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Random Voltage (No Common/Neutral reference point)

Posted by prepper2 (My Page) on
Tue, Mar 5, 13 at 17:16

Background: Built a new house in 2011, had a proper sub-panel installed for our "critical" circuits, with a proper double throw disconnect. Sub-panel was designed for a generator. Had a 30 amp. 250 volt plug installed on outside of house, ready to accept a patch cord from my generator.Get big snow, power goes out. Time to fire up the generator. This is a 10Kw, two cyl. Diesel; 1800 Rpm; 41 amp unit of Chinese manufacture that I bought new at a construction company going out of business auction. I had started it up a few times over the last 4 years just to keep it ready but had never put it to use. It has outlet for (2) 120 v and (1) 240 outlet. All three are 3 pronged female plugs with 3 matching male plugs that can be hardwired to feed your load. I made up a 8 gauge cord to mate up to the house and used the 240 male end to plug into the 240 female end.
Problem/Question: I immediately started getting random voltages both high and low, brighter than normal lights, refrig. cycling on and off, dull light on freezer etc. Started taking volt readings at various outlets supplied by the sub-panel. Maybe 49 volts here, maybe 180 there. Crazy readings in the panel. So I quickly disengaged the system but not before high voltage had damaged several devices. Started trouble shooting. Discovered that there is NO NEUTRAL wire on the 3rd prong of the generator plug, there is a space, but no wire feeding it. There is only the two, hot 120 (each) supply. Also discovered there is no ground in the 3rd prong of the 120 volt plugs. One electrician said I have a "floating voltage" generator, designed to supply a straight 240 to construction type machinery that just needs a 240 supply, and that it is/was not designed to feed a house panel with conventional 240 volt supply. He further said that if I could trace the source of the neutral supply, for the 120 outlet, and bring a wire from the source to the 240 outlet, that this would give me a REFERENCE point and the problem would be solved.
A second opinion by another electrician was that providing a neutral would not change anything, that the problem is in the design of the windings or just the way the generator was made to operate.
Can I fix this? Can I bring up a neutral and create a "reference point" or do I give this thing a quick sell and move on?


Follow-Up Postings:

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RE: Random Voltage (No Common/Neutral reference point)

One of your advisors is mostly correct and one is mostly wrong. But I do not know which is correct or vice-versa. A knowledgeable person inspecting the inside of your generator will have the correct answer. I suspect that the generator cannot have a proper neutral added- but do not know for sure. If it has no 120 volt receptacles, the possibility of a neutral is even less likely. At considerable additional cost, the generator could feed a transformer with a center tap to create the neutral. I suspect that the proper autotransformer would do that. Never personally tried it.


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RE: Random Voltage (No Common/Neutral reference point)

These forums request no cross-posting. When this showed up on another forum, I thought that my post had failed to register.


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