TDLR calculations practice

Why the Calculations part is the one to train

• It is scored separately. 70% on the calc part, on its own, with no help from a strong code score.
• Only 20.56% pass it. The math is not deep, but doing it under a 110-minute clock is.
• The traps are in setup, not arithmetic. Pick the wrong table or the wrong rule and a clean calculation gives a clean wrong answer.

Practice every calc type, one step at a time

Each lesson walks one calculation type. You watch one worked, then solve one yourself step by step. Any line you don’t follow breaks all the way down, so nothing ever appears from nowhere. That is what fixes the “where did that number come from” problem the calc part punishes.

• Voltage DropVoltage drop is the voltage you lose pushing current down a long run of wire. Too much and motors run hot and lights dim.
• Conduit FillConduit fill checks that the wires don't take up more of the pipe than code allows, so they can shed heat.
• Box FillBox fill adds up the cubic inches every conductor, device, clamp, and ground takes up, then checks it against the box.
• Dwelling LoadA dwelling load adds up everything a house can draw, takes the demand discounts code allows, and sizes the service.
• Motor CalculationsMotor wiring sizes off the table full-load current, not the nameplate, and the conductor carries 125% of it.
• Continuous Loads & EVSEA load that runs three hours or more is continuous, and code wants a 25% cushion baked into the conductor and breaker.
• Ampacity & DeratingA conductor's ampacity starts at a table value, then gets knocked down for heat and for crowding it with other current-carrying wires.
• Transformer SizingTransformer current comes straight from the kVA and the voltage. Single phase divides by voltage, three phase divides by voltage times 1.732.

See all calculation lessons →