Reviewing the Diversity of Electrical Panels for Buildings

Electrical panels used in industries and buildings are categorized into various types. The primary functions of these panels include protecting circuits, controlling and directing them, and managing power distribution within buildings and electrical equipment. Components related to the protection and control of these panels include automatic switches, magnetic switches, circuit breakers, control relays, and displays. These circuits effectively prevent hazards such as short circuits, overloads, fires, and electric shocks, aiding us in the easy startup and control of electrical equipment. Below, we will examine the various types of building electrical panels.

Diversity of Building Electrical Panels:

1. Main Distribution Panel (MDP)

2. Common Area Panel (GDB or GDP)

3. Unit Panels, Miniature Panels (SDP or SDB)

4. Low Voltage Panel

5. Elevator Panel (if required)

6. Diesel Generator Power Distribution Panel (if required)

7. Uninterruptible Power Supply (UPS) Panel (if required)

Main Distribution Panel (MDP)

The Main Distribution Panel, or MDP, is one of the primary types of electrical panels used in buildings to protect and control the main electrical circuits. This panel, equipped with advanced protective and control components, ensures the highest level of safety and efficiency for the building’s electrical system.

Upon the entry of the main power cable into the building, it connects to the Main Distribution Panel, also known as the meter panel or MDP. This panel is responsible for supplying power to all units within the building as well as common areas. The Main Distribution Panel is one of the main types of building electrical panels and is divided into three main sections:

1. Power Entry Section (related to the power company)

2. Meter Section

3. Service Section

Introduction to the Power Entry Section (related to the power company):

The input to the Main Distribution Panel consists of a 4-core cable with a cross-sectional area of 16 square millimeters. This cable has three-phase conductors and one PEN conductor. The three-phase conductors connect to the input of the automatic switch, and these connections are essential for balancing and supplying power to the main building system.

The output of the automatic switch provides power to two main sections:

Glass Fuse Input:

This section is designed to protect signal lights and a three-phase digital multimeter.

Secondary Fuse Section Output:

The output of each glass fuse connects to a signal light, and the other end of the signal light connects to the neutral. Additionally, the outputs of the secondary fuse are placed on separate phase buses to connect the input of each meter to these buses.

In the next stage, branching is achieved using a busbar. This busbar consists of a metal strip with multiple holes.

Input and output wires are secured using cable ties and insulated with protective sleeves to prevent contact with the busbar body. This section of the panel is sealed by the electrical department, and the responsibility for maintenance and safety measures lies with the electrical department. The fourth wire, serving as a protective-neutral conductor, first connects to the ground bus and then connects to the neutral bus jumper.

Meter Section:

The Main Distribution Panel or Meter Panel plays a vital role in distributing power within the building. This panel is installed at the building’s entry point and is responsible for supplying power to all units and common areas. Typically, this panel is represented as MDP on electrical blueprints. The main cable enters from the bottom to the fuse switch of this panel (which is of the load-break type).

After entering the building, the main cable is connected to this panel, and the number of meters is determined based on residential units and the presence of a communal panel. For example, a four-story building with a main panel containing five meters, one of which is related to the communal panel and the others to the units. Unit meters are installed as single-phase, and if there is an elevator in the building, a three-phase communal panel will be used; otherwise, it will be single-phase.

In the central section of the panel, electrical circuits are arranged for distribution to the units. Contactors are installed in this section to route the output of each fuse switch to the meters. During the connection of phases to the meters, balancing the load across the phases is important, and labels are used to provide the phase name next to each input line to the meter. For this reason, in some panels, they utilize phase control relays.

The phase control relay has a crucial role in circuit protection against overvoltage, voltage drops, imbalance, and phase sequence. This relay is installed at the beginning of the circuit, following the fuse. The neutral bus must be placed on insulating supports (insulator bases). For each unit in the main electrical panel, a neutral bus is essential. If this point is not observed, a Residual Current Device (RCD) is used in the miniature panel of the unit.

At this stage, wires and cables are intricately connected to the neutral bus, and the phase is established with the relevant electrical equipment. The phase buses, with appropriate strength and without insulation covering, maintain distinct coloring for phases, facilitating the connection of phases to the respective equipment.

The grounding busbar is directly installed on the panel, and the location of the grounding busbar installation must be free of any color. If there is color on the panel, the section where the grounding busbar connects to the panel must be scraped. Failure to scrape the colored section may result in improper connection due to the presence of insulating color in the panel. The metal bodies of the panels must be securely connected to the ground.

The outputs of the meters are connected to the miniature switches of each unit. The outputs of the miniature switches of each unit are connected to the 30-milliampere current protector of that unit. The output of the 30-milliampere RCD is connected to the terminals of RCT, and the power is supplied from the terminal outputs to the floor panel. A three-phase switch is used for the communal panel, and its output is connected to the communal panel.

After connecting the wires to the busbar, they are shaped. To create order in the installation of wires inside the panel, ducts are used, and in some specific cases, plastic belt ties are employed. During the installation of wires, cables, and wires must be labeled.

About the Meter Panel Design

The Meter Panel, known as MDP, operates with a three-phase electrical system using input cables with diameters of 3*10mm2 and 1*6mm2. The selection of the main feeder for this panel is done adequately based on the building’s requirements. Three-phase wires enter this panel and connect to load-break type fuse switches, which are installed at the bottom of the panel, at the entry point of the main cable.

Main Electrical Meter Panel

The three wires corresponding to the phases L1, L2, and L3 are connected to the terminals of the lamps, and the other ends of the lamps are connected to each other. Each lamp is equipped with a glass fuse at its path. Due to the extensive use of neutral and ground wires, each busbar (copper strip) or terminal is considered for each. The cross-sectional area of the busbar must be carefully calculated. Each output from the fuse switch must be connected to a separate busbar so that the input of each contactor can be connected to these busbars after dividing between phases. The grounding busbar must also be connected to the metal body of the panel and its doors.

Key Points Regarding the Main Meter Panel

– The design of the main meter panel is the responsibility of the power distribution company, and they are accountable for it.

– The installation location of the meter panel should be optimized and considered near the entry point for allocating the power branch. The final installation location of the panel is determined through coordination between the power distribution company and the project supervisor.

– In large commercial and residential complexes, the meter panel is not installed in the intermediary floors.

Electrical Panels for Building Units

A multi-strand copper wire, known as the grounding well, is introduced to the meter panel’s grounding busbar. The cross-sectional area of this wire must comply with standards and the recommendations of the power company, and it should be specified in the blueprints.

Efforts to provide electricity to a section of the building used collectively by all residents highlight the significant importance of the Common Electrical Panel (GDB). This equipment is used to supply power to common areas such as parking lots, courtyards, rooftops, and stairwell devices, and its installation should be easily accessible.

The common electrical panel is often installed in utility rooms and is marked with GP on electrical blueprints. Additionally, this panel is used to meet the needs of central antenna systems, intercoms, elevators, machinery rooms, and fire alarms. To construct this panel, the required lines must first be estimated, and the blueprints for the common panel circuits should be provided to the manufacturer. This estimate includes counting circuits for lighting, water pumps, intercoms, and other shared components.

The common panel has 13 lines, and after estimating the lines, the panel frame is mounted on the wall. If the wall is made of plaster, the frame can easily be secured with plaster. However, if the use of supports is required, the frame must be installed using suitable means. After installing the frame, piping is done for the lines under the frame, and then the pipes are cut or fitted as needed. Following this, the main wiring and cable laying stages commence, and in the final stage, the panel is closed.

For the entry of electricity into the common panel, the selection of miniature circuit breakers and three-phase switches is based on the intended panel’s consumption level. Three wires related to the phases enter the three-phase miniature circuit breaker, providing power to the common circuits. Additionally, one output is dedicated to a 2-ampere glass fuse feeder, serving the protection of signal lights. Another output is utilized for supplying power to the fire pump, while the third output is employed for powering other common circuits. The installation and execution of this panel strictly adhere to safety standards to ensure the optimal provision of electricity to the common spaces of the building.

Details related to the blueprint of the common electrical panel for the building:

The common electrical panel plays a fundamental role in providing electricity to the shared sections of the building, using a cable with a diameter of (5*6 mm2) as the input. The selection of a three-phase switch and miniature input breaker is based on the panel’s consumption level. The line voltage system (phase-phase) is provided at 400 volts, and the phase voltage (phase-neutral) is supplied at 230 volts.

After entering the panel, the main switch is connected to the rotary switch 0-1 to control the main power of the panel with a single on/off switch. The phase wires are connected to three-phase fuses, and the rated current of the fuses is calculated based on the panel’s consumption. Three signal lamps are used to indicate the presence of the electrical panel for each phase.

This electrical panel is designed to meet the electricity needs of shared utilities among all units. This includes service lighting for areas such as stairs, parking, machinery rooms, elevator shafts, courtyards, rooftops, and other spaces. For this purpose, multiple lines with 1.5mm2 wires and 10-ampere fuses are considered for lighting, and several lines with 2.5mm2 wires and 16-ampere fuses are designated for outlets. Each line is labeled with the respective phase name.

If there is an elevator or a machinery room for heating and cooling systems, a three-phase GP panel is utilized, and a three-phase output line with a three-phase fuse is considered for the elevator panel. The size of the output cable from the common panel to the elevator panel is 5*6mm2, and it is specified by using a three-phase miniature switch with a capacity of 20 or 25 amperes.

The outputs of the common electrical distribution panels in the building are organized in a specific and systematic manner to meet various needs:

– If the common panel is installed on the building’s roof, a single-phase output is required for the central antenna system booster. This output should consist of three wires with a minimum cross-sectional area of 1.5 square millimeters and a 10-ampere miniature switch of class B.

– For supplying power to the intercom in the main common panel, an output with three wires and a minimum cross-sectional area of 1.5 square millimeters, along with a 6-ampere miniature switch of class B, is considered.

– If there is a fire alarm control center in the main common panel, a single-phase miniature switch with a rated current of 10 amperes and class B, with three wires and a cross-sectional area of 1.5 square millimeters, should be taken into account.

– For lighting in the building’s common areas, typically, one or more outputs with a 10-ampere miniature switch of class B and three wires with a cross-sectional area of 1.5 square millimeters are considered.

– Considering the presence of several outlets in the building’s common areas, multiple outputs in the main common panel with a 16-ampere miniature switch of class C and three wires with a cross-sectional area of 2.5 square millimeters are designated for them.

– In the case of an exhaust fan, one or more outputs and a 10-ampere miniature switch of class B based on the requirements are considered for supplying power from the common electrical distribution panel.

For booster water pressure pumps and fire pumps, a Class C miniature switch is used, taking into account the motor power.

The installation method of equipment inside the common electrical distribution panel is one of the vital aspects for the proper and legal functioning of electrical panels. For a regular and precise installation inside the common panel, ducts and, in some specific cases, plastic belt fasteners are used. During installation and wiring, it is recommended that cables be clearly labeled for identification.

The neutral busbar is placed on insulator supports, and the ground busbar is also installed on the panel in a way that there is no color underneath it. In the case of coloring the panel, the connection point of the ground busbar to the panel must be trimmed to prevent issues related to improper connection due to unauthorized coloring.

Special Note: Using a wire with a cross-sectional area of 2.5 square millimeters for a 25-ampere miniature switch in electrical panels contradicts national building regulations. Inspectors must carefully consider the cross-sectional area of wires and the amperage of miniature switches. Also, due to the three-phase nature of the panel, load distribution must be done symmetrically and evenly.

One of the advantages of this method is that, in the event of any errors or interruptions in a section of the building, repairs and modifications can be easily carried out. The installation of these panels on the building outlet plans is visible with the symbol DP.

The explanation of the electrical unit distribution panel map, known as the DP (Distribution Panel) unit distribution panel, is used in electrical maps. This panel is powered by a 3*4 square millimeter cable and three strands of NYY cables with a cross-sectional area of 4 square millimeters. The choice of input cable is based on the consumption load, and a PVC cable with two layers of plastic insulation of the NYY model is used.

After passing through the main miniature fuse, the phase wire enters the miniature switches corresponding to each line. Some of these panels have signal lamps to indicate the status of the power connection or disconnection in the panel.

In the output lines of this panel, the ground, neutral, and phase wires, where the miniature fuse is located in their path, must be present. The type of line (such as lighting or outlets) must be specified on the panel.

According to standards, the allowable current for lighting circuits is 10 amperes, and for outlets, it is 16 amperes. For special devices such as air conditioners, the wire cross-sectional area and fuse amperage must be selected based on the device’s power, following the calculations.

Ensuring secure wire fastening under screws and terminals is crucial, as improper functioning can lead to circuit interruptions and serious damage.

When using a staircase timer for stairway lighting, the timer must be directly connected under its own timer.

When using a three-phase pump in a building, it is installed in the control panel for the phase and the respective contactor. The wires are connected to the pump through the terminal under the contactor.

The distribution panel for units is one of the essential tools in providing power for lighting circuits and outlets in each residential unit. These panels are used to improve the wiring system instead of scattered distribution boxes in old buildings. With this method, each electrical circuit is executed separately and independently for low-current systems, lighting, and electrical outlets, utilizing distribution panels.

To achieve the ideal design for the distribution panel in residential units, consider the following important points:

1. The installation location of the distribution panel in apartments should be near the entrance and utility ducts to provide the best access and connection to the power network.

2. Installing a Residual Current Device (RCD) with a residual current of 30 milliamperes after the main miniature switchboard and on the load side is essential and safe.

3. Pipes related to the input cable of the distribution panel for residential units should pass through the building’s electrical installation ducts for easy use in installation and connection.

4. The number of panel lines should be coordinated with the specified number of lines in the lighting and outlet diagrams to provide separate connections for each device and circuit.

5. The number of reserve lines should also be determined according to reasonable needs to have additional connections available if necessary.

6. The cross-sectional area of the input and output cables of the distribution panel should match the information specified in the riser diagrams of the panels and the diagrams of lighting and outlets.

7. Separate grounding for the distribution panel should be considered to prevent electrical disturbances.

8. Coordinating the size of the panel cables with the requested load, temperature correction factors, permissible voltage drop, permissible current, and other technical factors are among the points that should be considered for the correct selection of wiring and cables.

The power distribution outputs in residential units are determined for various purposes:

– Lighting outputs use a wire with a minimum cross-sectional area of 1.5 square millimeters (NYAF 3*(1*1.5)mm2) and a 10-amp miniature switch, Class B.

– Power socket outputs use a wire with a minimum cross-sectional area of 2.5 square millimeters (NYAF 3*(1*2.5)mm2) and a 16-amp miniature switch, Class C.

– Output for gas or split air conditioning systems uses a wire with a minimum cross-sectional area of 4 square millimeters (NYY 3*4mm2) and a 20-amp miniature switch, Class C, considering the appropriate choice of the miniature switch.

– For audio systems, CCTV cameras, motorized curtains, jacuzzis, special lighting, coil fans, and similar equipment, suitable outputs are considered with the right number of wire strands, appropriate cross-sectional area, and suitable miniature switch.

– At least two reserve lines with currents of 10 and 16 amps for lighting and socket circuits are usually considered.

– The electrical rating provided by the power company to each residential unit is 25 amps at 220 volts. Therefore, the total installed capacity and the maximum power demand per distribution panel for a 5-kilowatt unit, with a power factor of 0.9, are restricted to watts or kilowatts.

Elevator Power Distribution Panel Outputs

The outputs of elevator power distribution panels are considered vital components in building infrastructures. When designing these panels, the following aspects must be taken into account:

– Accurate drawings of elevator distribution panel layouts are essential as a fundamental part of the building’s electrical system.

– The elevator distribution panel is directly connected to the main distribution panel for common areas and, if there is a diesel generator, it is connected sequentially to the ATS panel and then to the elevator distribution panel.

– The power consumption of the elevator shaft is directly supplied from the main elevator panel.

– The installation location of the elevator distribution panel should be inside the elevator machine room without interference with the machine room door.

– The elevator panel input includes a miniature switch and a three-phase cable, depending on the panel’s consumption requirements.

Outputs of Building Common Areas Power Distribution Panel

The outputs of these panels also pass through various miniature switches:

– A single-phase 10-amp miniature switch for the lighting of the machine room with three wire strands and a cross-sectional area of 1.5 square millimeters.

– A single-phase 10-amp miniature switch for the lighting of the elevator shaft with three wire strands and a cross-sectional area of 1.5 square millimeters.

– A single-phase 16-amp miniature switch to power the outlets of the machine room and the elevator shaft with three wire strands and a cross-sectional area of 2.5 square millimeters.

– A three-phase 20 or 25-amp miniature switch to supply power to the elevator control panel with five wire strands and a cross-sectional area of 6 square millimeters, dependent on the elevator motor current.

Due to the absence of a service section in the main electrical panel at present, some panels do not have this section. This section allows the installation of items such as an intercom transformer and telephone lines.

In some cases, common areas miniature switches are also installed in this section and used as a common areas panel. In such situations, it is crucial to prevent low-voltage noise from being transmitted to telephone and intercom sections. If the wiring in common areas is extensive, it is recommended to install a separate panel for common areas.

The number of telephone lines is determined by the owner and then communicated to the telecommunications. The telecommunications terminal is connected to the panel body using screws. The main pair telecommunication cable is connected to the input of this terminal, and the unit pair cables are connected to its output in order and respecting the pair colors. Telecommunications terminals are available in two different types in the market.

Choosing a Building Electrical Panel

When selecting a building electrical panel, carefully consider the following factors:

1. Design Type: Examine the building’s needs to choose an appropriate electrical panel, including internal and external components and the type of control switches.

2. Design Standards: Ensure that the electrical panel complies with relevant design and safety standards for improved performance and safety.

3. Panel Size: Select the electrical panel size based on the building’s electrical requirements, including existing electrical equipment.

4. Sheet Thickness: Using quality and appropriately thick sheets for the electrical panel ensures safety and durability.

5. Installation Location: Decide whether the electrical panel will be installed indoors or outdoors and consider environmental resistance.

6. Wire Entry and Exit: Determine the exact path for wire entry and exit to facilitate easy installation and maintenance.

7. Build Quality: The electrical panel should be made from high-quality materials and advanced technology for better longevity and performance.

8. Special Applications: Consider special needs such as automatic controls and other features, and choose the electrical panel accordingly.

9. Protection: Decide whether the electrical panel needs a protection system, and if so, specify the type of protection required.

10. Price: Based on your budget, choose a quality electrical panel with features and capabilities that align with its value and price.

In this article, topics related to electrical distribution panels in residential and commercial environments were carefully examined. First, various outputs of electrical distribution panels in buildings, including power supply for lighting, outlets, intercoms, and various systems, were discussed. Then, the design considerations for these panels, such as suitable installation locations, the use of miniature switches, and proper internal and external connections, were explored.

Additionally, an explanation was provided regarding the equipment inside the panels, the installation and commissioning of various devices, and power supply for different building components. Finally, the examination of panel diagrams and circuits, as well as main electrical panel services, was covered.

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