FAQ
TL;DR: Two-way (staircase) control needs 3 working conductors; "There. 4 wires will be enough." Use 5‑core to include PE and N; if your 3‑core includes blue or yellow‑green, use a bistable relay with bell pushes instead. [Elektroda, elpapiotr, post #19589478]
Why it matters: This helps DIYers and renovators wire safe, compliant staircase switches or choose a clean workaround when cabling is wrong.
Quick Facts
- Yellow‑green is PE only and blue is N; don’t use them as travelers between switches. [Elektroda, stanislaw1954, post #19589433]
- Compliance‑friendly plan: run five‑core between boxes (three working conductors plus N and PE). [Elektroda, zbich70, post #19589453]
- With only 3‑core and wrong colors present, fit a bistable relay (e.g., Zamel) and two bell‑push switches. [Elektroda, piwko, post #19591013]
- Label first: identify power feed, lamp lead, and interconnect before wiring anything. [Elektroda, Tadek67, post #19589440]
- You can control three lamps from three locations using two‑way and cross switches. [Elektroda, elpapiotr, post #19589478]
How do I wire two staircase switches with supply, lamp, and a cable to the second switch?
Use two SPDT staircase switches and two traveler conductors between them. Keep neutral and PE out of the switches. How‑To: 1. Label supply (Z), lamp (L), and interconnect. 2. Connect supply L to COM on switch A; link A’s two travelers to B’s two travelers. 3. Connect COM on switch B to the lamp’s switched line; join neutrals and PEs together, not to the switches. [Elektroda, Tadek67, post #19589518]
Which conductor colors are allowed between switches?
Do not use yellow‑green (PE) or blue (N) as travelers. Those colors are reserved and must keep their functions. Use phase‑colored cores for travelers only. If your interconnect includes blue or yellow‑green, change the cable or use a relay solution. [Elektroda, stanislaw1954, post #19589433]
What cable should run between switch boxes to stay compliant and flexible?
Run a five‑core cable between the boxes. That provides three working conductors plus neutral and protective earth. It aligns with good practice and avoids misusing reserved colors during two‑way wiring or later changes. [Elektroda, zbich70, post #19589453]
I only have a 3‑core between boxes; can I still get two‑way control?
Yes—use a central bistable relay with two momentary bell switches. “A bistable relay, e.g., Zamel, and two monostable so‑called bell switches.” Each press toggles the light, so color limits no longer block you. [Elektroda, piwko, post #19591013]
How do I identify supply, lamp, and interconnect safely?
Before any connections, determine which cable is the power feed, which goes to the lamp, and which links to the other box. Mark them clearly. This prevents mistakes and simplifies correct two‑way wiring. [Elektroda, Tadek67, post #19589440]
Can I re‑mark blue or yellow‑green to use as live?
Never repurpose yellow‑green. Blue should remain neutral. Masking with markers or heat‑shrink is called bungling and should be condemned. Replace the cable or adopt a relay approach to stay safe and consistent. [Elektroda, zbich70, post #19589566]
What goes wrong if I wire colors incorrectly?
Using blue or yellow‑green as live misleads future work. It increases shock risk and violates color‑code rules. Keep travelers on phase‑colored cores and reserve blue and yellow‑green for neutral and PE only. [Elektroda, stanislaw1954, post #19589433]
How can I control multiple lamps from multiple places?
Combine two‑way and intermediate (cross) switches. Example: two staircase switches with cross switches between them. Statistic: three lamps can be controlled from three places as shown in the shared setup. [Elektroda, elpapiotr, post #19589478]
Is using markers or heat‑shrink an acceptable permanent fix?
You can mask miscolored cores with marker or heat‑shrink, but it remains a botch. It is not a compliant remedy. Replace cabling and respect reserved conductor colors for a lasting solution. [Elektroda, zbich70, post #19589533]
Developer installed the wrong cable—what recourse do I have?
Document the issue and request correction. Forum guidance suggests demanding or threatening replacement at the installer’s expense when reserved colors are misused. This motivates proper remediation. [Elektroda, zbich70, post #19589566]
Do you have a clear diagram for the standard two‑way connection?
Yes. Follow the diagram showing supply into switch A, two travelers to switch B, and the switched line from B to the lamp. It clarifies terminal roles and conductor paths. [Elektroda, Tadek67, post #19589518]
Why did someone call this layout an “error in art”?
Because the inter‑switch cable included cores reserved for PE and N. That violates good practice and complicates correct two‑way wiring of the staircase circuit. [Elektroda, elpapiotr, post #19589424]
Can anything be done without ripping out wires?
Yes. Install a bistable relay and use two bell‑push switches. This avoids abusing reserved colors and gives reliable two‑point control with limited cabling. [Elektroda, piwko, post #19591013]
Do I even need staircase switching here?
Verify your real need before rewiring. The original poster decided it was optional and closed the topic after finding a simpler solution. Confirm the use case first. [Elektroda, cmik21, post #19592093]
