I’ve finished the basic installation of my emonPi. Very happy with it.
By basic I mean it only measures the whole house (with one CT on one of the two thick cables between the meter and the consumer unit).
I would like now to start monitoring specific circuits. In particular, I have a circuit going to the kitchen, and I’d like to measure the consumption in the kitchen separately. From what I can tell however, there is only one flat grey cable going out of the back of the consumer unit towards the kitchen (twin-core+earth I’m guessing). From what I understand (from Learn | OpenEnergyMonitor) I cannot put a CT around that cable, since the current will flow in opposite directions in it.
Short of calling a sparkie to “split” that cable allowing me to clip the CT on the live or neutral core only, is there anything I could do?
A cast-iron certainty, I think. It’s probably got “6242Y” moulded into the cover at intervals along the length. Is it 4 mm2 (dimensions over the cover approx. 6 mm × 12 mm) or more, or is it less? If less, (5.5 × 10.5 mm), I think there should be two cables (a ring main).
I would open up the consumer unit and put the c.t. on the line (or neutral) conductor inside - assuming you can find room.That’s legal because you won’t actually be changing anything, but unless you’re happy to work inside there and know what you’re doing, don’t. If it’s a modern C.U. with MCBs, there shouldn’t be any accessible live bits of copper and hence almost no danger (unless you’re very silly and damage a wire), but if it’s old, there might well be.
And if you don’t want to, short of calling an electrician in, there’s no easy way to do it. They would refuse to split the cable externally to the C.U. anyway.
In theory, you should be able to put a Hall effect sensor on the edge of the cable to sense the magnetic field (which will be a lot stronger on the edge from one conductor than the other), but you’re talking a lot of electronics and a big problem with calibration and repeatability.