Michelle T. here in Phoenix. Discovered something interesting during an energy audit last week. Large retail client on APS Schedule E-32 TOU has been running with a dead phase on their meter for who knows how long. The weird part is their bills have been relatively consistent month-to-month, so nobody caught it. Makes me wonder how many three-phase accounts out there are getting underbilled due to failed CTs or wiring issues. Anyone have experience with how utilities handle historical adjustments when they can't prove exactly when the problem started?
Three-phase meter with dead phase - how long before someone notices?
Alvin H. in Texarkana. Seen this several times over the years. The scary part is that if the load is reasonably balanced across the other two phases, the customer might not even notice operationally. I had one case where we estimated the dead phase had been out for over two years based on the customer's production records versus billed consumption. Utility eventually agreed to go back 18 months but fought us on anything longer. How did you catch it Michelle?
Alvin, we caught it during a power quality study. Customer was complaining about equipment issues and when we hooked up our analyzer, one phase showed zero on the revenue meter side but full load on the customer side. Turned out to be a corroded connection in the meter socket that finally failed completely. APS is trying to claim it's recent but the corrosion pattern suggests it's been deteriorating for months. Michelle T.
Wendell T. from Billings here. Had a similar situation with NorthWestern Energy a few years back. Dead CT on a grain elevator - took almost a year to discover it during a routine meter test. The utility wanted to bill the customer retroactively based on the previous year's usage pattern. We argued that their equipment failure wasn't the customer's fault and got them to limit it to six months. Document that corrosion Michelle - that's your evidence it wasn't a sudden failure.
David C. in Seattle. This is why I always recommend annual infrared scans of meter installations for large commercial accounts. You can often catch these issues before they become complete failures. Michelle, what's the monthly kWh impact we're talking about? That might influence how aggressively APS pursues historical billing. If it's a huge amount they'll want to go back as far as possible.
David, we're looking at roughly 30,000 kWh per month underbilled, so about $3,600 monthly at their TOU rates. Customer's actual usage is around 90,000 kWh monthly but they've been billed for about 60,000. APS is definitely motivated to recover the revenue. The infrared scan idea is good - I'll recommend that going forward. Michelle T.
Michelle, this is a significant underbilling situation that APS will absolutely pursue aggressively. Randy Dawson here from Memphis. The key legal issue is whether the utility can prove when the failure occurred versus gradual deterioration. If you can establish that the corrosion was a gradual process, you may be able to limit their lookback period. I'd recommend getting an independent electrical engineer to examine the failed connection and provide a professional opinion on the timeline of deterioration. Document everything with photos before APS removes the equipment.
Randy, that's exactly what we're doing. Got an electrical engineer lined up to examine the connection tomorrow before APS replaces it. The corrosion is pretty extensive so hopefully we can establish this was a long-term deterioration rather than sudden failure. Will update once we get the engineer's report. Thanks for the advice. Michelle T.