November 22, 2023

How to calculate wire and auxiliary materials in low current monitoring project proposal list?

ForewordHi everyone, I'm Mr. Lin. In planning process, I often come across wire configurations such as: calculating length of wires, choosing wires, choosing a groove for pipes, etc., according to above questions, we have now sorted out method of setting up wires. Text

How to calculate wire and auxiliary materials in low current monitoring project proposal list?

1. Cable length estimation

Estimation of cable length is divided into two cases: with drawings and without drawings:

1. There are drawings

Find out direction of line on drawing and determine location of observation room, if this is a construction project, you need to determine distance and location of autonomous well of observation room.

The general principle of engineering layouts is to follow nearest straight line and avoid detours whenever possible. The length of furthest line for a single gun usually depends on length and width of building area plus sum of length of offline observation room line and reserved line at front.

The standard calculated line length is: 1.5 meters reserve for front cannon and rear ceiling-to-ground length, which is vertical distance from ceiling to monitoring cabinet, typically 3.5 meters, and leaving 2 meters for observation cabinet. travel distance) So length of line allotted for gun is 1.5+3.5+2=7 meters, and then total length of line is calculated according to length and size marked in actual drawing environment. An example is the following figure:

How to calculate wire and auxiliary materials in low current monitoring project proposal list?

The building is 40 meters long and 30 meters wide, and monitoring center is in middle of room, so length of gun A line is 40 meters + 15 meters (half of width of 30 meters) + 7 meters (reserved line) = 62 meters. However, according to actual experience of engineering department, in wiring process, cable corners, turns, etc. must be passed, and original length is usually increased by 15%, which is 62 * 10% = 10 meters, so actual length of gun A is 62 meters + 10 meters = 72 meters.

The length of wire for gun B is 10 meters + 15 meters + 7 meters = 32 meters plus 15%, total length of wire for gun B is 37 meters, then prepare 110 meters of video 75-3 cables for each of two guns, power cable RVV2 *0.5 and monitor cable RVVP3×0.5 is sufficient, and length of pipe slot is same as length of cable.

2. No drawings

In absence of drawings, it is necessary to obtain basic information about outlets from enterprise, such as building height, area, location of linear wells and other basic information. Then estimate vertical length based on height of floor (total floor height is 3.5 meters and ground floor is 7 meters high), and then calculate approximate total cable length from horizontal distance of cabinet. offline is good.

3. Elevator wiring

If there is an elevator in wiring of building, floor from which cable enters elevator should be calculated using following formula: floor ÷ 2+1, and result is actual number of floors. Let's take a 16-storey building as an example, 16÷2+1=9 should be connected to elevator on 9th floor.

Second, choice of cable type

Video lines typically use special lines such as lines 75-3 and 75-5, as well as a few special lines for elevators. The transmission distance of 75-3 video is usually 200 meters, and transmission distance of 75-5 is usually 400 meters. The power cord should be selected according to actual situation.

At present, power supply distance of 24V and 12V transformers commonly used by company cannot exceed 50 meters, and one transformer can power 6 guns, and maximum number is no more than 7 guns. The power consumption of one cable is usually 5-12W, and it is enough to use a two-core wire РВВ2*0.5, see table below:

How to calculate wire and auxiliary materials in low current monitoring project proposal list?

Quick reference table for power wire diameters

Which type of wire to choose, first of all, it is necessary to determine which layer input equipment is mainly concentrated on. If wiring distance is more than 50 meters and number of guns is large, power line can be connected as a busbar, and transformers are evenly placed. Inside box front end equipment.

By checking power wire diameter quick lookup table, we know that maximum current draw for 3*0.075 wire diameter is 4A, and gun is calculated based on 10W power input and number of guns available for 3*0.075 wire diameter power cord 0.75 is 88, calculation formula: 4A * 220V / 10W = 88 pieces. Conversely, this formula can also calculate how much wire thickness 88 gun needs: 10W * 88/220V = 4A, and then check 4A comparison table, wire diameter is 3 * 0.75.

Third, channel slot selection

The company's commonly used 25¢ PVC pipe can carry 8 video lines 75-3 and 6 lines 75-5; mixed thread can use 5 video lines 75-5 + 1 power line if it is 25¢iron pipe. routing is reduced on original basis (because iron pipe is thicker than PVC pipe).

The location where equipment is concentrated can choose to use main slot. The slot size is determined by number of lines to be placed in main slot. Generally, slot full speed (slot full speed refers to proportion of space occupied by cable once placed in slot) specification requires low current slot full speed to be 40% and high current slot full speed to 50%.

Comparison table of capacity of pipes and cables (we will take five types of lines as an example, other types of lines are similar, you can refer to it)

1. PVC tank (model) 20*10 24*14 39*19 59*22 99*27 99*40100*100

2. Category 5 wires (number) 2 4 9 16 32 48

3. PVC pipe (model) f16 f20 f25 f32 f40 f50

4. Category 5 wires (number of wires) 2 3 6 9 15 24

5. Zinc box (model) 25*25 25*50 25*75 50*50 50*100 100*100

6. Category 5 wires (quantity) 7 15 22 30 60 120

Capacity formula: Pipeline tank capacity = INT (pipe tank area * K). For CAT5UTP, K = 0.012

Example: PVC slot 100*100

Algorithm: 100*100*0.012

Result: 120 roots

Fourth, calculation of auxiliary materials

1. Statistical information scores, including each room and computer room, complete score distribution table;

2. Determine if it is too long? If it is too long, where and how many connection rooms should be equipped? If there is a connection room, number of switches will change accordingly.

3. Determine direction of cause;

4. Determine model and length of each bridge. Calculation method: (length × width) × 0.4/28, result is number of information points, standard bridges are generally used: 300×100, 200×100, 100×100, 100×50, 50×50, other bridges. needs to be configured.

How to calculate wire and auxiliary materials in low current monitoring project proposal list?

Note. If branch cause is of same bridge type, calculate their lengths separately and finally calculate total length of bridge type.

5. Calculation of pipes ø25 and ø20 (usually 6 wires can be laid out for ø25, and 4 wires for ø20). When calculating, take ø20 as a reference, and middle data point needs a length of ø20 from bridge frame to terminal. If it is A, then we can calculate that all data points need a length of ø20, i.e. B=A×(total points/4 ), and in real engineering ø20=2/3×B, ø25=1/3×B.

How to calculate wire and auxiliary materials in low current monitoring project proposal list?

6. Calculation of a steel corner (30×30). Angle steel length = 30cm × (total bridge length m/1.5m), that is, average length of each angle steel is 30cm, and an angle steel is required for every 1.5m of distance.

7. Keel calculation (75×45). Keel length = 70 cm × (total points / 2), that is, each keel is 70 cm long, usually arranged as a two-port panel.

8. Calculation of auxiliary materials such as keel clamps, pipe joints, couplings, rivets and hacksaw blades. = Total cost of accessories × 10%

9. Calculation of bottom drawer (86×86). Number of bottom drawers = total points / 2

V. Calculation of equipment and materials

1. Cable calculation



Furthest point is furthest point from engine room to information point;

The nearest one is information point in computer room, usually 20 meters away;

Points are data points covered from computer room. If there is a room with additional wiring, then points are data points covered from room with additional cables. 0.1 out of 1.1 is a margin which is 10%. . 305 - length of each box line is 305 meters.

If there are connection spaces, they should be calculated separately and formulas are consistent. That is: number of cables needed to cover data points in central computer room + number of cables needed to cover data points in connection room + number of cables needed to cascade lines from connection room to central computer room.

Please note that number of network cables is usually around 300m, less than 305m. If number of cables in this project is relatively large, this is also taken into account. For example, cable length reserved at end of threading equipment must also be considered comprehensively and also in accordance with overall construction process of your construction team.

2. Module calculation. number of information points;

3. Number of two-port panels: total points/2;

Calculation of cross-connects with 4 and 48 ports. The total number of points /48, if there is a sub-switching room, then it must be calculated separately, that is, number of information points covered by each /48, and then summed up, 4U;

5. Calculation of line manager. The 48 port patch panel does not need a line manager (standalone), it is mainly for switch, if there is a connection room, then it must be calculated separately. 1U;

6. Cabinet lintel (2 m). Jumper from switchboard to circuit breaker + cascade line between circuit breakers.

7. Workstation jumper. Total points;

8. RJ45 head. (cabinet jumper + workstation jumper) × 2 × 1.1;

9. AboutRJ45 head shell. number of RJ45 heads;

10. The number of three types of large logarithms. The distance from weak electric well to turbine hall through bridge frame + margin (greater, since large logarithm cannot be connected);

11, switchboard 110DW2-100FT (2U). One is 100 pairs;

12, 110 through wire slot. Corresponds to number of 110 patch panels;

Backplane 13, 110 (4U). For: 110DW2-100FT number of switchboards/2;

14, junction block 110C4 (pack of 10).

The 110DW2-100FT distribution block has 100 pairs, that is, 100 telephones, consists of four parts, each of which has 25 pairs, that is, it consists of 5 C4 connection blocks and 1 C5 connection block (5 × 4 + 1 × 5 = 25), i.e. 100 pairs of large logarithms require 20 C4 connection blocks and 4 C5 connection blocks.

15, junction block 110C5 (pack of 10). Same as before;

16. Telephone jumper (drive/100 meters). Each telephone jumper requires 1.5 meters.

17, RJ11 head. Determined by number of phones, for example, 200 phones (200 pairs of large pairs) need 200 RJ11 heads (the other end is directly connected to RJ11 distribution frame);

18. Telephone cabinet (200 times). Determined by number of telephone points;

19. Cabinet (42U, 24U). Calculate height (U) of a 48-port distribution board, cable manager, RJ11 distribution board, switch, server, etc.;

6. Optical fiber configuration

Explanation: The second floor contains central computer room as well as connection room. There is also a connection room on 4th and 7th floors. Each of 3 connection rooms is equipped with 6 indoor multimode optical fiber.

Connection method: Fiber consumables and ST multimode optical fiber connectors are required;

Fusion splicing method: ST single-chip multimode pigtail required, fiber consumables and ST multimode fiber connectors not required.

Seven, how to accurately calculate number of cables

First of all, number of cables must be calculated according to construction drawings. We do construction according to drawings, and calculation according to drawings is basis of entire project estimate. After receiving construction drawings, it is usually necessary to compare direction of bridge frame on site according to drawings to see if it matches design of drawings, determine direction of bridge frame, and basically determine main line. .

For calculation of vertical part and horizontal part, especially calculation of cable in a low-current well, first thing to pay attention to is height of floor, and then distance between installation location of low-current well. well equipment and bridge frame, comprehensive consideration and comprehensive calculation.

Of course, calculateNumber of cables, partly from drawings, partly from site, partly from experience, partly from construction team.