Checking the ac outlets

To help ensure safety and reliable operation, check the ac outlets.

1. Turn off the branch circuit breaker that powers the rack. To the circuit breaker switch, attach tag S229-0237, which reads Do Not Operate.
   Note: All measurements are made with the receptacle faceplate in the usual installed position.
2. Some receptacles are enclosed in metal housings. For this type of receptacle, complete the following steps:
   1. Using a multimeter, check for less than 1 volt from the receptacle case to any grounded metal structure in the building, such as a raised-floor metal structure, water pipe, building steel, or similar.
   2. Using a multimeter, check for less than 1 volt from the receptacle ground pin to a grounded point in the building.
      Note: If the receptacle case or faceplate is painted, ensure that the probe tip penetrates the paint and makes good electrical contact with the metal.
   3. Using a multimeter, check the resistance from the receptacle ground pin to the receptacle case. Check the resistance from the ground pin to the building ground. The readings should be less than 1.0 ohm, which indicates the presence of a continuous grounding conductor.
3. If any of the checks that you made in step 2 are not correct, remove the power from the branch circuit and make the wiring corrections. Recheck the receptacle after the wiring is corrected.
4. Use a ground-impedance tester to check for infinite resistance between the ground pin of the receptacle and each of the phase pins. The test checks for a wiring short to ground or a wiring reversal.
5. Use a ground-impedance tester to check for infinite resistance between the phase pins. The test checks for a wiring short.
6. Turn on the branch circuit breaker.
7. Use a multimeter to measure for the appropriate voltages between phases. If no voltage is present on the receptacle case or grounded pin, the receptacle is safe to touch.
8. Using a multimeter, verify that the voltage at the ac outlet is correct.