Mains monitoring question

Been using my Iotowatt for a few months now and decided I would like to start monitoring the mains.

I’m in Canada, have a 400A service to my house (2x200A panels). Picked up 2x200A CTs from Iotawatt stuff.

Now I’m wondering if I needed 4 of these?

I guess what I’m really looking for is some brief instructions for mains monitoring… Did a little searching but couldn’t find anything…


Probably, unless you have access to the mains cables before they split to the two panels. If that’s the case, you can do it with two CTs at that point. If your combined load can exceed 200 Amps, then those two CTs would need to be larger. The ECS24200 also come in a 300A and 400 amp variant by special order. I can get them in a month or so, and would accept a return of the 200As.

The othe4 option is to put 200A CTs on both panels where you would need 4 total and 4 IoTaWatt inputs.

Thanks. I’ll prob order a couple more…

Can I use a 3.5mm combiner to save some inputs on the iotawatt?

Instead of using 4 (2 x 2 legs of each 200A), combine each 200A into 1 x 3.5mm?

I feel like I read something about this previously?

Thanks again…

Thanks for reminding me that I was going to over this in the docs.

Yes, you can combine CTs into a single input with a standard headphone splitter, but you have to follow some basic rules:

  • All of the CTs must be the same model.
  • The total current measured cannot exceed the maximum for one of the CTs (if you combine two 50A CTs, the total current cannot exceed 50A)

When setting this up, you should first plug in each of the CTs individually and be sure they are not reversed.

ordered 2 more 200A CTs…

Thanks for your help.

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