Which wire(s) for usa emonpi ct clip?


i’m trying to install my emonpi in the USA.

i’ve changed the config file to specify 110 instead of 230.

  1. i don’t know which wire i should use to attach the ct clip
  2. the clip just barely fits around the wire, do i need to buy larger ones?

Hi Paul,

Does the CT fit the wire so tight you can’t move it? (i.e rotate or slide it on the wire?) If so, you more than likely need one with a larger wire window, as the tight fit might prevent the mating surfaces of the ferrite from touching each other. The jaws need to close completely, or the CT won’t yield accurate measurements. Be careful, the ferrite jaws are brittle and easily cracked or snapped. If that happens, the CT becomes unusable. If you can rotate the CT and/or slide it on the wire with a minimal amount of force, you should be good to go.

If you need a larger CT, the use in North America page has info on suitable substitute CTs and where to get them.

Which breakers do you want to monitor? the 70s, the 100s or both circuits?

If you want to monitor both circuits, attach your CT to either wire that’s attached to the silver colored lugs at the back of the box, midway between both sets of breakers. Going by the picture, it looks as if the wire attached to the top lug would be the easiest to use. Use care when working near either of those two wires. Unless you have a disconnect or another breaker upstream of them, they are live all the time. The wires attached to the breakers are safe if the breakers are switched off.

Judging by the picture, it appears the wires attached to the silver lugs are one or two guages smaller than the wires attached to the 100 Amp breakers. So if your aim is to monitor both circuits, you’ll probably find the CT fits the wires attached to the lugs with a little room to spare.

If you want to monitor only the 100s, the CT is OK as pictured if it turns out the fit isn’t too tight. You could attach the CT to the wire on the other 100 Amp breaker if need be, and again, if the fit is OK.

If you want to monitor only the 70s, put the CT on either wire attached to the 70 Amp breakers.

Hi Bill.

Thank you so much for the speedy, thorough reply.

This seems like a very helpful forum, I’m really glad that it’s here to help me.