and through at least one of said orbiting and non-orbiting scroll members into one of said compression chambers;
• a control for selectively operating said compressor at each of said multiple distinct speeds, in combination with the optional operation of an economizer circuit associated with said scroll compressor;
• said control identifying a desired capacity level, and then achieving said desired capacity level by actuating the economizer circuit if increased capacity is desired, or not actuating the economizer circuit if extra capacity is not required, and also operating the motor at selected operational speeds to provide further fine control over the provided capacity to match the desired capacity level;
• and
• said control also taking an additional step by operating or not operating a unloader function to provide further control over the provided capacity to better match the desired capacity level, and in combination with controlling the speed of operation of the motor.