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We don' need no steenking expansion joint!


Jim Katen
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Scanning the chart referenced, you only need expansion joints in lengths of conduit over 25 feet. I don't see much electrical conduit over 25 feet in residential construction.

The other place you might see them is where a service lateral comes out of the ground and up into a meter can. If the conduit settles in the trench, it's nice to have some slack to prevent it from pulling the can off the wall.

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  • 9 years later...

Nice pictures, at the risk of sounding stupid, care to elaborate?

I'll give it a try:

The electrical conduit in the first pic should have an expansion joint or two so that that plastic can expand and contract without exposing the cable. It looks like it has pulled loose at a union that might have been poorly glued or not glued. It needs better support as well, more clamps.

The flexible conduit is not rated for that usage and it is susceptible to damage, like a kid spinning through there on a bike could catch a pedal on it.

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Warning, Jim K has traveled back to Dec 31, 2001 and has been bumped to the first reply position on this thread! With his knowledge of the events of the last 10 years, there's no telling what he will do in 2002. [?]

Jim sent a telepathic message re: expansion joints on service laterals. Here's an example of a need for an expansion joint between the panel and the ground, a distance of only about 3 feet. The smaller conduit to the cable box has also dropped several inches.

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tn_201171722292_conduit%20gap.jpg

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Don't need an expansion joint there, John.

They just needed to install it right.

See it quite a bit around here with houses built on hillsides.

Electricians get a pretty penny for fixing it. Especially when there's a ton of water in the conduit.

-

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Warning, Jim K has traveled back to Dec 31, 2001 and has been bumped to the first reply position on this thread! With his knowledge of the events of the last 10 years, there's no telling what he will do in 2002. [?]

Jim sent a telepathic message re: expansion joints on service laterals. Here's an example of a need for an expansion joint between the panel and the ground, a distance of only about 3 feet. The smaller conduit to the cable box has also dropped several inches.

Click to Enlarge
tn_201171722292_conduit%20gap.jpg

47.8 KB

I thought that a slip joint for ground movement is something different than an expansion fitting.
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I thought that a slip joint for ground movement is something different than an expansion fitting.

I think you are correct. An expansion joint is listed for a predictable amount of expansion/contraction between two fixed points. Frost heave or ground settlement are less predictable. What Carlon calls a "slip meter riser" is longer than an expansion joint. I've been confused by this, in part because the informational note for 300.5(J) mentions "expansion joints" and isn't really correlated to the UL standards for such products.

http://www.carlon.com/Master%20Catalog/ ... ochure.pdf

I like the idea of the product in the link above because it will also function as a drain.

Douglas Hansen

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Doug, your "slip meter riser" could really solve a lot of problems around here, IF they would have installed them. Unfortunately, I've NEVER seen one around here, though I've seen a LOT of conduit pulled apart and/or broken due to ground movement.

-

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Doug, your "slip meter riser" could really solve a lot of problems around here, IF they would have installed them. Unfortunately, I've NEVER seen one around here, though I've seen a LOT of conduit pulled apart and/or broken due to ground movement.

Now we have something to recommend for that.

The service conduit rising from the earth to the meter box is broken or discontinuous, likely because of settlement of the soil around it. This leaves the service conductors within it exposed and unprotected. An electrician should install a "slip meter riser" on this conduit.

Sounds simple but it's likely a lot of work, and expensive.

Marc

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The undewrwriter inspectors working in my area have been calling for meter slip joints for the past 10 years or so.........they're seen everywhere here.

Greg

Greg - When you run into one of these again, could you take a picture to share with us? It certainly seems like a product we should be using out here, though I have never seen it.

I have a project right now with two conduits going from a meter pedestal down to two buildings that are about 25 feet lower in elevation. It seems that these slip joints would solve the problem of water rising in the conduits at the buildings. The other ways we deal with the water problem are to have a drain/pull box outside the downhill structure, or to put an upside down wye in the riser.

Thanks

Douglas Hansen

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