Record power demands during the last two winters caused electrical distribution zones to trip off-line. “The outages were caused by the high demand — nearly triple the usual load — placed on [electric] heaters in the cold temperatures,” said Jeff Rogers, a spokesman for Gulf Power Co. The sudden load losses caused voltages to shoot up above the legal limits at points-of-use in zones that remained on-line. This overvoltage caused damage to electrical equipment of all types, including HVAC equipment, circuit boards, relays, reversing valves, as well as posing a fire risk for the end users. A noticeable increase in the number of reported incidents (including fires) in the last few years is the result of the combination of the increasing number of heat pumps installed during the past decade (which must necessarily use supplemental electric heat in temperatures below 20˚F), and the recent record cold weather temperatures that dipped below 20˚.
Some electric heaters used in air conditioning units and heat pumps were protected from overheating by safety fuse links which disconnected the heaters when overvoltage was present. In some cases, overvoltage was not recognized as the cause of the blown fuse links. The heaters were then mistakenly blamed for the no-heat complaints instead of overvoltage. As a result, the electric heaters were then replaced with heaters having only automatic reset temperature limits to control overheating, which do not contain safety fuse links.