Reverse/Autosensing question


I have a 3 phase installation, and I’ve always used the reverse checkbox in the input settings to make it correct.

However, today I was reading the documentation and it states:
“While merely convenient for single-phase systems, correct orientation is a necessity in three-phase installations because the IoTaWatt cannot automatically sense a reversed CT and correct for it.”

Does that mean that this setting shouldn’t be used in 3-phase install and I need to set it properly?


Short answer is no. There is no difference between physical reversing and using the “reverse” input attribute. That said, with three-phase, I strongly recommend that all three CTs be physically oriented the same way during installation. It’s very easy to do and eliminated any question of proper orientation.

Well, not always very easy to do unfortunately.

In Oz, it must be done by an electrician, and some of the one he put are behind the panel, hard to reach. And they are the closed type. So that requires to rewire things.

So if it’s the same as having the reverse input check, why do you strongly recommend it?

The hardest ones to reach are reverse, so I guess I could always make them all reverse.

Simply put, the majority of installs that require assistance are caused by reversed CTs. There are 42 combinations of CT orientation and phase assignment - only one of them is correct. Knowing all of the CTs are physically oriented the same way reduces that to six. Identifying the phase A CT reduces it to two. So it saves a lot of time with folks telling me they are oriented the same when they are not.

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yeah, I can imagine.
I just go a new circuit installed. I had no idea which phase it was connected to.

I knew the unit (water heat pump) used about 900W, I tested many kind of configuration before finding the one to use (which was the one closest to 900W).

A little trick: regardless of which phase a circuit is assigned to, the amps will always be correct. So plotting amps for the three mains and the new circuit, you should see equal changes in the corresponding main. Assuming you have the mains phases right, you now know the phase of the new circuit.

I didn’t have a sensor for the main on that phase, but each individual circuit. And I set an output that is the sum of all circuits in that phase.

Problem now is that there are only 14 inputs on the iotawatt.

I’m getting a new 3 phase circuits installed next months. This will require it’s own iotawatt I’m afraid.

Is there a way to make a iotawatt a slave of another so the data can be all accessed from one site?

Sorry, no slave relationship, but you can upload your data to influx or Emoncms to aggregate.