# Solar numbers not adding up

Presently it is once again reading the draw from the house incorrectly, the solar is generating about 600watts, the house is drawing about 3300 watts with the solar panel breaker turned off. I believe to draw from the house should remain steady at some value and once the solar breaker is turned on, the solar panels and utility will both supply that same load splitting it between these two sources depending on how much sun is shining. This is not what’s happening.

With the solar panels off the sense sees the entire house load correctly as 3000 watts, then when I turn the solar breaker on, generating 500 watts, the sense sees the house load drop by 500 watts to 2500 watts, this is not correct. The house load is still 3000 watts but 500 of those watts are being supplied by solar.

Sense on the other hand incorrectly thinks the house load has dropped to 2500 watts and it sees the solar supply 500 and utility supplying 2000 watts, this is incorrect. The house remained at 3000 watts and 500 watts was now supplied by solar and 2500 was supplied by utility.

I have attached two screen shots to illustrate my issue. In the first picture you can see the solar production at 586 Watts and the utility is supplying 2566 Watts, therefore the total the house is drawing at that moment in time is 586+2566= 3152 Watts, therefore the solar is supplying (586/3152)x100= 18.59% of the house total power draw.

However the second picture was taken 1 second after the first picture so the values have not changed but the second screenshot is where the problem is. In the second picture we can see the solar is the same (+2 watts) at 588 but the “power triangle” seems have taken the power sensed at the main utility input wires and subtracted the power coming in from the solar panel wires and labelled this as the power “from grid”, it has then labelled the actual power coming in from the utility power wires as “Home” at the top of the triangle. It has then calculated the solar power contribution incorrectly using the total house power as 2563 Watts (instead of the correct 3152 Watts), while keeping the solar contribution correct at 588 Watts; therefore the calculation is as follows (588/2563)x100= 22.94%.

Lastly I’d like to let you know that if I turn the solar inverters off completely then the power triangle input from the utility no longer subtracts the solar contribution and the “Home” total at the top of the triangle becomes correct at approx. 3100 watts.

See attached screenshots.

Hi @wayne_penno. If you’re a new user, you may be temporarily restricted from posting images.

Since this is a reoccurring issue, I recommend reaching out to our support@sense.com. My first guess is this issue is related to installation, but Support will be able to confirm/deny that.

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As Justin suggests, you should probably check in with support@sense.com. But I don’t see any inconsistency between these screenshots, except for the 100W differences that could occur with a small change in time. The home # on the left and the plug # on the right are close (2500-2600W), and the solar numbers are close (500-600W). That tells me that your “from grid” is both pictures is about 2000W. 621W solar / 2667W total house usage gives 23%.

You don’t have a screen shot of what it looks like with solar inverter turned off, but I would have predicted that solar goes to zero and total house usage stays at 2500W to 2600W.

I think the source of confusion might be that you put the main Sense CTs on your pre-breaker box mains and you are expecting the Sense total consumption reading to show the net flowing into the house after the solar contribution, but Sense is already compensating for that to give you actual house consumption.

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Hello Kevin

I have opened a ticket with support@sense.com. What you missed in my last email is that the entire house load was around 3200 watts, not 2500 watts. The way sense says to wire the solar sensors is not correct. The sense app and web app both take the power measured from the solar clamps and subtract it from the total house load, and then label that as “Home” on the solar screen and “plug” on the power screen. Using this logic the “Home” load is constantly changing in relation to the amount of solar generation. This is not what is happening in reality. If the “Home”, in this case my house, is base loaded at a constant usage of, for example, 3000 watts of light and heat. This base load will be fed from 2 sources in my case, solar and grid. The amount of solar goes up and down depending on the sunshine and the grid will supply the remainder to always supply the “Home” at 3000 watts. Therefore as long as the house base load does not change the solar and grid when added together should always be 3000 watts. Or in other words the house load is always completely independent of how it is being fed whether all by solar or all by grid or a combination of both. I had to reconfigure the sense clamps and wires as shown in the attached pic to make the whole app work out correctly.

• the solar clamps register only the solar.

• the mains clamps must include every source that is feeding the load, therefore the solar panel wires must pass through these clamps also.

In this configuration both web app and phone app seem to be working as they should. I will include some screen shots for illustration purposes. Pic 1 will be with no solar, Pic 2 is with solar turned on and showing the “Solar Screen” and Pic 3 is with solar on and showing the “Power” screen. Pic 4 is illustrates the way I have sense wired up. Pic 5 is of my utility company supplied power monitor showing that the grid is supplying the house with approx 940 watts which now agrees with Pic 2.

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Very interesting. I also have a Rainforest Automation product (an Eagle) and I didn’t have to do the loopback of the solar backfeed through the mains CTs that you describe. It will be interesting to see what support has to say… I’m wondering if your solar backfeed isn’t as simple as a typical solar backfeed.

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Thanks for the info Kevin. Can you explain what I am seeing on the Eagle? Is the -2.146kw what you are pushing onto the grid? If so then that seems to jibe with you sense “solar” screen. Is your setup wired as per sense guidelines? If so that is curious because would not work in that configuration. Another very odd thing that was happening with the sense wiring configuration is, as my solar production increased it would cause my house load to decrease in lockstep. If the solar gen exceeded the house load then the house load would go into negative territory and be off the bottom of the graph where it could not be read. I’ll post a screen shot of that here

PS ignore the power reading in the top right of the screenshot, they are readings at the time of the screen shot which was scrolled back a day on the graph.

Here is a screenshot of the new wiring configuration and you can see the house load stays independent of the solar gen coming in, the only thing changing now as solar goes up and down is the grid contribution to make up the rest of load demand

@wayne_penno, the Eagle is showing the net usage coming from my utility smart-meter. So yes, when negative, it is showing my “to-grid” output. When positive, it is showing my “from-grid” amount. BTW, the numbers don’t always jibe, but are usually within 100W our so. My meter only updates the Rainforest Eagle every 4 seconds or so, with the RMS for that 4 second interval. Sense does the same, but for a 1/2 second interval, so even if you get a snapshot at the same point in time, as I did, they will present aggregate power data for two different time periods.

And yes, my Sense is hooked up per the installation directions almost to a “T”, with one minor difference. I have a 400A service that splits into two busses out of the meter, so I had to put the CTs on the pre-meter mains instead of where they enter my main box at the top.

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When I first wired it up exactly as shown in the sense guide I assumed the whole reason of having a dedicated “solar” application was so the programming could take care of adding and subtracting the gen versus the load to give all the correct readings. This did not happen. I uninstalled everything and reinstalled then rebooted the whole device and it still gave me the wrong and weird readings, subtracting things in weird ways that did not seem to make any sense. After a while of playing with it and getting frustrated I left it alone for the long weekend and went camping and over the weekend had the idea that it was somehow not wired correctly. Upon returning home I had to change the wires around as I showed in the new modified installation diagram, it no longer matches the sense wiring but now seems to be working. I am wondering if the sense box is not programmed correctly or somehow corrupted. I have had to reboot it several times before I finally figured out the wiring had to be changed around to make it work. Also I keep getting this error

I would check in with support. Your first Power Meter snapshot in this series is similar to several other problematic solar setups I have seen on the forum (total usage influenced by solar). Example here:

It may be that your solar and battery combo (I assume that’s where your inverter shunts the extra solar when it is in “0” mode) confused your initial Sense install and calibration. Or it could be just one of those installs that didn’t quite go right. Looking at your second screenshot, it seems like your ECO worked, but it might have side effects downstream.

I would definitely pursue the support@sense.com team hard on this one, even if you have it working, albeit with the error messages. An if you do need to go through setup again, I would try to use the solar initially in pure production mode for the calibration step. I can see the zero mode potentially confusing the calibration setup.

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I dont understand the terms pure production mode and zero mode? My battery is simply a battery bank that I have to manually tie in at night after I open the main breaker. During the day a charger recharges the batteries. Its entirely a manual system. My setup of the sense device was done during the day without any battery input at all.

Hi @wayne_penno. After learning a bit more from your posts, I second Kevin’s suggestion to work with Support here. They have access to a lot more information on their end that can be used to pinpoint the issue here as opposed to our speculation in the forums .

Showing the power used by your inverter is an error that the sense techs can fix from their end. Mine did the same thing from the first day of install. The techs fixed it from there end and sunbelt the sense unit started detecting devices in the house.

OK thanks for all the input, I’ll forward a link to this thread to support@sense.com
I’ll update when I find out more.

Thanks, Wayne

Sorry if I misinterpreted something, but I thought your solar inverter matched house usage and vectored any excess solar production to the batteries. Good luck with support and let us know how things turn out.

No I don’t have a very elaborate system, the 2 solar arrays are “grid tied” and the battery bank is stand alone (990amp/hours). It’s a very simple system, the grid supplements the solar during the day (including powering the stand alone battery charger), then at night I flip off the main breaker and close the battery breaker. There is a momentary power interruption (15 secs) and the batteries supply the house for the next 12 hours, supplemented by any solar that is left in the evening or morning till I get up in the morning and flip back to the grid. So the solar is always connected and either the grid or the batteries supplement the solar. Both the grid main wires (panel feed from utility) and the battery bank wires run through the main sense CT clamps in the same direction. The solar grid tied inverters sync to the Grid in the day and sync to the battery 240V inverter at night. I installed my sense unit and attempted many restarts but all in the day when there was at least 500watts solar minimum to allow the solar calibration. I was totally at a loss to understand why it wouldn’t work until I hit upon the idea of re-configuring the wires through the CT’s and now it seems to be mostly working but I’ll see what the support team can come up with. The only drawback there is they seem to be always waiting for more info to filter in and it takes a long time going through them. I will just have to be patient now and not do any more re-configuring or resetting to factory defaults until I hear something from them.

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Update:
Sense support asked me to wire my panel as shown in this diagram they sent me. The second set of “solar” leads shown are actually my batter inverter leads. I did this and they reconfigured something on their end and now it seems to work properly. The only issue will be when im on battery it will appear as solar but that’s OK because in my custom setup the battery appeared as grid. I’ll easily be able to tell how much battery I use since I log the times I switch from grid to battery. Below is there explanation:

"That said, for your reference, the issue here appeared to be that the previous (sense solar) configuration was not properly adding the solar production back into the mains. Thus, when Sense detected solar readings, it simply subtracted them from your main readings and the solar was still reporting. When you were using more energy than solar produced, the mains were getting pulled negative, as a result, and flatlining at 0 in your readings.

With the current configuration, however, the main readings should no longer be impacted by your solar production. Whether you are producing or not will not cause these readings to fluctuate."

It seems to be working so far since they made the change at 9am this morning. Now I have to see if the signal check works or not, mine has consistently remained at 0% until finally bringing in the error message and halting. Hopefully I can get things moving along now and start device detection soon.
I will be asking sense to readjust my 60 day return policy to start only after the signal check is complete and the first device has been successfully detected. I think that is only fair.

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wiring diagram from sense: