What is an Approved PVC Strap

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durraniguy

Member
I received a violation from a Biscayne Village inspector (in Miami Fl.) stating "PVC conduit must be strapped with PVC straps". The conduit in question is strapped with a unistrut strap. Also is it required that the inspector give you a code article to justify his comment. I questioned him and all he gave me was his years of experience and a $50 re-inspection fee.
 

iwire

Moderator
Staff member
Location
Massachusetts
In my opinion the inspector is right to fail a typical unistrut strap used with PVC.

352.30 requires PVC supports allow movement for expansion and contraction. There is no way to leave a strut clamp loose enough for that without it being useless.

Not everyone agrees with my opinion though ... :)
 

augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
:grin: Unfortunately "approval" is a AHJ issue, but if you check 352.30 you will note the requirement that PVC be secured in a manner that allows for movement from thermal expansion.
The topic of unistrut strapping for PVC (when expansion is an issue) has come up here numerous times and I don't recall a definitive solution.
I have seen "Sleeving" thru a strapped larger PVC, fattening of PVC saddle straps, and twohole straps with spring nuts. Someone here may have a
a better idea.
 

e57

Senior Member
I've never seen PVC written on the side of a strut strap - but then again I rarely use PVC above grade.... And wasn't looking for it.

But on that note - Is tie wire approved, or metal 1 hole straps, or zip-ties, or the many other seemingly unorthodoxed methods I have used to support conduits of all kinds?
 

durraniguy

Member
Thanks Guys, I agree

Thanks Guys, I agree

I checked the article, and i does seem to indicate that It requires a PVC strap. So are metal locknuts approved to be used with PVC male adopters? Also is there a requirement for the EI to give a code article?
 

iwire

Moderator
Staff member
Location
Massachusetts
But on that note - Is tie wire approved, or metal 1 hole straps, or zip-ties, or the many other seemingly unorthodoxed methods I have used to support conduits of all kinds?

Those methods can allow movement for expansion and contraction. :)
 

hardworkingstiff

Senior Member
Location
Wilmington, NC
OK, let me get this straight. PVC strapping needs to allow for movement. This means in a vertical run, since movement needs to be allowed for, the strapping cannot offer significant vertical support for the conduit system. All of the vertical support is transfered to the lowest part of the conduit system that has support that does not allow movement.

Eventually, during hot periods, there is a height limitation to how far up (in the vertical) a PVC conduit can be installed. Anyone know what that is? Is it 100's of feet or 1,000' of feet?
 

iwire

Moderator
Staff member
Location
Massachusetts
Eventually, during hot periods, there is a height limitation to how far up (in the vertical) a PVC conduit can be installed. Anyone know what that is? Is it 100's of feet or 1,000' of feet?


300.19 effectively limits vertical runs to a maximum of 280' but in most cases 100' or less.
 

durraniguy

Member
here is a pic

here is a pic

This is the actual conduit, also would it have been OK to wire both disconnects thru the 2" pvc, with the feeder for the right panel passing thru the middle one?
 

kwired

Electron manager
Location
NE Nebraska
I checked the article, and i does seem to indicate that It requires a PVC strap. So are metal locknuts approved to be used with PVC male adopters? Also is there a requirement for the EI to give a code article?

1. The article only requires the support to allow movement from thermal expansion. PVC straps are designed for this but are not required. If using a rigid/IMC strap and you make it tight fitting is does not allow for thermal movement.

2. As far as metal locknuts on a PVC adapter I am not sure. Many non metallic flex fittings and cord grips have a metal locknut installed on them in the box they come in so they are most likely allowed there.

If installed in a grounded metal enclosure I see no problem at all, the locknut will be grounded by the metal enclosure that it is tightened against. But a terminal adapter with a metal locknut in a nonmetallic enclosure will not be grounded.

I have also seen nonmetallic flex connectors and cord grips that come with a nonmetallic locknut. I have seen many that are installed and the locknut has broken and the flex connector or cord grip has pulled away from the enclosure. I would rather see the metal locknut even if it is not grounded in this case. That locknut is not very likely to become energized.

BTW they do make locknuts with provisions for attaching a grounding conductor.

3. The requirement for an EI to give a code reference for violations of the code are up to the AHJ and lawmakers. I would like to think that it is required most everywhere. Otherwise it allows the inspector to make up his own code. If you are going to have rules you need to be able to provide a reference to them to prove that the rules have been broken otherwise why have the rules?

Just saying "you violated the NEC and the rules are in there somewhere" I suppose could work, but now you either give in and do as inspector requests or you get your book out and try to prove the inspector wrong.
An inspector that can not get out a code book or local amendments to that code and find an article to show you your violation is incompetent and should not be an inspector.
 
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