Archived Forum

I assume you're running a pump motor. How many wires, not counting a protective earth if there is one, go to the motor? If there are only two, then the motor is running on 240 V, and you only need to look at the CT on the single wire (and it doesn't matter which wire it's on - it'll read negative if it faces the wrong way for the wire it's on). Have you looked at this in Building Blocks? The situation you're in is the 240 V load in Fig.4c.  There's no graph visible to me for the 1-wire CT, so I can't tell whether that looks sensible or not. The CT that's on 2 wires should be reading zero, or very close to zero, and it's redundant. If the vertical scale in your dashboard is watts, then what you're seeing there is just noise or leakage currents, or a bit of both. What's happening is the same current is flowing in both black and white wires but in opposite directions, each is cancelling the other and the sum is zero.

If there are three wires to your pump (2 lines plus neutral - which seems unlikely), then you need to do one of the arrangements in Fig.3 (same Building Blocks article). Fig.3c is the cheapest, needing only one CT and input channel.

You'll probably find "CT sensors - Introduction" and "CT Installation" (both also in Building Blocks) helpful too.