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Transfer Switch Sizing

Pick the ATS amperage, pole count, and rating type from the load and the service configuration.

Inputs

Inputs and assumptions

A service-entrance rated switch can replace the utility disconnect.

A switched neutral is needed when the generator is a separately derived system.

A switch that can shed a group keeps the ATS amperage down.

Result

Transfer switch rating
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Load current
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Floor set by the service rating
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Switched poles to specify
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What to check

  • Utility service and disconnect arrangement
  • Whether the generator is a separately derived system

Related calculators

Screening-grade sizing. Manufacturer load-acceptance curves, ISO 8528-5 transient limits, and the adopted electrical code edition govern the final selection; an engineer signs off before hardware is ordered.

Saved calculations

Keep the assumptions with the result.

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