Requirements for Grounding Wires in Container Houses

The grounding wires in container houses must meet the following requirements:

I. Situations Requiring Grounding

If electrical equipment (such as air conditioners, lighting, sockets, etc.) is installed inside a container house, the metal structure must be grounded for lightning protection and electrical safety to avoid the risk of electric leakage. According to national standards:

• GB 50303-2015 specifies that the grounding resistance of temporary metal-structured buildings must be ≤10Ω;
• GB 50169-2016 clarifies that for mobile buildings (including container houses), the grounding resistance should be ≤4Ω in humid environments and ≤10Ω in dry environments.

II. Selection of Grounding Materials

• Grounding Electrodes: It is recommended to use 40mm×4mm galvanized flat steel or round steel with a diameter ≥10mm (in accordance with GB/T 21431-2015). Alternatively, galvanized steel pipes or angle steel with a thickness of 5 cm can be used.
• Connecting Wires: Yellow-green bicolored copper wires with a cross-sectional area of more than 4 square millimeters must be used. For repeated grounding, the cross-sectional area of copper conductor wires must be ≥16mm², and aluminum conductor wires must be ≥25mm² to prevent fusing due to excessive current.

III. Depth and Construction of Grounding Electrodes

• Ordinary Areas: Grounding electrodes must be buried 2.5-3 meters underground, avoiding frozen soil layers. In areas prone to thunderstorms, they must be dug 4-12 meters deep until they reach groundwater.
• Areas with High Soil Resistivity: The depth of grounding electrodes should be ≥0.6 meters, and resistance-reducing agents should be added to lower the resistance.
• Construction Requirements:
  • Must be operated by professional electricians to avoid loose connections or rusting.
  • At least two grounding electrodes must be buried, spaced 3-5 meters apart and ≥1.5 meters from the house.
  • The metal frame of the container must be firmly welded, and the door must be grounded separately. Welding points should be painted with anti-rust paint.
  • Grounding terminals must be welded at the bottom, and connection points must be treated for corrosion resistance. After burying the grounding electrodes, bolts must be used to tighten the contact area to ≥100mm².
  • When stacked, all containers must be grounded in parallel to avoid potential differences. In humid environments (such as coastal areas), copper-clad steel grounding rods should be used to enhance corrosion resistance.

IV. Inspection and Maintenance

• Regular Inspection: The grounding resistance must be inspected every six months (once in spring and once in autumn), with a focus on inspection before the rainy season each year. Connection points with severe corrosion must be replaced promptly.
• Testing Conditions: Inspections must be conducted after three consecutive dry days following non-rainy weather to avoid inaccurate data. Simply using a multimeter for measurement is inaccurate; a professional grounding resistance tester (such as the Fluke 1625) must be used.
• Corrosion Protection: The welding points between the grounding electrodes and the house must be coated with anti-corrosion materials such as asphalt to extend their service life.