UPS 120, UPS 150, UPS 250, UPS 300, UPS 301, UPS 500, UPS 600, UPS 750 and UPS 900 Uninterruptible Power Supplies Caterpillar

Description

Illustration 1	g01270179
(1) Zig Zag Overload Relay

The Zig Zag Overload Relay (ZZOL) (1) is mounted on the rear panel. The Zig Zag Overload Relay is also known as OLR1. The OLR1 (1) is required for maintaining the ground reference of the 3-phase output when the system is in discharge mode and the system is disconnected from the utility input.

The Overload Relay (1) is used with the internal resistor (R19) to provide a solid ground for the system.

Removal Procedure

Refer to Systems Operation, Testing and Adjusting, RENR9988, "Internal Component Preremoval Steps (SMS Bypass Cabinet)" in order to shut down the system and gain access to internal components.

1. Disconnect the wires from the ZZOL Relay (1). Verify the labeling of the wires for subsequent installation.

2. Remove the rail stop on the right side of the ZZOL Relay (1) by loosening the two screws. Slide the rail stop off the rail.

3. Remove the ZZOL Relay (1) by sliding the relay off the rail.

Installation Procedure

1. Attach the ZZOL Relay (1) onto the rail by placing the top of relay on the top edge of the rail. Snap the bottom of the relay into place. Refer to Illustration 1 for placement.

2. Slide the rail stop over the rail and attach the rail stop. Fasten the rail stop in place with two screws.
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   Illustration 2	g01270235
   Zig Zag Overload Relay Wire Connections

3. Attach the wires to the ZZOL Relay (1). Verify the labeling of the wires with the location of the wires. Refer to Illustration 2 for wire connections.