Schneider Electric support forum about Protection Relays, Substation Controllers & RTUs, Arc Flash Devices & Systems in Medium Voltage and Low Voltage. A place to get support on product selection, installation, commissioning and troubleshooting.
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2024-12-0309:56 AM
GV2 and GV3 MCB sizing
Please forgive me if I posted this in the wrong forum. When sizing a MCB and contactor, referring to the TeSys GV and LC1 series, does the NEC rule still apply that you size these MCBs per the 125% continuous load rule? I'll provide the details.... We have a 20HP motor that is tripping the MCB our panel manufacturer sized and installed (MCB: GV2P22 & Con: LC1D25). Before I was aware of the situation, our field guys were sent (2) GV2P32 MCBs as "upgrades", which were both tripping as well. They were asking to send a third and that's when I was brought into the situation. I looked into it and determined that the setups were undersized using the NEC information..... 20HP motor = 27 FLA => @ 125% continuous load rule we're looking at 33.75 FLA. Which tells me this is why we keep tripping these MCBs. I suggested these need to be upgraded to the GV3P40 and LC1D38 and adjusted to the 33-34A to function properly. The panel manufacturer comes back saying these specific MCBs are designed with the 125% already factored in and it is unnecessary to change these. Can someone point me in the right direction, or to the info that will shed some light on this. I am more than willing to accept any correction if I'm wrong in this case. Also, whatever situation we get figured out, this will need to be the change on 12 of these panels we have on hand and others in the future.