PVC expansion fitting

[anthonysolino]

I have a straight of conduit between two fixed boxes, 25' long with a 60F temp change, my calculation is 5/8-7/8" I had a manufacture I called instructed me to install this fitting in the middle (which was done shortly after my conversation) despite only having to need ONE joint, then I was sent a PDF (after the conduit was ran) of a NEMA article instructing me to install this joint "close" to the box and securely fasten the barrel, which I did, utilized a 1" clip, the rest was 1/2" now I have to go cut this joint out and move it over close to one of the boxes, does any one have any thoughts? if it were to be left in the middle, would the other end simply come out? I would think so, but maybe there is something I am missing here.


thanks every one!

 

[infinity]

IMO in your installation it doesn't matter where in the run you put it.

 

[anthonysolino]

IMO in your installation it doesn't matter where in the run you put it.

this is a excerpt from the NEMA document, FB 2.40 they emailed me after it was already installed, i saved the PDF its a 34 page document on expansion fittings (if any one would like it)

5.1.3 Expansion Fitting Placement 5.1.3.1 One Expansion Fitting Placement
Proper placement and installation of expansion fittings and conduit allow for the correct functioning of the expansion fittings. For example, if one expansion fitting is needed between two boxes, the barrel of the fitting should be securely fastened close to one box. The conduit must be fastened loosely to allow for movement during expansion and contraction.


5.1.3.2 Multiple Expansion Fitting Placement
If there is more than one expansion fitting used, fittings are installed at the boxes with the center of the conduit run rigidly fixed. With two expansion fittings used, the center of the conduit must be fixed to properly proportion expansion or contraction between the two fittings. Otherwise, the expansion or contraction would only occur at the free fitting, while the tighter fitting would not move.
In a very long run, two or more fittings should be placed in series with one another. The barrels of each expansion fitting must be anchored to allow each length of conduit to expand or contract freely. Each section acts independently. See Figure 6


I know theres no article reference, but Carlon is telling me one thing, then 45 minutes later sends me this article, you feel its best to remove it? and place it closer?

 

[synchro]

I have a straight of conduit between two fixed boxes, 25' long with a 60F temp change, my calculation is 5/8-7/8" I had a manufacture I called instructed me to install this fitting in the middle (which was done shortly after my conversation) despite only having to need ONE joint, then I was sent a PDF (after the conduit was ran) of a NEMA article instructing me to install this joint "close" to the box and securely fasten the barrel, which I did, utilized a 1" clip, the rest was 1/2" now I have to go cut this joint out and move it over close to one of the boxes, does any one have any thoughts? if it were to be left in the middle, would the other end simply come out? I would think so, but maybe there is something I am missing here.


thanks every one!

Just to clarify what you have now, is there an expansion joint in the middle and another joint with its outside barrel secured next to a box?
If so, what direction is the outside barrel of the middle joint pointed: 1.) toward the joint near the box, or 2.) toward the other box without a joint?
If it's case 1.) then adjust it so both joints are close to being centered, clamp down the barrel on the middle joint, and you're done. The joint near the box will compensate for conduit expansion on that side, and the middle joint will compensate for expansion on the other side. It's overkill but that's OK.
If it's case 2.) then you need to cut out the middle joint and replace it with a solid section of conduit. As you said the one joint next to the box will easily handle all of the expansion.
On these joints the outside barrel is supposed to be secured so it doesn't move, and the inside part is allowed to shift as needed. The following document from Carlon covers how it should be used. It shows using 2 joints secured in the middle and pointed in opposite directions, but what you posted from NEMA about having the two joints at the boxes and centering the conduit by securing it at the middle will work just as well.

https://carlonsales.com/techinfo/installationtraining/IT-ISEXPJT.pdf

 

[anthonysolino]

yes there is just two single gang FS boxes on a horizontal run, 25'. the guy I spoke to from Thomas and betts said put the expansion in the middle of the conduit run between the two boxes, THEN, after I installed he he sends me a link to this nema article stating when using ONE joint that it needs to be installed close to one box, I don't WANT to cut the joint out and move it, but I don't want to come back in 6 months and have my conduit pulled out of the box.

 

[infinity]

5.1.3 Expansion Fitting Placement 5.1.3.1 One Expansion Fitting Placement
Proper placement and installation of expansion fittings and conduit allow for the correct functioning of the expansion fittings. For example, if one expansion fitting is needed between two boxes, the barrel of the fitting should be securely fastened close to one box. The conduit must be fastened loosely to allow for movement during expansion and contraction.

This says should be close to the box. If the movement is allowed then IMO install the fitting wherever you want. The word should is in no way mandatory.

 

[GoldDigger]

If you securely fasten the barrel of an expansion fitting at the center of the run, it will only allow for expansion in one half of the conduit length. It should be fine to leave the barrel supported but unrestrained if you have only one fitting in the run.
If you have two such fittings, then you have to fasten the barrel of at least one of them to prevent the whole section between the fittings from moving and pulling lose at one end.
Note: Since no part number was specified, I am assuming that the expansion joint in question is a simple one in which the outer barrel is securely fastened to one conduit piece and the inner part of the joint is securely fastened to the other conduit piece. Or else the second conduit piece is free to slide inside the barrel.
If the expansion joint is instead similar to a compression joint fitting for a water pipe, where two ordinary pipe pieces enter opposite ends of the barrel, then it is essential to secure (immobilize) the barrel. And if two joints are used the conduit joining them together would need to be secured somewhere near the middle.
You should be able to apply common sense to the mechanism of whatever type of expansion joint you use to figure out the right action in your situation.