Amperage (Amps)

Understanding Amperage

Amperage calculations are fundamental to safe LED wall installation. Incorrect sizing causes tripped breakers, overheated cables, and potential fire hazards. Getting it right requires understanding the relationships between power, voltage, and current.

Basic Electrical Formula

**Ohm's Law for Power:** P = V × I (Power = Voltage × Current)

Rearranged for current: I = P ÷ V (Current = Power ÷ Voltage)

Single Phase Calculations

**Formula:** Amps = Watts ÷ Volts

**Example:**

• LED wall: 8,000W maximum
• Voltage: 208V
• Current: 8,000 ÷ 208 = 38.5A
• Circuit needed: 50A (80% rule)

Three Phase Calculations

**Formula:** Amps per phase = Watts ÷ (Volts × √3)

**Example:**

• LED wall: 12,000W maximum
• Voltage: 208V three-phase
• Current: 12,000 ÷ (208 × 1.732) = 33.3A per phase
• Circuit needed: 50A three-phase

Wire Gauge Requirements

Current determines minimum wire gauge:

| Amps | Copper Gauge | Distance Limit | |------|--------------|----------------| | 15A | 14 AWG | 50 ft | | 20A | 12 AWG | 50 ft | | 30A | 10 AWG | 50 ft | | 50A | 6 AWG | 50 ft | | 100A | 3 AWG | 50 ft |

*Longer runs require larger gauge*

Circuit Breaker Sizing

**NEC 80% Rule:** Continuous loads (>3 hours) must not exceed 80% of breaker rating.

**Calculation:** Required breaker = Load amps × 1.25

**Example:**

• Calculated load: 32A
• Minimum breaker: 32 × 1.25 = 40A

Power Factor Considerations

**Real vs. Apparent Power:** LED power supplies have power factor <1.0, meaning they draw more current than simple calculations suggest.

**Adjustment:** True amps = Calculated amps ÷ Power Factor

**Example:**

• Calculated: 40A
• Power factor: 0.9
• Actual draw: 40 ÷ 0.9 = 44.4A

Common Voltage References

**North America:**

• 120V single phase (residential)
• 208V single/three phase (commercial)
• 480V three phase (industrial)

**International:**

• 230V single phase (common)
• 400V three phase (common)

Best Practices

**Always Calculate Maximum:** Use full power specs, not average.

**Add Safety Margin:** 20% headroom beyond breaker 80% rule.

**Verify On-Site:** Measure actual voltage—it varies.

**Document Everything:** Record circuits, loads, and distribution.

Troubleshooting

**Tripping Breakers:**

• Load exceeds rating
• Check actual consumption
• Rebalance phases
• Upgrade circuit if needed

**Voltage Drop:**

• Long cable runs
• Undersized wire
• Causes brightness variation
• Use larger gauge or shorter runs