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Upsizing a UPS without changing the input breaker or wire size

D

DC_Brad

New User
Location
California
Occupation
Engineer
My client has a 20kW UPS (208/120V, 3 phase) currently installed. The recommended overcurrent protection for the 20kW UPS is a 90A breaker. My client would like to upsize the UPS to 40kW (recommended input breaker for the 40kW UPS is 175A), but he wants to run the new 40kW UPS with the existing 90A feeder. The wire connected to the 90A breaker is properly sized per the NEC. My client will upgrade the input breaker and wire to 175A sometime next year once he has the budget. The UPS can be set to alert my client when is starts to approached the rating of the 90A breaker. If the UPS were to be overload the input breaker would trip. Is their any reason (per the NEC) my client cannot run his 40kW UPS on the 90A breaker? Again, the wire is properly sized for the 90A breaker per the NEC. Any NEC sections that show this is allowed would be appreciated.
 
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