How to Lay Electrical Cable Underground | This Old House

Summary

In this video, Heath and Kevin discuss a solution to remove overhead wires by taking everything underground. They dig a trench, place PVC conduits, and deal with challenges like ledge and rock walls. They use a 'mouse' to pull a string through the conduit and install 400 amps of underground wiring, a significant upgrade from the original 100 amps. The process involves meticulous installation and careful terminations, culminating in an inspection and utility company tie-in.

Takeaways

• 🛠️ The project involves removing overhead wires and installing underground conduits.
• 📏 The trench needs to be dug deep enough to place the conduits 18 inches below the finished grade.
• 🪨 Due to the rocky ground, the team faced challenges in digging and had to raise the grade.
• 🧱 Custom bends were made in the PVC pipe to accommodate the existing rock wall.
• 🔌 Schedule 40 PVC pipe was used to run underground wires and connect them to the meter box.
• 🐭 A 'mouse' tool was used to pull a string through the conduit by blowing it through with air.
• ⚡ The house's electrical capacity is being upgraded from 100 amps to 400 amps.
• 🔋 The team used THWN conductors suitable for underground installation.
• 🔧 Over 300 feet of copper wire, weighing more than 400 pounds, was pulled for the project.
• 💰 The cost of the copper wire alone was around $2,400, with final steps involving inspections and utility tie-ins.

Q & A

What is the main purpose of the project described in the transcript?

The main purpose of the project is to take electrical wiring underground to eliminate overhead wires.

How deep do they need to dig the trench for the conduits?

They need to dig deep enough to have 18 inches from the top of the conduit to the top of the finished grade.

What is the issue they encountered with the site's ledge?

The issue is that they couldn't dig down too far due to the presence of a lot of ledge, so they had to bring the grade up instead.

What material is used to protect the conduit?

They use three inches of sand to soften up everything around the conduit for protection.

What type of PVC pipe is used for the underground conduit?

They use Schedule 40 PVC pipe for the underground conduit.

How did they deal with the original rock wall and ledge issues?

They had to heat some pieces of Schedule 40 PVC pipe, do custom bends, and fit them into the rock wall.

What is a 'mouse' in the context of this transcript?

A 'mouse' in this context is a device used to help clean the conduit line and pull a string through it.

How do they get the conductors through the conduit?

They use a blower to push the mouse through the line, which then pulls the string attached to the conductors.

What is the difference in the amount of amps being pulled to the house before and after the project?

Originally, they were pulling 100 amps overhead, but after the project, they are pulling 400 amps underground.

How much wire did they estimate to have pulled for the project?

They estimated to have pulled a little over 100 feet of conduit and around 300 feet of wire in total.

What is the cost of the copper used in the project?

The cost for the copper used in the project was about $2400.

What are the next steps after the wires are pulled?

The next steps are to disconnect the wires pulled through with the rope, make up the terminations in the panel, have an inspector call it in, and then the utility company can tie in the overhead.