FAQ - about Shelly device features

The Shelly Bypass (R2) is recommended in cases where there is no neutral wire and the load is less than 20W. It is compatible with the first-generation Shelly 1L and the Shelly Dimmer2 devices, ensuring flicker-free operation and reliable performance for your smart home setup. The Shelly Bypass (R2) is sold separately and not included in the relay package, though it may be available in promotional bundles.

For newer third-generation devices like the Shelly 1L Gen3 and Shelly 2L Gen3, the Bypass (R3) is required, which is included in the relay box and differs from the R2 version.

Ensure that the motor runs on AC power and is actively consuming current. For best results, control each shutter with a separate Shelly device. If calibration fails, adjust the open/close time:

If multiple motors are connected to one module, disconnect all but one during calibration.

Devices still respond immediately when temperature or humidity thresholds are crossed.

Yes, Bluetooth is not only for pairing but, once Bluetooth gateway is enabled, the relays can also be controlled via Shelly Bluetooth remotes or wireless switches.

Technically possible but not recommended, as it reduces measurement accuracy and system reliability.

Yes, but only with the Shelly UNI device.

Yes, you’ll need a Shelly UNI or Shelly Plus Add-on, connected to a Shelly Plus 1/1PM/2PM/I4, and a compatible voltage-output moisture sensor.

Yes, with Shelly EM devices using current transformers, which support four-quadrant measurement (consumption and generation).

Yes, using a reed switch connected to the "SW" input or with a Shelly Plus 1 and Plus Add-on.

No, only 120A CTs are supported. Each transformer is calibrated to a specific port.

No, Shelly devices are not compatible with dimmable switches.

Not recommended; they can cause inaccurate readings.

Only on/off is supported. Speed control is not possible, even with Dimmer2.

No, using different phases or voltages can cause immediate device failure. All PM devices are strictly single-phase.

No, only Shelly Pro devices support LAN/Ethernet.

Yes, Shelly Pro series features an RJ45 port and supports LAN connectivity.

No, only 3V batteries are safe. Higher voltage may damage the device.

No, the "dry contact" function is not suitable for use as a transformer.

No, maximum is 16A. For over 20A loads, use an external contactor.

Yes, current voltage is shown in the app. Historical voltage data can be downloaded from the web UI.

No, all 'EM' devices require a neutral wire.

Yes, via the "Range Extender" function (disabled by default).

Most cannot, but exceptions include:

These are for lighting control only.

Only Shelly BLU temperature and humidity sensor is outdoor-capable.

No, it requires a compatible relay (like retrofit Shelly relays).

No, it works like a relay output (max 24VAC or 36VDC, 100mA, 300mW).

For switching small loads:

All Shelly relays. It’s recommended for inductive loads like motors or fans.

Depends on your router. Each device connects as a separate host, so ensure your router supports enough connections.

Up to 5 pcs of DS18B20 sensors.

They stay in sleep mode; a low-power secondary processor monitors sensors and wakes the main CPU if needed.

Options:

Yes, but an SNTP server is needed for time sync. Devices still work over local network.

Not recommended. Sudden power cuts may shorten lifespan.

Use Shelly PM or EM devices for energy monitoring combined with window status sensors to set push notification alerts.

An optocoupler, for connecting a 230V AC switch to the device.

The PCB may reach 55–60°C without load. At 95°C, overheat protection shuts it down. To reduce heat:

Most often due to incorrect wiring. Check wire connections and CT installation.

Use Shelly EM / Pro EM / 3EM with an external contactor.

Yes, using HTTP commands or Scenes, even without internet.

Yes, it auto-switches to USB and disables battery power.

Verify if a schedule or scene is set in the mobile app.

Install an RC snubber between the output and neutral to suppress voltage spikes.

It means input and switched circuit voltages can differ. See wiring guide in the Shelly Knowledge Base.

PWM signal at 1 kHz frequency.

Due to frequent power loss or rapid switching. Solution:
Disable “Factory reset from switch” in device settings.

Depends on model: options include battery, 12V DC, 24–60V DC, or 110–230V AC. Check the product page for exact specs.

Yes, data is stored locally and downloadable as CSV.

These are input-only devices without a relay. App button reflects switch state.

Measurements occur every minute. If change is <0.1°C, only the display updates. Larger changes also update the app.

Night Mode requires constant power. Don’t cut power via switch.

Relays/Controllers:

Battery sensors:

Use Gen2/Gen3 devices with custom scripts. Examples on GitHub:

Scripts fetch price data and toggle loads accordingly.

No, once overwritten, original Shelly firmware cannot be restored.

Typical for inductive/capacitive loads. Use Shelly Pro 1PM for more accurate measurement near the device.

Yes:

Yes, via app or web UI (Auto On/Off). Use scenes, webhooks, or scripts for complex timers.

No, it’s for indoor use only. Not waterproof and battery life is reduced outdoors.

No, this feature is not currently supported.

No. Only compatible with Shelly Plus (Gen2), Gen3, Gen4 Wi-Fi retrofit devices. Compatibility list:
​https://kb.shelly.cloud/knowledge-base/shelly-plus-add-on