5 volt difference between legs

Generac, Guardian, Honeywell, Siemens, Centurion, Watchdog, Bryant, & Carrier Air Cooled Home Standby generator troubleshooting and repair questions
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Joined: Fri May 22, 2020 2:15 pm

Just installed a 22kw Guardian and when testing power I noticed there is a 5 volt diff between the two legs 245v (125/120). It doesn't sound out of limits, but I ask because during ops checks I lost a sump pump and a furnace blower. Both motors were over 12 years old and ran a LOT so I'm inclined to think that they were just old and the power switching just put them over the edge. I can find no other issue in the gen except the voltage beta. Grid power is a solid ,if not slightly high, 250v (125/125) 60hz and when the gen is running its a consistent 245v (125/120) 60hz, load and no load. Any thoughts on the this topic would be appreciated. Thanks
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Location: Clawson, MI

It sounds more like a loose neutral connection somewhere. Did you check the voltage at the furnace and sump pump during the test? A sump pump motor is pretty forgiving for voltage variations since it's just a motor and has no controls.
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Birken Vogt
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Also a single phase motor does not care if legs are unbalanced so long as its 2 terminals stay within spec. 120+125 = 245 which would be fine for that motor. It may be a symptom of another problem or it may just be the way it is.
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