Nortel Passport 15000 Preparation Manual page 126

126 Chapter 4 Power and grounding preparation
241-1501-205 5.2S2
To determine the minimum gauge of cable you can use, calculate the input
current that your system configuration requires by doing the following:
1 Determine the power consumption in watts for each Passport 15000 or
20000 by totalling the maximum power consumption of the individual
parts. Use the table "Power consumption for hardware parts for a
Passport 15000 or 20000" (page 127), which is sorted by part number.
The information in the table (sorted by PEC) enables you to calculate the
total typical and maximum power consumption. Always use the
maximum value in your calculations.
Note: Most sparing panels show 0.0 W consumed because they get their
power from at least one FP that connects to it. The power consumption
values for the electrical FPs take into account how much a sparing panel
will draw (about 0.8 W average except for NTQS31).
2 Divide each shelf's total maximum consumption in watts either by the
worst case voltage (36.5 V or -46.0 V with a system of ac rectifiers), or
by the low drop-out voltage (for example, 43.5 V) at the BIP input if your
system uses a low voltage disconnect device. (For example, this
calculation gives you the current in amps (single feed maximum) that
each shelf requires. See "Sample calculation of maximum input current"
(page 130) for an example.
3 Choose a gauge of power cable that is rated for the current in amps that
each shelf requires, and rated according to the distance between the
power source and the BIP to ensure the voltage drop is less than 1.75 V.
Note: To prevent nuisance tripping of the breakers, they need to be rated
at least 25 to 30% above the calculated amperage for your system, to a
maximum of the 100 A breaker rating.