# Solar Inverter Not Showing Negative During Night

#1

I have a US Tesla install with a Solivia TL inverter (7600kw system). I have two CTs on the inputs coming from the inverter to my main panel which is located at the bottom of the panel in ports 13 & 14 of the IoTaWatt.

Right now, there is power (no much due to bad weather), and both report a positive values which I would expect for energy production.

Today, I take my mains (positive consumption) and subtract the value of solar energy production which deducts the production from consumption for my total usage and exporting. The solar when producing energy is positive based on how the CTs are configured right now. However, I would assume (and I’m sure wrongly) that if energy was flowing in reverse (mains to inverter) to supply power to the inverter during the night that it should be a negative value instead of a positive one During non-production periods, to keep the inverter operational the manual claims the device requires a draw of 5w-7w until it starts to receive power the next sunny day.

Both “Solar_1” and “Solar_2” ports on the IoTaWatt have the checkbox to allow for reverse values as seen below. If at night I try to reverse the value to be negative by checking the “Reverse” box, it sets both night and day to throwing off my production/consumption values. It is not a bug deal, but over long periods of time, the 5-7w of mains draw now showing up as production (positive) adds up.

Just wondering what I’m doing wrong to not see the negative values at night or if the 5-7watts is too low to make a difference? Should I have to reverse one of the two CTs to correctly detect the direction of the flow like a 240v circuit? Happy to try anything people can recommend.

#2

I’d need to see the config file to diagnose this.

Doing the numbers:
You are trying to measure 5W on a 240V circuit. That’s 5/240 = 20.8mA on the primary of the CT which is 1:1000 ratio. So the CT output will be 20.8uA, which is 1/2400 of the range of the ADC using 2048 counts. So maybe it’s as simple as that. IoTaWatt filters out low signals as noise.

Understand that’s the same as a 2.5W load on a 120V circuit.

So what I would recommend, notwithstanding anything that may be amiss in the configuration, is to pass the two 240V inverter feed conductors through one CT, reversing one of course, so as to double the current through the primary. That might just fix the problem.

You should be OK to do that as long as your inverter doesn’t put out more than 12kW AC.

#3

Thanks for the input and thoughts @overeasy. I more wanted to ensure I was not missing something and I fully understand that a constant 5w during the night to power the inverter is not much, yet you give us this wonderful tool and visibility I want to make sure I’m using it correctly. Often when I have a look, the first circuit “Solar_1” is the one that the inverter is taking the grid to power by and “Solar_2” is often 0w. Again, not a big deal at all, and I have to say thanks again for the PVOutput.org connection. I’m really liking this added views to my solar; even on bad days like yesterday and today.

Thanks for the feedback and always the quick reply.