OPEN NEuTRAL

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j rae

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I have a 100 3-phase panel 120/208.
Had a question that if I were to lose the neutral in the panel wouldn't I get 208 volts to any equipment that is turned on. I seen this happen before on a multi wire ckt and if fried microwave and other kitchen equipment
 
j rae said:
I have a 100 3-phase panel 120/208.
Had a question that if I were to lose the neutral in the panel wouldn't I get 208 volts to any equipment that is turned on. I seen this happen before on a multi wire ckt and if fried microwave and other kitchen equipment
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The voltage you will see at equpment will be entirely dependent on what is connected "in series" between the two phases. I say "in series" because if you lose the neutral to the source but all other neutral connections are intact you now have a 208 volt circuit with a mid point where the lost neutral belongs. Should you have three equal resistance 120 volt loads all connected from each phase to this "mid point" then all three of those loads will still see 120 volts. If you only have two 120 volt loads of equal resistance on separate phases the mid point of 208 becomes 104 volts across each load. Now if you throw in unequal resistance loads you can have anywhere between (near) zero and up to 208 volts across any load and will all depend on resistances of individual loads and where they are in series with other loads.

Here is something I have posted before on this topic, it is not 208 volts in that example but the basic concepts are still the same:


 
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