Issue:
Lost Neutral - effects on loads and UL1449
Product Line:
All Back-UPS, Back-UPS PRO and Personal Surge
Environment:
Lost Neutral in electrical infrastructure.
Cause:
Lifted neutral at utility panel.
Resolution:
In a typical balanced load with all loads using the neutral return and the neutral is severed, the voltage from each Phase appears across each load and is added on itself. This is a typical fault condition. Underwriter's Laboratories realized that this fault condition is common and it is not up to the Surge Protection Industry to prevent these failures but in the event of this common failure, UL addressed this condition by requiring all Surge Protectors to pass a fault of 240 VAC at different current levels to simulate different loads. These currents are: 125 mA rms. 500 mA rms. 2.5 A rms. and 5 A rms. They also require an unlimited current test (1000 A rms. or greater). 240 VAC is used because most household wiring is 120/240 3 wire single phase and a lost neutral produces 240 VAC. The unit during this test has cheesecloth wrapped around it. The unit may not emit flame nor can it char the cheesecloth nor can it create an opening in the housing that exposes live metal parts large enough for a child's finger to be inserted. After the test, the unit may not allow leakage currents of > 0.5 mA from Line to Ground and Neutral to Ground also it must withstand a dielectric voltage of 240 VAC for minute between each protected mode. Our units have passed this stringent test requirement in order to get UL recognition and to insure the safety of our customer's lives and property.