OhmZone
Electrical Engineering Toolboard
A working panelboard for the calculations I run all the time — each tool is its own feeder breaker, one click to open it. New feeders get added over time, and existing ones keep getting refined.
Cable Tray Fill
Calculates fill ratio from tray specs and circuit schedule, checks against code-allowed occupancy, with metric/imperial toggle and a design title block.
Voltage Drop
Checks feeder voltage drop under CSA C22.1 — enter system voltage, conductor size and run length to see if it clears the allowed percentage.
Plant Load Single-Line
Plant-wide electrical load allocation as a single-line overview — shows distribution branches and load spread, with sizing recommendations.
Small Transformer — Cable Sizing & Protection
Cable selection and protective device setup for small dry-type transformers — primary/secondary conductor sizing plus overcurrent protection settings.
Motor Circuit — Cable, Protection & Starting Current
Sizes motor branch-circuit conductors, overload and short-circuit protection, and starting current per CSA C22.1 motor tables.
Maximum Short-Circuit Current Study
Estimates maximum available short-circuit current at a bus from source impedance and conductor data, for equipment rating and coordination checks.
Power Factor Correction — Capacitor Sizing
Sizes shunt capacitor kVAR/µF to correct lagging power factor, with a harmonic/resonance risk check and standard bank sizing.
Conduit Fill Calculator
CEC Table 8 raceway fill — individual conductors or whole multiconductor cables, with a project-specific cable schedule built in.
MV Transformer — Primary Cable Sizing
Ampacity, voltage drop and short-circuit thermal withstand for medium-voltage transformer primary feeders — Cu/Al, with or without known protection clearing time.
Battery Bank Sizing
IEEE 485 capacity sizing — multi-period duty cycle, temperature/aging/margin factors, series-parallel configuration and C-rate check.
LV Equipment Cable Selection
Feeder cable sizing to MCC/switchgear/switchboard/panel per CSA C22.1 Tables 1–4 — terminal temperature, 80%/100% breakers, parallel sets beyond 750 kcmil.
Harmonic Emission Assessment
Screening-level harmonic current emission and PCC voltage distortion per CSA C61000-3-6 / Hydro-Québec C.25-01 — device spectra, summation law, resonance check.
Protection Coordination / TCC Study
Log-log time-current curve screening — manual POI fault current (ETAP/EasyPower style), transformer inrush & withstand, generic device curves, custom datasheet points.
Fire Alarm Battery Sizing
Secondary (standby) power calculation per NFPA 72 §10.6.7.2 — 2019/2022 correction factor, device load list, 48h recharge check, UL 1989/2054 reminder.
Fire Alarm Voltage Drop & NAC Load
NAC circuit end-of-line voltage drop per NFPA 72 §18.3.7 — NEC Table 8 wire resistance, CUSTV/UL 464 minimums, NAC loading check, max length solver.
Fire Alarm Audibility & Line Loss
NFPA 72 Ch.18 audibility (public/private/sleeping mode), inverse-square distance attenuation, wall loss, and audio circuit dB loss for 25V/70.7V speaker lines.
Fire Alarm Detector Spacing & Coverage
NFPA 72 Ch.17 smooth-ceiling spacing — 0.7× rule, wall clearance, corridor centerline mode, high-ceiling performance-design flag, to-scale layout diagram.
Next Feeder
Reserved slot — new calculation tools will be wired into this panel over time.