Expansion coupling or not?

[Ponchik]

In response to this thread,
http://forums.mikeholt.com/showthread.php?t=155203

I like to take a pole as to how many of you install expansion fittings?

Thank you.

 

[iwire]

I can't answer your poll because there is no option for 'when needed'

 

[eHunter]

I can't answer your pole because there is no option for 'when needed'

+1 :thumbsup:

 

[ActionDave]

Same here X 2. If it is a complete conduit system and required then yes. If it is something like a sleeve over exposed direct bury rated conductors then no.

 

[goldstar]

EC's in my area require them irrespective of whether it's a continuous PVC run or not (I think it's a CYA type thing). I did a repair last week where I had to re-attach a meter enclosure that had been pulled off the house. The lineman for the POCO told me that if the PVC went straight down (with no bend) and the feeders were direct burial I wouldn't need the expansion fitting. However, if the PVC had a 90 on the bottom then I would. He had no way of knowing what was below.

The part I have trouble understanding about using an expansion fitting in this scenario is if the ground settles and pulls down the PVC, doesn't the wire also get pulled down with it ? In the service I just repaired the neutral was just about pulled all the way out of the lug and there was no slack. Instead of the wires being fed up and bent around and fed into the top of the lugs they were fed straight up and right into the bottom of each lug.

 

[Ponchik]

Sorry about the misspelling. It was my first poll so I was not sure how to set it up.

 

[Gregg Harris]

EC's in my area require them irrespective of whether it's a continuous PVC run or not (I think it's a CYA type thing). I did a repair last week where I had to re-attach a meter enclosure that had been pulled off the house. The lineman for the POCO told me that if the PVC went straight down (with no bend) and the feeders were direct burial I wouldn't need the expansion fitting. However, if the PVC had a 90 on the bottom then I would. He had no way of knowing what was below.

The part I have trouble understanding about using an expansion fitting in this scenario is if the ground settles and pulls down the PVC, doesn't the wire also get pulled down with it ? In the service I just repaired the neutral was just about pulled all the way out of the lug and there was no slack. Instead of the wires being fed up and bent around and fed into the top of the lugs they were fed straight up and right into the bottom of each lug.

It would be a CYA.
In New Jersey the highest temperature difference is 91/10. So with a maximum 81 degree temperature difference, and this would be ambient only not considering ground temperature, and you had a 10' piece between the meter enclosure to the 90, and it was securely mounted in the ground you would have a total expansion of 0.032 inches.

A long ways from 1/4".

Expansion joints are tested and listed for above ground thermal expansion and not ground heave. The couplings are adjusted to anticipated thermal difference of the ambient air.

 

[don_resqcapt19]

... Expansion joints are tested and listed for above ground thermal expansion and not ground heave. ...

But the code rule requires protection from ground movement.

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.

Informational Note: This section recognizes ?S? loops in underground direct burial to raceway transitions, expansion fittings in raceway risers to fixed equipment, and, generally, the provision of flexible connections to equipment subject to settlement or frost heaves.

 

[Gregg Harris]

But the code rule requires protection from ground movement.

The point I was trying to make don was that the expansion joints have an adjustment for temperature difference and not ground heave. Ground heave can be much greater than the temperature expansion and would not protect the conductors from movement in the same that adding an "S" to the conductors to prevent strain on the lug connections.

It gives you a temperature range to adjust but does not consider how much adjustment is needed for ground heave or how to determine it.

 

[dhalleron]

I didn't even know they existed for a long time. The electricians that taught me never used them.

In my part time electrical business since 2010 I have never needed them since I have not installed pvc where it would be needed.

For 20 years, I worked part time for another contractor who never used them. Years before that I never heard of them.

My neighbor's house could have used one on his underground service. The pvc has pulled out of the adapter going into the meter socket. This could be a ground heave issue though.

 

[infinity]

It would be a CYA.
In New Jersey the highest temperature difference is 91/10. So with a maximum 81 degree temperature difference, and this would be ambient only not considering ground temperature, and you had a 10' piece between the meter enclosure to the 90, and it was securely mounted in the ground you would have a total expansion of 0.032 inches.

Where did you come up with 91/10?

 

[Gregg Harris]

Where did you come up with 91/10?

From ACCA Manual J it gives the temperatures throughout the US and Canada for determinig load calculations for HVAC. I just picked the widest range in NJ a place called Patterson

 

[iwire]

Expansion joints are tested and listed for above ground thermal expansion and not ground heave. The couplings are adjusted to anticipated thermal difference of the ambient air.

You put it in the middle of it's range and hope for the best when used for ground movement. Most of the ones I see move at least 6" or 8"

Are you suggesting doing so is a violation? :?

 

[jusme123]

The point I was trying to make don was that the expansion joints have an adjustment for temperature difference and not ground heave. Ground heave can be much greater than the temperature expansion and would not protect the conductors from movement in the same that adding an "S" to the conductors to prevent strain on the lug connections.

It gives you a temperatre range to adjust but does not consider how much adjustment is needed for ground heave or how to determine it.

...have you ever seen a 2" PVC expansion fitting? If the ground heave is greater than that, you may want to consider overhead install.

 

[iwire]

...have you ever seen a 2" PVC expansion fitting? If the ground heave is greater than that, you may want to consider overhead install.

Kind of what I was thinking.