Comprehensively consider the weak current design and wiring of structured intelligent buildings

Abstract: The two advantages of structured integrated wiring, combined with the actual weak current system of the building, are only the development and instability of the telephone system and the computer network system. For other weak current systems, such as automatic fire alarm systems, security monitoring systems, broadcasting systems, cable TV systems, etc., have a high root fixed, and the location will generally not move, with a fixed building, these systems Once the equipment is selected, the possibility and necessity of frequent replacement are very low.

For the weak current design of modern intelligent buildings, especially office buildings, the use of structured integrated wiring system has become a consensus, but there are currently two views (or practices). One is to advocate that all weak current systems are built on the platform constructed by structured integrated wiring, that is, to replace all traditional weak current wiring with structured integrated wiring; the other is to advocate computer network wiring and telephone wiring Incorporated into the structured integrated wiring, and other weak current systems still use their unique traditional wiring. Which kind of wiring method is more reasonable should be combined with specific projects, and the conclusion can be drawn from the comprehensive consideration of the advancedness, rationality, and economy of the scheme used.

1. The basic idea of ​​the determination of the weak current program of the intelligent building

Let us first analyze the advantages of structured integrated wiring. First, the structured integrated wiring uses standardized cables and plug-in modules, which is very convenient for the management of information points between each floor and this floor. Just pull out the plug, insert it into a new location, and then do jumper processing in the weak current equipment room or just make some software changes, you can put it back into use. Unlike traditional wiring, there is no unified standard. When the equipment needs to be moved, it will bring a lot of management inconvenience or need to re-wire, and will cause greater damage to the building performance. The second advantage of using structured integrated wiring is that this wiring has a strong expansion ability, because it can provide 155Mbps of information transmission capacity for five types of unshielded twisted pair, in addition to meeting the needs of various current networks The need for future development.

According to the two advantages of the structured integrated wiring mentioned above, combined with the actual weak electric systems of the building, only the telephone system and the computer network system have development and instability. For other weak current systems, such as automatic fire alarm systems, security monitoring systems, broadcasting systems, cable TV systems, etc., have a high root fixed, and the location will generally not move, with a fixed building, these systems Once the equipment is selected, the possibility and necessity of frequent replacement are very low. According to the above, we generally integrate the wiring of the telephone system and the computer network system into the structured integrated wiring in the weak current design, while other weak current systems maintain relative independence and still use the traditional wiring method.

However, there are other reasons for adopting the above method: For example, the current systems of most weak current equipment manufacturers are not compatible with structured integrated wiring systems. To make these weak current systems operate on the structured integrated wiring platform, it is necessary to add conversion equipment. For example, the video signal output by the camera of the security monitoring system is usually transmitted by coaxial cable. If it is included in the structured integrated wiring system, it is necessary to add signal conversion equipment at both ends of the line, as shown in Figure 1. Obviously, this is both troublesome and uneconomical.

2. Problems in the application of integrated wiring

According to a period of application practice, we found existing integrated wiring products. The cross-sections of the unshielded twisted pairs of the third and fifth categories are all 0.5mm2 (American wire gauge AWG24). The matching distribution frames and outlets can only be used for cables with a cross section of 0.5mm2. Therefore, it has limitations or deficiencies in supporting the following weak electronic systems.

1. Broadcast System (PAS)

According to China's electrical specifications, generally, the operating voltage of electrical equipment is 220 / 380V (AC 50Hz), and the AC signal with an effective value below 24V is determined as a weak current signal. In the broadcasting system, if the constant voltage output is used, the line voltage can be divided into three levels: 70V, 100V, and 120V. Therefore, the use of integrated wiring in the broadcast system will cause overvoltage on the cable, and long-term use will adversely affect the life of the cable. In addition, the cross section of the line for the broadcast system is generally 1.0 to 2.5mm2, rather than shielded twisted pair The core cross section of the wire is only 0.5mm2, which is far from the same.

2. Fire Alarm and Control System (FAS)

According to the current design specifications of the automatic fire alarm system in our country: the cross section of the core line of the signal transmission line of the automatic fire alarm system, the insulated wire laid through the pipe should not be less than 1.0mm2; the insulated wire laid in the wire groove should not be less than 0.75mm2. The cross-sectional area of ​​the unshielded twisted pair as an integrated wiring system is 0.5mm2, which obviously cannot meet the requirements of the design specifications of China's automatic fire alarm system. In addition, in the fire alarm system of the bus system, the power line and the control line mostly use 1.5-2.5mm2 wires, and the integrated wiring system cannot meet the requirements.

In particular, it should be pointed out that China's current fire codes require that all fire signal lines and communication lines cannot be co-laid with non-fire lines. Therefore, to use integrated wiring products to support fire alarm and control systems, you must first obtain a license from the local fire department.

3. Common antenna TV system (CATV)

The use of integrated wiring products to support CATV generally uses optical fiber. Therefore, adapters must be installed at both ends of the line amplifier, distributor, and brancher. This will undoubtedly increase investment and reduce the reliability of the system due to the increase of intermediate links .

The above describes some of the problems that the integrated wiring system currently supports in various weak current systems in China. Does it mean that the structured integrated wiring system cannot support the above weak current systems? the answer is negative. For a building with a high degree of intelligence, under the premise of the specification permitting and obtaining a concession, the optical fiber and various logarithmic unshielded twisted pair cables of the integrated wiring product can be used to support the computer network and telephone communication system. Axis cable supports CATV and CCTV (monitoring TV, using special order unshielded twisted pair with a cross section of 1.0 ~ 1.5mm2 to support FAS, PAS).

3. Conclusion

In summary, in the current intelligent buildings, some weak electronic systems cannot be fully integrated into the structured integrated wiring. It is recommended that the relevant units research and produce as soon as possible integrated wiring products that can meet the requirements of various wire diameters and different transmission signals, so that the goal of incorporating all weak current systems into structured integrated wiring can be achieved.

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