My generator when running showed proper voltage on both the 220 and the 110 outlets, and when wired to a house panel during a power outage it reads the proper voltage at the panel. However, when I start throwing breakers on, and putting a load on it, the full 220 volts jumps to one of the 110 legs, and when the breakers are off it is back to normal.

I have lost many appliances. I took it to what I thought was a reliable repair shop, and they said they fixed it. Well, needless to say, one more power outage and the same thing, lost my entire kitchen again.

I have built many houses with this generator using the 110 outlets, saws, compressors, and all at the same time, and it has kept up with the whole crew, and it always starts on the fist pull. I hate to get rid of it, I have not seen any one online with this problem. Please help.

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    When you build a house with it, are you plugging into the 120V receptacles on the generator itself? When you hook up your house, are you using the 230/240V receptacle? – Harper - Reinstate Monica Nov 18 '18 at 16:30
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    Sounds like it might be an issue of house ground & neutral vs. generator ground & neutral. – manassehkatz-Reinstate Monica Nov 18 '18 at 16:35
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    What receptacles does your generator have on it? – ThreePhaseEel Nov 18 '18 at 16:43
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    You are doing something wrong when you hook it up to your panel. – Kris Nov 18 '18 at 16:50
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    Are you back feeding through a receptacle from the 230/240 plug on the generator? – Kris Nov 18 '18 at 16:56

Without more information I'm guessing a bit, but I'll bet that you're connecting your generator's 220VAC across your house's two 120VAC phases, with no neutral connection. That will work fine, IF you are drawing equal amounts of power from the two phases.

But what if you aren't? Let's say you plug a 1500W hair drier into one 120VAC outlet, and a 100W lightbulb into another 120VAC outlet, and they're on opposite phases. The only path for the current from the generator goes as follows:

  • From one generator output into the hair drier
  • Out of the hair drier into the house neutral
  • Out of the house neutral into the lightbulb
  • Out of the lightbulb back into the generator

So, you've basically connected the hair drier and lightbulb in series across the generator. But, since the hair drier's impedance is so much lower than the lightbulb, the lightbulb will bear the brunt of the 220VAC generator output, and will blow before the hair drier even starts to get warm.

(This is a general principle; if you have two devices in electrical series, the one with the greatest resistance will dissipate the greatest amount of power.)

So, as you flick the circuit breakers on, you're inevitably adding unbalanced loads to the two sides of your breaker panel. Bingo: the less-loaded side will see higher voltage, perhaps even a drastically higher voltage.

(Note that even if your generator has a neutral, and you're using it, there's no guarantee that drawing a lot of current from one of the two phases won't mess with the voltage on the other phase.)

For way too much detail, here's a simplistic calculation, based on the standard voltage, current, resistance and wattage calculations:

  • Current (amps) = Voltage (volts) / Resistance (ohms)
  • Power (watts) = Voltage * Current = Voltage^2 / Resistance

Based on its wattage, the resistance of the lightbulb is:

  • 100 Watts = 110V^2 / Resistance
  • 100 Watts = 12100 / Resistance
  • Resistance = 12100 / 100 = 121 ohms

Based on its wattage, the resistance of the hair drier is:

  • 1500 Watts = 110V^2 / Resistance
  • 1500 Watts = 12100 / Resistance
  • Resistance = 12100 / 1500 = 8 ohms

The total current of the circuit is:

  • Current = Voltage / Resistance
  • Current = 220 / (121 + 8) Ohms
  • Current = 1.7 amps

Voltage across the hair drier is:

  • Voltage = 1.7 amps * 8 ohms = 13.6 volts

Probably not enough to even spin the blower. But, what's happening to our poor little 100W lightbulb? Let's see:

  • Voltage = 1.7 amps * 121 ohms = 205 volts.
  • Power = Voltage * Current = 205 * 1.7 = 350 Watts. (Pop!)

(To check the calculations: if you add the two calculated voltages, you get 205V + 13.6V = 218.6V, which is close enough to 220V for our purposes.)

  • I thank you for your answer, but I lose one of the legs completely, and the full two 220 goes to only one side of panel, and I have wired other geerator into other house the same way with no problem – Genos Nov 18 '18 at 19:15
  • Well then, we'll need more info; please add a circuit diagram, and make/model of your generator, to your original question. – Daniel Griscom Nov 18 '18 at 20:05
  • @Genos describe for us how you connect the generator to the house panel. Have you ever connected this “problem” generator to another home panel? – Kris Nov 19 '18 at 0:40
  • Yes it happens every house I have ever attempted, I have hooked up many other genny to houses but never had this problem, I feel it's something to do with the generator, I wired the generator to the house pannel using a 100 amp breaker and the common to the common bar and the ground to the ground bar, it is as if the generator is switching inside maybe something with the coil? – Genos Nov 19 '18 at 2:32
  • @Genos this is beginning to sound like a question that a electric motor repair shop should answer. – Kris Nov 19 '18 at 16:17

Im betting your breaker is is not hitting on both leads or the panel. Most panels alternate legs on the hot bar. Some run on one side and one leg on the other. Some light up the whole thing. Im bettin your panel config is different than what your used to. Generaters dont make their own stinger leg

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. – Daniel Griscom Oct 22 '19 at 12:02

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