Control Sequence of Operation

When less than 5 seconds remain before compressor start, a starter test is conducted to verify contactor states prior to starting the compressor. The following test or start sequence is conducted for ‘‘Wye-Delta’’ starters: Also refer to Figure 24.

A. Test for transition complete contact open (2A1-J12-2) –160 to 240 msec. An MMR diagnostic will be generated if the contact is closed.

B. Delay time - 20 msec.

C. Close start contactor (2K1) and check for no current - 500 msec. If currents are detected, the MMR diagnostic ‘‘Starter Fault Type I’’ is generated.

D. Stop relay (2A1-J10-3 to 1) closes for one second for test “C” above.

E. Delay time - 200 msec. (Opens 2K1).

F. Close shorting contactor, (2K3) and check for no current - one second. If currents are detected the MMR diagnostic ‘‘Starter Fault Type II’’ is generated. (Starter Integrity test)

G. If no diagnostics are generated in the above tests, the Stop Relay (2A1- J10) is closed for 2 seconds and the Start Relay (2A1-J8) is closed to energize the start contactor (2K1). The shorting contactor (2K3) has already been energized from (F) above. The compressor motor (4M1) starts in the ‘‘Wye’’ configuration, an auxiliary contact (2K1-AUX) locks in the start contactor (2K1) coil. Additonally, 2K11 pulls in to hold the oil pump on. This is parallel to 1A7 contacts.

H. After the compressor motor has accelerated and the maximum phase current has dropped below 85 percent of the chiller nameplate RLA for 1.5 seconds, the starter transition to the ‘‘Delta’’ configuration is initiated.

J. The transition contactor (2K4) is closed through relay 2A1-J2, placing the transition resistors (2R1, 2R2, and 2R3) in parallel with the compressor motor windings.

K. The shorting contactor (2K3) is opened through the opening of relay 2A1-J4 100 msec after the closure of the transition relay 2A1-J2.

L. The run contactor (2K2) is closed through relay 2A1-J6, shorting out the transition resistors 260 milliseconds after the opening of the shorting relay 2A1-J4. This places the compressor motor in the ‘‘Delta’’ configuration and the starter module waits to look for this transition for

2.35seconds through the closure of the transition complete contacts 2K2- Aux at module 2A1-J12 input)

M. The starter module must now confirm closure of the transition complete contact (2K2-AUX) within

2.32to 2.38 seconds after the run relay (2A1-J6) is closed. Finally, the transition relay (2A1-J2) is opened de- energizing the transition contactor (2K4) and the compressor motor starting sequence is complete. An MMR diagnostic will be generated if the transition complete contacts (2K2- AUX) do not close. A diagram of this test or start sequence is shown in Figure 24.

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American Standard CH530 manual Delay time 200 msec. Opens 2K1