Revision 6 HC900 Process & Safety Controller User and Installation Manual 197
21 April 2017
EXPLOSION HAZARD Class 1, Division 2 Installations
SUBSTITUTION OF COMPONENTS MAY IMPAIR SUITABILITY FOR CLASS I, DIVISION 2.
EXPLOSION HAZARD Class 1, Division 2 Installations
DO NOT DISCONNECT EQUIPMENT UNLESS POWER HAS BEEN SWITCHED OFF OR THE
AREA IS KNOWN NOT TO BE HAZARDOUS.
Replacing the Power Supply
The power supply for the HC900 Process Controller is available in two models and is used in the local
(controller) rack and in the remote (I/O expansion) racks, in 4-, 8-, and 12-module sizes. This reduces
required inventories of spare parts, and also simplifies removal and replacement procedures.
Removing the power supply from a rack will remove all DC voltages from the rack that powers the
Controller Module or Scanner Module, and from all I/O modules within the rack.
NOTE:
The power supply includes an internal fuse, rated at 5 amperes. This fuse is not replaceable in
the field. If desired, the user can provide an external fuse that has a current rating lower than that
of the internal fuse. See page 71.
Table 34 – Power Supply Replacement (all except C75)
ATTENTION: This procedure does not apply to C75 power supplies.
If the power supply to be replaced is powering a rack that is currently controlling a running
process, then:
Either:
Ensure that powering the rack down will not have adverse consequences on any running
process.
Or:
Bring the process to a safe and orderly shutdown.
Using an external, user-supplied switch, disconnect the power supply from the source of site AC
power. Use a meter to ensure that power is off.
Depending on the type of wire lugs used, loosen or remove the three screws on the terminal
board, and remove the three wires from the terminal board.
NOTE: DO NOT remove the nut that secures the lug for the PE Ground wire (green) to the
grounding stake at the bottom of the rack.
At the top and bottom of the module, loosen the captured screws that secure the module in the
rack, and remove the power supply from the rack.
Place the new power supply in the rack. (cont’d)
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