13,800V installed on the customer side of the service disco

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Pierre C Belarge

Pierre C Belarge

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Westchester County, New York
I do not inspect a lot of 13800 customer installations.

In reviewing the NEC, for underground installations, I was somewhat surprised at the requirements for installation.

I know local codes may be different...does anyone know of a reason to install concrete duct for 13800V installed in PVC in underground installations when not used as service conductors?
 
Pierre C Belarge said:
does anyone know of a reason to install concrete duct for 13800V installed in PVC in underground installations when not used as service conductors?
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EE specs? Bad day for alot of people if you hit it with a backhoe?

Not according to 300.50(as I'm sure you know)

Pierre, can you tell us more about this install? What kind of disco? How is this metered? What type of industry?
 
The concrete duct banks are to both protect the wire and a backhoe operator from destroying the install if hit by a backhoe. If an operator hits a ductbank he should try to expose what he hit and hopefully he will see markout tape across the top and stop digging. It is very common by me but i have also installed 13kv direct burial. We put fiberglass planks about a foot above the cable for some protection. And we put conductive markout tape at about a foot from finished grade. I dont think it is a building code but more a quality spec from an Architect/Engineer.
 
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I do not have many details, my information was from a phone call for a job that is going to be installed soon.
I reread my first post here, and I do not believe I posted too well.

The contractor mentioned that the 13800V install is "after" the service and is not utility conductors.

My question should have been...
Is there a requirement for the PVC to be installed in a concrete duct as per code, in the underground portion of the install?
 
Pierre C Belarge said:
I do not have many details, my information was from a phone call for a job that is going to be installed soon.
I reread my first post here, and I do not believe I posted too well.

The contractor mentioned that the 13800V install is "after" the service and is not utility conductors.

My question should have been...
Is there a requirement for the PVC to be installed in a concrete duct as per code, in the underground portion of the install?
Click to expand...
My question should have been...
Is there a requirement for the PVC to be installed in a concrete duct as per code, in the underground portion of the install?

I hope so.... when I get to digging....
 
Pierre C Belarge said:
I do not have many details, my information was from a phone call for a job that is going to be installed soon.
I reread my first post here, and I do not believe I posted too well.

The contractor mentioned that the 13800V install is "after" the service and is not utility conductors.

My question should have been...
Is there a requirement for the PVC to be installed in a concrete duct as per code, in the underground portion of the install?
Click to expand...

It is not unusual to have some utility installation requirements apply on the customer side of MV services. Unless the service equipment contains the customer's overcurrent protective devices our local utilities get to dictate how the unprotected conductors are installed.
 
I had a job in an industrial area in which the GRC conduits were installed above ground with no cover at all. The conduits were grouped together an laid on concrete strips that were about 8"x8"x10 ft. The utility, as you know, will bury URD cable about 40" deep. They will install primary cable in duct at about 40" deep but no concrete. I believe they use the depth of burial as the protection for the system. They do sometimes lay the yellow plastic warning strips about 12" below grade above the ducts hoping the back hoe operator will stop when he sees the strips.
 
Concrete duct ads considerable expense to an installation as it usually involves spare conduits for future expansion and a huge amount of concrete. Also a lot of added labor in chairing the conduits together and staking them down securely so they do not float to the top of the pour. They usually run other utilities in the same trench although they are not supposed to.
 
I do not see where the NEC requires the PVC underground installation to be in concrete for the 13800V install.
The POCO will not have a word in this portion of the install.
I was somewhat surprised as I mentioned earlier about the lack of a requirement for concrete ducts. Not only that, but Table 300.50 permits the 13800V in PVC at a depth of only 18 inches. Superscript 2 comes the closest I see to requiring concrete encasement.


The definition of Electrical Duct is located at 310.60, page 141 ('05 NEC), and it includes PVC buried in earth as a duct.
 
Pierre,

This is from the 08 notes to 300.50

b Listed by a qualified testing agency as suitable for direct burial without encasement. All other nonmetallic systems shall require 50 mm (2 in.) of concrete or equivalent above conduit in addition to the table depth.

Not highlighted so without going to the truck to get the 05, I'm assuming its the same. But I'm guessing you've read this also.
 
Pierre C Belarge said:
I do not see where the NEC requires the PVC underground installation to be in concrete for the 13800V install.
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That is correct. Concrete encasement is not required if the PVC is listed for direct burial.

The POCO will not have a word in this portion of the install.
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IMO the POCO always has a word in it... they can refuse to provide service! Perhaps the refusal wouldn't hold up in court.. but who wants to fight the POCO to that extent?
 
I think the first answer by quogueelectric is the most correct. However, I take exception to his statement, "They usually run other utilities in the same trench although they are not supposed to." The electric utilities usually are required to follow the NESC and the NESC requirements permit quite a bit of latitude when utilities agree to share joint trenches.

Hello Pierre.
 
ductbank is typical for wasterwater treatment plant. This is not require by code or city but I wil always spec for ductbank or encase concrete with tape for short run.
 
charlie said:
I think the first answer by quogueelectric is the most correct. However, I take exception to his statement, "They usually run other utilities in the same trench although they are not supposed to." The electric utilities usually are required to follow the NESC and the NESC requirements permit quite a bit of latitude when utilities agree to share joint trenches.

Hello Pierre.
Click to expand...


Hello Charlie
This is something to think about.
When installing different utilities or whatever in the "same" trench, and the trench is filled in, are all of those items still in the "same" trench? or are they just underground in close proximity?


It is my understanding the the NEC and the NESC permit different utilities i the "same open" trench, as long as the prescribed measurements are followed.
 
The table Chris refered to lists "Rigid Nonmetallic Conduit". That's Schedule 80 PVC only, right?

So Schedule 40 PVC would require 2" of concrete above it, right?

Steve
 
I would say that 300.50(A)(2) should cover it, but as someone else said it may be an EE requirement. Like you Pierre, I never see this kind of voltage in town on the customer side. I never see anything over 480.

I get those notes on plans every once in awhile, along with the question, why do I have to do this? Because the owner wants it.
 
The old saying is "when it rains it pours". Today I came to look at another service. The contractor neglected to tell me or put on the application the conductors are 13800V.

After some discussion and visually inspecting the work, we realized the conductors are not service conductors, they are subfeeders as in my other job.
These in fact were installed above grade in Rigid Metallic Conduit.
 
Pierre C Belarge said:
When installing different utilities or whatever in the "same" trench, and the trench is filled in, are all of those items still in the "same" trench? or are they just underground in close proximity?

It is my understanding the the NEC and the NESC permit different utilities in the "same open" trench, as long as the prescribed measurements are followed.
Click to expand...

We would call the installation random lay where there is no intentional separation. Normally, we would not random lay with gas, water, or sewer. However, we would with telephone and CATV.
 
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