Pvc expansion joints
- Thread starter jimbo9927
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ItsHot
Senior Member
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- A little piece of heaven!
Welcome!
Welcome!
Welcome to the forum Jimbo! I don't think the expansion joints are required. Notice I said"think"!! I should say I do not know!!:smile:
Welcome!
Welcome to the forum Jimbo! I don't think the expansion joints are required. Notice I said"think"!! I should say I do not know!!:smile:
if the conduit turns vertical and extends out of the ditch to a "fixed" enclosure or fitting, an expansion joint is often used (sometimes required) to compensate for ground movement. Often times the conduit without an expansion joint will "settle" and pull loose from the enclosure.
I do not believe that the slip (type) expansion joints are not listed for ground movement
ptonsparky
Tom
- Occupation
- EC - retired
We are required to use expansion joints under those circumstances. Mostly for the movemnet of the earth. Not linear expansion of the conduit.
A run of 100 feet will move (expand or contract) 4" (4.06" per the table) if subjected to a 100 deg temp (swing)increase or decrease. This assumes the raceway is installed at maximum or minimum temperature. If the installation is made on a 50 degree day and the ambient is 100 deg as a high and 0 deg for a low, the run would be expected to move 2". Predicting the length of change is best done by calculation.
M. D.
Senior Member
300.5 (J) basically says that,.. where direct-buried raceways are subject to movement by settlement or frost, raceways shall be arranged to prevent damage to theenclosed conductors,.. the use of an expansion fitting is one way to prevent damage to the enclosed conductors
Carlon has what, to me, is a new product that appears to be a brother to the standard expansion joint and is designed for just such applications.
http://www.carlon.com/Master Catalog/Slip_Meter_Riser_Brochure.pdf
http://www.carlon.com/Master Catalog/Slip_Meter_Riser_Brochure.pdf
I've seen those note they do not mention expansion. I think mid West came out with a similar product years ago.
Carlon does make a fitting for ground movement that may be buried. I have never installed one and I would describe it as two coupelings connected with a inner tube. I don't bknow how you would pull wire through it??
roger3829
Senior Member
- Location
- Torrington, CT
Not a new product. We have been using them here for 20 years on underground services. POCO requires them.
apparently they just didn't "catch on" around here. EC's here use the "standard" expansion joint.
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
As Gus has stated, it may depend on the temperature swing from one season to another where you live.
Read the FPN that follows the section you are referencing.
Also notice there is no reference to minimum or maximum size of the conduit...it is for all sizes.
It'll move 4" as the temperature changes from 0 to 100 degrees regardless of the temperature during installation.
Possiably I did not make my self clear
My intent was a temp swing of 100 degrees (as an example). If you install in January at 0 degrees (disregard the lable on the glue can) and if the temp in july is 100 degree. then a 100 foot runb will expand 4.06" (per the table).
If you instal on a 50 degree day you would expect only 1/2 or 2.03" of movement. Sorry I was not more clear. Actually you should crunch the numbers using the formular that the mfg supplies. to get an acurate number of joints and to determine the set point of the race way before installing the hard hanger.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
True, but you should gauge your installation length based on ambient temperature. If it's cold, extend it; ifr it's hot, shorten it.
The 4.06" (or the adjusted 2.03") of movement is for a run in ambient air temperature. An undergroiund run is not subject to the same ambient temperature or swings. For an area with a 100? ambient air temperature swing through all four seasons, an ambient soil temperature swing at 2' BFG may only be 50? (just a WAG).
I agree with both of these points. I was just disagreeing with cpal about how much expansion to expect, according to the table. It's going to move 4 inches. If it's 50 degrees when installed, it will contract 2 inches as the temp moves toward zero. When springtime arrives the conduit will move back to where it was, but as the summer temps approach 100 degrees it will expand 2 inches. That's four inches total.
I don't know, maybe we're just nitpicking over words again. It doesn't matter. Never mind.....
I have installed literally miles and miles of PVC since the 70's and I never even heard of an expansion fitting until I started reading the electrical message boards.
It has the "where subject to" clause in the code. Maybe it's a regional thing? The desert here is pretty stable.
I wonder how plumbers deal with it?
It has the "where subject to" clause in the code. Maybe it's a regional thing? The desert here is pretty stable.
I wonder how plumbers deal with it?
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