CT Fittment Problem - need help

Hi All,

I have most of the monitors in place that I want, EXCEPT one of the mains. I am trying to use a pair of the 200A x 25mm clamp-on CTs and only one leg of the incoming line is accessible. Are there lower profile units that could work, or is there a reasonable alternative?



If the wire isn’t accessable, no CT will work. You might get better suggestions with a picture of the wire/panel.

Please excuse the extreme fugliness…

You need about 1/2" under the cable. An electrician might be able to persuade it up a bit without cracking the main CB. But also, consider that you need to put the cover on, and so will probably need to rotate that left clamp a bit. Also note that those clamps sometimes have a piece of paper between the faces to protect the surface. They usually fall out on installation but it’s better to check and make sure the two halves mate firmly.

WRT the bit of paper, saw that, that thanks. I played a bit with the feeds to the main - properly dressed of course, and there is just no room. In fact I took a spare CT and removed some of the plastic, put some heat shrink to protect the windings, and that was not enough.

I was hoping that in part I could check the balance between the 2 hots…


@overeasy have you tried any of the flexible CT’s?

I didn’t know that there was such a thing - any pointers?



I think you are talking about rogowski coils. I have looked into it but don’t support them with IoTaWatt.

Right… they look interesting for this and a few other applications I’ve seen in the forum.