Subpanel & Feeder Sizing for North Bay Industrial Facilities

By matching the feeder to the total load its subpanel serves — the sum of the connected loads with the code-required demand and continuous-load factors applied — and to the distance it runs. The conductor must safely carry that current and keep voltage drop within limits over the run. Undersizing causes overheating and nuisance trips; oversizing wastes money. It starts with an honest load assessment of everything the subpanel will feed, present and planned, which is the industrial equivalent of a residential load calculation and the foundation of correct sizing.

Because voltage drops as current travels along a conductor, and industrial facilities are large enough that feeders often run long distances — far enough that the drop becomes significant. If a feeder isn’t upsized to compensate, equipment at the far end receives less voltage than it should, causing poor performance, overheating, and premature wear. So the feeder’s size depends not just on the load but on how far it travels to reach the subpanel. Accounting for voltage drop over the run is a real, code-relevant part of sizing, not an optional refinement.

Undersized feeders overheat under load, trip protective devices, and can’t support the equipment they feed — constraining operations and creating safety risks. Worse, correcting undersized feeders in an operating facility is expensive and disruptive, often requiring re-pulling conductors through conduit and coordinating around production. That’s why sizing them correctly, with appropriate headroom, from the start matters so much. An undersized distribution system becomes a chronic bottleneck that limits what the facility can run and forces costly rework precisely when the business wants to grow, not shrink.

Enough to accommodate realistic growth without over-building wastefully — the right headroom depends on your plans. Facilities commonly add equipment, production lines, or new loads like forklift and EV charging over time, and sizing feeders and subpanels with room for that foreseeable growth is far cheaper than re-pulling feeders later. The goal isn’t to double everything speculatively, but to look at your likely expansion and electrification plans and build distribution that won’t need replacing the moment you add a machine. An electrician can right-size headroom against your actual growth outlook.

Near the loads they serve. Placing subpanels close to the equipment and areas they feed keeps feeder runs shorter (reducing voltage drop and cost), keeps each area’s capacity organized and accessible, and simplifies maintenance and future changes. Poor placement — subpanels far from their loads — means long runs, tangled circuiting, and harder troubleshooting. Good distribution planning treats subpanel placement as part of the facility layout, so power is available where the work happens with sensible, well-labeled feeders. It’s a design decision that pays off throughout the facility’s life.

Yes, though it requires planning to minimize disruption. Adding subpanels, upsizing feeders, or reorganizing distribution in a running facility means coordinating around production — scheduling shutdowns of specific areas, phasing the work, and maintaining safety throughout. It’s more involved than doing it in new construction, but it’s routine industrial work when a facility has outgrown its distribution or is adding significant load. We assess the existing system and the new demand, plan the upgrade to fit your operations, and execute it as permitted, code-compliant work with as little impact on production as the scope allows.