CT hardware questions before purchase

Hello. I love the idea of Iotawatt and I’m excited to get one installed. I have a few questions about the hardware.

I have a 200A main breaker and a Tesla solar inverter. There is no space below the main breaker for clamps. There is a little space above, but I would have to remove the plastic shroud to place clamps there, as shown in the second photo. Can you recommend what kind of clamps would fit here? I live in California.

My Tesla car charger is on a NEMA 14-50 outlet with 2 hots, neutral, and ground. But as far as I know it runs purely on 240V. Would it be ok to use just 1 clamp here and double it? Reading through Tesla forums, it seems like lots of people use NEMA 5-50 outlets instead without neutral.

For individual 20A circuits, is there any benefit to buying 20A clamps instead of 50A? They seem to be the same price and size.

What is the recommended operating temperature range for the Iotawatt? I live in the high desert where it occasionally gets to 125ºF and I expect this to increase in the future as our climate warms. It also drops below freezing in the winter. (By comparison, Sense is listed as 32 - 154 F, which would be a problem for many cold parts of the world.)

Can you recommend any resources where I could learn more about how the voltage reference transformer works? I’m wondering why other similar products (e.g. Sense) don’t require this.

Is there some way to attach an external Wifi antenna? I’m concerned that the metal box might block the signal.

By the way, you might notice in the photos I already have a few CT clamps. This was included as a bonus with my Tesla solar system, but the Powerblaster measurement devices is junk. It shows all kinds of spurious data and they’re unwilling to fix it, so that’s why I started looking for alternatives. But I think the clamps are fine, so I’d like to solder some 3.5mm plugs to those and reuse them. Do you know if this kind of clamp will work? They are unlabeled.

Possibly Rogowski coils. You don’t have many breakers in the panel so another alternative would be to measure all of the loads and add them up for the total.

It’s OK to use one CT if there is no neutral.

Practically speaking no.

Never actually tested for extreme temperature. I expect it would work OK.

All meters need a voltage reference. Sense connects directly to 120V and measures it internally. IoTaWatt uses an external transformer and as such can adapt to any voltage with the proper transformer. Most of the world is 230V.


No, I don’t know if they will work. Experience suggests that they won’t.

Voltage references. This is a decent write up on them and why they are needed:

You don’t have a lot of space in there to measure the mains. Think about what you data you need. I rarely look at the mains. I do look at the individual circuits that are interesting. The main has too much “information” so it frequently looks more like noise.