How do I connect a shorting contactor to an ATS48 soft starter without using an interposing relay?

The Altistart 48 (ATS48) soft starter requires a shorting contactor. You may connect this contactor directly—without an interposing relay—only if the contactor’s coil voltage and current are within the ratings of the ATS48 R2 relay.

The R2 relay is a dedicated relay inside the ATS48 used exclusively to energize the shorting contactor coil. It cannot be reassigned to any other function.

R2 Relay Electrical Limits:

Ensure your shorting contactor coil does not exceed the following limits:

• Minimum switching capacity: 10 mA at 6 VDC
• Maximum switching capacity (inductive load):
  • 1.8 A at 230 VAC
  • 1.8 A at 30 VDC
• Maximum voltage: 400 VAC

⚠️ If the contactor coil exceeds these limits, you must use an interposing relay to prevent damage to the soft starter’s internal circuitry. Refer to FA234738 for installation instructions using an interposing relay.

Wiring Instructions:

1. Supply an external voltage to the R2C terminal. This voltage must match the shorting contactor coil requirements.
2. Connect R2A on the soft starter to one side of the shorting contactor coil.
3. Connect the other coil terminal to the common or neutral of the power supply feeding R2C.
4. Connect Line 1, Line 2, and Line 3 from the incoming three‑phase power supply to L1, L2, and L3 of the shorting contactor.
5. Connect the load side of the shorting contactor to terminals A2, B2, and C2 at the bottom of the soft starter.
   ⚠️ Observe correct phase rotation — do not cross phases.

No parameter changes are required in the ATS48 to enable the shorting contactor.

The R2 relay closes automatically when:

• The acceleration (ACC) time is complete, and
• Motor current drops below 110% of the motor FLA

At this point, power is applied to the contactor coil and the shorting contactor closes.

If this article does not answer your question, check out our FAQ database that has answers to more commonly asked questions:

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