Setting your power source and running Auto-size

Written By Kelson Reiss

Last updated 14 days ago

Required role: Member · Tier: Base

A Power Source is needed for both SLD and Auto-size. Your Power Source is usually the most upstream distribution equipment (for example, the utility transformer).

Setting your power source

  1. In the top toolbar, click Power source.

  2. Click the marker that represents the utility connection.

Each electrically separate circuit needs its own power source. The next circuit lights up after you assign one.

If a new connection joins two circuits that already have power sources, a Multiple Power Sources Detected dialog opens. Pick the one to keep.

Build your layout first

Auto-size needs a complete electrical chain to work from. Make sure the design includes:

  • A power source (usually the utility transformer or service entrance)

  • Any distribution equipment between the source and the loads (sub-panels, switchgear, additional transformers)

  • The panel or switchgear that feeds the chargers

  • The chargers themselves, or any other loads to size

Each piece needs to be its own marker on the map.

One run per pair of items. Draw a separate line for each pair you're wiring together. To go transformer → panel → charger, that is two runs (transformer to panel, then panel to charger), not one shared line through all three. If a run is missing or shared across more than two items, Auto-size will not know what feeds what.

Running Auto-size

⚠️ Note: Auto-size is not widely available yet. We are rolling it out soon to all customers as a beta feature. You may not see it in your app yet.

  1. Click Auto-size system on the Design map. The button reads Auto-sizing… during the run.

  2. The assistant panel opens and tracks progress: a pre-flight check, equipment sizing, then wire and conduit sizing.

  3. Sized values appear on equipment and runs, and the assistant posts an explanation along with any voltage or phase mismatches it found.

Re-run Auto-size system after any design change to re-size against the new configuration.

Wire and conduit sizing

After equipment sizing, every run in the chain is sized too:

  • Wire from NEC copper ampacity tables (75°C), upsized to keep voltage drop under 3%. Large feeds split into parallel conductor sets
  • Ground wire per NEC 250.122
  • Conduit sized for fill: EMT indoors, PVC Schedule 40 outdoors

Numbered badges on the map match each run to its line in Auto-sizing Results (for example Wire: 2× #3 Cu, Ground: #6 Cu, Conduit: 2" PVC SCH40). Green values changed in this run; gray values were already set.

A conduit/wire assembly is created and assigned to each sized run. Sizing uses built-in NEC tables, so it works before the parts are in your price book. To add a missing part, open the run and click Add missing wire to pricebook or Add missing conduit to pricebook.

Runs that already have an assembly are validated instead of resized. The results list the assembly by name, and anything that fails validation appears under Attention needed.

If Auto-size cannot run

Pre-flight stops the run and points to what to fix:

  • No power source on a circuit. Assignment mode opens with the affected circuit highlighted. Click a marker on it, then re-run.

  • Power source is missing required fields. Click a listed field to jump to the marker.

  • A load is not fully characterized. Open the highlighted marker and fill in voltage, phase, or rated power.

  • Existing equipment is missing fields. Equipment marked as on site still needs enough detail to size around.

  • No downstream loads. Add at least one load and connect it to the circuit.

  • Items share a run. Each pair of items needs its own conduit/wire run. For transformer → panel → charger, that is two runs (transformer to panel, then panel to charger), not one shared line. Draw the missing runs and re-run.

  • Missing equipment in the chain. Auto-size cannot infer a panel that is not on the map. Add any distribution gear sitting between the source and the loads, wire it in, and re-run.

Tips

  • A voltage mismatch usually means a transformer belongs between the source and the mismatched loads, not a setting change on the load.

  • Auto-size only fills blanks. Pin any value (e.g., a specific breaker size) by typing it in and re-running.

See the full flow

This one-minute demo shows the complete journey: laying out a site, running Auto-size, and generating the SLD.