Flares FAQ & References

Common questions about how Flares validates off-grid, hybrid, and grid-tie solar setups, with the underlying NEC and PEC tables it draws from. Reference material, not engineering advice — read the Terms of Use before acting on anything here.

How the Flares rules engine works

Every edit re-runs a flow-based rules engine. It traces power from each source along your wires, port by port, works out which connections are actually live, then runs ~30 checks across four lenses:

• Connections — follows each wire end to end, flags reversed polarity and AC phase mismatches, and understands series strings (panels or batteries wired in series are summed, not mistaken for parallel).
• Ports — validates every port's direction (in / out / bi) and catches orphan ports and an unterminated inverter AC output.
• Loads — sizes the array against daily load, checks inverter continuous + surge headroom, and warns when an AC load sits on a supply run with no branch breaker (AC-LOAD-OCPD).
• Electrical — ampacity (NEC 1.25×), OCPD / breaker sizing, PV string voltage against the MPPT window, PV overcurrent / disconnect / string fuse, battery match and discharge headroom, plus a notice when a hybrid inverter has no battery (HYBRID-NO-BATTERY).

Findings are graded error / warning / info and point at the exact nodes and wires involved, so you can jump straight to the problem.

1. Why does my AWG 10 wire show "undersized"?

Flares applies the NEC / PEC continuous-load rule: any circuit that carries current for 3 hours or more (every solar circuit during sun) must use a conductor rated at 125% of the actual current. A 30 A continuous load wants a 37.5 A conductor. AWG 10 Cu at 75°C is rated 35 A → flagged. Reference: NEC 210.19(A) / 215.2(A); PEC 2017 Sections 2.10.19 and 2.15.2.

2. What ampacity table does Flares use?

NEC 310.16 @ 75°C, copper and aluminum, single conductor in raceway. 75°C matches the terminal rating on most consumer breakers, lugs, and inverters; NEC 110.14(C) / PEC 1.10.14(C) cap usable ampacity at the lowest-rated terminal, so the 90°C column on THHN/THWN-2 insulation usually doesn't buy you anything.

3. NEC 75°C ampacity table

Source: NFPA NEC 2023, Table 310.16. The same values appear in PEC 2017 Table 3.10.1.16 with the size column in mm².

4. AWG vs mm², quick reference

Filipino suppliers usually sell cable by metric cross-section (ASTM B258 nominal areas). Quick crosswalk for popular sizes:

• AWG 14 → 2.08 mm² (≈ 2.0 / 2.5 mm² PNS)
• AWG 12 → 3.31 mm² (≈ 3.5 mm²)
• AWG 10 → 5.26 mm² (≈ 5.5 mm²)
• AWG 8 → 8.37 mm² (≈ 8.0 mm²)
• AWG 6 → 13.3 mm² (≈ 14 mm²)
• AWG 4 → 21.2 mm² (≈ 22 mm²)
• AWG 2 → 33.6 mm² (≈ 38 mm²)
• AWG 1/0 → 53.5 mm² (≈ 50 mm²)
• AWG 2/0 → 67.4 mm² (≈ 60 / 70 mm²)
• AWG 3/0 → 85.0 mm² (≈ 80 / 100 mm²)
• AWG 4/0 → 107.2 mm² (≈ 100 / 125 mm²)

Note: locally-sold "approximate" cables (3.5 / 5.5 / 8.0 mm²) often run 10–20% under the stated cross-section. If you buy these, derate one size when sizing against the table.

5. How does Flares size breakers?

For each breaker the rule splits connected neighbors at the breaker's own port direction: upstream = source, downstream = load. Required amperage is max(source capacity, summed downstream load) × 1.25. Outlets count as a max (their amperage IS the breaker rating they pair with), and multiple loads on one breaker are summed. Reference: NEC 240.4 / 210.20; PEC 2.40.4 / 2.10.20.

6. Why is my solar array flagged as undersized?

SOLAR-UNDERSIZED (warning) is a daily energy budget. The engine sums every panel's wp × count, multiplies by 5 PSH (peak sun hours, conservative for the Philippines), and compares against the sum of every AC load's w × duty% × 24h. It fires when array output is more than 15% short of daily load — the battery drifts down over time. The 15% tolerance absorbs modeling noise, so only real shortfalls fire.

7. Why 2/0 cable for a 3500 W / 24 V inverter?

DC input current = 3500 W / 25 V (LiFePO4 nominal) ≈ 140 A. NEC continuous derate × 1.25 = 175 A required ampacity. From the table: 2/0 Cu = 175 A (at the limit), 3/0 Cu = 200 A (comfortable), 4/0 Cu = 230 A (long runs / high ambient). Doubling battery voltage halves DC mains current: the same inverter at 48 V draws ~73 A and only needs AWG 2 (115 A). That's why most off-grid 3 kW+ builds go to a 48 V bank.

8. What's still not enforced?

The validator is a sanity check, not a permit-ready design. Not yet enforced:

• NEC 310.15 ambient-temperature correction (a PH attic ≥ 35°C drops a column).
• Conduit fill derating (4+ current-carrying conductors → 80%).
• Voltage-drop limit (3% branch, 5% combined) is computed but not a hard rule.
• GFCI / AFCI requirements aren't modeled (ground bonding is).
• Motor branch 250% breaker rule (NEC 430.52).

A licensed electrician / PEE / REE will catch what we miss.

9. References

• NFPA, NEC (National Electrical Code) home
  www.nfpa.org
• IIEE, Philippine Electrical Code 2017 (PDF)
  iiee.org.ph
• Meralco, Solar Net Metering (Residential)
  www.meralco.com.ph
• NREL, PVWatts methodology
  www.nrel.gov
• ASTM B258, AWG ↔ mm² standard
  www.astm.org