You can't fit as many wires in schedule 80 PVC as you can schedule 40 PVC conduit of the same size

[jar546]

Someone check my math. Are you aware of this?

To illustrate a situation where a wire could fit into a 1.5-inch Schedule 40 PVC conduit but not into a 1.5-inch Schedule 80 PVC conduit, according to the NEC, let's consider a 4 AWG THHN/THWN copper wire.

The approximate area of a 4 AWG copper THHN/THWN wire is about 0.1293 square inches per conductor. According to the NEC, the conduit fill should generally not exceed 40% for more than two conductors.

The approximate internal area for 1.5-inch Schedule 40 PVC conduit is 1.767 square inches, while for 1.5-inch Schedule 80 PVC conduit, it's 1.443 square inches.

Schedule 40 PVC Conduit:​

• Maximum fill would be 1.767×0.4=0.70681.767×0.4=0.7068 square inches.
• Number of conductors that can fit: 0.7068÷0.1293≈5.460.7068÷0.1293≈5.46.
• Rounding down, 5 conductors of 4 AWG could fit into a 1.5-inch Schedule 40 PVC conduit.

Schedule 80 PVC Conduit:​

• Maximum fill would be 1.443×0.4=0.57721.443×0.4=0.5772 square inches.
• Number of conductors that can fit: 0.5772÷0.1293≈4.460.5772÷0.1293≈4.46.
• Rounding down, only 4 conductors of 4 AWG could fit into a 1.5-inch Schedule 80 PVC conduit.

So in this example, you could fit 5 conductors of 4 AWG copper wire into a 1.5-inch Schedule 40 PVC conduit, but only 4 conductors would fit into a 1.5-inch Schedule 80 PVC conduit, all while complying with the NEC guidelines.

 

[steveray]

Pipe is ID referenced, tubing is not....

 

[jar546]

Pipe is ID referenced, tubing is not....

I don't understand the context of this post.

 

[steveray]

I don't understand the context of this post.

Pipe keeps a consistent I.D....Tubing does not, as wall thickness changes, so does the ID of tubing...Hence EMT ENT...seems like conduit runs like tubing not pipe...So it makes perfect sense, and you gave a great real world example....

 

[mtlogcabin]

Jar:
You are correct that schedule 80 has a smaller inside diameter than schedule 40.

PVC Conduit for Electrical Wiring​

Phil, the couplings and fittings for schedule 40 and schedule 80 PVC are the same size, here’s why:
Differences Between Schedule 40 and Schedule 80 PVC Conduit

• The inside diameter is smaller with schedule 80 PVC because the wall of the conduit is thicker.
• The inside diameter of schedule 40 PVC conduit is larger because the wall of the conduit is thinner.
• The outside diameter of both SCH 40 and SCH 80 is the same.

Selecting the Right PVC Conduit for Electrical Wiring​

• PVC Conduit for Electrical Wiring – (Poly Vinyl Chloride).
• PVC conduit is commonly used for underground electrical wiring.
• The gray color makes it easy to identify Electrical PVC Conduit.
• Schedule 40 PVC is the most commonly used for underground wiring.
• Schedule 80 PVC has a thicker wall to provide more protection to the electrical wire.
  Schedule 80 PVC is commonly used in above ground applications where the conduit is vulnerable to damage.