Quote:
Originally Posted by Ron342
So you're reading one hot leg of the 240v to ground?
If so , isn't it going to read half of your real usage?
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With many devices that run on 240, the neutral wire isn't present. They have 3 terminals: line 1, line 2, and chassis ground. What goes through line 1 equals what comes through line 2. The ground connection is isolated for shock protection. Large window shakers and baseboard heaters rig up like this.
Some units have a 4 wire connection, and have a neutral terminal. A number of unit makers cheat and use the neutral and one line leg for some low-power components. Electric dryers and ovens do this with lights, clocks and mechanical timers. Even in these "cheater" units, the stuff that only uses 120 volts account for very little of the operating power. Unless, of course, you use your oven for a night light or something.
In theory, you could rig 2 kill-a-watt units to a 240 volt circuit so they each read a line leg with reference to the neutral, then connected to a 240 volt device, and you could add the two readings to get the total power draw. You could subtract one reading from the other to tell if there was an imbalance somewhere. In reality, a rig like this would violate more than a few rules in the electrical code. That's why they sell 240 volt kill-a-watt meters.