Last week I went over the importance of the Megohm test. As a reminder, we run every heater through an 8-point testing and Inspection check list. Once the heater passes the Megohm test, the second electrical test every heater must pass is the High Potential (high voltage) test.
High Potential (high voltage) test or “Hipot” is designed to stress an electrical system with high voltage to detect if the internal insulation can withstand the high voltage stress. In our case, the HiPot test evaluates if our heater insulation can withstand high voltage spikes and that no pathways exist for the electrical current passed through the resistance coil can short to ground.
The importance of Hipot Testing allows for a nondestructive test that determines the adequacy of electrical insulation in situations of normally occurring over voltage transient. We Hipot test all Watt-Flex® heaters under a high-voltage stress test (1000 volt RMS plus twice the rated voltage of the heater). The testing device has a built in “trip amperage” of 5mA that sounds an alarm if it is tripped – ie a positive hipot.
Any heater that breaks the tester’s circuit is rejected.
Hipot failure are caused by a variety of reasons such stray wire strands or braided shielding, conductive or corrosive contaminants around the conductors, terminal spacing problems, and tolerance errors in cables.