HP StorageWorks 2405 Disk System - Manual (Page 32)

32 Installation
Caution Adding disk systems to 120V circuits rapidly increases amp
requirements. Always make sure that the total current drawn does
not exceed circuit capacity.
Circuit breakers must be adequately rated for inrush and operating currents.
Hewlett-Packard recommends magnetic-type circuit breakers, which are capable
of handling large inrush currents for short durations (10 to 12 cycles) and are
rated adequately for steady state currents.
Choosing PDUs
Peak power requirements and PDU capacity affect the number of disk systems
that can be installed in a rack. For example, to install more than four disk systems
in Hewlett-Packard legacy racks (HP C2785A, C2786A, and C2787A), you must
upgrade to 19-inch PDUs.
Besides rack density, the following factors can help you choose PDUs:
■ Redundant power source. To connect redundant power supplies to separate
PDUs, install redundant PDUs.
■ Number of cords to the AC source. Using 30-amp PDRUs instead of 16-amp
PDUs reduces the number of cords to the wall.
■ Future needs. Installing surplus PDU capacity allows you to add disk system
units later.
■ Inrush margins. For installations that require four or more 16-amp PDUs,
Hewlett-Packard recommends HP 30-amp PDRUs (E7681A, E7682A) for
their inherent inrush protection.
■ On/Off switch capability. Some PDU/PDRU options support the use of a
single-point on/off switch.
The following tables show how many and what kind of PDU/PDRUs are needed
to install one or more disk systems in an HP rack. Data assumes 220V AC
Table 2. Maximum Operating Current
Incoming Voltage
AC RMS
Maximum RMS Current Drawn
by One Disk System
100 – 120 volts 4.8 amps
200 – 240 volts 2.0 amps