SRNE phase balancing: big consumers on one phase trip the inverter on battery
Problem
When the site runs on battery (grid outage, typically evening or night), switching on a large single-phase load such as a heater or fan trips the inverter off until the load is removed. This causes an outage for the whole site.
Evidence (2026-08-11)
Per-phase active power read directly off the SRNE ASP48120SH3 (bus-quiet mbpoll on gw-aaron):
| Phase | On mains (state 2) | On battery (state 3) |
|---|---|---|
| L1 | 102 W | 145 W |
| L2 | 230 W | 327 W |
| L3 | 212 W | 291 W |
| Total | 544 W | 763 W |
L1 consistently carries about half of L2 and L3. Total load is small (under 1 kW against the inverter rating of 12 kW / 24 kVA, roughly 4 kW / 8 kVA per phase), so the trip is not a total-capacity overload. It points to the big consumers being concentrated on one phase: a large load landing on an already heavier phase, plus its switch-on inrush, can overload that single phase or trip protection while the other phases sit nearly idle.
Action
- Rebalance customer phase assignments toward an even split. Prefer balancing by measured load rather than by simple 4-3-3 count.
- Identify the big consumers and move them off the loaded phases (L2 and L3) onto the lighter phase (L1).
- Re-measure per-phase load after rebalancing to confirm the spread has narrowed.
Use the backup-phase-dashboard phase-balance analysis (reads the customer meter CSVs) to plan the reassignment.
Also check (a separate, compounding cause)
Protection and power-save settings may make the trip worse on battery. Read (read-only) the power-save level E207, eco mode E20C, overload auto-restart E20D, and overload bypass E212. Off-grid there is no mains to bypass to, so an overload just shuts the inverter down.
Tracking
GitHub issue: Nearly-Free-Energy/nfe-modbus-energy-logger #70