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パネルサイジングツール

総 負荷 監査

必要な総容量を決定するために複数のデバイスと機械を集約します。パネルサイジングとインフラ計画に不可欠です。

ネットワークデバイスを追加

パネル負荷レジストリ

アクティブ回路レジストリ

まだ負荷が追加されていません。最初のデバイスを定義して開始してください。
総電流
0 A
推奨ブレーカー
0 A

*推奨ブレーカーには125%の連続負荷安全係数が含まれています。

負荷計算式

総負荷は、引き込まれる電流、必要なブレーカー、そして回路が安全なサイズかどうかを決定します。

総回路電流
I = ΣWatts ÷ Voltage

回路上のすべての負荷をワットで合計し、供給電圧で割って総電流需要を求めます。

ブレーカーサイズ(NECルール)
Breaker ≥ Total Amps × 1.25

NECは、連続負荷(3時間以上稼働)がブレーカー容量の80%を超えないことを要求しています — これはブレーカーを負荷の125%でサイジングすることと同等です。

How to Calculate Electrical Load

A load calculation determines how much current a circuit, panel, or service must supply to all connected devices. Accurate load calculations prevent overloaded circuits, nuisance breaker trips, overheated wiring, and fire hazards. They are also required by electrical codes before adding circuits or service upgrades.

The 80% Rule for Continuous Loads

Any load that operates continuously for 3 hours or more is a "continuous load" under the NEC. Continuous loads must not exceed 80% of the circuit breaker's rating. A 20A breaker can sustain no more than 16A of continuous current. This prevents breakers from operating near their thermal limit indefinitely, which reduces reliability and lifespan.

Types of Electrical Loads

  • Resistive Loads: Electric heaters, incandescent bulbs, toasters. PF = 1.0. Current and voltage are in phase — easiest to calculate.
  • Inductive Loads: Motors, fans, compressors, transformers. PF typically 0.7–0.9. Draw additional reactive current beyond what wattage suggests.
  • Capacitive Loads: Certain electronic power supplies and long cable runs. PF leading. Less common in typical building loads.
  • Non-Linear Loads: Variable speed drives, computers, LED drivers. Introduce harmonic currents that can cause overheating in neutral conductors and transformers.

Step-by-Step Load Calculation

  1. List All Loads: Include every device connected to the circuit or panel — lights, outlets, fixed appliances, HVAC, etc.
  2. Note Each Wattage: Use nameplate ratings. For receptacle circuits, NEC allows 180VA per outlet as a standard assumption.
  3. Classify Continuous vs. Non-Continuous: Apply the 80% rule only to loads running 3+ hours continuously.
  4. Sum the Total Amps: Divide total watts by supply voltage to get current. Add motor startup surge separately if needed.
  5. Select Breaker and Wire: Choose a breaker rated above your calculated load (with the 125% rule for continuous loads), and size wire to match using NEC ampacity tables.