Yes, many contractors prefabricate PVC Schedule 80 duct banks under certain circumstances. Here's a breakdown of the criteria that would make prefabrication a good option

Advantages of Prefabrication (Why you'd WANT to do it):
Labor Cost Savings

This is often the biggest driver. Assembly in a controlled shop environment is typically faster and more efficient than field assembly. You can use jigs, fixtures, and specialized tools. Lower labor rates in a shop (compared to a field electrician) can also contribute.

Increased Quality Control

A shop environment allows for better supervision and adherence to standards. Consistent gluing, proper spacing, and accurate measurements are easier to achieve. Less environmental factors (rain, mud, etc.)

Reduced Field Congestion

Prefabricated sections arrive ready to be installed, reducing the amount of material and personnel on the job site, minimizing clutter and tripping hazards.

Faster Installation Time

Prefabrication significantly reduces on-site assembly time, allowing for quicker project completion. This is particularly beneficial in fast-paced projects.

Reduced Waste

Material can be managed more efficiently in a controlled environment, minimizing waste and potentially saving on material costs.

Improved Safety

Less cutting, gluing, and handling of materials in the field reduces the risk of injury.

Repeatability

For projects with many identical duct bank sections, prefabrication is ideal.

Criteria for Deciding to Prefabricate (When it MAKES SENSE)



Project Size and Complexity



Large Projects

Prefabrication is most cost-effective for projects with a significant amount of duct bank to be installed. The initial setup costs of prefabrication are offset by the savings on a larger scale.

Repetitive Sections

If the duct bank design includes repetitive sections (same number of conduits, same spacing, same lengths), prefabrication becomes much more attractive.

Complex Configurations

While it might seem counterintuitive, complex configurations with many bends, sweeps, and offsets can benefit from prefabrication. The precision possible in a shop can be invaluable.

Job Site Conditions



Congested Site

If the job site is cramped and difficult to work in, prefabrication can be a lifesaver.

Limited Access

If access to the installation area is restricted, prefabricated sections can be more easily maneuvered.

Weather Constraints

Inclement weather can significantly impact field assembly. Prefabrication allows work to continue in a controlled environment.

Transportation Considerations



Size and Weight

Can the pre-made sections be easily transported to the job site and maneuvered into position? Consider the size and weight limitations of trucks, cranes, and other equipment. This is a major limiting factor. Overly long or heavy sections will negate any time saved in the field.

Fragility

PVC, especially schedule 80, is relatively robust, but consider potential damage during transport. Proper packaging and securing of sections is crucial.

Design Stability



Confirmed Design

The duct bank design must be finalized and unlikely to change. Modifications to prefabricated sections can be costly and time-consuming. You need ACCURATE measurements!

Cost Analysis



Compare Costs

A thorough cost analysis is essential. Compare the cost of prefabrication (including shop labor, material, transportation, and setup) to the cost of field assembly (including field labor, material, potential delays, and rework).

Available Resources



Shop Space

Do you have access to a shop or warehouse with sufficient space to assemble the duct bank sections?

Equipment

Do you have the necessary equipment (saws, gluing stations, jigs, lifting equipment) to efficiently fabricate the duct bank sections?

Skilled Labor

Do you have trained personnel who can accurately assemble the duct bank sections according to the design specifications?

Company Capabilities



Experience

Does your company have experience with prefabrication? If not, consider starting with a smaller, simpler project to gain experience.

Coordination

Effective communication and coordination between the design team, the prefabrication shop, and the field installation crew is critical for success.

Specific Considerations for Schedule 80 PVC



Weight

Schedule 80 is thicker and heavier than Schedule 40. This increases transportation and handling challenges. Consider breaking the duct bank into smaller, more manageable sections.

Glueing

Proper gluing techniques are critical for Schedule 80 PVC. Ensure that your shop personnel are properly trained and that you are using the correct primer and cement. Use only approved glue and cleaners for schedule 80.

Support Spacing

Follow manufacturer's recommendations for support spacing, especially for buried duct banks. Prefabrication can help ensure that supports are properly placed and secured.*

Expansion/Contraction

PVC expands and contracts with temperature changes. Consider expansion joints or other methods to accommodate movement. Proper planning is more important with longer prefabricated runs.

In summary:

Prefabrication of PVC Schedule 80 duct banks can be a very worthwhile endeavor, especially for large, repetitive projects in congested or weather-sensitive environments. However, careful planning, a detailed cost analysis, and a thorough understanding of the project's constraints are essential for success. The single most important factor is determining if the time saved in the field is worth the cost of transportation of these large pieces. If the sections are very large, and require special permitting and transportation, it may not be worth the effort. Flag for review