Understanding 208V Setup

Hello! IoTaWatt looks amazing and comes highly recommended from some friends. I’ve been planning out my install, and then as I was about to order, realized that I live in a US high-rise condo where half the building is commercial and my mains supply is 208V over 3 wires (including neutral, 200A capacity), not a traditional split-phase system. This threw me for a loop, and I’ve since read a bunch of posts on this forum on how to deal with that, but want to make sure I fully understand what I’m talking about here. First, here’s a picture of my panel:

In order to wire this panel up with IoTaWatt, I believe I would need to do the following:

  1. Connect 2x 200A CT to mains
  2. Connect VREF plug to outlet. This will be on sub-circuit 3 in row 2. This must be phase A.
  3. Connect hairdryer (or similar) to same circuit and measure increase in usage.
  4. Measure hairdryer on a circuit in a different row. If increase in electrical usage matches phase A, it’s phase B. If lower, it’s phase C. Let’s assume C for rest of this post.
  5. My panel wiring does not appear to be reliably color coded, but rows in circuit panel should be alternating, so if row 1 is phase C, row 2 is phase A, row 3 is row C, row 4 is phase A, etc…, correct?
  6. With that knowledge I can add CT’s to any sub-circuit and combine probes with a splitter to a single port as long as they are on the same phase.
  7. For higher voltage circuits that span 2 rows, I have to use 2 ports assigned to their respective phases (unless they are a pure 208V circuit, in which case 1 probe should be enough. It’s unclear to me to know which ones are 3 wire vs 2 wire, since the neutral wires aren’t paired together, but worst case I can assume I need 2 probes for all 208V circuits)
  8. I obviously can’t measure all sub-circuits from a single IoTaWatt. If I get 2, does the 2nd one need to measure mains as well to be able to derive the third phase, or can all 14 ports be used for sub-circuits?

Is this correct or do I have large gaps in my understanding?

Thanks so much for the help! Excited to get this all working hopefully.

I think you’ve got it. Second IoTaWatt doesn’t need mains I’d start with one and see how much of your usage that will cover.

Sweet, thanks for the fast reply! Per your advice, placed my order for one kit to get started. Can’t wait to get it setup :slight_smile: