Electrical equipment

Cables, transformers and switchboards, which look alike and are not. Three things decide whether any of it makes money. A cable is sized by whichever of three quite separate requirements binds — the current it carries once derated for hot soil and the circuits beside it, the volts lost down the run, and surviving the short circuit — and the screen names which one decided it, because that is what the consultant argues about. Copper is most of a cable's cost and the price moves daily, so a firm quotation is a position on the metal whether the works meant it or not: the conductor mass is computed from the design and the order book shows what today's copper has done to every job on it. And a buyer with any sense picks a transformer on what it costs to own rather than to buy, so the no-load and load losses are capitalised over the evaluation life and the comparison shows the dearer machine winning, which it usually does. Panels get the same treatment for heat: watts in, surface area, temperature rise, and a refusal to ship a board that will cook its own breakers in August.