Calculation Method of Monitoring Engineering Wire and Auxiliary Materials

In the process of making the plan, we often encounter wire configuration such as: wire length calculation, wire selection, pipe groove selection, etc. According to the above problems, we have sorted out the wire configuration method.

Cable Length Estimation

The cable length estimation is divided into two cases: with drawings and without drawings:

1. There are drawings

Find out the direction of the line on the drawings and determine the location of the monitoring room; if it is a building project, the distance and location of the offline well of the monitoring room should be determined.

The general wiring principle of engineering construction is to walk in a straight line and try not to bend as much as possible. The longest line length of a single gun is generally based on the length and width of the building area plus the sum of the offline length of the monitoring room and the reserved line at the front end.

The standard calculation length of a line is: the front-end gun is reserved for 1.5 meters, the rear end from the ceiling to the ground, that is, the vertical distance from the ceiling to the monitoring cabinet, generally 3.5 meters, and the monitoring cabinet is reserved for 2 meters (for short-distance movement of the cabinet) In this way, the length of the reserved line for a gun is 1.5+3.5+2=7 meters, and then the total length of the line is calculated according to the length dimension marked in the actual environment of the drawing.

The building is 40 meters long and 30 meters wide, and the monitoring center is in the middle of the room, then the length of the A line is 40 meters + 15 meters (half the width of 30 meters) + 7 meters (reserved line) = 62 meters, but according to the engineering department The actual work experience also needs to go through cable corners, turns, etc. during the wiring process. Generally, it will increase by 15% on the basis of the original length, that is, 62*10%=10 meters, then the actual length of A is 62 meters + 10 meters = 72 meters Meter.

The length of the cable for B is 10 meters + 15 meters + 7 meters = 32 meters, plus 15%, the total length of the cable for B is 37 meters, then the two guns each prepare 110 meters of 75-3 video cable, RVV2*0.5 power cable , RVVP3×0.5 monitoring line is enough, the length of the pipe groove is the same as the length of the cable.

2. No drawings

In the absence of drawings, it is necessary to obtain the basic information of the outlet from the business, such as building height, area, location of line wells and other basic information. Then estimate the vertical length according to the floor height (general floor height is 3.5 meters, the first floor is 7 meters high), and then calculate the approximate total length of the cable according to the lateral distance of the off-line well of the cabinet.

3. Elevator wiring

If there is an elevator in the wiring of the building, the floor from which the cable enters the elevator should be calculated according to the following formula: floor ÷ 2 + 1, and the calculated result is the actual number of floors. For example, in a 16-story building, 16÷2+1=9 should be connected to the elevator at the 9th floor.

Choice of cable type

Video lines generally use 75-3 and 75-5 lines, as well as special lines such as a few elevator special lines. The 75-3 video transmission distance is generally 200 meters, and the 75-5 transmission distance is generally 400 meters. The power cord is selected according to the actual situation.

At present, the power supply distance of 24V and 12V transformers commonly used by the company cannot exceed 50 meters, and a single transformer can supply 6 pieces, with a maximum of 7 pieces. The power consumption of a single branch is generally 5-12W, and the selection of RVV2*0.5 two-core wire is sufficient.

Power Cord Diameter Quick Lookup Table

What type of wire should be used? First of all, it is necessary to determine which layer the front-end equipment is mainly concentrated on. If the wiring distance is more than 50 meters and the number of guns is large, the power line can be wired by bus, and the transformers should be placed in the front-end equipment. inside the box.

The maximum current load of 3*.075 wire diameter is 4A by querying the power line diameter quick reference table, one is calculated according to the power consumption of 10W, and the number of guns available for a 3*0.75 wire diameter power supply line is 88. The calculation formula: 4A*220V/10W=88 pieces. Conversely, according to this formula, you can calculate how thick the 88 wires need to be 10W*88/220V=4A, and then check the comparison table 4A, the wire diameter is 3*0.75.