Schedule 20 PVC

Status
Not open for further replies.
charlie b

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Semi-Retired Electrical Engineer
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?
 
I used "DB120" pvc on an underground utility job and it was fine, but easy to break
 
charlie b said:
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?
Click to expand...
Just from the fact that there is only mention of schedule 40 and 80 in chapter 9 makes me believe it cannot be used.
 
Dennis Alwon said:
Just from the fact that there is only mention of schedule 40 and 80 in chapter 9 makes me believe it cannot be used.
Click to expand...
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
 
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.
Click to expand...
 
Dennis Alwon said:
Well this is from 2023 in chapter 9 in the index
Click to expand...
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
 
Last edited:
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.
 
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 said:
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.
Click to expand...
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.

charlie b said:
I see that that article does require listing. But how does that bring "type EB" into play?
Click to expand...
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
 

Ingredient Search & Raw Materials Search Engine | Prospector

Search 1,000's of ingredients and raw materials to find TDS, SDS, formulations and articles from leading suppliers. | Prospector by UL.
www.ulprospector.com www.ulprospector.com

UL prospector is free and you can search companies, listings, product codes, etc.

I will say that the search function and results are wonky and you can end up with a lot of stuff you don't care for.
 
This is from Nema in 2020

1720641604963.png
Click to expand...


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
 
Dennis Alwon said:
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
Click to expand...

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.
 
Status
Not open for further replies.
Top