Cooling unit control

1. A method comprising:

at a start time, by a computing device, controlling a cooling unit to start the cooling unit in a mechanical mode in which the cooling unit receives return air, cools the return air, and releases the cooled return air as supply air, the supply air being air supplied to a cooled volume; and

controlling, by the computing device, the cooling unit to transition, after waiting a wait interval from the start time and over a transition interval, the cooling unit from the mechanical mode to an economizer mode in which the cooling unit receives outdoor air and releases the outdoor air as at least a portion of the supply air, wherein 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 the transition interval being either a configurable interval or based on the humidity of the supply air to transition the cooling unit from the mechanical mode to the economizer mode without resulting in a humidity of the supply air dropping below a minimum threshold.

2. The method of claim 1 , wherein the wait interval is a period during which a humidifier media of the cooling unit is able to become saturated with liquid to support the transitioning of the cooling unit from the mechanical mode to the economizer mode without resulting in a humidity of the supply air dropping below a minimum threshold.

3. The method of claim 1 , wherein the wait interval is approximately 45 minutes.

4. The method of claim 1 , wherein the wait interval is approximately 30 to 60 minutes.

5. The method of claim 1 , further comprising:

monitoring, by the computing device, a humidity of at least one of the supply air, the cooled volume, and the return air by receiving one or more signals indicative of one or more humidity level measurements of the at least one of the supply air, the cooled volume, and the return air during the transition interval; and

controlling, by the computing device, the cooling unit to adjust respective proportions of the received return air and the received outdoor air based on the humidity.

6. The method of claim 5 , wherein controlling the cooling unit to adjust respective proportions of the received return air and the received outdoor air comprises controlling one or more dampers of the cooling unit.

7. The method of claim 5 , wherein controlling the cooling unit to adjust the respective proportions of the received return air and the received outdoor air based on the monitored humidity comprises controlling the cooling unit to adjust respective proportions of the received return air and the received outdoor air to maintain a humidity of the at least one of the supply air, the cooled volume, and the return air above a minimum threshold and below a maximum threshold.

8. The method of claim 7 , wherein controlling the cooling unit to adjust the respective proportions of the received return air and the received outdoor air to maintain the humidity of the at least one of the supply air, the cooled volume, and the return air above a minimum threshold and below a maximum threshold comprises increasing the proportion of the received return air and decreasing the proportion of the received outdoor air to increase the humidity of the at least one of the supply air, the cooled volume, and the return air.

9. The method of claim 7 , wherein controlling the cooling unit to adjust the respective proportions of the received return air and the received outdoor air to maintain the humidity of the at least one of the supply air, the cooled volume, and the return air above a minimum threshold and below a maximum threshold comprises decreasing the proportion of the received return air and increasing the proportion of the received outdoor air to decrease the humidity of the at least one of the supply air, the cooled volume, and the return air.

10. A system comprising:

a cooling unit comprising a humidifier and cooling coils, the cooling coils for cooling air supplied to a cooled volume;

a humidity sensor configured to measure humidity of supply air;

a computing device comprising processing circuitry, the computing device configured to:

at a start time, control the cooling unit to start the cooling unit in a mechanical mode in which the cooling unit receives return air, cools the return air, and releases the cooled return air as the supply air, the supply air being air supplied to the cooled volume; and

control the cooling unit to transition, after waiting a wait interval from the start time and over a transition interval, the cooling unit from the mechanical mode to an economizer mode in which the cooling unit receives outdoor air and releases the outdoor air as at least a portion of the supply air, wherein 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, the transition interval being either a configurable interval or based on the humidity of the supply air to transition the cooling unit from the mechanical mode to the economizer mode without resulting in a humidity of the supply air dropping below a minimum threshold.

11. The system of claim 10 , wherein the wait interval is a period during which a humidifier media of the cooling unit is able to become saturated with liquid to support the transitioning of the cooling unit from the mechanical mode to the economizer mode.

12. The system of claim 10 , wherein the wait interval is approximately 45 minutes.

13. The system of claim 10 , wherein the wait interval is approximately 30 to 60 minutes.

14. The system of claim 10 , the system further comprising second humidity sensors, wherein the computing device is further configured to:

monitor the humidity of the supply air with the humidity sensor and a humidity of at least one of the cooled volume and the return air with respective ones of the second humidity sensors by receiving signals from the second humidity sensors and the humidity sensor, the signals being indicative of humidity level measurements of the supply air and the at least one of the cooled volume and the return air during the transition interval; and

control the cooling unit to adjust respective proportions of the received return air and the received outdoor air based on the humidity.

15. The system of claim 14 , wherein the computing device is configured to control the cooling unit to adjust respective proportions of the received return air and the received outdoor air comprises controlling one or more dampers of the cooling unit.

16. The system of claim 14 , wherein to control the cooling unit to adjust respective proportions of the received return air and the received outdoor air based on the humidity, the computing device is configured to control the cooling unit to adjust respective proportions of the received return air and the received outdoor air to maintain a humidity of the at least one of the supply air, the cooled volume, and the return air above a minimum threshold and below a maximum threshold.

17. A system comprising:

a data center storage volume comprising a cooled volume;

a cooling unit comprising a humidifier and cooling coils, the cooling coils for cooling air supplied to the cooled volume;

a humidity sensor; and

a computing device comprising processing circuitry, the computing device configured to:

at a start time, control a cooling unit to start the cooling unit in a mechanical mode in which the cooling unit receives return air, cools the return air, and releases the cooled return air as supply air, the supply air being air supplied to the cooled volume; and

control the cooling unit to transition, after waiting a wait interval from the start time and over a transition interval, the cooling unit from the mechanical mode to an economizer mode in which the cooling unit receives outdoor air and releases the outdoor air as at least a portion of the supply air, wherein 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, the transition interval being either a configurable interval or based on the humidity of the supply air to control a drop of humidity in the cooling unit as the cooling unit transitions from the mechanical mode to the economizer mode without resulting in a humidity of the supply air dropping below a minimum threshold.

18. The system of claim 17 , wherein the wait interval is a period during which a humidifier media of the cooling unit is able to become saturated with liquid to support the transitioning of the cooling unit from the mechanical mode to the economizer mode.

19. The system of claim 17 , wherein the wait interval is approximately 45 minutes.

20. The system of claim 17 , wherein the wait interval is approximately 30 to 60 minutes.