On a long run over 100 feet from a low voltage transformer, what size wire would be best suitable?

On a long run over 100 feet from a low voltage transformer, what size wire would be best suitable?

• A. 10-2
• B. 16-2
• C. 18-2
• D. 12-2

Answer: (D)

Voltage drop on long runs in a 12 V landscape lighting circuit is the key factor. The farther a fixture sits from the transformer, the more resistance the wiring adds, so the voltage arriving at the far end decreases. To keep lights bright enough, you want a conductor thick enough to minimize that drop. Wire gauge directly affects resistance: thicker (lower gauge number) wire has less resistance per foot, which reduces the drop for the same current and distance. Over 100 feet, smaller gauges (like 18 or 16) would incur a larger drop and can cause dimming, while a thicker gauge like 12 AWG keeps the voltage within a reasonable range. Although 10 AWG would further reduce drop, it isn’t usually necessary for typical fixture loads and costs more. So, 12 AWG is the practical, best-suited size for a run over 100 feet from a low-voltage transformer.

Voltage drop on long runs in a 12 V landscape lighting circuit is the key factor. The farther a fixture sits from the transformer, the more resistance the wiring adds, so the voltage arriving at the far end decreases. To keep lights bright enough, you want a conductor thick enough to minimize that drop. Wire gauge directly affects resistance: thicker (lower gauge number) wire has less resistance per foot, which reduces the drop for the same current and distance. Over 100 feet, smaller gauges (like 18 or 16) would incur a larger drop and can cause dimming, while a thicker gauge like 12 AWG keeps the voltage within a reasonable range. Although 10 AWG would further reduce drop, it isn’t usually necessary for typical fixture loads and costs more. So, 12 AWG is the practical, best-suited size for a run over 100 feet from a low-voltage transformer.