Installation guide

Checking Mainline Electrical Power Outlets
If you are qualified technically, and have the necessary equipment, you should do the
following safety check on each mainline electrical power outlet.
CAUTION:
Do not touch the power outlet or the power-outlet face plate with anything other
than test probes before you have met the requirement in step 8.
1. Find and switch off the branch circuit CB (circuit breaker). (Attach tag Z229-0237,
which reads “Do Not Operate”.)
Note: All measurements are to be made with the power-outlet face plate in its
normal installed position.
2. Some power outlets are enclosed in metal housings. When making voltage
measurements on power outlets of this type, do the following steps:
a. Check for less than 1 volt from the power-outlet case to any grounded metal
structure in the building, such as a raised floor metal structure, water pipe,
building steel, or similar structure.
b. Check for less than 1 volt from the power-outlet ground pin to a grounded point
in the building.
Note: If the power-outlet case or face plate is painted, ensure that the probe tip
penetrates the paint and makes good electrical contact with the metal.
c. Check the resistance from the ground pin of the power outlet to the power-outlet
case. Check the resistance from the ground pin to building ground. The reading
should be less than 1.0 ohm, which indicates the presence of a continuous
grounding conductor.
3. If any of the three checks made in step 2 is not correct, remove the power from the
branch circuit and make the necessary corrections to the wiring; then check the
power outlet again.
Note: Do not use a digital multimeter to measure grounding resistance.
4. Check for infinite resistance between the ground pin of the power outlet and each of
the phase pins. This is a check for a wiring short-circuit to ground or a wiring
reversal.
5. Check for infinite resistance between phase pins. This is a check for a wiring
short-circuit.
CAUTION:
If the reading is not infinity, do not proceed. Make the necessary corrections
to the wiring before you continue. Do not switch on the branch circuit CB
until all the above steps are satisfactorily completed.
6. Switch on the branch circuit CB. Measure for the appropriate voltages between
phases. If no voltage is present on the power-outlet case or grounded pin, the
power outlet is safe to touch.
7. With an appropriate meter, verify that the voltage at the power outlet is correct.
Installing and Testing the 7133 Model T40 3