circuit·IEC 60617·electrical, residential·complexity 2/3·since v0.1.0
Two-way stair light
A correct two-location lighting circuit using two SPDT switches and a pair of traveler conductors, with a fused live feed and neutral return.
For the electrical installer
circuit·§ IEEE 315
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Scenario
A stair or hallway lamp must be operable from either end. That requires a changeover switch at each location and two traveler conductors between them; two ordinary on/off switches in series do not provide the same behavior.
Annotation key
- Both
S1andS2usetype=switch_spdt, exposing one common and two throws. traveler_aandtraveler_bconnect the two throws of the switches.feedis the fused live common onS1;switchedis the lamp-side common onS2.L1 ... type=lampuses a load-appropriate designator and the lamp symbol.
How to read
Each switch selects one traveler. The lamp is energized when both switches select the same continuous path and de-energized when they select different paths, so changing either switch changes the lamp state. Neutral returns directly from the lamp to the source on the lower rail.