Appendix A - Specifications LTPH-UM-1031-03, Issue 3
60 September 12, 2003 H4TU-C-319 List 1
POWER CONSUMPTION
The three most important power parameters of an H4TU-C are its maximum power consumption, maximum
power dissipation, and maximum current drain.
Table 20 describes line-powered and locally powered (remote) circuits on the maximum reach condition (34 kft.)
using 26 AWG wire.
MAXIMUM POWER DISSIPATION
The maximum power dissipation measures the power converted into heat which 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. Use this limit and the parameters in Table 21 on page 61 to
determine the maximum number of H4TU-C circuits that can occupy one CO bay.
The thermal loading limitations imposed when using the H4TU-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 H4TU-C consumes or draws from the shelf
power source. This parameter is needed when the H4TU-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 Table21 to perform this analysis.
Table 20. H4TU-C Power Parameters
-48 Vdc Power Consumption
(Watts) Heat Dissipation (Watts) -42.5 Vdc Current (mA)
Number of
Doublers
Remote Power
Source Typical Maximum Typical Maximum Typical Maximum
None Locally powered 7.6 8.4 5.9 6.4 179 197
None Line-powered 11.0 12.1 6.2 6.8 259 285
1Locally powered 14.6 16.1 6.6 7.2 344 378
1Line-powered 20.0 22.0 7.1 7.8 471 518
2Locally powered 26.7 29.4 8.4 9.2 628 691
2Line-powered 32.9 36.2 9.3 10.3 774 852
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.