Ty Raps to support rigid PVC??

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ssandoval

ssandoval

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League City,TX
I can't find anywhere in the NEC that specifically prohibits using ty raps to fasten PVC to building frame members. I have a contractor fighting me on this issue. We have a newly constructed greenhouse at our new high school; the interior is classified as a wet location. I made them remove tie wire in a couple of areas where they had to run conduit parallel to existing strut. Since unistrut straps will only work on a perpendicular install, they went back with ty raps. I'm trying to get the engineering firms to get them to add strut where neccesary, but in the meantime I'm trying to find out if ty raps are prohibited for use as a means of "fastening". ??
 
I do not think the NEC prohibits using ty-raps. There have been some previous threads on this subject, and that seemes to be the consensus. It was also offered that the AHJ would have to approve the method you submit.
db
 
ssandoval said:
I can't find anywhere in the NEC that specifically prohibits using ty raps to fasten PVC to building frame members. I have a contractor fighting me on this issue. We have a newly constructed greenhouse at our new high school; the interior is classified as a wet location. I made them remove tie wire in a couple of areas where they had to run conduit parallel to existing strut. Since unistrut straps will only work on a perpendicular install, they went back with ty raps. I'm trying to get the engineering firms to get them to add strut where neccesary, but in the meantime I'm trying to find out if ty raps are prohibited for use as a means of "fastening". ??
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Not sure about PVC but its OK for MC as a means of securing. 352.30 dosen't mention by what means.
 
ssandoval said:
I can't find anywhere in the NEC that specifically prohibits using ty raps to fasten PVC to building frame members. I have a contractor fighting me on this issue. We have a newly constructed greenhouse at our new high school; the interior is classified as a wet location. I made them remove tie wire in a couple of areas where they had to run conduit parallel to existing strut. Since unistrut straps will only work on a perpendicular install, they went back with ty raps. I'm trying to get the engineering firms to get them to add strut where neccesary, but in the meantime I'm trying to find out if ty raps are prohibited for use as a means of "fastening". ??
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Using a menralac one hole pipe clamp with a uni-strut nut will allow securing to the uni-strut in any direction, and I agree the NEC allows wire ties to secure conduit, but the problem with PVC is expansion, like vinyl siding it must be allowed to move, this means the straps or clamps used must allow the pipe to slide through them, and expansion joints must be used when runs are over a certain length, or you wind up with a spaghetti mess. 352.30

When a job call for exposed PVC I tend to install more supports than the code requires, to keep it running straight table 352.30 allows 1/2"-1" to be supported every 3' on 1/2" I do 2' supports, I even go over board with expansion joints, when the conduit is between fixed points, or 90? turns, but here we can have over 90? temp in the summer and go down to -10? in the winter.
Inside runs are not as much a problem in a controlled environment, but it does seem to shrink over time when exposed to high temps, which can pull out of boxes and fittings.
 
Thanks to all for the replies. I'm going to try to go with the fact that the installation literature for ty raps considers them to be "cable ties", I'll let everyone know how it pans out.
 
There are SS cable ties available...
A regular cable tie has a breaking strength, the suitable of that tie would depend on the weight of the conduit with wires included.
 
What's the reasoning behind all this?

You just don't like zip ties? Or does their conduit look like crap?

If everything else is installed correctly, amount of straps and exp. fittings where required, etc who cares what they use for strapping as long as it's sufficient to hold the pvc in place?

Like anything else, if you have a preference, you should of put it in the specs...
 
Nothing wrong with using tie wraps, tie wire or even duct tape. It isn't a matter of what you want to see but a matter if it does the job or not.

I have installed many of a feet of 2 inch and larger by simply laying in the bar joist with nothing to hold it in place except the bracing of the bar joist.

Remember you want it to be able to move not be rigidly locked in place so it can?t move.
 
Wow. I'd never consider tie wraps as an acceptable support for conduits. IMO, I don't see how this complies with the NEC.

But I'm apparently in the minority (or even all alone!!).

Edit: I re-read the original post - the first time I read it I didn't see that the conduit was resting on framing members. I might be able to accept tie-wraps for securing - I thought they were using them to support the conduit.

Still, I wonder how they will hold up in the sunlight??
 
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Hendrix said:
Not sure about PVC but its OK for MC as a means of securing. 352.30 dosen't mention by what means.
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Is Tie wire a listed or approved means for supporting anything? I mean I do it all the time especially supporting pipe runs on top of bar joists, but I didn't think in was a listed method.
 
Pizza said:
Is Tie wire a listed or approved means for supporting anything? I mean I do it all the time especially supporting pipe runs on top of bar joists, but I didn't think in was a listed method.
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Didn't know that anything needed to be listed that was used to secure or support PVC

352.30 Securing and Supporting.

PVC conduit shall be installed as a complete system as provided in 300.18 and shall be fastened so that movement from thermal expansion or contraction is permitted. PVC conduit shall be securely fastened and supported in accordance with 352.30(A) and (B).


(A) Securely Fastened. PVC conduit shall be securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, conduit body, or other conduit termination. Conduit listed for securing at other than 900 mm (3 ft) shall be permitted to be installed in accordance with the listing.

(B) Supports. PVC conduit shall be supported as required in Table 352.30. Conduit listed for support at spacings other than as shown in Table 352.30 shall be permitted to be installed in accordance with the listing. Horizontal runs of PVC conduit supported by openings through framing members at intervals not exceeding those in Table 352.30 and securely fastened within 900 mm (3 ft) of termination points shall be permitted.

 
Whats Listed for support

Whats Listed for support

I would say first place would be to look at Ty-wraps Specs and see what it is listed for. If it carries a UL listing approving it as a conduit support, then you could determine what it is rated to support. But I would imagine that it will be found to be rated only as a cable tie. The manufacturer should be able to provide you with an answer quickly.
 
Make them put in the unistrut ... and watch them fasten the strut with cable ties:happyyes:

Isn't the cable tie just as much of a fastener as a bolt or screw? It can have a different load limit than a bolt or screw. Bolts and screws all have different load limits based on size. So do cable ties.
 
This is based solely on my opinion. If I was to look at a job you did using zip ties for pvc support in my opinion it would be a crappy installation an in my opinion you were either too lazy or too cheap to do it right.
 
buddhakii said:
This is based solely on my opinion. If I was to look at a job you did using zip ties for pvc support in my opinion it would be a crappy installation an in my opinion you were either too lazy or too cheap to do it right.
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Just what is right? The way you do something or the way I would do something? If it is code compliant is it right?
 
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