Seeing only one main



Hi all,

I am having an issue where despite having a professional electrician install the Sense, the monitor can only see one Main and not both. It used to be that it can see one and occasionally it wouldn’t see anything anymore, seeing a phantom of the other main (showing a bunch of 0 readings instead of no readings) and then switch back. Does that make sense?



It is showing 0 or no reading, and not a negative number, correct?

I’ve seen some users that had to wiggle the connector where the clamps plug into the orange Sense box to get both to detect.

If you have already done that, make sure to open a support ticket direct with Sense, as something may be physically wrong.


How safe is wiggling the clamps, @MallocArray?


Not the clamps themselves, but they are connected to 2 wires and those two wires have a connector on them that plug into the sense box. That connector is what others have wiggled to make sure it was fully seated.

You could also confirm that the clamps look fully closed around the mains. In some installations, like mine, when the cover goes back on, it can push on the clamps and open them slightly, so they may need to be readjusted.

(PS Turn off the main circuit breakers when working inside the panel just to be safe)


Could one of the current transducers be upside down?


I’m pretty sure it would show a value, just a negative one if it was upside down


I would swap the CT’s from leg A to B and B to A and then see if the problem moves. If it moves it tells me you have a CT issue while if it doesn’t move it says there is an issue with the orange box.


Unfortunately, swapping the CT’s will not fix this issue. Swapping CT’s will end in losing data. Please contact customer support at and we can resolve this issue with one of our support agents.


In order to see that negative value, you’d have to look in the settings -> sense monitor page. On the main screen it’ll read as zero.

My money is on 1̶)̶ ̶b̶a̶c̶k̶w̶a̶r̶d̶s̶ ̶C̶T̶ or 2) faulty CT. If you go to the settings and see a negative value there, check to make sure your CTs are both installed in the correct direction.


Hey guys, just a quick FYI - for the Sense system to work, it is important that you not move the CTs to another line after the initial power-on. If your Sense unit is not working, please contact We have been growing our customer support team, so our response time is steadily improving. :slight_smile:

Attempting to diagnose the problem yourself is not recommended, as Sense replaces all hardware if we suspect any of it is not functioning properly. In case you would have a loose pin problem for example, the above-mentioned procedure would mistakenly diagnose it as a monitor problem, not a CT problem. Hope this helps!


So after over a months, I finally figured it out.

Despite paying a professional electrician to install it it wasn’t done correctly. What was wrong is now obvious to me but not knowing anything about household electricity and assuming the installation was done correctly, I didn’t question the basics.

The key issue is that only one main was being sensed. It was simply because only one of the clamps was attached to a main (see photos). The other one was simply connected to the “Range”, see photos included. Once I figured that out, it was just a matter of figuring out a way to move things around a bit without getting electrocuted and clamping to an actual second main.

Now the monitor is reporting two mains (through one is quite a bit lower the other currently but that could just be a function of us being in the kitchen with no other room lit up).

Now I need to figure out if, as @Maarja-Liis might have alluded to, I can rely on the sensor as is, if it needs to be reset or replaced. It had never detected any appliance after a month. It had detected 250W of always on but I don’t know how reliable this was in this circumstances.

I do feel that Sense support who I relentlessly engaged during that time could have diagnosed the issue better. Instead I was left to my own device (pun intended).



Hope you get your money back from that electrician. An electrician who cannot identify a main? Was their name “Melvin?”


I didn’t think swapping CT will be a bad idea. I had to clean up the install wiring on mine and didn’t pay much attention to where each one was clipped.


I had only suggested swapping to try to see if the problem moved. If you swap you would have to reinitialize Sense and start over - it was just a trouble shooting idea.

closed #16