Abstract: A method includes, at a start time, controlling a cooling unit to start the cooling unit in a mechanical mode and controlling the cooling unit to transition, after waiting a waiting interval from the start time and over a transition interval, the cooling unit from the mechanical mode to an economizer mode. In the mechanical mode, the cooling unit receives return air, cools the return air, and releases the cooled return air as supply air. The supply air is air supplied to a cooled volume. In the economizer mode, the cooling unit receives outdoor air and releases the outdoor air as at least a portion of the supply air. Transitioning the cooling unit from the mechanical mode to the economizer mode includes transitioning, over the transition interval, from receiving only the return air to receiving progressively less of the return air and progressively more of the outdoor air.

Abstract: In general, techniques are described for overriding a programmed set-point of an air moving component of a cooling unit, in order to control an extent of a refrigeration load on an air cooling component of the cooling unit. In one example, an air cooling unit that is configured to be coupled to an electrical bus of a data center includes an air cooling component, an air moving component that is configured to supply air to the air cooling component at a volumetric flow rate according to a fan speed set-point of the air moving component, and a unit controller that is configured to adjust the fan speed set-point of the air moving component to limit power draw by the air cooling unit from the electrical bus to within a bounded range of values that is defined in part by a power draw set-point of the air cooling unit.