Is Schedule 40 OK for use under a residential driveway?

[Coffee Cup]

My interpretation would be yes. The Inspector says Schedule 80 is required. I am in Massachusetts and there is only one state code not a flavor for each town. Supply house chit chat goes both ways on this. Where is the physical damage? The depth requirements take care of that.

I have looked at:

352.10 (H) Underground Installations; shows that PVC is rated for direct burial as well as permitted to be encased in concrete See 300.5 and 305.15 (Not applicable as it is under 1000 volts. In the 2023 National Electric Code Handbook code handbook it states in the notes that “Schedule 40 and Schedule 80 are both permitted for underground installations, such as under driveways, provided that the required burial depth is met” though not official NEC it clarifies this issue.



300.5 (A) states for minimum cover requirements see table 300.5 (A)

300.5 (D) Protection from Damage

Ss (1) addresses minimum cover distance below grade to protect the conduit, no mention of Schedule 40 or 80 in this.

Ss (2) Mentions emerging from grade to 8’ needing protection I used Schedule 80 for that for the pole riser.

Ss (3) addresses the warning ribbon, which is there

Ss (4) Enclosure or Raceway Damage. More for direct buried cables that may get damaged. I assume sharp rocks, ledge or unable to meet depth requirements should use Schedule 80 or RTRC-XW (I would not consider properly installed conduit under a driveway as subject to physical damage)

Table 300.5(A) the applicable Column is 3

Location of wiring method or Circuit

“Under Streets, Highways, roads, alleys. Driveways and parking lots” The minimum cover is 24”. If you stop here you would think 24” but the location below is “One and two family dwellings driveways and outdoor parking areas, and used only for dwelling related purposes” Column 3 shows minimum depth as 18” over the Conduit and the table does not address Schedule 40 or Schedule 80 specifically.

Mass Code Amendment 300.5(A) informational note states: “Cables suitable for direct burial are often sleeved in various raceways for design reasons. If such cable is installed with sufficient cover for direct burial, then the characteristics of that raceway need not be evaluated. Other rules of this Code that apply to raceways generally may apply. See 300.5(H)”. Since the cable being installed is rated for direct burial the raceway seems irrelevant other than the fact it may want to be used differently in the future, I would want to do the job properly regardless.

Did I miss something?

Thanks in advance.

 

[shortcircuit2]

Under Streets, Highways, roads, alleys. Driveways and parking lots” The minimum cover is 24”. If you stop here you would think 24” but the location below is “One and two family dwellings driveways and outdoor parking areas, and used only for dwelling related purposes” Column 3 shows minimum depth as 18” over the Conduit and the table does not address Schedule 40 or Schedule 80 specifically.

Table 300.5 column 1 shows 18-inches for direct buried cable under residential driveways. Looks like when you get beyond the driveway back to 24-inches down for cables...unless you have a column 4 or 5 circuit

Column 3 is also 18-inches for PVC both under driveway and beyond.

Physical protection is an AHJ call...where SCH 80 may be required

 

[Coffee Cup]

Table 300.5 column 1 shows 18-inches for direct buried cable under residential driveways. Looks like when you get beyond the driveway back to 24-inches down for cables...unless you have a column 4 or 5 circuit

Column 3 is also 18-inches for PVC both under driveway and beyond.

Physical protection is an AHJ call...where SCH 80 may be required

I don't see any AHJ notes on requiring schedule 80 in any of 300.5 table. I would think the table speaks for itself. I would think that buried to depth would be the protection. in 352.10 in the 2023 handbook it says flat out you can use schedule 40 or 80 under driveways so long as table 300.5(A) is followed. I was planning to go down 24" regardless but at $75 per stick and a 300 foot run seems excessive.

 

[infinity]

IMO the inspector is wrong. How is a Sch40 PVC raceway going to be damaged buried under a driveway? You can even run UF if you want.

 

[Coffee Cup]

IMO the inspector is wrong. How is a Sch40 PVC raceway going to be damaged buried under a driveway? You can even run UF if you want.

Thats what I know, how am I going to convince him. and to top it off it's in the center of the drive with a wall on one side and a cliff on the other so it's hard to drive over the pipe

 

[infinity]

Thats what I know, how am I going to convince him.

Ask him the obvious question and to explain to you how something that is buried under the driveway is subject to physical damage?

 

[shortcircuit2]

Ground settlement over time from heavy truck traffic or freeze-thaw cycles? My fathers driveway developed 10-inch (tire) ruts in the pavement from the 20+ ton garbage truck that came weekly. Most residential asphalt driveways here in New England are finished for light duty vehicle use...1.5 inch binder and 1.5 inch top coat.
But I guess schedule 80 probably would have been damaged also in my old mans driveway.

352.10(K) Physical Damage. is new in 2023

I believe they are attempting to define physical damage in the 2026 NEC

 

[Joe.B]

What is the driveway made of? If gravel or asphalt then ask if they would accept 4 inches of concrete (or slurry) would be an acceptable means of protecting the conduit. Of course that may defeat the purpose of using the cheaper pipe to begin with, so maybe not...

 

[don_resqcapt19]

.....
I believe they are attempting to define physical damage in the 2026 NEC

Here is what the PI proposed.

Physical Damage
Damage that plausibly creates a risk to equipment’s function or safety.

I don't see that as being any less subjective than just using the term without a definition.

 

[Coffee Cup]

Thanks to input from this forum, and my own research I made my case to the inspector this morning and he said that schedule 40 would be ok, so long as it was 24" deep as required in Table 300.5(A) “Under Streets, Highways, roads, alleys. Driveways and parking lots”, Progress but I said did you just stop when you saw driveways, and he said Yes. I asked him to look at the line below where it refers to one and two family driveways, and he said "I stand corrected you only need 18". My friend/customer bought 300 feet of 3" schedule 40 last fall and would be stuck with it and then need 300 feet of Schedule 80at about $80 a stick is unacceptable when the code says 40 is ok. but polling several electricians at a few supply houses and HD they all automatically say Schedule 80. We are all guilty of hearing somebody say you got to do it this way because joe got flunked because he didn't on a lot of things. Then somebody actually researches it and realizes what they heard for years was wrong. It becomes standard practice and the inspector says do it this way and we shake our heads yes. We all deal with a very complex document and it is hard to mis interpret the code or take it out of context. I flunked an inspection because the electrician didn't use green ground screws. I would swear I read that and I looked and looked and found out it was for a ground screw in a fixture or fixture bar shall be substantially green in color somewhere in 401, but he changed them and I took a little heat but I was wrong and I apologized. I was glad the inspector did his research and we both learned something.

Short Circuit, I think that if you were buried at 24" the 40 would have worked fine. Did they actually break?

John

 

[infinity]

The fact that the NEC allows direct burial cable under a dwelling driveway would indicate to me that being subject to physical damage is a non-issue for a raceway.

 

[Coffee Cup]

Infinity, it seemed that way to me as well but a service I did in a neighboring town the inspector said it had to be schedule 80, it wasn't worth arguing for 20' of two inch. But 300 feet of 3" seems to be worth the argument.

Another thing that some inspectors have done locally is require traceable metallic warning ribbon for services. Not in the code and it you need a special metal detector to trace it. Having done Digsafe for a number of years for a power company I had no trouble tracing wires with electricity running through them at all. If we used plastic wires I may agree, but until the laws of physics change that won't be happening.

 

[cabledawg]

From what I see, schedule 40 for the underground and schedule 80 for the stub up's(for protection).

 

[letgomywago]

Here is what the PI proposed.

I don't see that as being any less subjective than just using the term without a definition.

I wish there was more black and white with this honestly. Or some flat out examples of what isn't subject to physical damage.

 

[don_resqcapt19]

I wish there was more black and white with this honestly. Or some flat out examples of what isn't subject to physical damage.

In my opinion that is a term that cannot be defined, and just like what one Supreme Court Justice said about obscenity, " I will know it when I see it".
One of the issues that the same term is used with MC and NM as well as other wiring methods. There are areas where I would seen NM as being subject to physical damage and not permit it to be installed, but would not see MC installed in the same location as being subject to physical damage.

"everything you can see, and lots of things you can't see are subject to physical damage"

 

[letgomywago]

In my opinion that is a term that cannot be defined, and just like what one Supreme Court Justice said about obscenity, " I will know it when I see it".
One of the issues that the same term is used with MC and NM as well as other wiring methods. There are areas where I would seen NM as being subject to physical damage and not permit it to be installed, but would not see MC installed in the same location as being subject to physical damage.

"everything you can see, and lots of things you can't see are subject to physical damage"

That's why I want the term "subject to limited abrasion" then that could be used to justify exposed mc or even carflex in a tool shed or shop or carflex whip from a disconnect or motor vs romex or UF. Physical damage I think should require striking with equipment or tools not just the risk of someone laying a shovel against it or a random piece of 2 inch trim board scrap.

 

[Jpflex]

Physical protection is an AHJ call...where SCH 80 may be required

I was actually wandering about this. If scheduled 80 is required for protection of wires leaving a trench and up to 8 feet to termination then why have schedule 40 pvc?

 

[cabledawg]

JP, I think its presumed that underGround Is presumed protected but not clear on that

 

[tortuga]

The local utilities here use a flimsy conduit that is not even schedule 40 reminds me of common irrigation pipe but its gray. You see it spooled up on the directional boring rigs. They often switch to sch 80 when going back up a pole. Not that they are subject to the NEC or anyhting but their engineers dont want to be replacing crushed conduit either.

 

[kwired]

Here is what the PI proposed.

I don't see that as being any less subjective than just using the term without a definition.

leaves the mud about as clear as it always was.