Initial CT setup in software double option


I just got the iotaWatt wired and setting up the software and it is not clear on how the software should be setup for the CT’s. I did not have enough CT’s for everything so I placed the two 200 amp clamps on the two bus bars, and my Air Conditioner I only put a CT on a single leg. So when configure these CT’s for the mains do I select double since it is 240 that comes into the house or leave that un-checked? For the Air conditioner it is 240 with two breakers with a single CT so do I select double on that one as well? It is not clear when to select double, is that basically doubling the value or just doubling the voltage for 120v systems here in the U.S?

I also have two 100 am clamps for solar panels feeding into the panel.


Are you saying that the docs are not clear? Have you read the split-phase section?

When you use one CT for a 240V circuit, you should double. When you use two CTs, do not double.

Use one CT for a two-wire circuit (no neutral), and two CTs for a three wire circuit (with neutral).

Your mains include a neutral so two CT, no double. AC units usually do not have a neutral, although not always. If you’d does not have a neutral, one CT and double.

240V Solar inverters usually don’t have a neutral.

so for two pole breakers (i.e. solar, spa, AC) sounds like you should just place one CT’s on them is there any reason to add on both? You mentioned only of a neutral but I thought all lines had a neutral. I did one on each leg for my solar and left it at 120, and get two power readings and need to combine them to get the total. Is there a way in the graph’s to combine channels?

Have you read the docs?

No I had not read that section, just read it. One recommendation on the documentation as I was doing this installation with some electricians is to include more information for the installation. The Install doesn’t go into installing of the CT’s. It would have been good in the installation section to have more information about CT installs. For example I had read the CT basics and the arrow orientation but did not see anything about when placing the mains CT to place them in different orientations. So I did not catch that until so when the electrician installed the clamps on the mains he put them in the same order. So it should include at least the mains CT installs and something on CT. When trying to print instructions to provide to an electrician to install they really had no idea what this was.

Thanks for the feedback. Understand that IoTaWatt is in use in over 75 countries worldwide with many different types of power systems. The physical installation is of CTs is universal and standard. IoTaWatt firmware indicates reverse orientation and provides a way to reverse in the software setup. While it may seem like a good idea to add more and more detail to the docs, it’s hard enough to get folks to read them as it is.