A 20 kW (kilowatt) heat strip's amperage draw depends directly on the voltage at which it operates. This relationship is a fundamental principle in electricity, defined by the power formula.
For a common single-phase 230 Volt circuit, a 20 kW heat strip will pull approximately 87 amperes.
Understanding the Calculation for Amperage
The current (amperage) drawn by an electrical device can be calculated using the power formula. For a single-phase alternating current (AC) circuit, the formula is:
P = V × I
Where:
Pis Power in watts (W)Vis Voltage in volts (V)Iis Current in amperes (A)
To determine the current (I), you can rearrange the formula:
I = P / V
Since 1 kilowatt (kW) is equal to 1000 watts, a 20 kW heat strip consumes 20,000 watts.
Amperage at 230 Volts
Using the formula for a 20 kW (20,000 W) heat strip operating on a 230 Volt, single-phase circuit:
I = 20,000 W / 230 V ≈ 86.95 Amperes
When rounded, this is approximately 87 Amperes.
Amperage at Other Common Voltages
Heat strips are designed to operate at various voltages depending on their intended application, from residential to commercial settings. Here's how the amperage for a 20 kW heat strip changes with different common single-phase voltages:
| Voltage (V) | Power (kW) | Power (Watts) | Calculation (I = P/V) | Amperage (A) (Approx.) |
|---|---|---|---|---|
| 208 | 20 | 20,000 | 20,000 W / 208 V | 96.15 A |
| 230 | 20 | 20,000 | 20,000 W / 230 V | 87 A |
| 240 | 20 | 20,000 | 20,000 W / 240 V | 83.33 A |
Note: While larger commercial heat applications might use 480V or three-phase power, the most common calculations for heat strips in HVAC systems often pertain to 208V, 230V, or 240V single-phase systems.
For further information on the fundamental relationship between electrical power, voltage, and current, you can refer to resources on Electric Power.
Key Considerations for Heat Strip Circuits
Working with high-amperage heating elements like a 20 kW heat strip requires careful attention to electrical safety and code compliance:
- Circuit Breaker Sizing: Electrical codes, such as the National Electrical Code (NEC) in the United States, typically require that circuits serving continuous loads (those operating for 3 hours or more, like heat strips) be sized at 125% of the calculated full-load current.
- Example: For an 87 Amp load at 230V, the minimum breaker size would be 87 A * 1.25 = 108.75 A. This would typically require the next standard circuit breaker size up, such as a 110 Amp or 125 Amp breaker, provided the wire is also adequately sized.
- Wire Gauge: The electrical wiring connecting the heat strip to the power source must be appropriately sized to safely carry the maximum current without overheating. Higher amperage demands thicker wires (indicated by a lower American Wire Gauge (AWG) number). Always consult wire sizing charts specific to your wire type, insulation, and ambient temperature.
- Nameplate Information: Always refer to the heat strip's manufacturer nameplate. This label provides the exact voltage requirements, wattage, and rated amperage, which are the most accurate specifications for the specific unit.
- Professional Installation: Due to the significant power draw and potential safety hazards associated with high-voltage and high-amperage electrical work, the installation or servicing of a 20 kW heat strip should always be performed by a qualified and licensed electrician. This ensures compliance with local electrical codes and maximizes safety.
