PVC expansion fitted needed?

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69gp

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First off in MA and came across this today. 3" Schedule 80 rising out of the ground. There is no expansion fitting. Typically an expansion fitting would be installed due to frost heaves but I was not able to find in the code where one would be required. there is only about 40" of conduit sticking out so thermal expansion would not come into play. Am I missing it in the code somewhere?

thanks


IMG_20140414_130147355.jpg
 
69gp said:
First off in MA and came across this today. 3" Schedule 80 rising out of the ground. There is no expansion fitting. Typically an expansion fitting would be installed due to frost heaves but I was not able to find in the code where one would be required. there is only about 40" of conduit sticking out so thermal expansion would not come into play. Am I missing it in the code somewhere?

thanks

IMG_20140414_130147355.jpg
Click to expand...

You are not missing it. Some jurisdictions require them but they are designed for thermal expansion above ground. Thermal expansion will allow for increase and decrease when,expansion heave can take place multiple times without receding.
 
From the 2011 NEC but it has been the same for many cycles

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.
Click to expand...

That said, in that particular installation, if it is only supported by that one post on the right I would argue that the equipment will move as much or as little as the pipe due to frost heaves and therefore the expansion fitting would not be needed.

Of course it is up to the inspector to decide.
 
Depends on how deeply the PVC's horizontal run is buried, compared to how deep the support steel for the panel goes and where the frost line is.
As mentioned earlier, the two could rise and fall together or rise and fall separately depending on that information.
 
John120/240 said:
The left conduit-Is that a inch & quarter with a weather head ? Creative idea if so. Have never seen a weather head used in this manner.
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I'm guessing some communications cables there, but still don't know why one wouldn't bring the raceway right into the enclosure:? I guess it makes a good "expansion joint" doing it that way:cool:
 
kwired said:
I'm guessing some communications cables there, but still don't know why one wouldn't bring the raceway right into the enclosure:? I guess it makes a good "expansion joint" doing it that way:cool:
Click to expand...

The conduit going into the bottom of the combiner box is the DC feed, 2-400 MCM cables that goes back to the inverter. The combiner box comes pre-wired for string wiring you can see the MC4 connector ends with about 2' of cable. The short pvc with the weather head is for strings on another row about 20' away. Not the way I like to see work but to the owner the cost is driven down.
 
Regardless of code, I think liberal use of expansion couplings is a good thing. I hate PVC for above ground but it is a necessary evil often. I theorize the more flexibility in the assembly, the less likely it will be to break if it gets wacked or stressed. This picture illustrates correct usage. Its upside down, they are going into the ground. Note the use of two different sized strut clamps to angle the nut and bolt for easier installation - a handy trick sometimes.
 

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electrofelon said:
Regardless of code, I think liberal use of expansion couplings is a good thing. I hate PVC for above ground but it is a necessary evil often. I theorize the more flexibility in the assembly, the less likely it will be to break if it gets wacked or stressed. This picture illustrates correct usage. Its upside down, they are going into the ground. Note the use of two different sized strut clamps to angle the nut and bolt for easier installation - a handy trick sometimes.
Click to expand...

Neat little trick!
 
electrofelon said:
Regardless of code, I think liberal use of expansion couplings is a good thing. I hate PVC for above ground but it is a necessary evil often. I theorize the more flexibility in the assembly, the less likely it will be to break if it gets wacked or stressed. This picture illustrates correct usage. Its upside down, they are going into the ground. Note the use of two different sized strut clamps to angle the nut and bolt for easier installation - a handy trick sometimes.
Click to expand...
Some inspector that is anal about following listings will likely reject that trick:happyyes:
 
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