PEC Cable Sizing
A practical walkthrough of what each part of a PEC ampacity table actually represents, for anyone reading one for the first time.
An ampacity table can look like a wall of numbers the first time you open one. Here's what each part actually represents.
Lists the standard commercially available conductor cross-sections (in mm² under PEC) — always cross-sections that are actually manufactured and stocked, not arbitrary intermediate values.
Different insulation materials (PVC, XLPE, and others) have different maximum operating temperatures, which changes the base ampacity for the same conductor size — always confirm which insulation type's column you're reading from.
Ampacity depends heavily on how the cable is installed — in conduit, on a tray, buried, or in free air — since each method dissipates heat differently. A table is typically organized (or cross-referenced) by installation method, and using the wrong method's figures produces a wrong result even with the correct conductor size and insulation type selected.
Whatever ampacity the table shows is the starting point before temperature and grouping derating are applied — never treat the raw table value as the cable's real, usable capacity in your specific installation.
OhmWorks applies all of these lookups and corrections automatically — see the breakdown in the PEC Cable Sizing calculator.
Engr. Jason Morales — Founder, SolarEnergyPH & OhmWorks