# PVC expansion joints....



## B4T (Feb 10, 2009)

I am doing a service where the 2" horizontal run is (25) ft. and vertical run(20) ft. from meter pan to service head..

It comes out bottom of the MP.. (90) to horizontal run to (90) for vertical run to service head..

I read this as needing (2) expansion joints.. agree?

Is a service head considered a "conduit termination" since the conductors can move in the service head.. :blink:

352.44 Expansion Fittings. Expansion ﬁttings for PVC
conduit shall be provided to compensate for thermal expansion
and contraction where the length change, in accordance
with Table 352.44, is expected to be 6 mm (1⁄4 in.) or greater in
a straight run between securely mounted items such as boxes,
cabinets, elbows, or other conduit terminations.


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## erics37 (May 7, 2009)

B4T said:


> I am doing a service where the 2" horizontal run is (25) ft. and vertical run(20) ft. from meter pan to service head..
> 
> It comes out bottom of the MP.. (90) to horizontal run to (90) for vertical run to service head..
> 
> ...


As long as your expected temperature change will make the conduit grow more than 1/4" (probably will) then I'd say yep, two expansion joints :w00t:


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## Mr Rewire (Jan 15, 2011)

B4T said:


> I am doing a service where the 2" horizontal run is (25) ft. and vertical run(20) ft. from meter pan to service head..
> 
> It comes out bottom of the MP.. (90) to horizontal run to (90) for vertical run to service head..
> 
> ...


Is the service head a securely mounted item ?


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## B4T (Feb 10, 2009)

Mr Rewire said:


> Is the service head a securely mounted item ?


Yes..


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## Mr Rewire (Jan 15, 2011)

B4T said:


> Yes..


How do you securely mount it?


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## B4T (Feb 10, 2009)

Mr Rewire said:


> How do you securely mount it?


It is mounted on the PVC conduit.. :blink:


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## erics37 (May 7, 2009)

Unless you screw the service head directly to the structure I wouldn't call it "securely mounted."


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## B4T (Feb 10, 2009)

erics37 said:


> Unless you screw the service head directly to the structure I wouldn't call it "securely mounted."


So you are saying "securely mounted" only applies to parts screwed to the structure.. 

Got it.. I only need one expansion joint..


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## Mr Rewire (Jan 15, 2011)

B4T said:


> It is mounted on the PVC conduit.. :blink:


It's attached to the conduit it is NOT securely mounted. An expansion joint will not be needed ad the conduit cannot be separated from the service head because it is not securely mounted.


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## Mr Rewire (Jan 15, 2011)

B4T said:


> So you are saying "securely mounted" only applies to parts screwed to the structure..


This would be the definition of securely mounted


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## McClary’s Electrical (Feb 21, 2009)

The situation you describe doesn't call for any expansion joints.


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## B4T (Feb 10, 2009)

Mr Rewire said:


> This would be the definition of securely mounted


How is an elbow securely mounted.. :blink:

a straight run between securely mounted items such as boxes,
cabinets, *elbows*, or other conduit terminations.


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## Mr Rewire (Jan 15, 2011)

B4T said:


> How is an elbow securely mounted.. :blink:
> 
> a straight run between securely mounted items such as boxes,
> cabinets, elbows, or other conduit terminations.


With a screw


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## B4T (Feb 10, 2009)

Mr Rewire said:


> With a screw


This is why people "pile" on you.. :no:


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## HARRY304E (Sep 15, 2010)

mcclary's electrical said:


> The situation you describe doesn't call for any expansion joints.


Yes it does on the Horizontal run only he does not need one on the vertical part of the run because of the weather head.


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## Mr Rewire (Jan 15, 2011)

B4T said:


> This is why people "pile" on you.. :no:


You still don't need an expansion joint


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## HARRY304E (Sep 15, 2010)

B4T said:


> How is an elbow securely mounted.. :blink:
> 
> a straight run between securely mounted items such as boxes,
> cabinets, *elbows*, or other conduit terminations.


Use these clips they allow for expansion...


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## HARRY304E (Sep 15, 2010)

Mr Rewire said:


> You still don't need an expansion joint



On the Horizontal run..


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## Mr Rewire (Jan 15, 2011)

HARRY304E said:


> On the Horizontal run..


Right between the box and elbow not between the elbow an service head


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## McClary’s Electrical (Feb 21, 2009)

HARRY304E said:


> On the Horizontal run..


 

His elbow is not securely mounted either.


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## Mr Rewire (Jan 15, 2011)

mcclary's electrical said:


> His elbow is not securely mounted either.


It would be secured by the conduit straps


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## B4T (Feb 10, 2009)

Mr Rewire said:


> This would be the definition of securely mounted


Originally Posted by B4T 

So you are saying "securely mounted" only applies to parts screwed to the structure.. 



Make up your mind.. :blink::blink:^^^^^^^^


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## McClary’s Electrical (Feb 21, 2009)

Mr Rewire said:


> It would be secured by the conduit straps


 
I doubt very seriously he's strapping the elbow


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## Mr Rewire (Jan 15, 2011)

B4T said:


> Originally Posted by B4T
> 
> So you are saying "securely mounted" only applies to parts screwed to the structure..
> 
> Make up your mind.. :blink::blink:^^^^^^^^


Take off your blinders and don't take what I posted our of context.


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## Mr Rewire (Jan 15, 2011)

mcclary's electrical said:


> I doubt very seriously he's strapping the elbow


Am elbow can be In a ten foot solid piece and this could be securely fastened by means of a strap


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## erics37 (May 7, 2009)

The whole conduit run is supposed to be strapped but allow for expansion, that's the point. I don't think the expansion would travel well around bends in the pipe, so I think that's why the NEC explicitly mentioned elbows in that section as a divider between runs of conduit requiring expansion joints.


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## HARRY304E (Sep 15, 2010)

mcclary's electrical said:


> His elbow is not securely mounted either.



No it is not but once you change direction in his case a 90 after the 90 the clips will not allow the pipe to contract and it will pull out of the connector at the Meter socket .


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## McClary’s Electrical (Feb 21, 2009)

Mr Rewire said:


> Am elbow can be In a ten foot solid piece and this could be securely fastened by means of a strap


 

The wording does not say securely mounted conduit. It plainly says securely mounted elbow.


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## McClary’s Electrical (Feb 21, 2009)

erics37 said:


> The whole conduit run is supposed to be strapped but allow for expansion, that's the point. I don't think the expansion would travel well around bends in the pipe, so I think that's why the NEC explicitly mentioned elbows in that section as a divider between runs of conduit requiring expansion joints.


 
While I agree 100% with this concept, I don't think the wording supports it, even if it is their intent for it to. I clearly says securely mounted elbows.


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## Mr Rewire (Jan 15, 2011)

mcclary's electrical said:


> The wording does not say securely mounted conduit. It plainly says securely mounted elbow.


Now you are just picking fly **** out of the pepper


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## erics37 (May 7, 2009)

mcclary's electrical said:


> While I agree 100% with this concept, I don't think the wording supports it, even if it is their intent for it to. I clearly says securely mounted elbows.


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## HARRY304E (Sep 15, 2010)

erics37 said:


>


:laughing::laughing:


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## Magnettica (Jan 23, 2007)

B4T said:


> I am doing a service where the 2" horizontal run is (25) ft. and vertical run(20) ft. from meter pan to service head..
> 
> It comes out bottom of the MP.. (90) to horizontal run to (90) for vertical run to service head..
> 
> ...



I don't think you are required to use expansion fittings on either end, but doing that makes for a better design and an overall better job. Expansion couplings are a benefit to the customer so charge extra too!


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## BBQ (Nov 16, 2010)

mcclary's electrical said:


> The wording does not say securely mounted conduit. It plainly says securely mounted elbow.



You are just trolling, the conduit straps hold the elbow from moving. An expansion joint is needed if the calculations show more than .25" movement


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## BBQ (Nov 16, 2010)

Magnettica said:


> I don't think you are required to use expansion fittings on either end,



Why not?


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## Magnettica (Jan 23, 2007)

BBQ said:


> Why not?


Because is the service head really considered securely fastened? I'm thinking a space between two fixed points (like the bottom of a service meter to an LB) would require the expansion. A service head, hmm, not so much.


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## mbednarik (Oct 10, 2011)

BBQ said:


> You are just trolling, the conduit straps hold the elbow from moving. An expansion joint is needed if the calculations show more than .25" movement


i think the pvc can slip in the straps if you are using the correct straps. If the straps did hold it solid wouldn't you need one every 5' between straps?


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## electricmanscott (Feb 11, 2010)

Magnettica said:


> I don't think you are required to use expansion fittings on either end, but doing that makes for a better design and an overall better job. Expansion couplings are a benefit to the customer so charge extra too!


You absolutely need one in this case. Between meter and elbow. Not a benefit, a requirement.


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## Southeast Power (Jan 18, 2009)

BBQ said:


> Why not?


Bob,
Can you re post the pic of the large conduit PVC job you did that showed the special PVC unistrut straps?

Thanks,

John


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## Southeast Power (Jan 18, 2009)

This might help you with the calculations:

http://www.carlon.com/Installation_Training/IT-NEMAEXJTA.pdf


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## McClary’s Electrical (Feb 21, 2009)

BBQ said:


> You are just trolling,


 
Bob, have you ever known me to do that?:jester:


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## BBQ (Nov 16, 2010)

mcclary's electrical said:


> Bob, have you ever known me to do that?:jester:


Sorry, I must have been thinking of someone else, may God Bless you.


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## HARRY304E (Sep 15, 2010)

mcclary's electrical said:


> Bob, have you ever known me to do that?:jester:






BBQ said:


> may God Bless you.


:laughing::laughing::laughing:


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## leland (Dec 28, 2007)

Several services,I've not been called on, meter to LB into house(just a sleeve for SE). No Exp fitting,never up to the weather head.

Typically for under ground installs and verticals box to box,roofs etc.


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## BBQ (Nov 16, 2010)

leland said:


> I've not been called on, meter to LB into house(just a sleeve for SE). No Exp fitting,never up to the weather head.


In most cases the NEC would not require one for what you describe above.

The pipe from meter to LB is so short it would not move more than a 1/4".

The pipe up to the weather head is free to expand and contract assuming it is a straight up run and the weather head is not secured to the house.


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## leland (Dec 28, 2007)

I find that if I just use 4' for my guide- typically 4 or more I need one.


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## McClary’s Electrical (Feb 21, 2009)

leland said:


> I find that if I just use 4' for my guide- typically 4 or more I need one.


 
Why not just use this?:



*Table 352.44 Expansion Characteristics of PVC Rigid Nonmetallic Conduit Coefficient
of Thermal Expansion = 6.084 × 10​*​​​​−*5 mm/mm/°C (3.38 × 10–5 in./in./°F)
Temperature
Change (°C)
Length Change of
PVC Conduit
(mm/m)
Temperature
Change (°F)
Length Change of
PVC Conduit
(in./100 ft)
Temperature
Change (°F)
Length Change of PVC
Conduit (in./100 ft)*​*
*5 0.30 5 0.20 105 4.26
10 0.61 10 0.41 110 4.46
15 0.91 15 0.61 115 4.66
20 1.22 20 0.81 120 4.87
25 1.52 25 1.01 125 5.07
30 1.83 30 1.22 130 5.27
35 2.13 35 1.42 135 5.48
40 2.43 40 1.62 140 5.68
45 2.74 45 1.83 145 5.88
50 3.04 50 2.03 150 6.08
55 3.35 55 2.23 155 6.29
60 3.65 60 2.43 160 6.49
65 3.95 65 2.64 165 6.69
70 4.26 70 2.84 170 6.90
75 4.56 75 3.04 175 7.10
80 4.87 80 3.24 180 7.30
85 5.17 85 3.45 185 7.50
90 5.48 90 3.65 190 7.71
95 5.78 95 3.85 195 7.91​100 6.08 100 4.06 200


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## leland (Dec 28, 2007)

Less math.


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## Magnettica (Jan 23, 2007)

electricmanscott said:


> You absolutely need one in this case. Between meter and elbow. Not a benefit, a requirement.


Like this? 










Not exactly the best picture...


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## leland (Dec 28, 2007)

How does that expand? Push the meter up?
Also,looks upside down.


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## B4T (Feb 10, 2009)

Magnettica said:


> Like this?
> 
> 
> 
> ...


See post #40.. great info in that link.. 

It says expansion fittings are normally used in conduit runs greater than (25) feet..You have less than (6) ft. exposed..

_From the link.. "Expansion joints are usually used where the
straight run length is greater than 25 feet and
expected temperature change is greater than
60°F. Rigid PVC conduit has a coefficient of
expansion of 3.38 x 10-5 in./in./°F. A 10 foot
length will change in length about 3/8" with a
change in temperature of 100°F. This equates
to more than 4 inches over a 100 foot run."_


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## BBQ (Nov 16, 2010)

There are at least two diffrent reasons and code sections that may require us to use expansion fittings.

One is for expansion and contraction due to temperature changes, the other is ground movement.




Magnettica said:


> Like this?
> 
> 
> 
> ...


It looks like you have conduit strapped with strut which makes the expansion joints worthless.

In most cases you do not need expansion joints on such short runs.

However expansion joints are a good way to deal with ground movement as required by 300.5(J)



> *300.5(J) Earth Movement*. Where direct-buried conductors,
> raceways, or cables are subject to movement by settlement
> or frost, direct-buried conductors, raceways, or cables shall
> be arranged so as to prevent damage to the enclosed conductors
> or to equipment connected to the raceways.


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## Magnettica (Jan 23, 2007)

But the run was over 25'. This house was a tract house and we were brought in just to do the UG feeder. Not sure how that MB panel in the middle of the garage was ever approved but that is not my problem. The pics are from 4-5 years ago.


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## B4T (Feb 10, 2009)

Magnettica said:


> But the run was over 25'. This house was a tract house and we were brought in just to do the UG feeder. Not sure how that MB panel in the middle of the garage was ever approved but that is not my problem. The pics are from 4-5 years ago.


The temperature in dirt is constant.. there is no expansion..


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## Magnettica (Jan 23, 2007)

B4T said:


> The temperature in dirt is constant.. there is no expansion..


Right,the expansion takes place when the sun beats down all day on the plastic. The conduit will expand, but the conductors won't.


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## electricmanscott (Feb 11, 2010)

B4T said:


> The temperature in dirt is constant.. there is no expansion..


What are you saying?


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## B4T (Feb 10, 2009)

Magnettica said:


> Right,the expansion takes place when the sun beats down all day on the plastic. The conduit will expand, but the conductors won't.


But the conduit exposed at the MP is less than (5) ft... I don't see that ever being a problem since the conductors will be much cooler from being underground 24/7.. IMO..


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## Magnettica (Jan 23, 2007)

B4T said:


> But the conduit exposed at the MP is less than (5) ft... I don't see that ever being a problem since the conductors will be much cooler from being underground 24/7.. IMO..


My conductors are insulated. They'll be as warm as they need to be. :whistling2:


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## B4T (Feb 10, 2009)

Magnettica said:


> My conductors are insulated. They'll be as warm as they need to be. :whistling2:


:laughing::laughing:


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## B4T (Feb 10, 2009)

electricmanscott said:


> What are you saying?


I know.. you are going after the ground freeze/thaw cycle.. 

We had enough trouble getting a firm answer with the conduit on the side of the house..

Now you want to take the debate underground.. :laughing:


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## leland (Dec 28, 2007)

I call BS- From a bunch of [email protected]#$%^& Engineers. Who need to make themselves IMPORTANT.

These services have been installed for how long?
Not a problem for how long?
Suddenly,there is an issue?
How many services have we installed WITHOUT expansion fittings?

TOTAL BS- SOME ONE IS PROFITING FROM THIS.

Wires don't stretch. I don't care what you put in place. Neither do conduits.
Look at it. My physical connections-my conduit connections- what is gonna give? 20' is 20' .Period.


K- Nothing more to say- right now.

Tried and n true- thats 'bout it.


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## McClary’s Electrical (Feb 21, 2009)

B4T said:


> But the conduit exposed at the MP is less than (5) ft... I don't see that ever being a problem since the conductors will be much cooler from being underground 24/7.. IMO..


 

Mag, just curious . Why did you dig that instead of trench it?


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## McClary’s Electrical (Feb 21, 2009)

leland said:


> I call BS- From a bunch of [email protected]#$%^& Engineers. Who need to make themselves IMPORTANT.
> 
> These services have been installed for how long?
> Not a problem for how long?
> ...


 
Do you honestly think a piece of plastic in the sun doesn't change sizes?

They warp up like snakes without expansion couplings.


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## Magnettica (Jan 23, 2007)

mcclary's electrical said:


> Mag, just curious . Why did you dig that instead of trench it?


I didn't dig anything here. :no:


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## leland (Dec 28, 2007)

mcclary's electrical said:


> Do you honestly think a piece of plastic in the sun doesn't change sizes?
> 
> They warp up like snakes without expansion couplings.



I agree,they do change shape and sizes.

However: Do you think wires can grow/shrink? Longer-shorter- and enough to make a difference? I still go with BS. My pipes may move- but my wires don't. 

Even with the expansion couplings-If IMPROPERLY installed - as most are - Perfectly USELESS.

12' is 12' thats that. Another lets get 5-10 $ for what we can Item.

How many issues have YOU SEEN with services without expansion fittings? 

Seriously and honestly.

Not that there is not a science equation to it. 

But... Where is the practicality of it?


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## nrp3 (Jan 24, 2009)

I don't worry about the overhead, but I have seen pipes pulled right out of the bottom of meter sockets. I don't give it much thought, I just put expansions on and forget about it. Driving around I see all kinds of pvc falling apart.


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## B4T (Feb 10, 2009)

nrp3 said:


> I don't worry about the overhead, but I have seen pipes pulled right out of the bottom of meter sockets. I don't give it much thought, I just put expansions on and forget about it. Driving around I see all kinds of pvc falling apart.


That happens when the trench is not properly backfilled with dirt compacted under the 90..


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## Cletis (Aug 20, 2010)

*fill*



B4T said:


> That happens when the trench is not properly backfilled with dirt compacted under the 90..


He's right. I fill it, stamp it really good, and then put a flat rock under 90'. I think that helps prevent sagging somewhat along with an expansion fitting. Haven't had a callback yet...:thumbup:


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## leland (Dec 28, 2007)

nrp3 said:


> I don't worry about the overhead, but I have seen pipes pulled right out of the bottom of meter sockets. I don't give it much thought, I just put expansions on and forget about it. Driving around I see all kinds of pvc falling apart.



Me neither. $10-20- bucks- gonna break a job.

You should not have taken it.

Still BS on the expansion fittings. Ever (I'm sure you have) Seen how tight those connections in the meter socket are?

Ya, Like that $5 fitting is gonna change it.


BS all the way. Just one mans thought.


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## electricmanscott (Feb 11, 2010)

B4T said:


> I know.. you are going after the ground freeze/thaw cycle..
> 
> We had enough trouble getting a firm answer with the conduit on the side of the house..
> 
> Now you want to take the debate underground.. :laughing:


What's to debate? :no:


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## Magnettica (Jan 23, 2007)

Cletis said:


> He's right. I fill it, stamp it really good, and then put a flat rock under 90'. I think that helps prevent sagging somewhat along with an expansion fitting. Haven't had a callback yet...:thumbup:


:no:

300.5 (F) Backfill. Backfill that contains large rocks, paving materials,
cinders, large or sharply angular substances, or corrosive
material shall not be placed in an excavation where
materials may damage raceways, cables, or other substructures
or prevent adequate compaction of fill or contribute to
corrosion of raceways, cables, or other substructures.
Where necessary to prevent physical damage to the
raceway or cable, protection shall be provided in the form
of granular or selected material, suitable running boards,
suitable sleeves, or other approved means.


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## Southeast Power (Jan 18, 2009)

Maybe Cletis could call it "underfill" due to the amount of clay they have.


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## Southeast Power (Jan 18, 2009)

We have quite a bit of PVC expansion and contraction here in south Florida.
Our calculation for conduit exposed to the direct sunlight is 130 degrees. It has been known to get into the mid 20s here once every couple of years so we have 110 degrees of temperature change.

I can't explain how the bottom one got out of sync with the others:


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## jarhead0531 (Jun 1, 2010)

I'll jump in here too with my option. I don't think you need any expansion fittings. 

On the vertical the weatherhead is not attached so it is free to expand up. On the horizontal you would only need an expansion joint if your elbow is tight into a corner, otherwise with straps within a couple feet of the elbow it will allow all the expansion you'll encounter on that short a run.


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## markore (Dec 7, 2011)

*Carlon PDF Direct Link*

Carlon Expansion Fittings for PVC Rigid Nonmetallic Conduit

Lots of pictures, diagrams, and charts.


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