We recently installed a new generator (Mosa GE6000SX) and during the troubleshooting process for something else, the electrician noticed that when the generator was running but disconnected with no load (just the meter), he observed 40-50 volts between the neutral and the earth (it is a 240 Volt AC single phase generator).
The electrician seemed to think it was a fault with the generator that should be rectified by the manufacturer. However when I spoke with the supplier's technical support today, they informed me that a 40-50 volt reading between the neutral and the earth was "normal".
According to the manufacturer, it supports 110 V and 230 V modes. In 230 V mode, the windings inside are connected in series, while in 110 V mode, they are connected in parallel. As the generator offers split-phase 110 V, the earth is centre-tapped on the 110V windings. i.e. in 110 volt mode, it produces 110v with a centre tapped earth
Should I be concerned about this?
The generator ultimately powers an off-grid home when the renewable power system is low on battery and recharging (inverter bypass).
My understanding is that in a UK home, neutral should be tied to earth at the generation source, as safety features (such as the fuses in the plugs) don't operate on the neutral, so according to the electrician, this is a potentially unsafe configuration.
Best Answer
It turns out that the OP's model of generator is peculiar -- its 120V is set up in the UK jobsite fashion (i.e. two 60V hot legs and a neutral), which when combined with the way the 120/240V switching works on the 120/240V models of this generator, yields a neutral at an odd spot.
The only fix is to use a 240/240 isolation transformer to establish a new neutral point, or to rewire the generator (which'd void its NRTL listing).