Okay, let's break down the considerations for temporary power feeders to your buildings, focusing on overhead vs. underground, given the demolition/relocation context and the potential for construction vehicle interference.

Understanding the Situation Large Site

This likely means significant distances, potential for varying terrain, and a higher likelihood of vehicle traffic.

Building Relocation/Demolition

This is the core of the decision. The temporary feeders are exactly that - temporary. You want something cost-effective, reasonably safe, and easily removed. Relocation might mean needing to move or adjust the temporary feeders during the relocation process itself.

Service Size (200A-600A)

This dictates the cable size needed, the conduit (if used), and the support structure required. Higher amperage means heavier, more expensive cables and more substantial support.

Existing Underground Services

This tells us that the site already has underground infrastructure and potentially a pathway for it.

Construction Traffic/Machinery

This is your key concern, and rightfully so. Construction sites are dynamic, and overhead lines are particularly vulnerable.

Overhead Temporary Feeders: Pros & Cons Pros



Potentially Lower Initial Cost

Less digging and trenching. Potentially cheaper materials (depending on the length and whether you can use triplex or quadplex cable).

Easier Inspection/Troubleshooting

Faults are easier to see and access.

Faster Installation

Generally faster to install than underground, if you have suitable pole locations available or can install them quickly.

Cons



Significant Safety Hazard

Overhead lines are inherently a risk, especially on a construction site. Contact with machinery is a major concern. Requires significant clearance from any other site elements, current and planned.

Vulnerable to Damage

Wind, falling debris, and accidental contact can damage overhead lines, leading to outages and safety hazards.

Requires Poles/Support Structures

You'll need to install poles or other structures to support the lines, adding to the cost and time. Poles may need to be removed and disposed of after use.

Aesthetics

Not a primary concern for temporary services, but overhead lines can be visually obtrusive.

Difficult to Relocate

Re-routing or moving overhead lines is a complex task, requiring specialized equipment and qualified personnel.

Clearance Requirements

NEC (National Electrical Code) dictates specific vertical clearances for overhead conductors above ground, roadways, and other structures. These clearances must be met.

Underground Temporary Feeders: Pros & Cons Pros



Safer

Eliminates the risk of overhead contact. Less exposed to wind and falling debris.

Less Obstruction

Doesn't interfere with construction traffic or equipment movement once installed.

More Aesthetically Pleasing

Less visually intrusive.

More Secure

Less susceptible to vandalism or unauthorized access.

Cons



Higher Initial Cost

Requires trenching, conduit (in some cases), and backfilling.

More Difficult Installation

Slower and more labor-intensive to install. Requires excavation equipment.

More Difficult Troubleshooting

Finding and repairing faults can be more complex.

Potential for Damage During Excavation

Risk of damaging existing underground utilities. Requires careful planning and utility locating.

Ground Conditions

Soil conditions (rocky, wet, etc.) can significantly impact installation costs and time.

NEC Requirements

Must comply with NEC Article 300 on wiring methods.

May Require a Dedicated Trench

Depending on other site conditions.

Key Considerations for Your Situation


Vehicle Traffic/Machinery Routes

Map out the expected routes of all construction vehicles and machinery. This will help identify areas where overhead lines would be most vulnerable.2.

Existing Underground Infrastructure

Before making any decisions, absolutely perform a thorough utility locate to identify all existing underground utilities. This is critical for safety and preventing damage. Consider if you can utilize existing conduits or pathways.3.

Soil Conditions

Evaluate the soil conditions. Rocky or unstable soil will make trenching more difficult and expensive.4.

Relocation Process

How will the buildings be relocated? Will they be lifted, rolled, or moved in sections? This will impact the feasibility of overhead vs. underground.5.

NEC Compliance

Consult the National Electrical Code (NEC) and any local amendments. Ensure your temporary installation meets all applicable requirements. Article 590 covers Temporary Installations.6.

Cost Analysis

Get detailed cost estimates for both overhead and underground options, including materials, labor, permits, and any necessary equipment rentals. Don't forget to include the cost of removal and restoration.

Recommendations

Given the specific circumstances, underground temporary feeders are generally the safer and more practical option for this scenario, especially if construction vehicles will be operating nearby. The upfront cost may be higher, but the risk of damage, safety hazards, and potential delays associated with overhead lines likely outweigh the cost savings. The cost of an overhead line coming down because it was hit by a piece of equipment, and the subsequent injuries, power outages, delays, and equipment damage could easily be a much bigger cost than just doing it underground from the start.

Here's a recommended approach


Prioritize Safety

Underground is safer, period.2.

Utility Locate

Perform a thorough utility locate before any excavation.3.

Trenching

Consider using a narrow trenching machine to minimize excavation and disruption.4.

Conduit

Use rigid PVC conduit for mechanical protection of the underground cables.5.

Cable Type

Use direct-burial rated cable.6.

Route Planning

Carefully plan the route of the underground feeders to avoid existing utilities and minimize interference with construction activities.7.

Protection

Ensure adequate cover over the cables to protect them from damage.8.

Marking

Clearly mark the location of the underground feeders.9.

Phased Installation

Consider installing the feeders in phases, as needed, to minimize the impact on construction activities.10.

Permitting

Obtain all necessary permits before starting any work.11.

Qualified Electrician

Use a qualified electrician with experience in temporary power installations.

Important Considerations for Temporary Power (Based on NEC 590)



Ground-Fault Protection

Ground-fault protection of equipment (GFPE) is often required for temporary power systems.

Weatherproof Enclosures

All electrical enclosures must be weatherproof.

Flexible Cords and Cables

May be permitted for temporary power drops to equipment.

Inspection and Maintenance

Temporary power systems should be inspected and maintained regularly.

Removal: Remove the temporary power system as soon as it is no longer needed.By carefully considering these factors and consulting with a qualified electrician, you can make an informed decision that will ensure the safety and reliability of your temporary power system. Flag for review