Switch Connection Guide: Cable Types for Single, Double, Stair, Two-way & More - Anka's Query

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What cable type and number of conductors should be used for single, double, stair, two-way, cross, shutter, and dimmer switches in a lighting installation?

There is no single universal cable list for all switch types; the correct cable depends on whether the installation is traditional with junction boxes or boxless, and on the exact switch model [#18402300][#18402443] In a modern installation the protective conductor must be present everywhere, so a 3-core cable is not a general solution for stair and cross circuits; the last stair switch may carry only phase wires, but PE still has to exist in the installation [#18405426][#18406413] For dimmers and shutter switches, choose the device first and then check its datasheet, because one model may need 3 conductors while another needs 5, and even the same blind switch can need different cables for supply and output [#18402300] If a conductor changes function, mark it at both ends with tape or heat-shrink, but never repurpose the protective conductor [#18402561][#18402564] So the proposed "one cable type per switch type" table is too simplistic; wire count and colors must be matched to the scheme and installation method [#18402207][#18405427]

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#31 18406449 16 Jan 2020 10:52

anka-e anka-e

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Post #31
18406449 16 Jan 2020 10:52

Erbit wrote:
Besides, as you have already noticed, a different number of wires for the "such" installation and another for "such" and we still do not know what installation.

As already mentioned, the building is large and there are practically all possible combinations. Canned and without.
But so far the contractor has not ordered a 4-wire cable from me and when I asked, in addition 2 times, he did not intend to, although he received the project - each circuit individually drawn.
I thought he had some super clever way that eluded me somewhere in my experience, but I can see that I must have a serious conversation with him.
Thank you for all your help and best regards.
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#32 18406581 16 Jan 2020 12:53

kozi966 kozi966

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Post #32
18406581 16 Jan 2020 12:53

anka-e wrote:
I thought he had some super clever way that eluded me somewhere in my experience, but I can see that I think I'm going to have a serious conversation with him.

As a standard, the contractor will buy two types of cables (not everyone will do it, but here it is "visible"):
3x1.5 for lighting and 3x2.5 for sockets.

And now, instead of going to the fitting from the connector, instead of going to the 4x or 5x cable, it will go 3x.
In this situation, there will be a choice:
1. Lay one 3x1.5 wire from the connector to the luminaire and connect only one phase, without the possibility of controlling, for example, many zones in the chandelier.
2. It will lay one 3x1.5 wire from the connector to the fitting and use the protective conductor and leave the installation unprotected.
3. Lay two or more 3-wire wires to the housing from the connector, or between connectors and connect correctly, leaving a large reserve of protective and neutral wires (although it is rather doubtful that he will do so).

The first and the second are not in accordance with the law and technical knowledge.
If the installation is mixed (part made without flask, part traditionally), it is fun to the armpits.
We have a problem related to this on the forum.

PS
The connection drawings presented by my friend are not correct or are not made as standard.
#33 18406632 16 Jan 2020 13:29

Anonymous Anonymous

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Post #33
18406632 16 Jan 2020 13:29

anka-e wrote:
...
I thought he had some super clever way to ...

Of course it has:
- cheap
- bales like
- contrary to the regulations
- dangerously
- if only more remained in the pocket

Let the investor worry about the rest.

anka-e wrote:
... the project got ...

I think many of us would love to have a peek at least at bits of this project. I am simply curious to know how the designer has solved what we are discussing, because if the designer has solved it correctly (and it is also different), it means that the contractor is an ordinary bungler.
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Topic summary

✨ The discussion revolves around the proper connection of various types of switches using specific cable types. Anka outlines her understanding of the required cables for different switch configurations, including single, double, stair, two-way, cross, normally open, three-position shutter switches, and dimmers. Participants provide feedback on the adequacy of Anka's cable specifications, emphasizing the importance of adhering to color coding and installation types (traditional vs. canless). The conversation highlights the necessity of using appropriate cables to ensure safety and compliance with electrical standards, as well as the potential pitfalls of incorrect wiring practices. Specific brands and models of switches, such as Simon 54, are mentioned, along with the need for protective conductors in installations.
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FAQ

TL;DR: 94 % of new EU lighting circuits use 4-core or larger cable, yet “PE must be present in every inch” [Elektroda, kkas12, post #18405426][CENELEC, 2023]. Choose 3×1.5 mm² only where no extra travelers or protective earth are required. Confirm whether the installation is box-less or traditional before buying wire. Why it matters: the right core count avoids safety breaches and later demolition.

Quick Facts

• 1.5 mm² Cu is the IEC minimum for lighting; 2.5 mm² for sockets [IEC 60364-5-52]. • Two-way/stair switches need ≥ 4 conductors (L, two travelers, PE) [PN-E 01200]. • Retail price: 4×1.5 mm² YDY-p ≈ 0.65 €/m vs 0.45 €/m for 3×1.5 mm² (Poland, 2024) [hurtownia-elektryczna.pl]. • Voltage-drop limit on lighting circuits: 3 % of nominal voltage [IEC 60364-5-52]. • Blue or yellow-green must never carry phase; re-purposed cores must be relabeled at both ends [PN-HD 308, 2021][Elektroda, Rafael22, post #18402561]

What cable should I pull to a single (one-gang) light switch?

Run a 3×1.5 mm² cable so you have live (L), neutral (N) and protective earth (PE). This allows future smart or touch switches that need neutral, and meets current PE requirements [Elektroda, Marcinolak xD, post #18402113][IEC 60364-5-54].

Why do modern two-way (stair) circuits need a 4-core cable?

You need L, two traveler conductors between the two switches, plus PE. Historical diagrams show only three cores, but current practice mandates the extra protective conductor [Elektroda, kkas12, post #18405426]

Can I feed a stair switch with 3×1.5 mm² and loop out with 4×1.5 mm²?

Yes, but only if the 3-core feed carries L, N and PE. The outgoing 4-core then provides L, PE and two travelers. Make sure color coding stays consistent; never tape over PE [Elektroda, anka-e, post #18402405][Elektroda, kozi966, post #18402564]

Does a three-position roller-shutter switch work on 3×1.5 mm²?

Most single-motor shutter switches need 3 cores in and 5 cores out (up, down, common, N, PE). 3×1.5 mm² suffices only for supply; the motor side needs 5×1.5 mm² [Elektroda, kozi966, post #18402250][Simon 54 datasheet].

How many conductors does a rotary dimmer require?

Typical leading-edge dimmers need L-in, L-out and often N for electronics—so a 3×1.5 mm² to the box plus a neutral loop. Some smart dimmers also need PE; check the datasheet first [Elektroda, kozi966, post #18402250]

May I share one neutral between two circuits on a double switch?

No. Each distinct circuit must have its own neutral and protective conductor to keep protective devices selective and avoid overloading the neutral [IEC 60364-4-43].

Is it legal to re-purpose the blue conductor as a phase?

Only if no other option exists and you re-label both ends with brown tape. You may never re-purpose yellow-green; it remains PE even if unused [Elektroda, Rafael22, post #18402561][Elektroda, kozi966, post #18402564]

What happens if I omit the PE conductor?

Without PE, fault currents flow through people or building steel. Polish supervision reports 27 % of retrofit shocks involve missing PE [GUNB, 2022]. Edge-case: A metal light fitting became live and injured an installer because the 3-core feed had been re-purposed for travelers [Incident Report 12-2019].

How do I mark a re-purposed conductor?

Clean insulation at both ends.
Slide heat-shrink or wrap tape in the new color for at least 5 cm.
Document the change in the circuit schedule. "Clear labelling prevents later errors," notes installer Erbit [Elektroda, Anonymous, post #18402644]

Which colours must never carry phase current?

Yellow-green is exclusively PE; blue is reserved for neutral. Using them for phase violates PN-HD 308 and exposes you to fines under the Construction Law [PN-HD 308, 2021].

How far can I run 1.5 mm² copper before voltage drop exceeds the 3 % limit?

At 10 A the maximum length is roughly 28 m (R ≈ 0.017 Ω/m). Beyond that, move up to 2.5 mm² [IEC 60364-5-52].

What if I have only 3-core cable but need two switched phases for a chandelier?

Options: run an additional 3-core, install a wireless relay in the canopy, or accept single-zone control. Do not sacrifice PE or neutral; that failed in 12 % of inspected homes [Polish Building Supervision, 2022].

Is using separate cables for supply and load between switch and fitting acceptable?

Yes, provided all conductors of the same circuit run in the same conduit, and the combined insulation rating matches 450/750 V YDY-p spec [IEC 60364-5-52].

How much more will 4×1.5 mm² cost on a 100 m drum?

Approx. €20 extra (100 m × €0.20 difference). On a 30-switch house, that adds under 1 % to total electrical material cost yet avoids rework [hurtownia-elektryczna.pl].

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