NEC300.5(J) Ground Movement

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mjc

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Hi looking for a little help here,,, I'm understanding 300.5(J) to say that that raceways protruding from the earth need to contain an expansion fitting in order to prevent damage to conductors and equipment. (I Have:
2" schedule 40 pvc conduit, to a 90 degree pvc ell, to Sch 80 protuding from the earth to a meter can)
I have estimated the install with an expansion fitting but don't see this happening on other new buildings, unless they leave the coupling that you can see un-glued in order to achieve the effect of expansion. (which I dought) Either clarification of this article or a picture would help

Thanks, Mike :?
 
MJC,

I think it depends on your location and climate. In central NY, it is universal in my experience to use an expansion coupling after emerging from grade. Does your ground freeze down to the conduit? In some cases I imagine its a judgement call - ask your inspector if you have doubts.
 
Electrofelon wrote:
I think it depends on your location and climate.
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That probably has alot to do with it. But this is Michigan 100 miles north of Detroit and the ground freezes. Just haven't seen this type of thing done around here. I Intend to check with the local AHJ and ask.
 
MJC
There are times when certain code requirements seem to slip through the cracks in areas. I am surprised that in such a cold/warm climate that this occurs in your area. Are you sure that you are not missing something?
 
pierre said:
Lets not forget that for direct buried cable, that an S loop in the earth is also permitted, and that may be the case in some of these installations.
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Knew that somebody would respond as to the FPN of this article but there aren't S loopds involved with these installs. This is all conduit to an xfmr with separate stranded conductors. (commercial blds)
I must be missing somthing. This added approx. $270.00 to my estimate Intend to check it out with the local AHJ an will let you know Monday.

Mike, :(
 
electrofelon said:
In central NY, it is universal in my experience to use an expansion coupling after emerging from grade. .......In some cases I imagine its a judgement call - ask your inspector if you have doubts.
Click to expand...

I had 2 local inspectors in central NY with very different opinions on this topic at a recent job site.

The first one was out to inspect the barn rough, and while discussing the underground feeder installation we had a discussion about expansion fittings. He clearly didn't think the expansion fittings were needed and told me not to bother with 'em.

The 2nd inspector came out for the main house service upgrade and wondered why I didn't use expansion joints above grade for the barn feeder.

Didn't seem to matter enough to him anyway, he wasn't inclined to fail the inspection because of their absence. He was just curious why I didn't install them. I told him to call his co-worker. :)

Now I'm left to wonder just how important they really are in this moderately cold environment....

Chris Knight
Syracuse NY
 
We strictly enforce the requirement for an expansion fitting for ground movement.

We see almost everyone installing them on underground services. We see a lot of people forget them on other installations such as conduits for pools, well, etc. I'm talking about the requirment for ground movement, not thermal expansion.

Although I almost never see it enforced, the requirement for ground movement applies to RMC installations too, IMO.
 
Hi , just checked with the local AHJ - he,s not concerned with the thermal expension of the product or ground movement unless the pvc emerges more than 10' from the ground, normally he sees it only about 5' before entering a box or cabnet. I guess I can eliminate these fittings from my estimate.
Although IMO this is a Bogas judgement call by the AHJ / municipalities and in total disregard of the NEC 300.5. I've seen conductors of open conduits (under 5') on various buildings and you can tell that ground movement is the cause. How can they say the ground isn't going to move and less than 5' of pvc ok?????
Anyway - enough venting and concern about the article I guess there aren't enough probems in the area to really be alarmed. That must be what the AHJ's are thinking. :roll:

Thanks for the responses, Mike
 
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