The working voltage of your device must be the same as the power supply.Such as 12V device use 12V power supply.
The max use of your device's should be no more than 80% of the power supply's power rating.In other words,power supply's power ≥ device power × 1.25 times.For example 1000 watts power supply can be only be used with an device that uses up to 800 Watts(1000*0.8).
If running 7*24 hours, the load does not exceed 40% of power supply.
For Motor device, the peak power of the power supply needs to be more than 2 times of the motor.