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SCP-PLL723-010-04H
P
C
OWER
ONSUMPTION AND
The three most important power demands of a COLU on the COTS power supply are its maximum power
consumption, heat dissipation, and current drain.
COLU, on a per slot and per COTS basis.
The worst case conditions under which these parameters are measured include a 12,500 ft., 26 AWG loop,
a fully loaded COTS, and a -42.5 Vdc COTS battery voltage. The RT is assumed to be ringing one line with
a combined load of 5 REN, with one line off hook on each RT. Loop current sink at the COTS is assumed
to be 23 mA. Higher loop current feed than 23 mA restricts the number of COTS in a bay due to heating.
Maximum Heat Dissipation
The maximum heat dissipation measures the power that is converted into heat built up within the unit. It
contributes to the total heat generated in the space around the unit. This measurement is used to determine the
maximum number of fully loaded COTS per bay so as not to exceed the maximum allowable power dissipation
density in Watts per square foot.
In CO locations, the maximum heat dissipation for open faced, natural convection-cooled mountings is limited to
134.7 W per square foot as per Section 4.1.4 of the NEBS standard GR-63-CORE. The footprint of a standard
16 slot, 23-inch COTS is 7.042 square foot. The maximum bay dissipation is therefore limited to 948.6 W. At
54.4 W per COTS, this limits the number of fully loaded COTS to seventeen per bay with a heat baffle.
ADC recommends that the number of COTS per bay be limited to six, to allow the flexibility to deploy the widest
range of PG-Plus services from each COTS.
This is a worst case situation in that it assumes the entire CO is subjected to the maximum power density.
Conditions other than the worst case ones presented in this practice would permit increasing the number
of COTS per bay without jeopardizing the CO thermal integrity. Consider also that, due to the chimney
effect, it is recommended to install one heat-dissipating baffle between every COTS. Otherwise, the rated
operating temperature of the COLU units may be exceeded.
PLL-723 List 1
H
EAT
Table 1.
Power Consumption and Heat Dissipation
Power
Maximum Heat Dissipation
HDSL Line Power Off
HDSL Line Power On
Maximum Power Consumption
HDSL Line Power Off
HDSL Line Power On
Maximum Current Drain
HDSL Line Power Off
HDSL Line Power On
January 6, 2003
D
ISSIPATION
Table 1
lists the power consumption and heat dissipation for the
COTS
COLU Slot
19-inch
2.8 W
33.6 W
3.4 W
40.8 W
2.8 W
33.6 W
8.43 W
101.1 W
0.06 A
0.791 A
0.198 A
2.380 A
Power Consumption and Heat Dissipation
23-inch
44.8 W
54.4 W
44.8 W
134.8 W
1.054 A
3.174 A
3
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