Section 150-231-134
Revision 01
Page 6
7. POWER CONSUMPTION
7.01
The Maximum Current drain is the current
drawn from the shelf power supply when it is
at minimum voltage (42.5 VDC) under a worst case
application.
The doublers mentioned throughout this
practice refer to the HDU-451, List 3, part# 150-1143-
03, low power unit. The worst case application for the
HLU-231, List 3D occurs on a loop with one doubler,
four 9000 foot, # 26 AWG spans, and an HRU that is
providing 60 mA of CPE current. Under these
conditions the HLU current drain from the 42.5 VDC
battery is 0.58 Amps. This CO current and other
related power parameters for this doubler application
are listed in Table 1. The worst case current drain for
a non-doubler application is 0.43 Amps.
7.02
The maximum shelf current drain allowed is a
function of the shelf’s 48 VDC fuse. Table 2
lists the doubler shelf deployment guidelines, as a
function of the shelf fuse, for the more popular Type
220 mechanical configuration shelves. These
guidelines limit the maximum fuse load to 85% of shelf
rated capacity. Use Table 2 when selecting the
appropriate load fuses for the Building Distribution
Fuse Bus (BDFB) when deploying HiGain equipment
in COs. CAUTION: The HLU-231’s minor ALM
option must be set to DIS (disabled) when using
the Kentrox 23” T-TERM 220 shelf. The alarm
relay contancts on pins 20 & 21 (see Figure 4) are
in conflict with the T-TERMs DSX-1 equalizer
outputs which also appear on pins 20 & 21.
7.03
The maximum HLU-231 power dissipation is
the power that is converted into heat within
the unit. It contributes to the total heat generated and
is used to determine the maximum number of shelves
per bay that do not exceed the maximum power
dissipation density in Watts/sq. ft.
7.04
In CO locations, the maximum power
dissipation for open faced, natural convection
cooled mountings is 120 W/sq. ft. as stated in NEBS
standard TR-NWT-000063 section 4.2.3. The footprint
of a 13 slot 23” SXSS shelf is 7.024 sq. ft. Thus the
maximum allowable dissipation is 840 Watts. For an
SXSS shelf with 10 slots occupied, the maximum
power dissipation is 350 (10 x 35) Watts. This limits
the number of fully loaded shelves to 2.4 per bay.
Note that this is a worst case situation since it
assumes the entire CO is subjected to the maximum
power density. More favorable conditions would permit
increasing the number of shelves per bay without
jeopardizing the CO thermal integrity.
7.05
The thermal loading limitations imposed when
using the HLU-231 in CEVs or other
enclosures are determined by applying the HLU-231
power parameters to the manufacturer’s requirements
for each specific housing.
7.06
The Power Consumption listed in Table 1 is
the total power that the HLU-231 consumes or
draws from its -48 VDC shelf power source. This
parameter is needed when the 231 is located remote
to its serving CO. It determines the battery capacity
required to maintain an 8-hour stand-by battery
reserve for emergency situations. It thus limits the
maximum number of plugs per remote enclosure. Use
this data to perform this analysis on a case by case
basis.
