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44 Netra ft 1800 Installation Guide • February 1999
Note – The system On and Stby switches handle low voltage signals only; the high-
power circuits do not pass through these switches.
DC Source Site Requirements
The DC source site requirements are as follows:
■ Suitable for use in –48 Vdc ((classified SELV) nominal or –60 Vdc (classified
TNV-2) nominal systems.
■ The supply source must be electrically isolated by double or reinforced insulation
from any hazardous AC or DC source.
■ The DC source must be reliably connected to earth (that is, battery room positive
bus is connected to the grounding electrode).
■ The DC source must be capable of providing up to 925W of continuous power per
feed pair. The sum of all three feeds on one side will be less than 1500W for
single-feed and 3000W for dual feed.
Overcurrent Protection Requirements
Overcurrent protection devices must be provided as part of each host equipment
rack.
Circuit breakers meeting the requirements shown in
TABLE 3-1 must be fitted
between the DC source and the Netra ft 1800.
TABLE 3-1 Overcurrent Protection Requirements
Current rating 30A maximum
Voltage Maximum 60 Vdc rated in –48 Vdc power systems
Maximum 75 Vdc rated in –60 Vdc power systems
Type Fast trip
Protection Double pole breaking (both grounded and ungrounded conductor
open on fault)
Contact gap Minimum 3 mm
Nuisance tripping Circuit breaker must not operate when presented with an inrush
current of 27 amps and a duration of 2.5 microseconds
Quantity One per feed, up to 12 per system