Multiple IoTaWatt's with 1 Mains CT on Reverse Stereo Splitter


I’ve 2 IotaWatts installed finally. They are next to each other in a waterproof box outside near my service panel.

Can I use a reverse splitter to provide Mains_1 and Mains_2 to both IoTaWatts, this means using 1 CT per leg that feeds both IoTaWatts. Looking at type cable. The image is correct looking, the application photos appear to be take by photography experts not application of using the splitter experts.

Edit to add, standard USA 2x200 bus bars. Nothing exotic.

Thank you,

That will not work and should not be done.

So the only way is to install 3 CTs per main? I’m planning to order another base unit, pending full installation.
I have 60 some circuits in my panel due to all the updates to recent NEC. Not positive yet what I can combine because 1/2 the circuits are not marked properly (if marked at all). I’ve got a good 20 single slot breakers with dual circuits (legal 2 wire breakers).

Thanks for the answer unless there is another way, doubling 1 main is not doable, I have a large stable load imbalance due to 30 amps (single leg) for my data center.

I have multiple iotawatts. 3 phase (uk) supply is measured by one of them and all measurements (from both devices) are pushed to influxdb. You only need to measure the grid once.

Grafana does my routine reporting (showing energy consumed as cash spent) pulling the data from the influx db. I use home assistant and iobroker to pull data from other sources (heat pump brine temperatures, run time, hot water temp etc. and from some Shelly devices).

I use the iotawatt graphing if I want something ‘quick and dirty’ or need to investigate something.

I have more circuits than inputs on the iotawatts. I have an ‘everything else’ measurement (import minus measurements = everything else)

I move CTs if I need to.

Some CTs have multiple (same phase) cables running through them (e.g. measuring two lighting circuits together)

Once things settle down and a ‘norm’ is established the grafana dashboard is great for seeing if there are any funnies or unexplained changes in consumption that need to be investigated further.

Key questions are what are you monitoring it for? what is the minimum number of units and CTs that you can get away with to get that info? More importantly, once you have the info, will you change your behaviour?

As @philrob says, you do not need to monitor mains. It is true that you need to buy mains in a 120V kit, but you can get the 100A and you probably have circuits where you need those. In any event, using 100A for an ordinary branch circuit will work fine.

Hi Philrob,

Thank you for the insight that I only need to monitor the mains once. It wasn’t clear that I didn’t need to monitor them across all IoTaWatts.

Does this also mean the extra 2 ports on the IoTaWatt not monitoring the grid can be used for other circuits?

I’m monitoring for various reasons. Like pointing out to my SO that putting 1 shirt in the dryer for 30 minutes to fluff it up is a waste. Hunt down hidden power leeching devices. But my primary motivation is to move my home data center and home office off grid. I want to get summer and winter loads, figure out how much solar and LiPoFe4 I need to run my toys safely for a few days. Snow kills solar as everyone should know. Once I have all that figured out, I’ll see how much extra power I have from the solar and will be looking into an E-car for the SO.

I’m not changing my behaviors. Unless my kidney disease kills me, I’m going to keep all the toys running and keep moving forward with this project. Everyone already calls me the light police around here.

I could in the long run use some AI (if it doesn’t exist already) to push announcements through the entire house. “THE GARAGE LIGHT HAS BEEN ON 127 SECONDS WITHOUT ANY MOTION DETECTED.”
Or the “THE DIALYSIS DIALYSATE TANK STOPPED DRAWING POWER, IS THERE A DEAD CAT IN THE DIALYSIS ROOM?”. Continuing, “The garage door opened at 17:04 and did not close within 10 minutes. We don’t heat the outdoors in this house.” Possibilities…

Yes, 1 iotawatt = 14 inputs. Measure what you want just make sure that if you combine circuits through a single ct the phases are the same. Though I think that the US system (two phases at 180 degrees) might allow it with inverting one of the phases - a us user may confirm.

Iotawatt just measures, if you want automation or alerting you are going to need to add other devices to your setup.

I have a raspberry pi running influxdb (to capture the data) and Grafana to visualise it.

Influx comes in two variants 1.8 which uses a sql like query language and 2.x which uses a scripted language called flux. The 1.8 is not being actively developed but I find it easier to use.

I don’t have any “this circuit hasn’t drawn any current in past 12 hours alerts” I’m sure it is possible (somehow) but I have never tried it

I would suggest you start small. The learning curve for iotawatt plus influx plus grafana can be quite steep (but worth It)

Browsing this forum for posts on influx will help as will reading the documentation and setup instructions for the iotawatt (really carefully - there is masses of information there)