Check cable runs

A distro that "has room" still trips when the cable to it is too thin or too long. PowerSense compares each run with guideline values three ways: whether the breaker in front of it can protect it, whether the current stays within the cable's rating after derating, and the voltage drop over its length.

Add and configure a run

1. In Cable runs, press + Add run. Each list starts with one run called Feed.
2. Give it a Label (for example Feed → stage-left distro).
3. Current (A) defaults to auto: worst phase — the highest phase current of this list, after the safety margin. Type a value instead for a sub-run that carries only part of the load; clear the field to go back to auto.
4. Enter the Length — metres, or feet in North America mode.
5. Choose the Cross-section (mm²) or AWG gauge.
6. Set Protected by to the breaker in front of this run. It defaults to the feed's breaker; a sub-run plugged into a 16 A output of a distro is protected by that 16 A breaker.
7. Set System to 1-phase or 3-phase — what this cable actually is. The feed run on a 3-phase feed starts as 3-phase, every other run as 1-phase.
8. Say how the cable is laid: on a drum (none, one layer left on it, or two and more), bundled with other circuits, and a hot day (30 °C and more, or 40 °C and more). The card then shows the rating after derating next to the base value.

Read the verdicts

On a list fed by a generator the drop limits are 6 % (warning) and 8 %.

The base ratings are guideline values for flexible rubber cable (H07RN-F / SOOW) in free air. In Europe mode they run from 1.5 mm² (16 A) to 35 mm² (100 A). In North America mode they follow NEC Table 400.5(A)(1): a 3-phase run uses the column for three current-carrying conductors, AWG 14 (15 A) to AWG 2 (80 A); a 1-phase run the column for two, AWG 14 (18 A) to AWG 2 (95 A). Derating then lowers the rating for a drum, bundling or heat.

How the drop is calculated

• 1-phase: ΔU = 2 · ρ · L · I ÷ A, against the phase voltage.
• 3-phase, balanced: ΔU = √3 · ρ · L · I ÷ A, against the line voltage.
• 3-phase, uneven: the drop is also taken on the most loaded phase, line to neutral, and the larger value counts.
• ρ is copper at operating temperature — 1.25 × the 20 °C value of 0.0175 Ω·mm²/m — because a loaded cable is warm.

LED, switch-mode and the neutral

LED fixtures and switch-mode supplies draw current in short pulses. Their third harmonics do not cancel in the neutral of a 3-phase run; they add up, so a perfectly balanced LED rig can put as much current on the neutral as on a phase, or more. Mark a list mostly LED / switch-mode and PowerSense warns about it and rates the run's cable lower (× 0.86; in North America mode 80 % of the three-conductor value, because the neutral then counts as a current-carrying conductor). It does not size the neutral — that is the electrician's call.

The feeder rule of thumb

Under the runs, a hint reads Feed rule of thumb: X A per phase → min Y. It is derived from the same table as the check, for the feed's phase count, so the hint and the check agree on the feed run. Above the preset range it reads Feed above the preset range — have the electrician engineer the feeder. That is not a limitation to work around; it is the point where a professional designs the feeder.

What the run check does not cover

PowerSense does not check whether a fault trips the breaker fast enough (loop impedance and disconnection time), RCDs, earthing, the condition of connectors and sockets, or how the cable is really laid on site. A Schuko socket is also not meant for 16 A for hours — plan about 10 A continuous on one.