PHASE SEQUENCE RELAY (K5) TESTING AND REPLACEMENT

TM 9-4120-428-14

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UNIT MAINTENANCE

AIR CONDITIONER, HORIZONTAL, COMPACT

(NSN 4120-01-502-1319)

PHASE SEQUENCE RELAY (K5) TESTING AND REPLACEMENT

INITIAL SETUP:

Equipment Condition

Tools

Remove Return Air Louver (WP 0021 00)

Refrigeration Unit Service Tool Kit, WP 0000 00, Item

Materials/Parts

Phase sequence relay

Self-locking nuts (4)

RELAY DIAGRAM

NOTE

The relay will energize when all three phases of input power are in proper sequence and

when input voltage and frequency are within 10% of that specified (208 volt, 400 hertz).

TESTING

1. Ensure that power connections are properly connected.

2. Move circuit breakers CB1 and CB2 to the ON position.

3. Momentarily turn the mode selector switch to VENT and then back to OFF.

4. To check for correct input phasing, ensure that the blower is rotating counter-clockwise and facing shaft-end. If not,

reverse the two input leads at the power source and re-check.

5. To test the phase sequence relay, turn the mode selector switch to the COOL position and check to see if condenser

fan is on. If not, replace the phase sequence relay.

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