IBM x3550 M4 Type 7914 Installation And Service Manual page 291

v This equipment shall be located in the same immediate area (such as, adjacent
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.
v The dc supply source shall be located within the same premises as this
equipment.
v Switching or disconnecting devices shall not be in the earthed circuit conductor
between the dc source and the point of connection of the earthing electrode
conductor.
Statement 31
Chapter 6. Removing and replacing components
273