PVC direct bury

[Pete Olson]

We are currently estimating a project, the Engineer drawing up the prints has us installing Schedule 80 PVC underground with sand bedding. We asked the question why Schedule 80 and not schedule 40. His reply was, because schedule 80 was rigid and schedule 40 was not. He would be okay with schedule 40 but, we would have to cover it with a flowable fill or concrete this way it would be protected from damage. We sent him the code reference for PVC (Article 352) and he came back with, schedule 40 underground and it needs to be covered with flowable fill not sand.

Is there any way, to get the NEC reference 352 (G) to spell out Schedule 40 can be installed underground with native fill, sand bedding, or concrete encasement? Instead he is reading underground encased in concrete is the only way you can install it. His reply to our questions was; Schedule 40 shall be used in lieu of Schedule 80 for the duct banks.
How can we get the Code reference changed, to be more descriptive of the back fill? ie... Schedule 40 approved for direct bury / underground with native soil, sand bedding or concrete encased back fill.

 

[infinity]

Sch40 is installed in the earth everyday and is permitted to be installed that way by the NEC. Article 352 is for both Sch40 and Sch80 PVC. If Sch40 is not rigid PVC then what is it?

Welcome to the Forum.

352.1 Scope. This article covers the use, installation, and
construction specifications for rigid polyvinyl chloride conduit
(PVC) and associated fittings.

Says it right on it:

 

[Pete Olson]

That is what we tried to explain to him. Unfortunately, the code does not specify this procedure clear enough for him. We sent him the code reference, he still wants the flowable fill. Is there a way, to get the code to be more specific to the back fill methods and acceptable material?

 

[infinity]

Take a look at 300.5(F). That section applies to backfill for underground raceways.

300.5(F) Backfill. Backfill that contains large rocks, paving materials, cinders, large or sharply angular substances, or corrosive
material shall not be placed in an excavation where materials may damage raceways, cables, conductors, or other substructures or prevent adequate compaction of fill or contribute to corrosion of raceways, cables, or other substructures. Where necessary to prevent physical damage to the raceway,
cable, or conductor, protection shall be provided in the form of granular or selected material, suitable running boards, suitable sleeves, or other approved means.

 

[Pete Olson]

We have previously shown the engineer, the RIGID writing on the schedule 40 PVC. I will send the engineer the 300.5(F) reference as well. It is sad to see the extra expense being added to a project, where the client asking the contractor to keep the expenses down. Thanks for the discussion.

 

[Pete Olson]

Sometimes I wonder about engineers.

 

[infinity]

We have previously shown the engineer, the RIGID writing on the schedule 40 PVC. I will send the engineer the 300.5(F) reference as well. It is sad to see the extra expense being added to a project, where the client asking the contractor to keep the expenses down. Thanks for the discussion.

It's up to the client to explain to the engineer that he wants the less expensive Sch 40 PVC, after all I'm assuming that the engineer works for him. Unless there is a code reason why Sch 80 is needed Sch 40 is perfectly fine.

 

[oldsparky52]

The owner has the right to spec a job to a higher standard than an NEC code minimum standard.

 

[infinity]

The owner has the right to spec a job to a higher standard than an NEC code minimum standard.

I agree, but it sounds like in this case the engineer is more mistaken in his interpretation of what rigid PVC is.

 

[electrofelon]

If the engineer is that far off base on such a basic thing( I mean wow), I wouldn't want him involved in my project. I've been in the trade 20 years, and I cant recall ever using 80 underground (except 90s). Maybe show the client and engineer this thread after a few more people pile on

 

[infinity]

If the engineer is that far off base on such a basic thing( I mean wow), I wouldn't want him involved in my project. I've been in the trade 20 years, and I cant recall ever using 80 underground (except 90s). Maybe show the client and engineer this thread after a few more people pile on

Same here. I don't want to pile on the engineer who may have a good reason for wanting Sch 80 but saying that Sch 40 isn't rigid PVC is incorrect.

 

[steve66]

While I agree with the responses, engineers are free to specify above and beyond code requirements if they feel they have a reason too. So are you sure the engineer thinks its a definite code requirement, and it's not something that he just isn't willing to budge on? Just as an example, I don't think concrete encasement of underground conduits is ever required, but it is often specified and required by engineers.

If you are estimating the project, why not just include the Schedule 80 and move on? If you are bidding against anyone else, they should be bidding the same schedule 80.

 

[Hv&Lv]

If it were my license I would want to make sure I was covered.
the requirements in the NEC aren’t a ceiling to reach for, it’s a floor to build from

 

[electrofelon]

If it were my license I would want to make sure I was covered.
the requirements in the NEC aren’t a ceiling to reach for, it’s a floor to build from

So you would put in a bunch of un necessary BS that 99.9% of others wouldn't do, on the customer's dime just so you are covered?

That said, if I am pricing something based on plans, yes I go off the plans and, unless I have a relationship with the customer, I probably won't go around the engineer to the client to try and get things changed.

 

[Hv&Lv]

So you would put in a bunch of un necessary BS that 99.9% of others wouldn't do, on the customer's dime just so you are covered?

That said, if I am pricing something based on plans, yes I go off the plans and, unless I have a relationship with the customer, I probably won't go around the engineer to the client to try and get things changed.

I never said that.
never said I would go to those lengths either.

I’ve only specified schedule 80 one time. It was a creek crossing. But no sand bedding. I don’t see any need in that at all. We used to sand bed 40 years ago for direct buried primary cables before the jacket came on it.

He could be new, he could be inexperienced, he could be terrified since this might be his first project with his stamp.
maybe the engineer knows something the electrician doesn’t.

all I said was if it were my license I would make sure I was covered.

The NEC is minimum, plain and simple.

 

[ActionDave]

The NEC is minimum, plain and simple.

The NEC is quite adequate. When it stays within its original purpose as a safety standard and not a design manual there seldom is a reason to go beyond the requirements. The only time code minimum becomes an issue is when the authors of the NEC cross over into the realm of design or users make it an excuse for a poor design.

 

[oldsparky52]

I think I might turn in a bid based on schedule 80 and offer a savings if using schedule 40.

 

[Hv&Lv]

The NEC is quite adequate. When it stays within its original purpose as a safety standard and not a design manual

true, quite adequate...

but still minimum.

 

[kwired]

We have previously shown the engineer, the RIGID writing on the schedule 40 PVC. I will send the engineer the 300.5(F) reference as well. It is sad to see the extra expense being added to a project, where the client asking the contractor to keep the expenses down. Thanks for the discussion.

If contractor is following specifications it is difficult to keep this kind of expense down, such changes often need approval of the designer, so client should be asking the designer and not the contractor to keep expenses down on issues like this one.

Using aluminum instead of copper conductors, using raceways as EGC's instead of pulling a conductor - all similar design issues that many engineers often call for the more expensive option whether there is any major justification or not.

 

[steve66]

The NEC is quite adequate. When it stays within its original purpose as a safety standard and not a design manual there seldom is a reason to go beyond the requirements. The only time code minimum becomes an issue is when the authors of the NEC cross over into the realm of design or users make it an excuse for a poor design.

I'd say the NEC is usually adequate, but not always. Both from a design standpoint and from a safety standpoint. They couldn't anticipate every possible act of stupidity, and I can think of a few examples that make me cringe, that probably aren't covered in the NEC.

A lot of the design depends on the client. Some clients want everything as cheap as possible. But most clients are more concerned about having things done right. So to some extent, engineers have to adjust things to match the clients needs. Residential - sure the NEC is going to be good for 99% of that work. But healthcare or industrial where downtime can mean lots of lost revenue, and lives may even be at stake. Then going above the NEC often makes good sense.

Just as an example from a design standpoint, Sch 40 PVC is allowed underground. And so are Sch 40 standard radius sweeps and elbows. But what happens when the pull rope burns through a bend while pulling the wire in? I've seen posts here where that has happened.

In that case I think everyone will agree that Sch 80 long radius bends would have been much better. Or maybe even RGS elbows.

My guess is that the same people who criticize engineers for spec'ing anything above the code are going to be the first ones to go to the owner blaming the engineer when something like that happens.