Expansion fittings in Rigid

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EverydayElectrician

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Anyone ever seen rigid coming out of the ground, go up 5-6' in a box or LB with no expansion fitting?

I've seen it alot and the installation never seems any worse for the wear. Compared to PVC which almost always has an expansions fitting.

Thoughts?
 
I've never seen a rigid expansion fitting. Does rigid expand/contract any significant amount?

Based on the ambient temps around here, I use PVC expansion fittings when running a straight section more than 10 feet. I can't imagine 6 feet of rigid requires one.
 
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I've only seen them used on straight runs of Rigid steel conduit about every 100'. I've also seen them installed when conduit is leaving a steel structure that it is being supported by and going to a new structure such as a compressor skid. I don't know exactly how much RMC expands and contracts but, if conduit is being installed in an environment where the temperature could range in the +100°F in summer and down to -10°F in the winter, it will expand and contract.

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Normally used at building expansion joint.
Do you have one on the steel frame of your truck?
 
The expansion fitting for a conduit coming out of the ground is not really for thermal expansion. It is for ground movement such as frost heave. 300.5(J)
 
don_resqcapt19 said:
The expansion fitting for a conduit coming out of the ground is not really for thermal expansion. It is for ground movement such as frost heave. 300.5(J)
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Right, I wouldnt worry about the Rigid itself expanding/contracting like PVC does. Where I am we get alot of ground movement from Frost heaving, but as I said at the top of this post, I never see expansion fittings in rigid and everything always looks fine.
 
EverydayElectrician said:
Right, I wouldnt worry about the Rigid itself expanding/contracting like PVC does. Where I am we get alot of ground movement from Frost heaving, but as I said at the top of this post, I never see expansion fittings in rigid and everything always looks fine.
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If your underground run is below frost depth, you seldom have much issue with frost heave effecting the vertical portion of the run, even with PVC conduit.
 
EverydayElectrician said:
Right, I wouldnt worry about the Rigid itself expanding/contracting like PVC does. Where I am we get alot of ground movement from Frost heaving, but as I said at the top of this post, I never see expansion fittings in rigid and everything always looks fine.
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I have seen damage to the enclosures from the ground moving the rigid conduit many times around here.
 
kwired said:
If your underground run is below frost depth, you seldom have much issue with frost heave effecting the vertical portion of the run, even with PVC conduit.
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It is very rare to see any conduits below the frost depth around here.
 
don_resqcapt19 said:
It is very rare to see any conduits below the frost depth around here.
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It's probably rare to see conduit buried below frost depth in most places. I looked at a frost depth map for the entire US. Most of the country has a frost depth deeper than the 18" you are required to bury conduit in most situations.

I live at the 0" line which is why I never see rigid expansion fittings. :)
 

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Coppersmith said:
It's probably rare to see conduit buried below frost depth in most places. I looked at a frost depth map for the entire US. Most of the country has a frost depth deeper than the 18" you are required to bury conduit in most situations.

I live at the 0" line which is why I never see rigid expansion fittings. :)
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I live between the 50" and 60" marks, never seen frost deeper than ~48", and even that very seldom. Global warming?:blink::D
 
Coppersmith said:
It's probably rare to see conduit buried below frost depth in most places. I looked at a frost depth map for the entire US. Most of the country has a frost depth deeper than the 18" you are required to bury conduit in most situations.

I live at the 0" line which is why I never see rigid expansion fittings. :)
Click to expand...

I live right on that 30” line. We haven’t had 12” frost depth in I don’t know how long, maybe 20 years.
 
Also I think those frost depth values are absolute worst case. Like in a spot sheltered from the sun, all snow continuously removed, it got that deep once 24 years ago ;). I am in upstate NY where that map says 50-60". My water line is as shallow as 12" in some places and I've never had a problem.
 
electrofelon said:
Also I think those frost depth values are absolute worst case. Like in a spot sheltered from the sun, all snow continuously removed, it got that deep once 24 years ago ;). I am in upstate NY where that map says 50-60". My water line is as shallow as 12" in some places and I've never had a problem.
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It gets cold in upstate NY but don't you normally get 10 miles of snow depth to help insulate the ground from the even colder air above the snow?
 
electrofelon said:
Also I think those frost depth values are absolute worst case. Like in a spot sheltered from the sun, all snow continuously removed, it got that deep once 24 years ago ;). I am in upstate NY where that map says 50-60". My water line is as shallow as 12" in some places and I've never had a problem.
Click to expand...

Makes sense. Kind of like the “100 year flood plain”.
 
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