Schedule 20 PVC

[charlie b]

I am reviewing a design that shows Sch. 20 PVC in a concrete-encased ductbank. I never encountered Sch. 20 before, and NEC 352 does not address schedule choices. I just learned it exists, but I don't know whether it would handle being encased in concrete. Should I make a comment on this, or is it perfectly OK?

 

[acrwc10]

I used "DB120" pvc on an underground utility job and it was fine, but easy to break

 

[Dennis Alwon]

I am reviewing a design that shows Sch. 20 PVC in a concrete-encased ductbank. I never encountered Sch. 20 before, and NEC 352 does not address schedule choices. I just learned it exists, but I don't know whether it would handle being encased in concrete. Should I make a comment on this, or is it perfectly OK?

Just from the fact that there is only mention of schedule 40 and 80 in chapter 9 makes me believe it cannot be used.

 

[wwhitney]

Just from the fact that there is only mention of schedule 40 and 80 in chapter 9 makes me believe it cannot be used.

That's not correct, Chapter 9 also mentions Type A and Type EB. I'm guessing that Schedule 20 is the same as Type EB. Some of the manufacturers are calling it EB-20.

Cheers, Wayne

 

[Dennis Alwon]

This is from the enhanced view

The UL Guide Information for Electrical Equipment describes rigid PVC conduit, Type PVC, for use in accordance with Article 352. Schedule 40 is suitable for locations not subject to physical damage for underground, aboveground, indoor, and outdoor locations. Schedule 80 is suitable for locations where the conduit will be subject to damage. Types A and EB are intended for underground installations.

 

[Dennis Alwon]

That's not correct, Chapter 9 also mentions Type A and Type EB. I'm guessing that Schedule 20 is the same as Type EB. Some of the manufacturers are calling it EB-20.

Cheers, Wayne

Well this is from 2023 in chapter 9 in the index

 

[hbiss]

Schedule 20 is used for underground communications ducts.

-Hal

 

[ptonsparky]

We used Sched 20 extensively for rodent protection of DB cables. The only stipulations were that it must contain conductors rated for such and that it was at 24" or greater in depth. Then marking tape once that became a requirement.

 

[wwhitney]

Well this is from 2023 in chapter 9 in the index

I didn't check the index, maybe it's deficient. PVC Type A and Type EB are still there in Chapter 9 Table 4 in the 2023 NEC, pages 719 and 720.

So I think the appropriate comment is that for an NEC application, the Schedule 20 PVC must be listed (per 352.6), which if I understand correctly would be as Type EB.

Cheers, Wayne

 

[charlie b]

I'll take a look at chapter 9. The plans are calling for sch. 20 (1 inch) empty conduits with pull strings for future EV charging stations. They also call for the same for site lighting circuits. All are buried with 24 inches of cover.

I just noticed that portions of the site lighting runs are concrete-encased, while other portions are direct buried within sand. I am posting a comment asking why.

 

[charlie b]

What do "type A" and "type EB" mean?

 

[ptonsparky]

I" isn't big enough. For anything in the future.

Our suppliers had 2" and above.

ETA: maybe LED lighting but EV chargers, IDK.

 

[Elect117]

I am going to say no since Sch. 20 is not a method in the NEC. It is also not as strong as Sch. 40 and Sch. 80 leading me to believe it can be negatively impacted by pulling wire/rope, cement drying, or soil movement and compaction.

You also have to consider that the temperature of the soil, conductor, etc. might impact the conduits long term durability.

DB120 is also not listed. It is a approved method for utilities. That is why you will usually see it called "DB120 Utility conduit".

UL's product code for nonmetallic underground conduit for use with conductors (QQRK) only has Sch 40 and Sch 80 HDPE except for one company called Blue Diamond Industries that has a pipe type called "EPEC-B HDPE conduit, trade sizes 1-1/2, 2, 2-1/2, 3, 4."

 

[charlie b]

. . . the Schedule 20 PVC must be listed (per 352.6), which if I understand correctly would be as Type EB.

I see that that article does require listing. But how does that bring "type EB" into play?

 

[wwhitney]

I just noticed that portions of the site lighting runs are concrete-encased, while other portions are direct buried within sand. I am posting a comment asking why.

FYI, UL 651 says "1.3.2 Type EB (encased burial) rigid PVC conduit is intended for encasement in concrete in trenches outside of buildings. Type A rigid PVC conduit is intended for encasement in concrete in any location."

So sounds like any portion buried within sand would need to be Schedule 40.

I see that that article does require listing. But how does that bring "type EB" into play?

The types listed under UL 651 are Schedules 40 and 80 and types EB and A. From a brief web search, type EB seems to have a wall thickness that would correspond to Schedule 20.

Cheers, Wayne

 

[Elect117]

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[LarryFine]

I see it as a concrete form that stays in place.

 

[Dennis Alwon]

This is from Nema in 2020

I assume it was not compliant years ago as I have seen threads from 2009 where Don stated that EB-20 wasn't allowed for anything in the NEC. Looks okay now if it is encased in concrete

 

[Elect117]

This is from Nema in 2020




I assume it was not compliant years ago as I have seen threads from 2009 where Don stated that EB-20 wasn't allowed for anything in the NEC. Looks okay now if it is encased in concrete

I couldn't find a listing for it. The nonmetallic conduit section requires the conduit be listed. To be honest, any conduit that the utility allows is probably good enough for commercial/residential applications but I can't anything listed other than the Sch 40, Sch 80 and EPEC-B HDPE.

 

[charlie b]

So sounds like any portion buried within sand would need to be Schedule 40.

Looking again at their drawings, they have that detail right.