Checking The Earth Path - IBM 3907 Safety Inspection

Note: The customer supplied voltage is AC only.
DANGER:
Arc Flash/Arc Blast hazard when disconnected with power on. Turn off power before
disconnecting. (L015)
：
Gefahr:
Beim Trennen der Verbindung im eingeschalteten Zustand kann ein Bogenblitz
oder ein Kurzschlussbogen entstehen. Daher vor dem Trennen der Verbindung den Strom
ausschalten. (L015)
__ 1. Set the supply-power breaker to the OFF position.
__ 2. Using the CE meter, check to be sure that there is no voltage between each pin and the earth pin
(and receptacle shell, if metal).
__ 3. Using the CE meter, check to be sure that there is no voltage from receptacle earth to building
earth. A water pipe, building steel, or earthed raised floor panels are examples of building earth.
For metal receptacle shells, check for no voltage from the receptacle earth pin to the metal shell.

Checking the earth path

Perform the earth path check using either Procedure A or Procedure B on all receptacles the customer
uses to supply power to the frame. If the correct equipment is available, Procedure A is the preferred
method in the United States.
Procedure A
This procedure checks for an earth impedance of 1 ohm or less. At the receptacle earth pin, using the
Suretest tester (PN 25F9715) and Isolated Earth Adapter (00P7019).
__ 1. Set the supply-power breaker to the OFF position.
__ 2. Locate a live 120 V outlet near the receptacle that is being tested.
__ 3. Insert the Suretest tester into the 120 V outlet with the earth pin extended.
__ 4. Perform the impedance test as indicated in the instructions on the face of the Suretest tester.
__ 5. Unplug the Suretest tester.
__ 6. Plug the Suretest tester into the Isolated Earth Adapter.
__ 7. Attach the alligator clip from this probe to the earth pin of the receptacle to be tested.
__ 8. Reinsert the Suretest tester into the 120 V receptacle (you might need an extension cord).
__ 9. Repeat the test as specified in the Suretest tester instructions, looking for an indication of 1 ohm,
or less.
__ 10. If the connector has a metal shell or metal components, unplug the Suretest tester from the
receptacle. Reconnect the alligator clip to the metal, then reinsert the Suretest tester and repeat the
test.
Attention: If the Suretest tester is not removed, a spark might occur when the alligator clip is
reconnected.
For more information, see Electrical Safety for IBM Service Representatives, S229-8124, or equivalent
documentation for your geography.
Procedure B
__ 1. Set the supply-power breaker to the OFF position.
__ 2. Using the "CE" meter, measure the resistance from the earth pin of the receptacle to building earth.
The reading must be 1.0 ohm or less.
__ 3. For metal receptacle shells, also measure the resistance from the earth pin of the receptacle to the
metal shell. This reading must be 0.1 ohm or less.
1-4
3907 Safety Inspection
， / 。 ， 。
(L015)