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Generator voltage question

fitter30

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8k peak watt Champion. 4 wire plug. Have a generator sub panel off of the main panel with both generator and main tied to the grounding bar. Lost power from one leg at the generator cord to house. The leg with power jumped to 240 vac. With luckily only blew up a ground fault receptacle. Thinking that it has to do with the floating ground. Installed three volt, amp and 2 with amp reading on the gen side of the generator panel to that the voltage is good 120-240-120.
 
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ihateminimumwage

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Agree with wyliesdiesels, sounds like a loss of neutral issue. Check the output at the generator receptacle and check continuity through your cord to start.
 

Codyboy

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"Installed three volt, amp and 2 with amp reading on the gen side of the generator panel to that the voltage is good 120-240-120."

Wth does that even mean?

But yeah I agree with a neutral issue if you're getting or were getting 0-240-240.

That would indicate to me any how that you have no neutral at the panel and only 1 leg is loaded up . The other leg has 0 load.
 

Captain Spaulding

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Open Neutrals can cause weird symptoms
Not really weird. 120V loads are wired in series across the 240V lines with the loads on each side of the transformer in parallel. The neutral wire provides a bypass path for current flow to balance while keeping the voltage at the neutral junction constant. Without a neutral wire, the voltage of the neutral point moves toward the leg that’s most lightly loaded. If the loads are equal, everything works fine, but as soon as one side gets a heavier load the voltage on the other side goes up.
 
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fitter30

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Three meters are wired line side of the generator at the generator panel in the house.
That way the power from generator will be correct before flipping the breakers from house to generator power.
120 vac meters line to neutral
240 vac meter line to line
 

Codyboy

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Did you ever figure out where you lost the neutral connection?
Was the issue in the main panel, subpanel, or affected both?
 

mm08822

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Three meters are wired line side of the generator at the generator panel in the house.
That way the power from generator will be correct before flipping the breakers from house to generator power.
120 vac meters line to neutral
240 vac meter line to line
That's a good starting point, but.........high resistance connections can easily cause a voltage drop to occur across it and the load may see a different voltage than seen at no load. Watch the vm's as you apply the loads....they shouldn't swing too far from no load readings.
 

Captain Spaulding

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Three meters are wired line side of the generator at the generator panel in the house.
That way the power from generator will be correct before flipping the breakers from house to generator power.
120 vac meters line to neutral
240 vac meter line to line
A missing neutral does not show up on an unloaded circuit. Your meters will read exactly the same unloaded with or without a neutral in place.
 
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walta

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Not really weird. 120V loads are wired in series across the 240V lines with the loads on each side of the transformer in parallel. The neutral wire provides a bypass path for current flow to balance while keeping the voltage at the neutral junction constant. Without a neutral wire, the voltage of the neutral point moves toward the leg that’s most lightly loaded. If the loads are equal, everything works fine, but as soon as one side gets a heavier load the voltage on the other side goes up.
If you have not done the math it is very weird. the 500 Watt lamp will not light and the 5 Watt lamp will be super bright for a short time. 2025-07-30_20-11-43.jpg2025-07-30_20-11-43a.jpg
 
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Codyboy

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A missing neutral does not show up on an unloaded circuit. Your meters will read exactly the same unloaded with or without a neutral in place.
Very true. Those voltmeter with no load only provide a false sense of what's going on.
Maybe add a small resistive 120 volt load like small heater or even a hairdryer. A clothes iron would work too.
We would use a small hairdryer when checking for open neutrals at a customer's home.
Shut off the main to keep from damaging customers equipment.

Weird. I posted this or at least thought I did yesterday.
Phone service *****.
 
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fitter30

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Very true. Those voltmeter with no load only provide a false sense of what's going on.
Maybe add a small resistive 120 volt load like small heater or even a hairdryer. A clothes iron would work too.
We would use a small hairdryer when checking for open neutrals at a customer's home.
Shut off the main to keep from damaging customers equipment.

Weird. I posted this or at least thought I did yesterday.
Phone service *****.
If neutral is lost the 120vac meters would read 240 or a very little less because of the very little or no vac lost across two two meters would put them in series.
 
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fitter30

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not how a series circuit works
Have three meters. Meters are wired before the generator sub panel with its own breaker/ safety disconnect to two watt meters. Two 120vac meters wired from each watt meter to neutral panel bar. 240 vax meter is wired across each watt meter. If neutral from panel to gen is lost the 120vac meters are across 240 vac and the two meters are in series.
 

Captain Spaulding

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Have three meters. Meters are wired before the generator sub panel with its own breaker/ safety disconnect to two watt meters. Two 120vac meters wired from each watt meter to neutral panel bar. 240 vax meter is wired across each watt meter. If neutral from panel to gen is lost the 120vac meters are across 240 vac and the two meters are in series.
and two meters in series across 240V will each measure 120V.
 
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