Originally Posted by Ron342
It does help - i knew dryers used one leg to neutral to get 120 for the motor - i think the code changed in the 80s to require a 4 wire plug with the neutral so you didn't have a current carrying ground.
But the little ebay panel meter uses 1 current sensing coil and it looks like the other connection is to ground.
So instead of phase to phase for 240v, its seeing (and reporting?) One phase to ground?
If you rigged your eddymax meter to a "cheating" unit, wiring it between one line leg and neutral, then yes, it would measure only the power that flowed through that leg. This is assuming the eddymax only has a single current sensor in the one leg. If it had another sensor in the neutral, it may act super strangely if only a small current was flowing back through the neutral. We don't know what's in the box, but my money is on only one current sensor. Being calibrated for 120 volt operation, it would display half the power actually being used by the 240 volt circuit. It would, however, calculate the "cheater" power (flowing in the neutral through that leg) correctly.
The same error would show up in one of the peacefair 240 volt meters with the "cheater" power. The unit would calculate the 240 volt power flowing through the current sensor. If some of that power left through the neutral, it would be overestimated by a factor of 2. If it crept in the leg not being monitored, the calculated value would be underestimated by double the "cheater" power.