The scheduling approach is frequently used to categorize and determine thicknesses or conduit size, particularly those constructed of polymers like polyvinyl chloride (PVC). But how are the two most common types, schedule 40 and schedule 80, different from one another?
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Schedule 40 PVC conduit has a thinner wall, is lighter, has more wire spacing, and is more affordable than schedule 80 PVC conduit, despite the outside diameter being the same for both.
This article covers everything regarding conduits, notably the schedule 40 and 80 PVC conduits. We'll also discuss the distinctions between PVC conduits and PVC pipes, which are frequently confused by people. Continue reading for more information!
Differences Between Schedule 40 Vs. 80 PVC Conduit
A conduit is a sort of tube used to protect wires or cables. It is also known as an electrical conduit. Additionally, it makes it simpler to move, remove, or replace wires.
Conduits can protect electrical lines in the basement or attic from rodents or shield internet cables running along a home's façade from dampness and UV rays.
It can seal wiring away from heat, dangerous materials, or water in industrial and commercial locations to lower the risk of fire or malfunction.
Moreover, the schedule is an American Society for Testing and Materials (ASTM)-recommended pipes and conduits measurement standard.
The standard covers not just PVC but also aluminum, steel, and plastic tubing materials.
Contractors, engineers, plumbers, installers, and do-it-yourself (DIY) builders adopt scheduling. Schedules determine whether the conduits are appropriate for the intended purpose/s.
Professionals will select the schedule rating designed to meet and exceed the expected job demands while evaluating and comparing components and materials.
To put it another way, scheduling is used to choose the best tools for the project. Examining and comprehending the necessary conduit characteristics and variables related to and different from schedule ratings is crucial.
To understand the distinctions between schedule 40 and 80 PVC conduit, which are the two most widely used conduit schedules. Their differences are:
A schedule is used to specify the conduit's wall thickness. The higher the schedule value, the thicker the conduit wall will result in thicker material for conduits.
This conduit wall thickness is the primary physical distinction between schedules 40 and 80. As for the specified conduit size or schedule description, schedule 40 will have thinner walls than schedule 80.
The outside diameter of schedule 40 and 80 PVC conduit is the same. That is why you can use schedule 40 PVC conduit with schedule 80 and vice versa since they have the same outside diameter.
The schedule 80 pipe' extra thickness is applied inside, which reduces the pipe's inner diameter.
To illustrate the size difference, schedule 40 PVC conduit rated for 90° C wiring has a minimum wall thickness of 0.133"." In contrast, schedule 80 has a minimum wall thickness of 0.179" on the same outside diameter of 1.315”.
Weight is another aspect that could influence your decision regarding schedule PVC. Schedule 80 PVC is heavier than schedule 40 pipe because of its thicker wall.
For instance, conduits, which have an identical 1.315" outside diameter, weigh differently—0.327 lb for schedule 40 and 0.406 lb for schedule 80.
Because schedule 40 PVC has a wider internal diameter, pulling wires through it is simpler.
Contrary, schedule 80 conduit can accommodate fewer wires than schedule 40 conduit of the same nominal size because of its thinner interior diameter due to its thicker wall.
This thicker wall structure offers greater resistance to damage when constructing conduits in heavy traffic or high-hazard regions.
There are no color differences in signifying every conduit schedule. An electrical conduit is typically gray.
Sometimes a distinct color of conduit distinguishes some specific applications, such as orange for fiber optic systems, red for fire alarm systems, etc.
However, it is always advisable to double-check by reading the precise information printed on the sides of conduits.
Because schedule 40 is thinner, less material is used than schedule 80.
And so, the product can be weaker, and its acceptability for a project may be affected if the electrical integrity is in doubt for the intended usage.
Higher schedule conduits, such as schedule 80, which are thicker, will have more rigidity, structural endurance, and strain resistance.
The price of schedule 80 conduits is often higher than the price of schedule 40 conduits.
Schedule 80 costs more because of the additional material needed to create its thicker sidewalls and colorants (if desired), which will also contribute to the price increase.
The installation procedure and requirements for Schedule 40 and 80 pipes manufactured of the same material are the same.
Different pipe sizes with the same nominal pipe size have equal outer diameters according to ASTM specifications.
This specification allows pipes of various sizes to be linked together using the standard jointing technique.
The National Electrical Code (NEC), section 352, specifies how to use electrical conduit in general and PVC electrical conduit in particular.
It specifies that schedule 40 PVC electrical conduit is used for ceilings, floors, and walls, installing underground concrete enclosures, and exposure to direct sunlight.
However, schedule 80 PVC conduits can be used anywhere schedule 40 conduit is appropriate.
The NEC mandates schedule 80 PVC conduits for installation above ground in locations where physical damage is inevitable; this is necessary for safety reasons due to the additional wall thickness.
Can Schedule 40 and 80 PVC Be Used Outside?
If placed outside, it means being exposed to sunlight. When PVC is exposed to the UV component of the sun, the first exposed surface irreversibly changes, first with a loss of sheen and moving on to chalking and discoloration.
Concern has been raised about tapping pressure pipes exposed to UV rays. However, the PVC pipe industry has not discovered any evidence of tapping problems brought on by UV discoloration.
But for continuous outdoor exposed use, UL651-compliant Schedule 40 and Schedule 80 listed electrical conduit that has undergone sunlight resistance testing is recommended.
What Is The Difference Between Conduit And Pipe?
Both PVC conduit and PVC pipe resemble almost the same. Both are lightweight, hollow, and rigid cylinders manufactured of the same material.
But for everything in construction, the devil is in the details, where the variations between these materials become apparent. The distinctions are as follows:
PVC conduit is usually thinner than PVC pipe. The additional thickness keeps PVC pipe from bending and sustaining damage because it is used in applications where pressure is a factor.
PVC conduit producers stretch their resources by just building the conduit as thick as required to cover or route electrical wiring securely because the conduit doesn't need to endure high pressures.
PVC pipes typically have a white color and gray for conduits.
To make the PVC conduit gray, coloring may have been added. This can aid in visually differentiating the two pipes, especially if their diameter and thickness are the same.
PVC conduit is not pressure tested like PVC pipe is, which is one of the main distinctions between the two materials.
Water pressure plays a significant role in the stability and robustness of a plumbing system; this alters the applications for PVC pipe and PVC conduit.
Plumbing systems cannot generally use PVC conduit as leaks are possible because pressure testing is not done.
Polyvinyl chloride, a compound of vinyl and plastic, is used to create PVC conduit and pipe.
Chlorination of PVC conduit and pipe is occasionally used to combat corrosion and improve heat and fire resistance. This PVC pipe is referred to as CPVC (chlorinated polyvinyl chloride).
PVC conduit has a different function than PVC pipe. Plumbing and other pressurized systems are where PVC pipe is most frequently utilized.
Electrical systems are the primary application for PVC conduit. Thus, PVC pipe is utilized to transport water, while PVC conduit serves as the standard housing for wiring.
PVC conduit cannot replace PVC pipe since it has not been pressure tested, but it can be used in its place provided it has been produced to meet safety standards for flame and temperature resistance.
The only exception is when a drain pipe's water supply, for example, is not under pressure and instead is free to flow via a PVC conduit.
Is It OK To Run Romex In PVC Conduit?
The NEC does not prohibit the running of Romex through a conduit.
It is also important to note that the NEC encourages customers to run nonmetallic cables via tubes to shield them from hazardous substances.
So, if you have a stripped, exposed Romex cable outside, you should pass it via a conduit.
Romex is a brand and not a sort of standard wiring; hence the NEC makes no particular mention of Romex or conduits.
However, you may still use the knowledge the NEC has supplied about conduits to decide how to run your Romex cables and whether or not it makes sense to use a pipe.
But it is always safe to consult the local electrician or inspector as they are familiar with the local code and can explain what it says regarding conduits and Romex. The local code has priority over the NEC.
To Finish Up
Schedule 40 PVC conduit is typically appropriate for most household electrical applications.
The stronger wall schedule 80 PVC conduit is a better option if your wiring systems expose the PVC conduit to high-risk or high-traffic regions where it may be subject to bumps, impacts, or other hazards.
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