underground ducts

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donaldsullivan

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Can white schedule 40 PVC water pipe be used as an underground duct as stated in NFPA 70 310-60.(a)? The proposed cable is direct bury rated, 15 kV shielded power cable. The cable will be pulled into the pipe buried at 36" below grade.
 
Re: underground ducts

IMO The water pipe you are refering to is not listed as an electrical conduit. While other will say it is the same material I disagree. Our conduit is PVc and most plumbing pipe is CPVC. What differance this makes I do not know. However in 310.60 it referances listed for use as one of the qualifactions for this instalation.
 
Re: underground ducts

I would pass the installation due to the cable being rated for direct burial.
 
Re: underground ducts

Originally posted by donaldsullivan:
Can white schedule 40 PVC water pipe be used as an underground duct as stated in NFPA 70 310-60.(a)? The proposed cable is direct bury rated, 15 kV shielded power cable. The cable will be pulled into the pipe buried at 36" below grade.
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What are you using for sweeps, plumbing elbows? :roll:
 
Re: underground ducts

Oh yeah I forgot, the answer is no you may not use plumbing pipe for electrical raceways.

310.60(a) says a chapter 3 method you mentioned PVC.

352.6 Listing Requirements.
RNC, factory elbows, and associated fittings shall be listed.
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Re: underground ducts

A direct buried cable is already enclosed in an approved covering, the secondary covering can be anything for protection of the approved covering.
 
Re: underground ducts

Originally posted by bennie:
A direct buried cable is already enclosed in an approved covering, the secondary covering can be anything for protection of the approved covering.
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OK I'll buy that :eek: , all I picked up on was the code reference.
 
Re: underground ducts

How about this:
A landscaper is doing some digging and finds this white pipe and it's in the way for the job that he's doing. Now he checks to see if he has any water pipes in this area and he doesn't so he decides to cut it. I'll leave the rest up to your imagination.
 
Re: underground ducts

Then white water pipe meets the definition of identified for the use.

It's a judgement call, according to the definition of "identified" on page 70-36 Article 100.

[ March 17, 2004, 08:26 PM: Message edited by: bennie ]
 
Re: underground ducts

Identified (as applied to equipment). Recognizable as suitable for the specific purpose, function, use, environment, application, and so forth, where described in a particular Code requirement.
FPN:Some examples of ways to determine suitability of equipment for a specific purpose, environment, or application include investigations by a qualified testing laboratory (listing and labeling), an inspection agency, or other organizations concerned with product evaluation.
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How did you come to that conclussion!
 
Re: underground ducts

There is no code requirement that direct burial cable be inside listed conduit.

There is a code requirement to protect the buried cable from rocks and any other material that may damage the cable.

If this was my call, I would not have a problem with approving this pipe as being identified for the purpose it is being used.

As I stated "this is a judgement call" The method that has been approved, in the past, to protect buried cable, was to throw lumber dunnage over the cable.

I think enclosing it a pipe, of any kind, is superior to the wood covering.
 
Re: underground ducts

There is no code requirement that direct burial cable be inside listed conduit.
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No one said there was.
The point being is IF it is installed in conduit (as mentioned above), then there is a code requirement for the conduit to be listed.


352.6 Listing Requirements.
RNC, factory elbows, and associated fittings shall be listed.
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This means that NO judgement call is necessary.
 
Re: underground ducts

Dave, there is no mention of "conduit" in 300.50(A)(1) only a raceway "identified" for the use, and the FPN to the definition of "identified" gives this judgement call to the inspector as one example.

Roger
 
Re: underground ducts

Hi Dave, I don't realy know enough about the installation to make an assumption, but 300.50(B)would only be that portion of the run from the proper depth to the 8' height, point of entrance, or termination enclosure.

Roger
 
Re: underground ducts

The pipe is routed from manhole to manhole. I interpret underground duct in 310-60.(a) to be anything round in cross section and listed to be installed in the ground. As long as the direct buried cable is at the 36" depth it can be enclosed by the water pipe or any other round material listed for underground use. If code required only electrical conduit then why is other raceways another option in 310-60.(a)?
 
Re: underground ducts

Mr. Sullivan,

This statement,
I interpret underground duct in 310-60.(a) to be anything round in cross section and listed to be installed in the ground.
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is not even close to what the code states.
Electrical Ducts. As used in Article 310, electrical ducts shall include any of the electrical conduits recognized in Chapter 3 as suitable for use underground; other raceways round in cross section, listed for underground use, and embedded in earth or concrete.
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The code says "other raceways round in cross section, listed for underground use" not "anything round"! If this where true, we could use that plastic flexable corrugated drainage pipe that is typically used for drainage to run our electrical conductors in and save a whole lot of time and money! Heck, we could hire landscapers to install it for us!

As a Utility Engineer, do you really think this plumbing PVC is an acceptable raceway?
 
Re: underground ducts

Hi Dave I am not as sure this as cut and dry as we both would like it to be. :confused:

310.60 Conductors Rated 2001 to 35,000 Volts.

(A) Definitions.

Electrical Ducts. As used in Article 310, electrical ducts shall include any of the electrical conduits recognized in Chapter 3 as suitable for use underground; other raceways round in cross section, listed for underground use, and embedded in earth or concrete.
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It looks to me and I could be wrong, that this is saying a Chapter 3 raceway or other raceways listed for underground use.

I am no plumber but I think that the plumbers pipe is listed for underground use.

It seems to me if you can afford the HV cable the cost of electrical raceway would be minimal.
 
Re: underground ducts

do you really think this plumbing PVC is an acceptable raceway?
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I agree with Bennie. Since the cable is allready rated for direct burial, what difference does it make?

The raceway is serving as supplementary protection for the cable, not the primary protection.
 
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