What safety precautions must be taken before performing maintenance or working inside the unit?

A dangerous voltage remains in the input capacitors even after the unit is turned off — always wait 5 minutes after switching off before working on the unit, then verify that the capacitor voltage is near zero before touching any component. Turn off and disconnect input power, and lock out and tag the main disconnect switch before performing any installation or maintenance. Only qualified personnel should remove panels or covers for maintenance. (Pages 5, 8)