Mike in Cleveland here. Got a weird situation with FirstEnergy on a three-phase service Schedule GS tariff. During a routine inspection found that one of the three phases has been dead for unknown period - probably months. The meter is still reading and billing normal amounts though. CTs are 800:5 ratio with multiplier showing 10.67 on each phase. Should the billing be lower if only two phases are carrying load? How does this affect the multiplier calculation?
Three Phase Service - One Phase Dead, Multiplier Issues?
Walt D. from Pittsburgh. Had similar issue with Duquesne Light few years back. The multiplier doesn't change based on phases - it's still 160 (800 divided by 5) for each active CT. But your total consumption should definitely be lower with only two phases working unless the remaining phases are carrying extra load. What's the kW demand reading compared to historical usage?
Walt, that's the weird part. Demand readings are only down about 15% from normal, not the 33% you'd expect. The facility manager thinks some equipment automatically load-balanced to the working phases, but the motors that were on the dead phase should have been completely offline. Something doesn't add up with these readings.
Ed T. from Tulsa. Check if you have any single-phase loads that could have been fed from the other phases through transformers or panels. Also some three-phase equipment will operate on two phases but at reduced capacity and higher current. The meters might be reading correctly but your load distribution changed. Did FirstEnergy do a load survey?
Ed, FirstEnergy finally did the load survey and found the problem. Turns out two large single-phase loads had been rewired to pull from the good phases without updating their records. So the total facility load was almost the same, just unbalanced across two phases instead of three. Multiplier was correct all along - just a wiring issue that made the billing look suspicious.