User: Coastalguy1, Location: Virginia Beach, VA
Asked on: Tuesday, March 29, 2011 at 3:19 pm EDT
Answered on: Tuesday, May 14, 2024 at 3:26 am EDT
Question: I have been asked to look into a problem which exists on a commercial building. It has a 1600amp 277/480v 3ph 4w main breaker which is ground fault protected in accordance with NEC 230.95. In the past it has tripped when a maintenance man was changing a light bulb and shorted wires together. Most currently and frequently it trips when an air conditioning compressor shorts out (another problem our company is looking into!). The setting on the GFP main breaker is set to it's maximum allowable setting. Is a complete fault current study needed to correct this problem? Any help and advice will be appreciated as always.Coastalguy1
Possible Solutions
1. Ground Fault Isolation
Install a ground fault relay or monitor with a lower trip setting that can isolate the specific faulted circuit. This will allow other circuits to continue operating while the fault is cleared.
2. Surge Suppression
Install surge suppressors on equipment that is prone to electrical transients, such as the air conditioning compressor. This can help prevent short circuits caused by voltage spikes.
3. Arc Fault Circuit Interrupter (AFCI)
Consider installing AFCIs on specific circuits, such as those serving lighting fixtures or appliances. AFCIs detect and interrupt electrical arcs that can lead to faults.
4. Bonding and Grounding
Ensure that all electrical equipment and systems are properly bonded and grounded in accordance with applicable electrical codes. Improper grounding can contribute to ground faults.
Fault Current Study
A fault current study may not be necessary if the above measures are implemented and resolve the problem. However, if the tripping persists or the cause of the ground faults cannot be definitively determined, a comprehensive fault current study may be warranted to further analyze the electrical system and determine the appropriate protective measures.
Additional Considerations: Inspect the wiring and connections in the building for any loose or damaged components that could contribute to ground faults. Consider using a selective coordination study to ensure that the GFP main breaker trips before other lower-rated circuit breakers, preventing unnecessary power outages.* Train maintenance personnel on proper electrical safety procedures to minimize the risk of accidentally causing ground faults. Flag for review