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Home›Repair guides›PARTIAL COVERAGE SYSTEM (TRANSFER SWITCH WITHOUT CONTROLLER)

Cummins/Onan — PARTIAL COVERAGE SYSTEM (TRANSFER SWITCH WITHOUT CONTROLLER)

A Cummins/Onan service procedure — check it applies to your exact model before use.

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Before you start

  • AC power within the cabinet presents a shock hazard that can cause severe personal injury or
  • An electrical arc occurs during transfer that can ignite flammable vapors or gases, resulting in

Procedure

  1. The load is transferred to the generator set.
  2. The utility returns.
  3. The generator set control receives a signal from TB4-1/TB4-2 of the step down transformer to indicate that utility power is available.
  4. The generator set control signals the relay coil (K1), energizing the relay coil which opens K1-1/K1-9 and K1-2/K1-10 and closes K1-7/K1-11 and K1-8/K1-12 to move the transfer switch from the generator position to the utility position. The S1 auxiliary switch within the transfer switch mechanism breaks the signal to the ATS operator coil (C).
  5. Operation 6-2021 24 A065T489 (Issue 1) Copyright © 2021 Cummins Inc.
  6. The K1 relay de-energizes by opening K1-7/ K1-11 and K1-8/K1-12, and after the Return Delay timer expires, closing K1-1/K1-9 and K1-2/K1-10 to move the transfer switch mechanism signal to the ATS operator coil (C).
  7. Limit switch BSW removes the ground signal (TB4-6), signaling the transfer switch has disconnected from the generator set; then the ASW limit switch provides a ground signal to TB4-5, signaling that the transfer switch has connected to the utility. The generator set control receives a signal to indicate switch position on the utility side.
  8. The load is transferred to the utility.
  9. After a ten minute delay to let the engine cool down, the generator stops.
  10. Installation 6-2021 26 A065T489 (Issue 1) Copyright © 2021 Cummins Inc. Prior to installation, make sure the transfer switch is stored in a clean dry place, protected from dirt and water. Provide ample air circulation and heat, if necessary, to prevent condensation from gathering on the equipment. Be sure to adhere to the transfer switch storage and operating requirements listed below. Transfer Switch Storage Temperature Operating Temperature (Ambient) Humidity RA 100A, RA 200A -22 °F to +158 °F (-30 °C to +70 °C) -4 to +140 °F (-20 to +60 °C) Up to 90% @ 68 °F (20 °C) RA 400A -13 °F to +131 °F (-25 °C to +55 °C) -4 to +131 °F (-20 to +55 °C)

Source: manual:RSS100-200_Owner_Manual.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.