LZWSM16-1 switch wiring: S1 to L or COM?

User question

Can I connect the switch between s1 and line voltage instead of s1 to com?

Artificial Intelligence Response

Direct answer to the question

No — for the LZWSM16-1, the wall switch should be wired between S1 and COM, not between S1 and line (L). The manufacturer’s wiring diagram shows L as the mains live input, L1 as the switched output to the load, and the external switch connected only across COM and S1. (dwn.alza.cz)

Key points:

• L is the module’s line/live power input. (dwn.alza.cz)
• COM and S1 are the manual switch terminals in the published diagram. (dwn.alza.cz)
• The manual explicitly says to connect wires according to the wiring diagram and that installation should be done by a qualified electrician. (dwn.alza.cz)

Detailed problem analysis

From the official LZWSM16-1 manual:

• The product is a “1Gang Zigbee Switch Module No Neutral.” (dwn.alza.cz)
• The English manual includes a single-control wiring diagram where:
  • mains L goes to terminal L,
  • the lamp/load is connected via L1,
  • and the physical switch is drawn only between COM and S1. (dwn.alza.cz)

That means, electrically, the device is expecting the external switch to act as a contact closure on its designated control terminals, not to inject mains live into S1 from outside the documented path. (dwn.alza.cz)

As an engineering judgment:

• If the manufacturer wanted S1 to sense mains live directly, the diagram would normally show the switch tied to L, as many other smart modules do.
• Here, it does not; it shows a distinct COM terminal for the switch loop. (dwn.alza.cz)
• Therefore, wiring the switch to L instead of COM would be an unsupported wiring change.

So the safe answer is:

• Do not substitute L for COM unless the manufacturer explicitly states that COM is internally tied to L and interchangeable.
• In the documentation I found, it does not state that interchangeability. (dwn.alza.cz)

Current information and trends

For this model, the currently available manual still shows the same terminal usage:

• LZWSM16-1 with terminals L, L1, COM, S1 in the no-neutral version. (dwn.alza.cz)
• The manual warns: “Do not connect the neutral line, otherwise it will be permanently damaged.” That reinforces that this device has a specific internal topology and should not be rewired by analogy to other smart switches. (dwn.alza.cz)

Industry trend note:

• Some smart modules use dry-contact-style switch inputs (COM + S1).
• Others use line-sensing inputs where one side of the switch is tied to L.
• They are not interchangeable designs, even if the terminal names look similar.

Supporting explanations and details

Think of it this way:

• L = power input to run the module.
• L1 = controlled output to the lamp.
• COM/S1 = user input pair for the wall switch, according to this unit’s diagram. (dwn.alza.cz)

If you move the switch from COM to L, you are no longer following the documented sensing method. Best case, it may not work properly; worst case, it may damage the module or create an unsafe condition. That latter point is an engineering risk inference based on unsupported mains rewiring, not a direct quoted statement from the manual. (dwn.alza.cz)

Ethical and legal aspects

• This is mains-voltage wiring, so shock and fire risk are real.
• The manual requires installation by a qualified electrician in accordance with local regulations. (dwn.alza.cz)
• Deviating from the manufacturer’s wiring diagram can also affect code compliance, insurance, and product liability.

Practical guidelines

Best practice:

1. Power off at the breaker before touching any conductors. (dwn.alza.cz)
2. Wire:
   • supply live to L
   • load to L1
   • wall switch between COM and S1 (dwn.alza.cz)
3. Do not replace COM with L unless you have a manufacturer document explicitly permitting it.
4. If your existing wall box only has a line-switched loop and not a separate conductor for COM, the correct solution is usually:
   • rework the wiring, or
   • use a module specifically designed for line-referenced switch sensing.

Possible disclaimers or additional notes

• I did not find documentation stating that COM is internally the same node as L.
• Therefore I cannot recommend treating them as equivalent.
• One of your sample “online” answers appears to describe a different product family (Shelly-style line-sensed inputs), so it should not be applied to this LZWSM16-1 wiring question.

Suggestions for further research

If you want, send:

• a photo of the module label,
• a photo of the printed wiring diagram on the device,
• and a photo or sketch of the wires in your wall box.

Then I can tell you whether your specific installation can be adapted safely, or whether you need a different module.

Brief summary

For the LZWSM16-1, do not connect the switch between S1 and line voltage. The published wiring diagram shows the switch connected between S1 and COM, while L is a separate mains input terminal. Follow that diagram exactly. (dwn.alza.cz)

If you want, I can also help you map your existing house wires to L, L1, COM, and S1.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.