Posting this on a few forums to see if anyone’s run into the same thing or has ideas.
Setup: SigenStor (multi-module, ~40kWh usable), 9kW rooftop solar, running the standard smart port config for the hot water service — daytime window 10:00–16:00, only switches on with ≥2.0kW of surplus solar (i.e. after house load and battery are satisfied).
The problem: on days with patchy/variable cloud, I’m seeing the HWS element switch on and off repeatedly — one afternoon I logged (via Home Assistant history) roughly 10 on/off transitions in about 28 minutes, while raw panel output stayed comfortably above the 2kW threshold basically the whole time. So it’s not simply “cloud drops PV below 2kW, HWS turns off” — something noisier than that is driving it (my guess is momentary house-load fluctuations eating into the surplus number faster than the panel output itself moves, but that’s unconfirmed).
I’m not worried about the element — a resistive heating element doesn’t care about being cycled occasionally. What I am worried about is the switching hardware inside the smart port itself, actually making and breaking a ~4kW circuit each time. If that’s a mechanical relay or contactor, repeated switching under load causes real contact wear and arcing, and that kind of hardware has a finite cycle life. Patchy-cloud days aren’t rare where I am, so over the life of the system that could add up to a lot of cycles.
What I’m after: the obvious fix is a debounce/hysteresis timer — require the surplus condition to hold for a few minutes continuously before switching, in both directions — so a single passing cloud doesn’t register as a full on/off event at all. Standard anti-short-cycling pattern, used all over the place for exactly this kind of problem (compressors, relays, etc). Sigenergy doesn’t currently expose any way to configure that, or any Modbus control over the smart port’s decision at all — it’s fully inverter-side and opaque. I’ve sent them a feature request but wanted to ask around too.
What I’m deliberately not doing: the usual DIY answer here is “pull the HWS off the smart port and control it with a Shelly (or similar) instead.” I don’t want to go down that path, for two reasons — it kills any clean rollback to a fully stock, Sigenergy-app-controlled setup (matters to me if I ever sell the house — I don’t want to hand a buyer a system that’s been rewired around a third-party relay if they’d rather just run it stock), and it also removes the HWS from Sigenergy’s own consumption monitoring, since the load would no longer be metered through the smart port. So I’m specifically looking for a native/firmware-side answer, not a hardware workaround.
Questions for the group:
- Anyone else noticed the smart port cycling like this on variable-cloud days?
- Does anyone actually know whether the smart port’s switching element is a mechanical relay, a contactor, or solid-state? Can’t find it documented anywhere.
- Has anyone had any luck getting Sigenergy (or an installer) to add configurable dwell-time / hysteresis to the surplus threshold?
- Any other ideas for solving this without giving up native control/monitoring?
Happy to share the HA data/graphs if useful. Thanks in advance.