Ground Fault DiagnosisUpdate: The information below may not be accurate. Further reflection on the problem reveals one fallacy in Theory B: The charge controller should have been able to handle steady-state fault current from the PV array since it was sized to handle the PV charge current. The cause of the fire reamins a mystery. William Miller |
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This installation suffered a major fault which resulted in the flame-out of an RV Products SB50 charge controller. |
The flame was so intense that it almost caught the owner's warehouse on fire. Photos indicate the extent of the damage. |
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Layout of the installation. Note the short between the PV positive and the steel structure. Note also the dashed lines that indicate the conductance through the earth between the steel structure and the ground rod. |
This drawing shows the path for fault current under theory A: The fault current is from the battery. Theory A was rejected because fault current was flowing with both circuit breakers open. |
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Path for fault current under theory B: The fault current is all in the negative leg. Note there is no positive path through the charge controller as these circuit breakers are open. |
This drawing shows that, under theory B, a ground fault breaker would have opened the fault circuit and prevented the fire |
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Copyright 2006 Miller Power and Communications, all rights reserved
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