ADCP-80-526 • Issue 6 • December 2006

The alarm circuitry uses form C alarm relay dry contacts. During normal operation (power applied and all fuses operational), the normally open (NO) contacts remain open and the normally closed (NC) contacts remain closed. When a fuse fails on either bus or power to either is lost, the NO contacts close creating a connection from NO and common and the normally closed (NC) contacts open creating an open circuit between NC and common. The current rating for each set of alarm relay contacts (either two or three sets of contacts are provided) is 110 Vdc/125 Vac maximum voltage, 1.0 Amp maximum switching current.

Note: If a KLM or KTM fuse holder without a fuse is connected to a load, this situation causes the red LED to light and the alarm contacts to change states, same as would occur in a fuse failure. For other types of fuses (TPA and GMT), if a fuse holder without a fuse is connected to a load, the corresponding sensor remains inactive and no failure is indicated.

Warning: In a fuse platform with KLM fuses, the KLM-fused output terminals will show –48 Vdc even when there is no load and no fuse in the fuse holder. This “phantom voltage” is applied by the KLM circuitry alarm sensing function and will be less than 1 Amp.

1.14 Alarm Contact Connectors

The fuse platform is available with either screw-down barrier terminal strips or wire wrap pins for the alarm contact connections. The following describes both types of contact connections:

Warning: Use of one bus only on a dual bus panel will result in false alarms for the unused bus. Power is required on both buses on a dual bus panel for normal operation.

•Screw-down barrier terminal strip: Six terminals with 3-48 screws are mounted in a barrier type terminal block. The terminals are on 0.25 inch (6.35 mm) centers with a maximum distance between barriers (maximum connecting terminal width) of 0.20 inch (5.08 mm). The alarm terminal strip has two sets of three terminals (NO, C, and NC) for use with two alarm systems. The terminals can accept #16 to #30 AWG copper wire with insulation stripped back. In selecting wire size, follow local code referring to the ampacity guidelines provided in Appendix A of this manual.

•Wire-wrap terminal block: Nine wire-wrap pins are mounted in a terminal block for both buses. The alarm terminal block has three sets of three wire-wrap pins (NO, C, NC), for use with three alarm systems. The wire-wrap pins can accept #22 to #26 AWG copper wire with insulation stripped back. In selecting wire size, follow local code referring to the ampacity guidelines provided in Appendix A of this manual.

1.15Fuse Alarm Indicators

A visual fuse alarm indicator (red LED) is provided on the front of each fuse holder module. The fuse alarm indicator lights when any fuse in the corresponding fuse holder fails. The fuse alarm indicator is off when all fuses in the fuse holder module are operational. Loss of power to a bus will not cause the fuse alarm indicators corresponding to that bus to be lighted. For TPA and KLM fuses, there is one fuse holder per fuse and, therefore, a fuse alarm indicator for each fuse. For GMT fuses, there are four or ten fuses per fuse holder with a single fuse alarm indicator for the entire set of fuses.

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© 2006, ADC Telecommunications, Inc.