Mike Dolt Enterprises
Mike Dolt Enterprises
User: knoppdude, Location: Sacramento,ca
Asked on: Saturday, April 16, 2011 at 9:14 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:16 am EDT
Question: Installed several separately derived systems several months back, that at first used a system bonding jumper in the transformer, with the grounding electrode conductor connected to the transformer frame. A request was then made to remove the system bonding jumper, and replace the main bonding jumper in the panels, as this is what the inspector wanted. My question is this, as the conduit from the transformer to the panel contains both an equipment grounding conductor, and a grounded conductor, which still provides a path for the grounded conductor through the transformer, and provides a connection to the grounding electrode through the equipment grounding conductor, which is bonded to the interior of the transformer, is this a code violation as it stands? I say that it may be, but I am not finding anything in the NEC that says that it is.
NEC 250.24(A)(5) requires a system bonding jumper in each separately derived system. The purpose of this jumper is to ensure that there is a low-impedance path between the grounded conductor and the grounding electrode conductor. This path is necessary to prevent dangerous voltages from developing on the grounded conductor in the event of a fault.In your case, you have removed the system bonding jumper and replaced it with a main bonding jumper in the panels. This means that there is no longer a direct connection between the grounded conductor and the grounding electrode conductor. Instead, the only path for the grounded conductor through the transformer is through the equipment grounding conductor.The problem with this is that the equipment grounding conductor is not a reliable path for the grounded conductor. This is because the equipment grounding conductor is typically made of bare copper, which is subject to corrosion. If the equipment grounding conductor corrodes, it will lose its ability to carry current, which will break the path for the grounded conductor.If the path for the grounded conductor is broken, this could lead to dangerous voltages developing on the grounded conductor. This could pose a shock hazard to anyone who comes into contact with the grounded conductor.For these reasons, I believe that it is a code violation to remove the system bonding jumper and replace it with a main bonding jumper in the panels. I recommend that you reinstall the system bonding jumper in order to ensure that there is a low-impedance path between the grounded conductor and the grounding electrode conductor. Flag for review