When adding a full voltage bypass contactor (not end of start/shorting contactor) to an ATS22, should line power be isolated from the ATS22 when in bypass mode?


26 July 2022

Isolation of the softstart 22 when using a full voltage bypass

Product Line:
Altistart 22

All units equipped with a full voltage bypass.

Customer is installing a full voltage bypass contactor, not part of an enclosed system built by Schneider.

When a full voltage bypass is being used with an Altistart ATS22 product, an isolation contactor is recommended to disconnect the input voltage from the ATS22 L1/L2/L3 terminals when in bypass mode.  Certain ATS22 failure modes will allow voltage to pass through to the motor.  Utilizing an isolation contactor will prevent damage / danger associated with such situations.  

This Isolation contactor should be electrically and/or mechanically interlocked with the bypass contactor to ensure that only one can be closed at any given time.  Also, add an overload relay to the bypass contactor to provide motor protection when in bypass.

See the example drawing below.  **Note that a run command from Hand or Auto is still necessary for the system to run in bypass.

control power