Otis Singleton
Electrical drawings are visual representations of electrical systems and wiring for electricians and electrical engineers to reference. They include electrical components such as outlets, fixtures, switches, lighting, fans, and appliances. Electrical drawings are typically shown in 2D and consist of symbols, notes, and schedules. However, the inclusion of conduit routing in electrical drawings is a topic of discussion among professionals. Some argue that conduit routing is unnecessary and increases complexity and costs, while others believe it provides valuable information for contractors and helps avoid field conflicts. The decision to include conduit routing in electrical drawings depends on industry standards, project complexity, and specific client requirements.
| Characteristics | Values |
|---|---|
| Conduit drawings by country | In the US, conduits are shown for shop drawings, usually 20mm and above. In the UK, conduits are only shown for specific details or intentions. In Canada, only junction boxes are shown on contractor as-builts. |
| Conduit drawings by project type | Conduit drawings are more common for complex industrial projects. For residential projects, they are considered unnecessary and a waste of time. |
| Reasons for not drawing conduits | Drawing conduits is time-consuming and expensive, and the exact routing is often modified in the field. Electrical drawings focus on symbols, notes, and schedules, and conduit routing is rarely required for permits. |
| Reasons for drawing conduits | Conduit drawings provide valuable information for contractors, enabling more accurate takeoffs and estimates. They also help avoid field conflicts with other systems, such as duct or piping mains. |
| Conduit drawing practices | Conduit drawings may include conduit size, wire size, and routing information. However, combining wires into shared conduits is handled with caution due to potential code compliance issues. |
| Conduit drawing challenges | Modelling conduits, especially with offset bends, is challenging and may lead to unnecessary questions and issues. |
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What You'll Learn
Conduit size and type
When it comes to electrical drawings, conduit size and type are crucial considerations. The conduit size is typically determined by the number and type of conductors or wires that will be routed through it. Stranded wires, for instance, occupy more space due to the tiny air gaps between strands, whereas thicker wires necessitate more room. To ensure compliance with the National Electrical Code (NEC) and prevent issues like wire overheating or violation of NEC rules, it is essential to select the appropriate conduit size.
Conduit sizes are commonly designated by their "trade size," which serves as a standard naming system in the industry rather than an exact measurement. For example, a 1-inch conduit trade size does not equate to a 1-inch inner or outer diameter. Different types of conduits, such as PVC, EMT, RMC, and flexible metal, exhibit variations in wall thickness, resulting in discrepancies in inner space despite sharing the same trade size. Therefore, it is imperative to refer to a conduit size chart or the NEC book to ascertain the precise dimensions and select the appropriate conduit type for the specific application.
The scale employed in electrical plans also influences the depiction of conduit size and type. These plans are often drafted at the same scale as floor plans, with the most common scales being 1⁄4" = 1'-0" (1:50 metric) for small projects and 1⁄8" = 1'-0" (1:100 metric) for large commercial ventures. The scale aids in determining the size, length, and distance of equipment, and it is typically provided adjacent to or below the drawing title. Designers may occasionally enlarge equipment drawings, presenting their respective scales beneath them.
In terms of presenting conduit size and type in electrical drawings, it depends on the construction type, project size, and specific details being conveyed. For instance, in wood and drywall construction, it is common to use "free wire" inside walls, represented by a "circuit home run" in plans. In contrast, commercial or industrial projects tend to include more intricate details. Shop drawings typically exhibit conduits measuring 20mm and above, whereas small conduits under 32mm in diameter are often omitted from design drawings.
Ultimately, the decision to include conduit details in electrical drawings may vary across regions. For instance, in the US, it is not uncommon to encounter extensive arrangements of 4" conduits in underground and overhead runs. In contrast, the UK generally omits conduits from drawings unless they serve a specific purpose or meet a particular size threshold, primarily on site plans.
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Conduit routing
It is common for electrical drawings to be depicted using symbols, notes, and schedules, rather than detailed illustrations. This approach may be favoured due to time and budget constraints, as modelling conduits can be challenging and time-consuming, especially considering the flexibility of circuits and the potential for modifications in the field.
When drawing conduit routing, it is important to ensure there is sufficient space for multiple conduits running together and to pay attention to the bending radius. The bending radius varies depending on the size of the bender, and accurate measurements and formulas should be used to calculate the bending locations. Before bending, all electrical boxes should be installed, and the location of new boxes should consider the path of the conduit. By code, all bends must have an even radius with no kinks, and the conduit should bottom out in the fittings, laying flat against the wall without pressure.
In some cases, such as shop drawings, MRI projects, and industrial projects, it may be necessary or preferred to show all conduits. The decision to depict conduits may depend on industry standards, project complexity, and the specific requirements of the owner or tenant.
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Combining wires into shared conduits
Firstly, it is crucial to refer to local regulations and codes, such as the National Electrical Code (NEC) in the United States. These codes provide guidelines for combining different types of wiring, such as high and low voltage cables, to ensure safe installations. For example, while low voltage wires can be combined with control wiring, they must be at least 600VAC-rated to ensure safety.
Additionally, it is generally recommended to separate high voltage cables from low voltage signal cables, even if they are entering or leaving a control panel. While this practice may be allowed by code, it is not considered good practice as it increases the risk of issues. Similarly, combining power wiring with signal, communications, or control wiring is discouraged, as it can lead to adverse interactions between the different wiring methods.
To facilitate combining wires into shared conduits, it is essential to work closely with contractors and electricians. They can provide expertise on which wires can be safely combined and ensure compliance with local codes and regulations. Furthermore, combining wires may impact conduit size and fill, so it is crucial to consider the maximum capacity of the conduit to avoid overfilling.
In conclusion, combining wires into shared conduits can be a practical approach to streamline electrical drawings and reduce the number of conduits required. However, it requires careful consideration of wiring types, local regulations, and conduit capacity to ensure a safe and compliant installation. Close collaboration with electrical professionals is key to successfully implementing this practice.
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Conduit layout with junction boxes
When it comes to electrical drawings, the depiction of conduits varies across countries and projects. In the US, for instance, the inclusion of conduits depends on the construction type and size of the conduit. Wood and drywall constructions commonly use "free wire" inside walls for electrical rough-ins, represented by a "circuit home run" in plans. On the other hand, large arrangements of conduits are often seen in underground and overhead runs, which may be due to the difficulty of running medium voltage to projects and varying state regulations.
In the UK, conduits are generally not drawn unless they serve a specific detail or intention, such as conduits cast into a slab. Similarly, in Canada, only junction boxes are typically shown on contractor as-builts, mainly for commercial or data center projects.
The decision to include conduits in electrical drawings also depends on the industry and project complexity. More intricate industrial projects may require every conduit to be shown, whereas residential projects may consider it unnecessary. Additionally, the modelling of conduits can be challenging due to their flexible nature, and creating detailed drawings can lead to more complex questions and issues.
Now, let's focus on conduit layout with junction boxes. When running conduit to junction boxes, it is essential to follow the relevant codes and standards, such as the National Electrical Code (NEC). One common query is determining the requirements for conduit routing in relation to a distribution block. For example, if a wire must be a certain length inside a box, can the conduit enter from the side or back instead of running parallel to the block? Understanding and adhering to these codes are crucial to ensure safe and proper conduit installation.
Another consideration is the support of conduits near junction boxes. Per the NEC, conduits within 3 feet of a junction box must be secured and supported unless structural members prevent this, in which case the distance can be increased to 5 feet. This rule aims to prevent issues such as conduits pulling loose from junction boxes due to poor backfill practices.
In conclusion, while the inclusion of conduits in electrical drawings varies, the layout of conduits with junction boxes requires careful consideration of codes and support structures to ensure safe and effective installations.
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Conduit plans
The level of detail included in conduit plans can vary depending on the project and industry standards. In some cases, only conduit sizes and wire types may be indicated, while other plans may include more specific information such as routing and interconnections. For example, in the UK, conduits are typically only shown on drawings if they are for a specific detail or to convey a specific intention, such as conduits cast into a slab. Similarly, in Canada, contractor as-built drawings typically only show junction boxes, and these are mainly for commercial or data center projects.
In the US, the inclusion of conduits in drawings depends on the construction type and size of the conduit. For wood and drywall construction, it is common to use "free wire" inside walls for electrical rough-ins, which can be represented by a "circuit home run" in plans. However, for larger or more complex projects, more detailed conduit plans may be necessary. Some firms have a standard of including conduits of a certain size, such as 2" or larger, in their conduit plans.
To create effective conduit plans, designers need to coordinate with other construction trades to ensure accurate information. For example, a reflected ceiling plan (RCP) is used to provide the correct location of light fixtures, registers, and appliances. Additionally, plan notes are important as they specify details such as junction box size, wire types, and conduit routing instructions. Legends and abbreviation tables are also included in conduit plans to help users understand the electrical symbols and abbreviations used.
Overall, the creation and use of conduit plans vary depending on the project, industry, and regional standards. They are an important tool for electricians and electrical engineers, providing visual representations of electrical systems and allowing for efficient modifications and repairs.
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Frequently asked questions
Electrical conduit is often omitted from drawings because it is difficult to model, takes up a lot of space, and adds unnecessary time and cost to a project. However, not showing interior conduit runs can lead to field conflicts with other systems.
Conduit is typically shown on electrical drawings when it is a specific size, usually 2" or larger, and mostly on site plans. In the US, conduit is often shown for underground and overhead runs. In the UK, conduit is only shown for specific details or intentions.
The conduit size is determined by the cable schedule, which lists the conduit size for each cable. The size is typically based on the number of cables and their respective sizes.
Conduit routing is typically shown on a separate diagram, such as a riser diagram, which illustrates the conduit sizes and interconnections. On the electrical drawings themselves, symbols and notes are used to indicate the wire and conduit size for each circuit.
