1. Calculation formula for wire cross-sectional area (wire distance/voltage drop/current relationship)

Copper wire S=IL ÷ (54.4 × U) Aluminum wire S=IL ÷ (34 × U),  I-Maximum current flowing through the conductor (A); L-conductor length (m); U-allowable pressure drop (V); S-cross-sectional area of conductor (mm2).

2. Basic knowledge of wires and cables

1. One bundle length of electric wire: 100 meters, with a positive and negative error of 0.5 meters;  2. Wire model: BV single strand, BVR multi strand, BVV double glue single strand, BVVR double glue multi strand;  3. Common specifications of electric wires: 1 square meter/1.5 square meters/2.5 square meters/4 square meters/6 square meters/10 square meters, etc;  4. BV/BVR difference: BV is a single core wire, BVR is multi-stranded, and BVR is about 10% more expensive than BV;  5. Advantages of BVR over BV: a. Convenient water and electricity construction. b. It is not easy to break the wire during bending;6. Load current value of electric wire specified in national standard GB4706.1-1992/1998 (partial).  7. Home circuit design: Before 2000, the circuit design was generally 4-6 mm2 for incoming lines, 1.5 mm2 for lighting, 2.5 mm2 for sockets, and 4 mm2 for air conditioning. After 2000, the circuit design is generally 6-10mm2 for incoming lines, 2.5mm2 for lighting, 4mm2 for sockets, and 6mm2 for air conditioners.  8. Wire weight: 1.5 square meters weighs approximately 2.2 kilograms, 2.5 square meters weighs approximately 3.2 kilograms, 4 square meters weighs approximately 4.8 kilograms, and 6 square meters weighs approximately 6.5 kilograms.  9. The packaging label for multi-stranded wires (1 square, 1.5 square) with an area of 2.5 square meters or less is BV (B), and for single wires, it is BV.  10. Wire colors include: red, yellow, blue, green, black, yellow green (ground wire).