JS Power's own belt-pouch quick reference — ampacity, voltage drop, conduit fill, box fill, bend multipliers, motor & transformer math, protection maps — 14 dense sections, each with a worked example. Read Section 1 free.
Jason Mohoska · Owner-Operator, JS Power LLC
Licensed Pennsylvania Home Improvement Contractor · PA HIC #PA166735
Serving Pittsburgh & Western Pennsylvania
Section 01
Ohm's law & the power wheel
Four quantities run everything: E (volts), I (amps), R (ohms), P (watts). Know any two, the wheel gives you the rest.
E = I × R · I = E ÷ R · R = E ÷ I
Ohm's law — volts, amps, ohmsP = E × I · P = I² × R · P = E² ÷ R
Power (watts). For AC loads with power factor: P = E × I × PFThree-phase power: P = 1.732 × E(line) × I(line) × PF
kVA = 1.732 × E × I ÷ 1000. Watts = kVA × PF × 1000.
✎ Worked example
A 1,500 W space heater on 120 V: I = P ÷ E = 1500 ÷ 120 = 12.5 A. Its element resistance: R = E ÷ I = 120 ÷ 12.5 = 9.6 Ω. A three-phase motor load drawing 14 A at 480 V with PF 0.85: P = 1.732 × 480 × 14 × 0.85 ≈ 9.9 kW, and kVA = 1.732 × 480 × 14 ÷ 1000 ≈ 11.6 kVA.
Field rule: nameplate watts are what the load wants. The circuit has to supply the amps — always do the division before you plug anything in.
The other 13 sections are yours for $19
Section 1 is free above. The full reference — every table and worked example, printable, yours to keep — unlocks when you order.
🔒 Section 2: Ampacity quick table (copper THHN) with derating example
🔒 Section 3: Voltage drop: quick calc & distance table
🔒 Section 4: Conduit fill quick tables (Chapter 9 math)
🔒 Section 5: Box-fill allowances & box volumes
🔒 Section 6: Bend multipliers, deducts & shrink
🔒 Section 7: Motor nameplate math — FLC, overloads, 430.52
🔒 Section 8: Transformer kVA math & protection overview
🔒 Section 9: Series & parallel quickies
🔒 Section 10: AWG · metric · temperature conversions
🔒 Section 11: Torque values: where the real numbers live
Jason answers directly · Licensed PA HIC #PA166735
About the author
Need an electrician? Call JS Power LLC.
I'm Jason Mohoska, owner-operator of JS Power LLC (Licensed · PA HIC #PA166735), serving Pittsburgh and Western Pennsylvania. 20+ years in the trade. When you call, you deal directly with me: I quote the job, I do the work, and it's done to code.
Licensed Pennsylvania Home Improvement Contractor · PA HIC #PA166735
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