I appreciate all the answers and I’m happy to report that I’ve verified the Tx5 is capable of measuring power (and energy 
). 
At this point there’s 16 more circuits to hook up, but I’m no longer feeling anxious about having to get the hardware tested as fast as possible to make sure it works before the return window expires.
The problem was either a testing error or the clamp on ammeters being bad or incorrectly installed (maybe got bumped when I was putting the face back on the breaker box?). I’m going to kill power to the house and investigate tomorrow night. I’ll post back so people aren’t left wondering what happened.
It was hooked up in an acceptable manner the entire time. I had one power supply (emonVS) per device (Tx5 & Pi2) and a USB cable in between. I like the idea of just having one power supply and using an RJ45 splitter. That will leave me with an extra 1-phase emonVS lying around, but that’s fine. It’d probably cost more in shipping to return it than it’s worth, plus shipping something across the Atlantic has a higher environmental cost than I’m willing to pay.
Tying up loose ends
I’m fine with having a little inaccuracy. I expected it to just assume 120V instead of measuring the voltage, so it’s already exceeding my expectations. But since I have a 3-phase emonVS, I should be able to split the RJ45 output and measure both legs to get the extra accuracy. I’ll have to get a 240V outlet installed there next to the breaker before I can do this, but that can be done.
In the meantime, should I just multiply the power & energy by 2 in the feeds for all the 240V circuits to get the [more-or-less] correct power usage?
Additional questions
I’ll post most of my other questions in other threads to keep things organized, but one that is still on topic here is:
Can I take my 3-phase and 1-phase emonVS units and move some components to give me two 2-phase emonVS units? It seems like it should just be a matter of pulling some transformers, caps, and whatnot and then soldering them into the other unit, but I thought I’d check here first. If so, is there a guide for that, or some reference documentation I can look at to figure it out?
Docs I want
This list is mainly for me, both to remind me what I want documented, and to hold me to account for actually getting it done and upstreamed. If there are things in the list that are already documented, please do let me know so I can link to them from… well wherever it makes sense.
- emonVS pinout
- Should go Voltage sensors — OpenEnergyMonitor 0.0.1 documentation
- Info can come from emonVs voltage(s) - #7 by pev
- US power monitoring buying guide
- Not sure where it should go
- Will be very short and point to the emonPi2, explain the emonVS and the option to use a 240V supply to get more accurate measurements
- A separate section will talk about expanding monitoring capability with a emonTx5, including the option to connect them with USB or use the radios as well as getting AC voltage to them.
- The guide should mention that lots of other types of monitoring are possible
- Add a link to the getting started guide that shows how to get started if you don’t have a pre-flashed SD card
- linking to emonSD Download — OpenEnergyMonitor 0.0.1 documentation
- and I see that already has instructions on how to build the image yourself, which is
- Improve the instructions about configuration
- Might just be a matter of linking to some documentation for emoncms
- Will include that Pn is power (in Watts) and En is energy (in Wh) for circuit n
- Add some troubleshooting tips
- Not sure where these should go, but I saw @AberDino asking for this over here Request: Troubleshooting Tips
- Swapping emonVS units, swapping CTs around, checking for V1 or Vrms1 values, etc.