LV design errors and effects
When developing a low-voltage distribution system, a designer must avoid various mistakes and myths in order to give the end user a safe, efficient, and dependable solution. Despite the fact that there are numerous myths concerning electrical designs, the ones I’ll discuss in this piece are prevalent and likely to happen due to prices and a disregard for norms and regulations.
The top ten errors and misunderstandings in low voltage distribution system design
As a result, you will learn in this article how to prevent making such errors while still adhering to standards and norms by adopting the appropriate cost-saving strategy. Also, we will comprehend the significance of using specific design tools that will enhance the quality of the electrical design, such as the lux calculation tool DIALux, which helps with the efficient and uniform distribution of lighting fixtures.
After learning about common errors in low voltage design, you might want to enrol in my course bundle “Electrical Low Voltage System Distribution Design,” which consists of a video-based course and a coursebook, to learn more about how to design a full low voltage distribution design project from scratch.
- Selecting the incorrect electrical rooms
Each project’s electrical rooms must be chosen early in the design process, specifically when the project’s architect creates the architectural layout. A crucial undertaking, choosing the best placement for electrical rooms requires taking into account several design considerations. For instance, simplifying cable routing will result in cost savings.
Following are some inquiries that, if they are resolved, will help determine where an electrical room should be located. - Can the number of panels and electrical boards fit in the chosen room?
- Is the room close to a potentially dangerous region where a fire or explosion could break out?
- Is the transformer room close to the main electrical room?
- Does the room’s location allow for uninterrupted service to the entire floor?
In order to choose the nearby rooms, an electrical designer must consider the staircases and lift shafts. For example, selecting an electrical room near the stairs on the ground floor of a building will ensure that other electrical rooms are selected for the same place on the upper floors.
This will make it easier to route cables between distribution panels on all of the building’s floors.
Figure 1 shows the installation of electrical distribution panels in an electrical room.
Instead, certain electrical designs don’t offer practical places for electrical rooms, such as choosing a room close to a damp area that could expose the electrical panels to direct contact with water, perhaps posing a danger. Moreover, electrical rooms may be placed beneath stairs, which limits their ability to accommodate additional panels and complicates maintenance access.
A project might include one or more main panels that feed distribution boards on each floor through a number of sub-main panels that are situated on each floor. The quickest and simplest approach to connect wires between panels is to choose an electrical room next to a continuous stairway or elevator shaft that rises to the roof floor.
The aperture in the concrete slab known as a “riser” provides a continuous path for electrical feeders to reach all floors of the structure.
Electrical riser for cable trays and trunkings, Figure 2.
Electrical riser design drawing in Figure 3.
DB Schedules with Missing Spare Circuits
Not include spare circuits in Distribution Board (DB) schedules is one of the main errors that electrical designers need to avoid. There is always a potential for adding loads at any point. Consequently, having extra circuit breakers will make this process easier rather than requiring the inclusion of a new distribution board to handle the increased load.
25% of the total loads are advised for spare circuits. A three-phase DB schedule 12-way type, for instance, would include four ways as a backup. The user can connect up to 12 additional single-phase loads thanks to four ways of spares. According to the connected load type, the user can connect both single and three phases since each way represents three circuits: R, Y, and B.
As an illustration, a three-phase circuit breaker is necessary rather than a single-phase ELCB, MCB, etc. So, for practical purposes, electrical designers could designate the extra 25% circuits as “spares” and “spaces” during the addition of loads to the connected DB.
A 12-way DB timetable with an additional 25% of spares and spaces is depicted in the figure below.
Distribution board (DB) spares and spaces schedule, shown in Figure 4.
You’ll see that the additional “spare” circuit breakers are listed with their ampere ratings since they need to be installed inside the database at the site during the execution phases. It should be noted that “spaces” are simply left blank to denote that no breakers need to be installed and that the end user’s choice is left up to the end user depending on the connection type of the load.
The image below illustrates how a DB’s chambers seem after being protected from dust and insects with dummy covers for safety.
Figure 5 shows a blank cover for space circuits on a distribution board.
- Loads in DB Schedules that are Unbalanced
It is essential not to overlook the balancing of loads in a three-phase system. The next lines illustrate how this error could have serious repercussions on the effectiveness of the entire system. So, it is crucial to balance the loads after defining the loads and including them in the DB schedule to determine the demand and total connected load in a three-phase system.
In a three-phase system, Red, Yellow, and Blue phases are distributed among and linked to single- and three-phase loads, respectively.