HP Integrity rx7620 Site Preparation Guide, Fourth Editon - HP Integrity rx762 - Page 48

General Site Preparation Guidelines Electrical Factors Dual Power Source Grounding When dual power sources are utilized, strong consideration should be given to measure voltage potentials. The use of dual power might create an electrical potential that can be hazardous to personnel and might cause performance issues for the equipment. Dual power sources might originate from two different transformers or two different UPS devices. Voltage potentials from ground pin to ground pin for these sources should be measured and verified to be at or near 0.0 volts. Voltage levels that deviate or are measured above 3.0 volts should be further investigated. increased voltages might be hazardous to personnel, and should be further investigated. Cabinet Performance Grounding (High-Frequency Ground) Signal interconnects between system cabinets require high frequency ground return paths. Connect all cabinets to site ground. NOTE In some cases, power distribution system green (green/yellow) wire ground conductors are too long and inductive to provide adequate high-frequency ground return paths. Therefore, the server is shipped with a ground strap for connecting the system cabinet to the site grounding grid (customer-supplied). When connecting this ground, ensure that the raised floor is properly grounded. Power panels located in close proximity to the computer equipment should also be connected to the site grounding grid. Methods of providing a sufficiently high frequency ground grid are described in the next sections. Raised Floor "High Frequency Noise" Grounding If a raised floor system is used, install a complete signal reference grid for maintaining equal potential over a broad band of frequencies. The grid should be connected to the equipment cabinet and electrical service entrance ground at multiple connection points using a minimum #6 AWG (16 mm) wire ground conductor. The following figure illustrates a metallic strip gounding system. NOTE Regardless of the grounding connection method used, the raised floor should be grounded as an absolute safety minimum. HP recommends the following approaches: • Excellent-Add a signal reference grid to the subfloor. The grid should be made of aluminum strips mounted to the subfloor. The strips should be 0.032 in. (0.08 cm) thick and a minimum of 3.0 in. (8.0 cm) wide. Connect each pedestal to four strips using 0.25 in. (6.0 mm) bolts tightened to the manufacturer's torque recommendation. • Better-A grounded #6 AWG minimum copper wire grid mechanically clamped to floor pedestals and properly bonded to the building/site ground. 34 Appendix B