IBM System x3550 M4 Installation And Service Manual page 290

v This equipment shall be located in the same immediate area (such as, adjacent
v The dc supply source shall be located within the same premises as this
v Switching or disconnecting devices shall not be in the earthed circuit conductor
Statement 31
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IBM System x3550 M4 Type 7914: Installation and Service Guide
cabinets) as any other equipment that has a connection between the earthed
conductor of the same dc supply circuit and the earthing conductor, and also the
point of earthing of the dc system. The dc system shall not be earthed elsewhere.
equipment.
between the dc source and the point of connection of the earthing electrode
conductor.