how to install electrical disconnect box
The following are the detailed steps for installing an Electrical Disconnect Box, which are applicable to the scenarios of **disconnecting
outdoor equipment** (such as air conditioners, water heaters) or **disconnecting the main circuit**, taking into account both safety
and compliance:
I. Preparation before Installation
1. Determine the Type and Specifications
- **Type**:
- **Waterproof type** (IP54/IP66): It is a must for outdoor equipment, made of metal or plastic.
- **Non-waterproof type**: Only used in dry indoor environments.
- **Specifications**:
- Ampere rating: Match the power of the equipment (for example, 10-20A for air conditioners, 30-50A for water heaters).
- Number of poles: 2 poles for single-phase (live wire + neutral wire) or 3 poles for three-phase.
- Size: Select according to the number of circuit breakers (single pole/double pole).
2. Material List (Taking a Single-phase 20A as an Example)
| Material | Domestic Reference Specifications | Reference Price (￥) |
| Waterproof disconnect box | Plastic/Metal, IP66 | 80–200 |
| Circuit breaker (air switch) | 2P 20A, C-type trip | 30–80 |
| Copper-core wire | BV 4mm² (live wire/neutral wire) | 10/m |
| Ground wire | BVR 4mm² (yellow-green two-color) | 8/m |
| Insulating tape, expansion screws | - | 20–50 |
II. Step-by-step Installation Process
Step 1: Cut off the Power and Test for Electricity
- **Cut off the power supply**:
Turn off the upper-level circuit breaker (such as the corresponding circuit in the main distribution panel), and **test for electricity
with a multimeter** to confirm there is no voltage.
- **Note**: If it involves disconnecting the main power supply, you need to contact the power supply company to cut off the
power (such as replacing the disconnect box of the electricity meter box).
Step 2: Positioning and Fixing
- **Installation location**:
- It should be within ≤1.5 meters from the equipment (such as beside the outdoor unit of an air conditioner), and at a **height
of 1.5–1.8 meters** for easy operation.
- Avoid areas with moisture, high temperature, and direct sunlight.
- **Fixing method**:
- **Surface-mounted on the wall**: Fix the back panel of the box with expansion screws (for plastic boxes, the base needs to
be pre-embedded first).
- **Embedded installation**: Groove the wall, fix the pre-embedded box with cement, and make the surface flush with the
wall.
Step 3: Wiring Operation
**Taking a single-phase equipment disconnect box as an example (220V):**
1. **Inlet terminal**:
- Live wire (red): Connect to the left side of the upper port of the circuit breaker.
- Neutral wire (blue): Connect to the right side of the upper port of the circuit breaker.
- Ground wire (yellow-green): Connect to the grounding terminal of the box.
2. **Outlet terminal**:
- Connect the live wire/neutral wire to the lower port of the circuit breaker and connect it to the equipment.
- **Note**:
- Strip the wire ≤10mm and fix it with a crimping cap or terminal.
- For multi-strand flexible wires, tinning or using cold-pressed terminals is required.
Step 4: Install the Circuit Breaker and Test
1. **Circuit breaker installation**:
- Snap the circuit breaker into the guide rail inside the box and fix it with screws.
2. **Function test**:
- After closing the switch, use a multimeter to measure the voltage at the outlet terminal (220V±10%).
- Open the switch and use an electroscope to confirm that the inlet terminal is charged and the outlet terminal is not charged.
Step 5: Sealing and Marking
- **Waterproof treatment**:
- Seal the inlet hole with a **waterproof rubber ring** and apply waterproof silicone to the edge of the box cover.
- **Marking**:
- Use a marker pen to mark the purposes such as "Air conditioner disconnect" and "Emergency power off".
III. Key Points of Domestic Compliance (GB 50169-2016)
1. **Grounding requirements**:
- The metal box must be connected to the **PE wire**, and the grounding resistance ≤4Ω.
2. **Wire color**:
- Live wire: Red/Brown; Neutral wire: Blue; Ground wire: Yellow-green two-color.
3. **Distance limitation**:
- The horizontal distance between the disconnect box and the gas pipeline should be ≥0.3 meters, and ≥0.1 meters
from the water pipe.
4. **Qualification requirements**:
- For disconnecting the main circuit or above 200A, it needs to be operated by a **licensed electrician**, and in some areas,
it is necessary to file with the power supply bureau.
IV. Common Problems and Solutions
| Problem | Cause | Solution |
| The circuit trips after closing the switch | The ampere rating of the circuit breaker is too small | Replace it with a circuit breaker of a larger specification |
| There are water droplets in the box | The waterproof rubber ring is aging | Reapply waterproof silicone |
| There is no voltage at the outlet terminal | The wiring is loose or open-circuited | Check the terminal screws and test with the continuity file of a multimeter |
V. DIY vs Professional Installation
- **Suitable for DIY**:
Disconnect box for single-phase equipment (≤32A), surface-mounted, and with an electrical foundation (power off
operation is required).
- **It is recommended to find an electrician**:
Disconnecting the main power supply, three-phase circuit, embedded installation, or involving circuit modification.
**Summary**: The installation cost of a common single-phase disconnect box is approximately **￥200–500** (including
materials and labor). The key steps are **cutting off the power → positioning → correct wiring → testing for waterproofing**.
When operating, be sure to follow local regulations to ensure safety.
