Voltage drop sa tuloy-tuloy na load: 125%, laki ng wire, NEC/IEC
Pag-size ng EVSE, ilaw, at heater bilang tuloy-tuloy na load.
Ang tuloy-tuloy na load ay nagpapanatili ng kuryente nang ilang oras. Ang 48 A EVSE, 18 A lighting run, o 36 A heater ay kailangang suriin sa init at totoong voltage drop.
Buod
- 3 hours or more makes the load continuous in NEC practice.
- 125% sizing and voltage-drop calculation answer different questions.
- Use branch, feeder, and total voltage-drop budgets together.
- EVSE, lighting, heaters, and ventilation loads need sustained-current checks.
Ang tuloy-tuloy na load ay load na maaaring tumakbo sa maximum current nang 3 oras o higit pa. Ang voltage drop ay boltahe na nawawala sa impedance ng conductor. Ang ampacity ay pinapayagang current nang hindi lumalampas sa temperature rating.
Unahin ang 125% kung kailangan ng NEC 210.20(A), 215.3 o 625, pagkatapos kalkulahin ang drop gamit ang totoong sustained current, haba, materyal ng conductor at feeder budget. NEC and IEC references keep the thermal and performance checks separate.
The 125% continuous-load rule is a heat and protection rule; it does not erase the resistance of a 150-foot branch circuit.
— Hommer Zhao, Technical Director
Continuous-load design checks
Ang 48 A EVSE sa 240 V ay madalas na 60 A circuit. Sa 6 AWG copper at 165 ft one-way, ang branch drop ay mga 2.6%; kung may 1.8% sa feeder, total ay halos 4.4%.
| Load | Sustained current | NEC basis | Route | Design action |
|---|---|---|---|---|
| Level 2 EVSE | 32 A at 240 V | 40 A circuit | 130 ft | Compare 6 AWG Cu |
| High-output EVSE | 48 A at 240 V | 60 A circuit | 165 ft | Check feeder plus branch |
| LED lighting row | 18 A at 277 V | 125% review | 240 ft | Split row or upsize |
| Process heater | 36 A at 208 V | 45 A design current | 110 ft | Check 6 AWG and source |
| Exterior lighting | 12 A at 120 V | 15 A basis | 95 ft | Use 10 AWG or split |
For a 48-amp EV charger, document the 60-amp circuit sizing and check voltage drop at the sustained charging current.
— Hommer Zhao, Technical Director
Practical warning
Ang 125% rule ay para sa init at proteksyon, hindi para alisin ang resistance ng mahabang wire.
Use the wire size calculator, the NEC requirements article, and the voltage drop vs ampacity guide together before material is released.
Continuous loads turn small voltage-drop misses into daily operating losses because the circuit stays loaded for hours.
— Hommer Zhao, Technical Director
FAQ
¿Calculo al 100% o al 125%?
Use la corriente sostenida real para caída de tensión y el 125% para dimensionamiento cuando NEC lo exige.
¿Un cargador EV es carga continua?
Sí. NEC 625 trata el EVSE como carga continua; 32 A suele requerir 40 A y 48 A suele requerir 60 A.
¿Qué objetivo uso en iluminación?
3% en rama y 5% total son objetivos comunes; líneas LED largas van mejor cerca de 2-3%.
¿Cuándo subo calibre?
Cuando la ruta es larga, el alimentador ya usa cerca de 2% o el equipo trabaja más de 3 horas.
¿Cómo se compara IEC?
IEC 60364-5-52 coordina corriente de diseño, método de instalación, agrupamiento, temperatura y caída permitida.
Ihambing ang minimum wire at susunod na sukat bago maghila ng kable.
Start Calculating
Ready to apply these concepts to your project? Use our professional voltage drop calculator.
Open Calculator