142 Installing a -48 Vdc Power Distribution System
Practice 450-1011-201
(6) Place the dc serial ID label over the ac serial ID label (which gives the voltage
rating, frequency, model number, and so on) located on the input jumper.
(7) Remove the ac input jumper from the rear of cabinet 1 (the right-most cabinet as
viewed from the rear).
(8) Remove the horizontal jumper assemblies that interconnect the cabinets. Then
remove the terminating jumper assembly from the last cabinet in the lineup (the
left-most as viewed from the rear).
(9) Remove the two nuts securing the ac bus cover to the two studs on the lower
bus cover of each cabinet on which a box will be installed, that is, at least from
cabinets 1 and 2, and possibly from cabinets 5 and 8. (See Fig. 17-1.)
Note: Because the connection between the distribution box and the input box
may be fairly stiff, it may be necessary to perform Steps 10 and 11 at the same
time.
(10) Position the input box (with circuit breaker) at the bottom center on the rear of
the cabinet. The holes in the ‘ears’ on the side of the box should fit over the two
studs, and the two mounting holes on the upper flange of the box should
coincide with the two holes on the rear of the cabinet.
(11) Place the first distribution box (connected to the input box with conduit) on the
second cabinet in the same manner.
(12) Replace the nuts removed in Step 9, and tighten them to secure the boxes in
place.
(13) Secure the top of the boxes to the rear panel using the two short (1/4 inch)
screws supplied.
(14) For cabinet systems containing more than four cabinets, repeat the procedure
to install the additional distribution box in cabinet 5.
(15) For a cabinet system with eight cabinets, repeat the procedure to install the last
distribution box in cabinet 8.
(16) Reconnect all the jumper assemblies in their appropriate positions.
Note: For all the following instructions, the -48 V to +32 V Power Converter
SRUs must be located in positions 1, 2, or 3, which are defined as the three
right-most SRU postions in the top of a cabinet as viewed from the rear.
(17) Install the -48 V to + 32 V converter SRUs (NT4G50DA) as described in
Table 17-A. (Also see Figures 17-1 and 17-2.)
(18) Connect the distribution boxes to the Power Converter SRUs by attaching the
connector backshell housing to the rear of the cabinet. Drive two 1/2-inch
screws from the outside of the cabinet, and fasten them with the two nuts on the
inside of the cabinet rear pannel. Before fully tightening the screws, ensure that
each connector is aligned with the connector on the SRU so that full
engagement is achieved (Fig. 17-3).
(19) Ensure that the circuit breaker located in the input box is in the OFF position.
