277 to ground on the phase that was previously 12V to ground. Any clue on why that would make a difference? basically if that fan is hooked up that phase got to 12V to ground I unhook it and it's back to 277 to ground? Thank you. Jeff
That is easy. You have an ungrounded system, and there was a ground fault in the capacitor.
Most people are familiar with solidly grounded electrical systems. These are systems where one terminal of the system is intentionally connected to 'ground'. This _single_ connection to ground doesn't cause a short circuit because it isn't a circuit; there is not a closed loop that current can flow in. But with this intentional connection to ground, a second unintentional connection to ground (a 'fault') creates a short circuit, lots of current flows, and a breaker trips.
Your facility has a ungrounded system. There is no first intentional connection to ground. Instead the system 'floats' until a fault connects some part of the system to ground. Because the first fault creates the first connection to ground, there is no short circuit, and the system can continue to operate until the necessary repair can be safely accomplished.
One aspect of ungrounded systems is that any voltage measurement to ground is extremely sensitive to the state of the system. When everything is normal, phase to ground voltages can be just about anything. When there is a ground fault, the faulted phase to ground voltage falls to close to zero, exactly what you experienced.
This requires a maintenance staff that understands the system, and knows that as soon as the phase light is on there is a problem to be fixed. This sort of system is only appropriate where a shutdown due to a fault causes more safety risk than leaving a system energized with a fault. The code specifically spells out "Conditions of maintenance and supervision...."
IMHO
@Sarge590 , you are going to need to learn more about this system, or push the folk with the dollars to get the system converted to a solidly grounded system.
-Jon
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