Expansion fittings for underground services

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Ohms law

Senior Member
Location
Sioux Falls,SD
I personally would like to see underground services be required to have an expansion fitting. To many times I have ran across people pouring concrete patios and the slab settles which pulls the conduit out of the meter socket. Or I've even seen on new construction, the ground will just simply settle and do the same thing. Any thoughts?
 

hardworkingstiff

Senior Member
Location
Wilmington, NC
I personally would like to see underground services be required to have an expansion fitting. To many times I have ran across people pouring concrete patios and the slab settles which pulls the conduit out of the meter socket. Or I've even seen on new construction, the ground will just simply settle and do the same thing. Any thoughts?
I agree. Have you considered sending in a code modification form? Someone will probably post a link to it and give the proper name of it.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The common application of 300.5(J) already requires this.
300.5(J) Earth Movement. Where direct-buried conductors, raceways, or cables are subject to movement by settlement or frost, direct-buried conductors, raceways, or cables shall be arranged so as to prevent damage to the enclosed conductors or to equipment connected to the raceways.
Informational Note: This section recognizes ?S? loops in underground direct burial to raceway transitions, expansion fittings in raceway risers to fixed equipment, and, generally, the provision of flexible connections to equipment subject to settlement or frost heaves.
 

iwire

Moderator
Staff member
Location
Massachusetts
I guess I should talk to my city inspectors, considering I live in South Dakota and the frost line gets down to 4' or so. And then send in a modification form to the NEC to have 300.5 (J) reworded for areas like mine.
We can have frost down to about 3' and we are required to use the fittings based on the section posted without rewording.
 

Smart $

Esteemed Member
Location
Ohio
I guess I should talk to my city inspectors, considering I live in South Dakota and the frost line gets down to 4' or so. And then send in a modification form to the NEC to have 300.5 (J) reworded for areas like mine.
How is 300.5(J) insufficiently worded as is?
 

BPoindexter

Inactive, Email Never Verified
Location
MT Vernon, WA
I would think 300.5(J) would cover your area? Sounds as if you are wanting to require expansion fittings on all service risers regardless of area they are in?
 

Ohms law

Senior Member
Location
Sioux Falls,SD
Geese, I feel like I'm getting bombarded here. I'm just trying to figure out why this is not happening where I live. I know what the code states, so yes you would think it would be required. I'm just trying to get as much information as I can before I go and start talking to my AHJ. They can be real jerks.
 

Smart $

Esteemed Member
Location
Ohio
Geese, I feel like I'm getting bombarded here. I'm just trying to figure out why this is not happening where I live. I know what the code states, so yes you would think it would be required. I'm just trying to get as much information as I can before I go and start talking to my AHJ. They can be real jerks.
You may want to choose your words carefully when you talk to your AHJ. It is their lack of enforcement that is the reason why it is not happening there.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Geese, I feel like I'm getting bombarded here. I'm just trying to figure out why this is not happening where I live. I know what the code states, so yes you would think it would be required. I'm just trying to get as much information as I can before I go and start talking to my AHJ. They can be real jerks.
The section has been in the code for a number of cycles, but in many areas, enforcement of this section is fairly new.
 

kwired

Electron manager
Location
NE Nebraska
My opinion against this nonsense has always been that expansion fittings are for thermal expansion/contraction of the raceway, but do nothing to protect contained conductors from movement from settling earth or other similar activity.

If a raceway changes length what happens to the conductors inside that remain same length?

In the case of thermal expansion of a raceway the purpose of an expansion fitting is to allow the raceway to remain the same length without damage occuring.

How much ground settling or frost heave are we to allow somehow in the conductors?

I have seen where ground has settled and pulled on a raceway, the expansion fitting saved the raceway, but the conductor was also pulled and damaged terminations it was connected to.

Leaving a loop of conductor in a meter socket is not only difficult to do most of the time, it also still remains stiff enough that if pulled on will still put strain on a termination, especially for sizes over 1/0 or so.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
So what is your suggestion?

I agree it is not a perfect solution but it does at the least keep the raceway intact.
The only reliable way to allow for settling which does not also require slack in the conductors (with no good place to put it), would be a horizontal U or long horizontal section between the underground conduit and the box where it terminates. Besides requiring more material, and causing problems with pulling, it would look pretty mickey mouse. At least until it became the standard. :)

I suppose you could use an expansion fitting in the form of a box with room inside for a loop of conductor too.

If the underground portion is horizontal and below the frost line and it is not coming up through concrete a sweep can take up some horizontal movement.
If the problem is that slab settling but not the earth where the conduit lies, it should come up through a hole in the slab with a filler instead of being set into the concrete.
 
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Ohms law

Senior Member
Location
Sioux Falls,SD
My opinion against this nonsense has always been that expansion fittings are for thermal expansion/contraction of the raceway, but do nothing to protect contained conductors from movement from settling earth or other similar activity.

If a raceway changes length what happens to the conductors inside that remain same length?

In the case of thermal expansion of a raceway the purpose of an expansion fitting is to allow the raceway to remain the same length without damage occuring.

How much ground settling or frost heave are we to allow somehow in the conductors?

I have seen where ground has settled and pulled on a raceway, the expansion fitting saved the raceway, but the conductor was also pulled and damaged terminations it was connected to.

Leaving a loop of conductor in a meter socket is not only difficult to do most of the time, it also still remains stiff enough that if pulled on will still put strain on a termination, especially for sizes over 1/0 or so.
I understand what your saying. It may seem foolish but I have seen a poured concrete pad more than once pull the conduit out and the conductors and terminations where fine. I personally have never seen terminations damaged. If you have a decent size s-loop wouldn't this help?
 

kwired

Electron manager
Location
NE Nebraska
So what is your suggestion?

I agree it is not a perfect solution but it does at the least keep the raceway intact.
Burial depth should be below frost depth and it will not have as much tendency to move with the earth that is moving.

For settling problems, bury raceway at an undisturbed depth or compact soil all the way to disturbed depth so raceway doesn't settle. The vertical portion will not settle - the horizontal portion will settle with the dirt around it.

I understand what your saying. It may seem foolish but I have seen a poured concrete pad more than once pull the conduit out and the conductors and terminations where fine. I personally have never seen terminations damaged. If you have a decent size s-loop wouldn't this help?
So have I, this is a result of poor installation both by the person installing the slab as well as the person installing raceway. Put a sleeve around the raceway before the concrete pour so it is not attached to the slab as it settles.
 

Ohms law

Senior Member
Location
Sioux Falls,SD
Burial depth should be below frost depth and it will not have as much tendency to move with the earth that is moving.

For settling problems, bury raceway at an undisturbed depth or compact soil all the way to disturbed depth so raceway doesn't settle. The vertical portion will not settle - the horizontal portion will settle with the dirt around it.



So have I, this is a result of poor installation both by the person installing the slab as well as the person installing raceway. Put a sleeve around the raceway before the concrete pour so it is not attached to the slab as it settles.
Putting a sleeve around conduit is an obvious. But i can not be there to old everyones hand. I know what ill say to my AHJ, thanks for all the input.
 

kwired

Electron manager
Location
NE Nebraska
Putting a sleeve around conduit is an obvious. But i can not be there to old everyones hand. I know what ill say to my AHJ, thanks for all the input.
At a new installation where you know there will be concrete poured what is difficult about putting your own sleeve around said raceway when you install it? Do you do what you can to protect your installations (even in other situations) or do you expect other trades to do it for you?
 

Ohms law

Senior Member
Location
Sioux Falls,SD
At a new installation where you know there will be concrete poured what is difficult about putting your own sleeve around said raceway when you install it? Do you do what you can to protect your installations (even in other situations) or do you expect other trades to do it for you?
Yes I do what needs to be done correctly. On new construction, on the side of a house with rock landscaping, you would put some type of sleeve on the conduit? Who really does that?
 
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