Underground conduits emerging above ground – securing required

[stevenje]

I had a discussion with an electrical inspector about securing underground conduits (PVC) emerging from underground and terminating into a CT cabinet. The distance from grade level to the CT cabinet is less than 3 feet. Is there a code article that allows the earth, concrete or other to meet the requirement of NEC 352.30(A) "securely fastened"? Thanks.

 

[tom baker]

Seems like concrete would be securely fastened. No section specifically allows this. What if you fastened unistrut to the concrete on its side, then strut straps. Would look as odd as the AHJs requirement.

 

[ptonsparky]

Secure the expansion fitting, let the rest float.

 

[infinity]

IMO emerging from being embedded in concrete requires nothing further, same goes for emerging from the ground if within 3'.

 

[stevenje]

IMO emerging from being embedded in concrete requires nothing further, same goes for emerging from the ground if within 3'.

That was my thought too. Judging from the response from Tom, it appears that there is no specific code article to refer to. Thanks.

 

[infinity]

That was my thought too. Judging from the response from Tom, it appears that there is no specific code article to refer to. Thanks.

There is really little specific code (there are some exceptions) that tells you how something is properly supported and secured. In most cases that's up to the inspector to decide. In many cases it's judged by local tradition like using tie wire to support/secure MC cables.

 

[kwired]

Ultimately the dirt is supporting the structure you would otherwise fasten to.

 

[shortcircuit2]

352.30 provides direction on securing and supporting PVC and 352.6 requires associated fittings to be listed. Dirt is not listed.

 

[kwired]

352.30 provides direction on securing and supporting PVC and 352.6 requires associated fittings to be listed. Dirt is not listed.

So all of the buried portion of the run needs listed fittings to suppport it? And even if so what do you secure them to other than dirt?

 

[infinity]

If a fitting is used that fitting is required to be listed. 352.30(A) just says that is has to be "securely fastened" so it's up to the opinion of the inspector to decide if emerging from the ground meets the definition of securely fastened. IMO it does. As Kwired asked is it securely fastened and supported when it's buried in the ground?

 

[kwired]

If a fitting is used that fitting is required to be listed. 352.30(A) just says that is has to be "securely fastened" so it's up to the opinion of the inspector to decide if emerging from the ground meets the definition of securely fastened. IMO it does. As Kwired asked is it securely fastened and supported when it's buried in the ground?

Now let's complicate that a little. Is a tie wire a fitting? Might get some unfavorable inspection results if you use tie wires to fasten a raceway to structural roof steel yet same inspector may not say a thing about tie wires to hold it in place before pouring concrete around it to embed it into a slab.

 

[ptonsparky]

FWIW, at 3’ we wouldn’t worry about the expansion fitting either.

 

[infinity]

Now let's complicate that a little. Is a tie wire a fitting? Might get some unfavorable inspection results if you use tie wires to fasten a raceway to structural roof steel yet same inspector may not say a thing about tie wires to hold it in place before pouring concrete around it to embed it into a slab.

There's nothing to say about using tie wire to keep conduits in place before the pouring of a deck. They're not there for support or securing the raceway that's done by the concrete.

 

[kwired]

There's nothing to say about using tie wire to keep conduits in place before the pouring of a deck. They're not there for support or securing the raceway that's done by the concrete.

It secures/supports it before it is poured and until concrete hardens. If you don't secure them they can float to the top.

I have even more experience with underground runs and sometimes staking to hold in place so they don't move during backfill.

 

[ptonsparky]

It secures/supports it before it is poured and until concrete hardens. If you don't secure them they can float to the top.

I have even more experience with underground runs and sometimes staking to hold in place so they don't move during backfill.

I had wind blown sand sift under some 3” DB and float it up.

 

[kwired]

I had wind blown sand sift under some 3” DB and float it up.

Wind never blows in this state.


Ok only time it doesn't blow is in July and August when you wish it would just to give a little cooling effect.

 

[jusme123]

IMO emerging from being embedded in concrete requires nothing further, same goes for emerging from the ground if within 3'.

...what if the conduit is installed in the NE , and the ground heaves during season changes.

 

[ptonsparky]

...what if the conduit is installed in the NE , and the ground heaves during season changes.

Are you going to stop it from moving with a plastic two hole strap?

 

[jusme123]

Are you going to stop it from moving with a plastic two hole strap?

The plastic two hole strap is designed to allow the conduit to move, coupled with an expansion fitting, will make it NEC compliant

 

[kwired]

I find expansion fitting to be pointless on larger conduits (like about 1.25 or 1.5 or larger) if the length exposed from grade to the termination point is ~3 feet or less. Might not hurt anything to put one in but really think there is seldom any advantage to using them. 3 feet is short enough that thermal expansion isn't much problem most cases, which is really mostly what expansion fittings are for. If you have other physical movement and larger conductors involved you need to be more careful with what you do. Yes an expansion fitting can save the raceway, but if things are moving the contained conductors don't have expansion fittings on them and they better have room to move or they will strain connections, have seen it happen.

To greatly lessen frost heave issues you need to bury the lateral run below maximum frost depth, you also need undisturbed soil or well compacted soil below your lateral run so eventual settling doesn't try to pull it down.