The Energy Detective CT's

I have some 200A 600V Heyi CT601B current transformers from a TED installation and am curious if they can be converted for use with the IoTaWatt. I purchased the clamp-on ct’s from IoTaWatt but they are too big for my electrical panel.

Don’t know, but I’ve been led to understand that TED used voltage type current transformers, so I’m leaning to no.

Can you post a picture of your panel? I have other CTs, including some form-factors not listed in the store. The SCT019’s from YHDC work OK and are pretty small. Can you post a picture of the TED CTs for comparison?

As you can see it’s a tight fit and the clamp on ct doesn’t allow for the cover to be installed.

So that looks like another Siemens 200A panel. See these posts:


The best solution is to install the 200A Cts on the mains before the meter in the panel below the meter. If that is sealed and cannot be accessed, you are left with trying to put CTs on the mains cables in the breaker box. That’s not easy, and as you say, the 200A do not allow the cover to be installed.

But there is another issue with placing the clamps in the breaker box. The main breaker, while rated 200A overall, is actually a gang of four 100A breakers. Moreover, they alternate phases, which is tho say 1 and 3 are one phase, and 2 and 4 the other. So you need four CTs there to monitor your mains.

I don’t know how the TED CTs were connected, but you would have needed four of them as well. Perhaps you used two and doubled them, which would give an approximation, but not very accurate.

The TED CTs that you are showing are pretty much the same size as the AccuCT 100A. If you were able to install them on those mains, you could install the AccuCTs, but you would need four.

There is another approach, based on this user’s experience:


He has demonstrated that in his panel, the sum of all of the loads is within 1% of the mains. You have 20 branch circuits. The IoTaWatt can measure 14 circuits, so it would require some combining of six additional circuits to measure everything. The upside is that rather than dedicating four inputs to measuring your mains, leaving ten for individual circuits, you get details on 14 individual circuits or circuit combinations.

But again, the easiest and most straightforward solution is to find a way to install those 200A clamps in the lower left panel as illustrated in the referenced posts.

Thank you very much for your response. I did have 4 ct’s with TED but thought I could just double the ones for IoTaWatt. I like the idea of measuring all the circuits then, if I’m understanding correctly, I could prepare an output combining all the circuits to determine what’s on the mains. The only circuit that isn’t being monitored right now is the 100A feed to the sub-panel. I’m hoping I can use the ct’s from the mains on the sub-panel feed to accomplish what was described. Thanks again!