National Electrical Installation Standards

Standards as High as Your Own

Thursday, August 24, 2023


Hello Code Friends, I am working on new building where a fire pump is being installed. We installed a separate 277/480V, 400A service for the fire pump. The fire pump controller is service rated with integral OCPD, and part of a listed package with the 100 H.P. fire pump motor. We called for a service inspection to get the fire pump service approved, and the inspector failed the service stating the transocket for the fire pump service needed to be sized for the Locked Rotor Current (725A) of the Fire Pump motor 460V 100HP. The code section the inspector cited was 695.4(B)(2)(a)(1). Does the transocket need to be sized for the Locked Rotor Current? Thanks for your help in this matter, Frank Tracinski  


Hi Frank, thanks for your question. This one comes up from time to time and there are a few things at play here. In this scenario it sounds like the inspector may be misapplying the requirements found in Section 695.(B)(2)(a)(1). The requirements of Section 695.4(B)(2)(a)(1) apply when the power supply to a fire pump motor is by a traditional service with a service disconnect/OCPD. Then the OCPD must be sized to accommodate the Locked Rotor Current (LRC) of the fire pump motor, and Full Load Current (FLC) of any jockey/maintenance pump motors. This applies to the OCPD devices only and by relation the disconnect housing the OCPDs. This Section does not apply to the supply conductors, and any other associated equipment (including the transocket). The other key thing to mention is that you have installed a listed fire pump controller and fire pump motor assembly, which has different OCPD requirements covered by Section 695.4(B)(2)(a)(2).    

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