Testing & TroubleshootingQuestion 486 of 521
On a 120/240 V multiwire branch circuit, the shared neutral becomes open. What symptom is most characteristic?
a.Both 120 V loads simply stop working with 0 V at each
b.The two 120 V loads see unequal, shifting voltages, one above 120 V and one below, as their series combination divides the 240 V
c.The breaker trips immediately every time
d.Voltage to ground doubles equally on both lines to 240 V each
Explanation
With the neutral open, the two line-to-neutral loads are placed in series across 240 V; the voltage divides inversely to their resistances, so the lighter-loaded side rises (often damaging equipment) and the heavier side drops. They do not both read 0 V (a). An open neutral does not by itself trip the breaker (c) or raise each line to 240 V to ground (d).
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