Iotawatt measurements and energy provider mismatch

Hi everyone,

Months ago I’ve installed my iotawatt, with CTs into my switchboard and played with influxdb/grafana. I have measurements that seems to be OK, but didn’t payed attention on the actual figures.

Yesterday I’ve finally check the measurements of my main powerline, and compare them with my provider (full months) :

TTE (kWh) Iotawatt (kWh) Ratio
May 325 / 256 / 0,79
June 305 / 194 / 0,64
July 265 / 184 / 0,69
August 324 / 186 / 0,57

You can see that the error ratio is not fixed. I don’t have a maximum limit reached in my measurements (the max. value occured only once in 6 months.)

Pictures of some CTs I’ve installed :

I have declared them as “SCT013-000” (as it’s what I’ve thought I’ve ordered) :

I’m quite lost here, but I think I’ve had confusion with CT/VT. After reading the documentation (Configuring Power Channels (CTs) — IoTaWatt 02_03_20 documentation), I think I have VT types (we can see the label “60A/1V” on them).

If so, I have questions:

  • Should I declared my CTs as “VT → generic → calibration 60” ?
  • Is there a downside using generic VT (for example: precision ?), instead of a CT like the AcuCT-H063-100 that seems to work out of the box ?
  • Is it normal that I can retrieve measurements if my iotawatt is misconfigured ?

I have a AcuCT-H063-100 that was shipped with my iotawatt, tomorrow I’ll use it and compare daily measurements with my provider.

Edit: hmm… lots of info in this post : IoTaWatt with SCT-013-030 - config info? - #2 by overeasy - IoTaWatt - OpenEnergyMonitor Community

First let’s clarify that a “voltage typel CT is not a VT. VTs are used to measure voltage and you have only one in Input_0. The voltage type CT is simply a CT with an internal burden resistor installed.

Without a doubt your error is caused by using these voltage-type CTs and configuring them as a similar looking but completely different current-type CT.

The old forum post that you referenced explains some ways to somewhat salvage them, but I don’t recommend using them. Should you decide to try, at least you have an AccuCT to use for comparison of the result.