If you have a 120/240 load (with a neutral and 2 hots) you can use a single CT by putting one hot wire through the CT in the opposite direction of the other one. i.e. put the black leg through the CT from left to right and the red leg through the CT from right to left. If you have a 5 amp current on 1 leg and 7 amp current on the other, the CT will see a 12 amp current. Try doing a google image search for "120/240V load with single CT" Voltage reading should be taken from line to neutral (120 volts) readings won't be exact because it assumes that both legs are the same voltage. If you get a 0 watt reading you might need to reverse the direction of the wires going through the CT to get the current in phase with the voltage.
