1. Introduction
The SMTONOFF SMT21008 is an all-in-one smart IoT device designed for AC 230V/400V, 50/60Hz, single or three-phase circuits. It integrates electricity consumption measurement, prepayment options, remote control, and comprehensive protection features. This device allows for smart management of electrical systems in residential, commercial, and industrial settings via a 2.4G WiFi connection.
Key functionalities include:
- Remote control and monitoring via mobile app (Tuya Smart, Smart Life).
- Voice control compatibility with AI speakers (Amazon Alexa, Google Assistant, Yandex Alice).
- Programmable timing control for efficient energy management.
- Adjustable protections against over/under voltage, overcurrent, residual current (leakage), and high temperature.
- Auto-reclosing feature for non-attended operation after transient power issues.
- Prepaid metering functionality (optional).
- Local manual control without WiFi connectivity.
- Device sharing capabilities for family or team members.
2. Important Safety Warnings
Please read and understand these warnings before installation and operation to prevent injury or damage.
- This device is designed for three-phase electricity systems. Do NOT use it in single-phase electricity for long-term operation.
- The device features phase loss protection. All phases (N, L1, L2, L3) MUST be connected for proper functionality.
- For single-phase testing ONLY, connect N + L1 + L2 + L3. This configuration is not for continuous use.
- The prepaid function is OFF by default. If enabled, ensure the device is recharged, otherwise, it will not turn on. The default password for prepaid settings is 1234.
- If the prepaid function is enabled and you forget to recharge, you can either turn off the prepaid switch in the 'Expense' section of the Tuya Smart app or charge energy within the app.
- If the protector trips 3 times due to leakage, it will NOT auto-reclose until the fault is manually fixed by the user to ensure safety.
3. Specifications
| Feature | Detail |
|---|---|
| Brand Name | SMTONOFF |
| Model Number | SMT21008 |
| Communication Method | Wi-Fi (2.4G) |
| State of Assembly | Ready-to-Go |
| Poles | Three Phase 4P |
| Rated Voltage | AC 3x230V/400V (Over/Under Voltage Protection Adjustable) |
| Rated Current | 1~100A (Adjustable) |
| Frequency | 50/60Hz |
| Resistive Load Capacity | ≤13kW |
| Inductive Load Capacity | ≤6kW |
| Self-consumption | <2W |
| Mounting | 35mm DIN-rail |
| Certifications | CE, FCC, RoHS |
| Origin | Mainland China |
Dimensions
Figure 3.1: Product dimensions (approx. 127mm height, 90mm width, 67mm depth).
4. Package Contents
The package typically includes:
- SMTONOFF SMT21008 Smart Circuit Breaker
- WiFi Antenna
- User Manual (this document)
5. Installation
This device is designed for 35mm DIN-rail mounting. Ensure all power is disconnected before installation.
Wiring Diagrams
Proper wiring is crucial for safe and correct operation. Refer to the diagrams below for typical installations.
Figure 5.1: Application in a standard AC system (3 phase 4 wire).
Figure 5.2: Application in an AC + PV system (Bi-directional meter).
Antenna Installation
Attach the provided antenna to the device to ensure stable signal reception for Wi-Fi connectivity. The antenna is designed for 360-degree rotation and 90-degree tilt for optimal positioning.
Figure 5.3: Antenna attachment and flexibility.
Testing in Single Phase (Temporary Only)
This wiring is for device testing only in a single-phase system, not for long-term work. The device operates with a 3 phase 4 wire system normally.
Before testing, all input terminals N, L1, L2, L3 must be connected as shown in the picture below. If one of the terminals is not connected, the device will not work and Wi-Fi pairing may fail due to its open-phase protection.
Figure 5.4: Single-phase test wiring diagram.
6. Setup and Pairing
Follow these steps to set up your SMTONOFF Smart Circuit Breaker and connect it to the Tuya Smart app.
- Download and Install the App: Download and install the 'Tuya Smart' or 'Smart Life' app on your mobile device from your app store. Register an account if you don't have one.
- Power On and Enter Pairing Mode: Power on the protector. After a time delay countdown, the Wi-Fi signal indicator should flash fast to enter pairing mode. If it doesn't enter pairing mode automatically, long-press the 'down' key (triangle pointing down) for a few seconds until the Wi-Fi signal indicator flashes fast.
- Add Device in App: Open the Tuya Smart app. The app should automatically detect the new device. Tap 'Add' to proceed.
- Connect to Wi-Fi: Enter your 2.4G Wi-Fi network name and password when prompted in the app. Tap 'Next'.
- Completion: Once connected, the device will be added to your app. Tap 'Done'.
Figure 6.1: Tuya Smart App device adding process.
Figure 6.2: Device indicators and control buttons for pairing.
Video Tutorial: App Pairing and Control
Video 6.1: A short demonstration of connecting the device to the Tuya Smart app and basic control.
7. Operating Instructions
The SMTONOFF Smart Circuit Breaker offers multiple control methods and advanced features.
Control Options
You can control your device using four primary methods:
- Remote Control: Use the Tuya Smart or Smart Life mobile app from anywhere with an internet connection.
- Voice Control: Integrate with AI speakers like Amazon Alexa, Google Assistant, or Yandex Alice for hands-free operation.
- Timing Control: Set schedules for automatic on/off operations via the mobile app.
- Manual Control: Operate the device directly using its physical buttons and handle.
Figure 7.1: Remote control via mobile app.
Figure 7.2: Voice control with AI speakers.
Figure 7.3: Timing control for scheduled operations.
Figure 7.4: Manual control of the device.
Prepaid Metering Function
The device supports an optional prepaid metering mode. This function is off by default. To enable or disable it, navigate to the 'Expense' section in the Tuya Smart app. The default password for prepaid settings is 1234.
If prepaid mode is enabled, you must charge energy to the device, otherwise, it will not turn on.
Figure 7.5: Prepaid metering settings in the Tuya Smart app.
8. Adjustable Protections
The SMTONOFF Smart Circuit Breaker provides adjustable protection thresholds for various electrical conditions. These settings can be configured via the Tuya Smart app.
Figure 8.1: Adjustable protection settings in the Tuya Smart app.
- Overcurrent Protection: Adjustable range 1~100A (default: 63A).
- Over Voltage Protection: Adjustable range 250~400V (default: 275V).
- Under Voltage Protection: Adjustable range 90-210V (default: 110V).
- Residual Current (Leakage) Protection: Adjustable range 10~100mA (default: 50mA).
- Alarm Temperature Protection: Adjustable range 50~90℃ (default: 60℃).
- Tripping Temperature Protection: Adjustable range 60~100℃ (default: 70℃).
- Recovery On-Delay Time: Adjustable range 5~90s (default: 30s). This setting is done manually on the device by keys, not in the app.
Auto-Reclosing
The device features auto-reclosing to achieve non-attended operation. It automatically recovers after power failure or unexpected transient abnormal conditions to ensure uninterrupted power supply and save labor. However, for leakage protection, if the protector trips 3 times, it will not auto-reclose until the fault is manually fixed.
Figure 8.2: Auto-reclosing functionality.
Leakage Protection
The device provides leakage protection to safeguard your family and appliances from electrical hazards.
Figure 8.3: Leakage protection for household safety.
9. Electricity Consumption Monitoring
Monitor real-time electricity consumption and view statistics directly on your mobile phone through the Tuya Smart app. The app displays current (A), voltage (V), active power (kW), energy consumption (kWh), and temperature (℃).
The device also supports bi-directional metering, measuring positive active energy from the grid and negative active energy from solar PV systems.
Figure 9.1: Visible consumption and energy statistics in the app.
Figure 9.2: Bi-directional metering for solar PV systems.
10. Maintenance
The SMTONOFF Smart Circuit Breaker is designed for minimal maintenance. Regularly check for any visible damage or loose connections. Ensure the device is kept in a dry, well-ventilated area, free from excessive dust or moisture. For cleaning, use a dry, soft cloth. Do not use abrasive cleaners or solvents.
11. Troubleshooting
- Device not powering on:
- Ensure all phases (N, L1, L2, L3) are correctly connected. The device has phase loss protection.
- If the prepaid function is enabled, ensure sufficient energy balance. Recharge if necessary.
- Wi-Fi not connecting / LED not blinking:
- Ensure your Wi-Fi network is 2.4Ghz.
- Long-press the 'down' key on the device for a few seconds until the Wi-Fi signal indicator flashes fast to enter pairing mode.
- Verify your Wi-Fi password in the app.
- Device trips frequently:
- Check the set thresholds for overcurrent, over/under voltage, and leakage current in the app. Adjust if they are too sensitive for your load.
- If tripping due to leakage (RCD), and it trips 3 times, the auto-reclosing feature will be disabled. You must manually identify and fix the leakage fault before re-enabling the device.
- Monitor the temperature readings in the app; high temperatures can cause tripping.
- RCD (Residual Current Device) cannot be turned off:
- The RCD functionality is a critical safety feature and cannot be permanently disabled. If it's causing frequent trips, investigate the electrical network for leakage faults.
12. User Tips
- Always ensure all phases are connected, even for testing, to avoid issues with phase loss protection.
- If using the prepaid function, keep track of your energy balance to prevent unexpected power cuts.
- Familiarize yourself with the adjustable protection settings in the Tuya Smart app to customize the device's behavior according to your specific electrical environment and load requirements.
- For optimal Wi-Fi signal, ensure the antenna is properly installed and positioned.
13. Warranty and Support
For warranty information, technical support, or service inquiries, please contact your retailer or the manufacturer directly. Keep your purchase receipt as proof of purchase.