Electrical lighting design for modern office space

Modern office space is a working environment composed of a variety of visual tasks. Reading, drafting documents, operating computers and other office equipment all require comfortable, relatively glare-free and effective lighting conditions. Office lighting has become one of the main factors that directly affect office efficiency, and it has attracted more and more attention. Therefore, lighting design is an important part of modern office space decoration engineering.

Lighting quality

1. Determination of illumination level

The illumination level mainly depends on the needs of visual work and the possibility of economic conditions. my country's "Civil Building Lighting Design Standard" stipulates that the illumination value of general offices is 100-200lx, and the illumination value of corridors is about 50lx. The illumination value level of offices in developed countries is much higher than that of my country. The recommended illumination value of office lighting by the British Illuminating Engineering Society is 500-750lx, and the illumination standard of office building lighting in Japan is 500-1500lx. The office building of Aoyu Building belongs to the middle and high-end office space, and the office lighting design should refer to the British and Japanese standard values. Combined with national conditions, the illumination level of offices is determined to be 350-400lx and the illumination level of corridor public areas is 100-150lx during the design. After the design was completed and the disclosure was made to Party A, someone raised the question of whether the corridor lamps were arranged densely, the illumination was high, and it was not convenient for energy saving, which caused controversy. Since the height of the corridor ceiling is less than 2.1 meters, from the perspective of decoration, increasing the illumination can visually raise the height of the space relatively and reduce the sense of oppression in the space. Energy saving can be solved from two aspects: light source selection and lighting control. After the client conducted an on-site simulation and looked at the problem from a development perspective, it was finally decided to maintain the original design.

2. Glare control

Glare is the most important factor affecting lighting quality. Glare must be strictly controlled in modern office environments, otherwise it will significantly affect people's work.

Glare includes direct glare and reflected glare. To limit direct glare, factors such as the brightness of the light source, background brightness, and the location of the lamp installation are generally considered. The first method to limit reflected glare is to try to keep the worker out of the mirror reflection angle formed by the lighting source and the eyes, and the second is to use lamps with large luminous surface area and low brightness, or use special lighting fixtures with small reflected light flux in the visual direction (such as bat-wing lighting fixtures, etc.).

In addition to adjusting the installation position of lamps according to the workstation arrangement, the renovation project of Beijing Aoyu Building mainly controls uncomfortable glare from the selection of lamps. This design recommends Philips glare-free OA M5 lamps, with unique parabolic aluminum partition matte light guide lampshade, batwing-shaped light distribution curve, shading angle of 33°, and luminance of less than 20000cd/m above 67°, which will not cause reflected glare on the VDT screen, protect eyesight and improve productivity.

Selection of light sources and lamps

1. Light source

Fluorescent lamps are mostly used for office lighting. The office space of Aoyu Building uses Philips fluorescent lamp series light sources. The warm color series and daylight series will give people a warm and cold feeling. The white series has a color temperature of about 3500K~4000k. Bright white light can be perfectly combined with natural light, giving a bright feeling, a broad vision, and making people concentrate. This design adopts the neutral white series.

The public corridor lighting uses energy-saving lamps with a color temperature of 4000K, which is the same as that of the office. The power is 10W and the luminous flux is 600 lumens.

In areas with more complex ceiling shapes, such as the president's office on the 12th floor, the meeting room, and the boardroom, a combination of light strips, light troughs, and point light sources is used to meet the requirements of decorative effects. Incandescent lamps are used in places that require local lighting, such as indoor bookcases and murals, to fully reflect the bright colors of the furniture.

2. Lamps

At present, the fluorescent lamps used in offices include diffuse lamps, bat-wing lamps, herringbone lamps, etc. Among them, bat-wing lamps are the most ideal, because the light intensity of this type of lamp is strongest at 30°, and the light intensity at the bottom of the lamp is lower, so the reflected light from the work surface will not coincide with the line of sight and enter the human eye.

The public corridors mostly use fluorescent lamps or energy-saving ceiling lamps. The corridor lighting fixtures of Aoyu Building are selected in accordance with the decoration requirements, and energy-saving downlight series are selected. Since the ceiling elevation of the corridor is mostly around 2.1 meters, and some parts are less than 1.9 meters, small-caliber lamps should be selected as much as possible. However, considering that there are many pipes in the corridor ceiling and the installation space of the lamps is limited, the lower-power horizontal plug-in downlights are finally selected to relatively solve this contradiction.

Electrical design of lighting

1. Lighting power supply and distribution system

The design of the power distribution system should be determined according to the project scale, equipment layout, load characteristics and power consumption capacity. Since the lighting design of the Ao Yu Building is a secondary decoration design, the system configuration above the floor distribution box is adjusted by the original design unit according to the latest load calculation results, which will not be discussed in detail here. The following is a brief description of the adjustment and modification of the system below the floor distribution box.

a. Load calculation and adjustment of lighting circuit protection

In the secondary decoration design, the problem of small reserved capacity in the original building electrical design often occurs. There are two main reasons: First, the original civil engineering design was completed a long time ago, and the design standards at that time did not meet the requirements of modern office conditions. For example, the use of a large number of computer equipment has greatly improved the level of office automation, and the original reserved capacity is obviously too small. Second, the changes in the functions of the building space are quite different from the original design, resulting in insufficient reserved capacity. Therefore, the secondary decoration design must recalculate the power load, provide the calculation results to Party A, and adjust the line protection of the lighting distribution system (including sockets) at this level. Since the lighting fixtures of this project use high-efficiency energy-saving light sources, although the number of fixtures has increased, the capacity has decreased instead, which has no impact on the upper-level distribution system.

b. Design of distribution lines

In terms of power distribution lines, the following issues should be noted:

Whether the power lines, distribution trunk lines or branch lines use cables or insulated wires, they should all be made of good copper core cables or copper core insulated wires, and cables or wires with a thickness of less than 25mm?? should use cables or wires with equal cross-sections in the low-voltage 380/220V three-phase four-wire system.

Lighting circuits are usually powered by single-phase branch lines, or two-phase or three-phase branch lines can be used to power many lamps (the lamps are connected to each phase separately). Two-phase four-wire or three-phase six-wire power supply is superior to single-phase two-wire, as it reduces the power loss of the line and can also reduce the pulsation of the luminous flux for gas discharge lamps.

Each single-phase circuit of indoor lighting branch line generally does not exceed 15A.

The number of lamp holders (including sockets) connected to each single-phase circuit shall generally not exceed 25; when supplying power to light panels, light troughs or lighting devices with more than two fluorescent tubes, the number shall not exceed 50. However, circuits for flower lanterns, colored lights, large-area lighting, etc. are not restricted.

The load distribution of each phase on each distribution panel and line should be as balanced as possible.

2. Lighting arrangement

According to the "Electrical Design Code for Civil Buildings", general lighting in office spaces should be designed on both sides of the work area. When using fluorescent lamps, the longitudinal axis of the lamp should be parallel to the horizontal line of sight. It is not advisable to place lamps directly in front of the work position. Large-span offices should use a lighting arrangement parallel to the external windows.

3. Laying of electrical lines

The laying of electrical lighting lines in building decoration projects should pay attention to fire safety issues. Electrical lines are an important part of the electrical lighting system. Fires caused by electrical lines are caused by electric sparks and arcs generated by leakage, short circuit, overload, overvoltage, excessive contact resistance, and damage or breakdown of wire insulation. If the electrical line is short-circuited, it will generate a lot of heat in a very short time, causing the metal wire to melt and generate electric sparks and arcs. While the insulation layer of the wire is burning, it will ignite the surrounding combustibles and cause a fire. At present, most building decoration materials are combustibles. Therefore, in building decoration projects, the selection of materials such as wires and protective tubes should comply with the requirements of building fire protection regulations, and flame-retardant materials should be used as much as possible. As long as the cross-section of cables and wires is selected strictly according to the design requirements and the construction is carried out according to the regulations, fires in the lines can be prevented. For example, in the decoration project of Ao Yu Building, metal hoses are used to protect the lamp holder box and the lamps, and metal joints should be used for their joints. The wires are laid through metal pipes or metal wire troughs.

4. Lighting control

Light control must meet the requirements of safety, energy saving, easy management and maintenance, etc. Modern office spaces have many large openings, and the lighting control method adopts the method of multiple lights one control, and the method of one control for each partition is adopted.

The power supply for the public corridor lighting is derived from the emergency lighting power supply. The lighting branch circuit adopts a one-to-one control method for the lamps, and the building automatic control system selects to control one circuit to be turned on or two circuits to be lit at the same time. At night, only the night duty lighting is left. The duty lighting lamps are all equipped with automatic charging power supplies and can also be used for emergency lighting.

Several issues on changes during the construction of Aoyu Building

1. The original electrical design of the lighting conductor is BV type. According to the fire protection code for high-rise buildings, I suggest changing it to flame-retardant ZR-BV type. Since BV type has been used in the early construction area, it was finally decided to use flame-retardant conductors in the public area with dense pipeline equipment, and BV type is still used in the office area.

2. Thin-walled wire tubes are easy to construct and save investment. This design uses a large number of KGB thin-walled wire tubes in the suspended ceiling. When laying along the ground or wall, welded steel pipes are still used.

3. Public area lighting and emergency lighting are combined and controlled by the building automatic control system, which is easy to manage and energy-saving.

4. Lighting distribution branches should not cross fire partitions. This problem existed in the original electrical design of the corridor lighting in Ao Yu Building, but was corrected in the decoration design.