BROADCASTS.com

b'

In this short podcast, Bryan covers a common electrical myth about wire length and its relationship with the National Electrical Code. The NEC is concerned with safety\\u2014protecting buildings and people\\u2014but less so with making sure things work.

Wire sizing is a common topic, and length is important because it can contribute to the voltage drop in a circuit. In many cases, we refer to the MCA (minimum circuit ampacity) to select an appropriate wire size.\\xa0

If you run more current through an undersized conductor, it gets hotter and will experience a voltage drop\\u2014though not proportionally. It\\u2019s worth noting that nothing in the circuit is fixed; voltage, amperage, and resistance all follow Ohm\\u2019s law but are variable as different things start happening in a circuit.

In many cases, the NEC generally doesn\\u2019t require us to size conductors to accommodate for voltage drop. Conductors have some degree of resistance, so longer wires will result in a greater voltage drop than you would see in a shorter wire. It makes sense for the wire to overheat, but that won\\u2019t happen because the greater resistance in the circuit will reduce the current. There is less work being done.

Longer wires and circuits that are sized correctly shouldn\\u2019t overheat or present a safety issue. The NEC recommends but does not require voltage drop to stay below 5% across a conductor. That is a performance recommendation, not a safety concern. We need equipment to perform correctly, but NEC won\\u2019t prevent electricians from setting up branch circuits that are longer than the ideal length. Excessively long branch circuits are common in commercial structures, and it\\u2019s up to HVAC technicians to notice that and measure the voltage drop to make sure it\\u2019s not negatively affecting the equipment.\\xa0

\\xa0

If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE.

Check out our handy calculators HERE.