Since joining the Sense Solar beta program, I expected to have some communication channel with the Sense engineers to report feedback to them. So far, that doesn’t seem to have happened, so I’ll report my findings here instead.
The Sense Solar installation instructions said to connect the main supply current sensors with the labels facing towards the utility power source, and the solar sensors are installed with the labels facing away from the solar power source.
That seemed odd to me, and indeed it appears to be wrong. With the solar sensors installed with the labels facing away from the solar power source the solar setup appears to mis-identify the solar sensors. The solar sensor on phase L1 seems to be identified as supplying phase L2, and vice versa. The reason this is important is that the solar inverters don’t seem to provide perfectly balanced power on both phases. Sometimes one phase is 10W higher than the other. Now, in overall terms this is not significant. Out of 10kW, a mere 10W is just a 0.1% discrepancy. But for Sense it is important. A 10W increase in solar power to phase L1 gets mis-attributed to phase L2. So a temporary fluctuation in the solar power balance by 10W gets interpreted by Sense as a new load on L2 drawing 10W, and another load on L1 dropping by 10W, when in fact no change has occurred in power consumption in the house. Constant noise like this is going to confuse the Sense learning process.
The way I determined this was by temporarily removing one of the solar current sensors while looking at the “Sense Status” page. On the “Sense Status” page the “Mains” line shows the sum of utility power plus solar power. When removing the solar current sensors from the left phase, I’d expect to see the left “Mains” power to drop by that amount. Instead, the right “Mains” total power dropped by the amount that Sense was now not registering being fed into the left phase. When I removed the right solar current sensor the total power consumption on the left “Mains” total power dropped by that amount.
I reinstalled the solar current sensors with the labels facing towards from the solar power source like the utility current sensors, and repeated the solar setup, and now Sense recognises the solar power phases correctly.
The left solar phase is supplying the left “Mains” total, and the right solar phase is supplying the right “Mains” total.