IBM i 830, Repair Manual

Page: 349 / 1000

2. For each unit, check continuity from a conductive area on the frame to the
ground pin on the plug. Do this at the end of the mainline AC power cable.
The resistance must be 0.1 ohm or less.
3.
Ground continuity must be present from each unit receptacle to an effective
ground. Therefore, check the following:
v
The AC voltage receptacle for each unit must have a ground wire connected
from the ground terminal on the receptacle to the ground bar in the power
panel.
v
The ground bars in all branch circuit panels must be connected with an
insulated ground wire to a
ground point , which is defined as follows:
– The nearest available metal cold water pipe, only if the pipe is effectively
grounded to the earth (see National Electric Code Section 250-81, in the
United States).
– The nearest available steel beams in the building structure, only if the
beam is effectively grounded to the earth.
– Steel bars in the base of the building or a metal ground ring that is
around the building under the surface of the earth.
– A ground rod in the earth (see National Electric Code Section 250-83, in the
United States).
Note: For installations in the United States only, by National Electrical Code
standard, if more than one of the preceding grounding methods are
used, they must be connected together electrically. See
National Electric
Code Section 250, for more information on grounding.
v
The grounds of all separately derived sources (uninterruptable power supply,
service entrance transformer, system power module, motor generator) must
be connected to a
ground point as defined above.
v
The service entrance ground bar must connect to a ground point as defined
above.
v
All ground connections must be tight .
v
Check continuity of the ground path for each unit that is using an ECOS
tester, Model 1023-100. Check continuity at each unit receptacle, and measure
to the
ground point as defined above. The total resistance of each ground
path must be 1.0 ohm or less. If you cannot meet this requirement, check for
faults in the ground path.
v
Conduit is sometimes used to meet wiring code requirements. If conduit is
used, the branch circuits must still have a green (or green and yellow) wire
for grounding as stated above.
Note: The ground bar and the neutral bar must never be connected together
in branch circuit power panels.
The ground bar and the neutral bar in the power panels that make up the
electrical power network for the iSeries 400 system must be connected
together. This applies to the first electrically isolating unit that is found in the
path of electrical wiring from the iSeries 400 system to the service entrance
power panel. This isolating unit is sometimes referred to as a
separately
derived source . It can be an uninterruptable power supply, the system power
module for the system, or the service entrance transformer. If the building
has none of the above isolating units, the ground bar and the neutral bar
must be connected together in the service entrance power panel.
4. Look inside all power panels to ensure the following:
Intermittent PIPs
Chapter 3. Problem Isolation Procedures (PIPs), Failing Items, and Symbolic FRU Isolation
335