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Appendix A - Specifications
 
 LTPH-UM-1049-02, Issue 2
66
January 9, 2002
 H2TU-C-319 List 4E
P
OWER
 C
ONSUMPTION
The three most important power parameters of an H2TU-C are its maximum power consumption, maximum 
power dissipation, and maximum current drain. 
 describes line-powered circuits on 9 kft, 26 AWG loops without a regenerator.
M
AXIMUM
 P
OWER
 D
ISSIPATION
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 
 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 consumes or draws from the shelf 
power source. This parameter is needed when the H2TU-C 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 
 above to perform this analysis. 
M
AXIMUM
 C
URRENT
 D
RAIN
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 
 above to determine the shelf fusing requirements for your particular H2TU-C applications.
Table 26.
H2TU-C-319 List 4E Power Parameters
-48 Vdc Power 
Consumption 
(Watts)
Heat Dissipation 
(Watts)
-42.5 Vdc Current 
(mA)
Remote Power Source
Maximum
Maximum
Maximum
Line-powered
12.25
7.25
292.0
Local-powered with Sealing Current
8.7
6.75
207.0
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.