CT buzz?

i have two of the 100A max clip-on current sensor CT and one of them buzzes loud enough to hear thru the metal door of the fuse box. if I move it around the buzz changes and sometimes stops. is this normal? is it on backward?

There are 2 main reasons for CT’s to buzz, one is that there is an air gap in the split core, eg CT not fully closed, CT under strain or CT core’s fractured. the second is High current passing through the primary when the secondary winding is open circuit. Since there are protection diodes in these CT it is unlikely to be the latter unless it’s a very large current.

Check the clasp is fully closing and that the CT is loose on the cable it’s sensing. If nothing is obviously amiss there you will need to take a close look at the ceramic cores for cracks and chips etc.

Direction should not be a factor.

They are currently unplugged from the emonpi could that be the cause? I
can’t plug them in for a bit due to a house furnace fire but I’ll try asap

That’s definitely the cause, and it’s not good practice, and potentially dangerous. You are relying on the internal protection diodes to prevent damage and the danger of a nasty shock.

In general terms, you should NEVER disconnect a c.t. that’s on a current-carrying conductor.

You should remove the c.t’s from the cables, or short-circuit them, if they must be disconnected from their burden. (The easy way is just wind some bare copper wire around the length of the plug in a spiral, and twist up the ends, making sure you have contact to the tip and sleeve. The proper way is to use a spare socket that you’ve soldered a link between tip and sleeve.)

Oh yeah that’s it.