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152-388-100-02, Issue 2 Appendix A - Specifications
H2TU-C-388 List 1 June 6, 2000 49
POWER CONSUMPTION
The maximum power consumption and heat dissipation depends upon the type of remote units in the system and
the CPE power setting.
The three most important power parameters of an H2TU-C are its maximum power consumption, its maximum
power dissipation and its maximum current drain.
Table 18 describes line-powered circuits on 9 kft, 26 AWG loops.
MAXIMUM POWER DISSIPATION
The maximum power dissipation measures the power that is converted into heat that builds up within the unit. It
contributes to the total heat generated in the space around the unit. It is used to determine the maximum number
of fully loaded shelves per bay that does not exceed the maximum allowable power dissipation density in
watts per square foot to comply with GR-63.
In COs, the maximum power dissipation for open-faced, natural convection-cooled mountings is limited to
134.7 watts per square foot per GR-63-CORE. The footprint of a standard 28-slot, 23-inch HMS-317 shelf is
7.024 square feet. Therefore, the maximum bay dissipation is limited to 946 watts. Use this limit and the
parameters in Table 18 to determine the maximum number of H2TU-C circuits that can occupy one CO bay.
The thermal loading limitations imposed when using the H2TU-C in a Controlled Environmental Vault (CEV) or
other enclosures are determined by applying its power parameters to the manufacturer's requirements for each
specific housing.
The -48 Vdc power consumption is the maximum total power that the H2TU-C-388 consumes or draws from the
shelf power source. This parameter is needed when the H2TU-C-388 is in a location remote to the CO it is serving.
It determines the battery capacity required to maintain an 8-hour, standby battery reserve for emergency situations.
Battery capacity, therefore, limits the maximum number of line units which can be installed in a remote enclosure.
Use the data in Table 18 to perform this analysis.
MAXIMUM CURRENT DRAIN
The maximum current drain is the maximum current drawn from the shelf power supply when it is at its minimum
voltage (-42.5
Vdc). This determines the shelf fusing requirements. Use the -42.5 Vdc current data in Table 18 to
determine the shelf fusing requirements for your particular H2TU-C applications.
Table 18. H2TU-C-388 Power Parameters
-48 Vdc Power
Consumption
(Watts)
Heat Dissipation
(Watts)
-42.5 Vdc Current
(mA)
Remote Power Source Maximum Maximum Maximum
Line powered 12.5 7.0 294.0
Local powered 5.0 5.0 117.0
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.