PVC Expansion Couplings

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Richterfan

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My question is, if you run from a house underground 3 feet to a generator is an expansion coupling required coming out of the ground? Generally, and normally I install one from the house down into the ground, but my question is it required by code?
 
How long is the section of conduit once it emerges from the ground ?, how does it terminate ?
 
augie47 said:
How long is the section of conduit once it emerges from the ground ?, how does it terminate ?
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It just comes out of the ground in PVC then I have a 90, 10 foot length and then LB in to the house. I had an expansion coupling in the 10 foot length, but I was told it has to be the first fitting out of the ground. I know we normally do it but I am just wondering if there is a specific code that it has to be the first fitting out of the ground.
 
The NEC mandates expansion couplings based on thermal expansion, which in turn is based on length of segment, coefficient of expansion and temperature range. All of these are objectively calculable.
Expansion joints on a vertical section are usually needed to accomodate frost heave and/or ground subsidence. The best the Code could do here is pretty subjective and local practises may be more helpful.
 
GoldDigger said:
The NEC mandates expansion couplings based on thermal expansion, which in turn is based on length of segment, coefficient of expansion and temperature range. All of these are objectively calculable.
Expansion joints on a vertical section are usually needed to accomodate frost heave and/or ground subsidence. The best the Code could do here is pretty subjective and local practises may be more helpful.
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I get the vertical for frost /heave but is it required by code is my question. I always do it as a common practice I am trying to figure out if the ahj can make you put one in if the code doesn’t require it.
 
Local jurisdictions and sometimes POCOs can have requirements beyond the NEC
 
Richterfan said:
I get the vertical for frost /heave but is it required by code is my question. I always do it as a common practice I am trying to figure out if the ahj can make you put one in if the code doesn’t require it.
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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 cables and conductors 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.
 
don_resqcapt19 said:
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 cables and conductors 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.
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Thanks for reminding us that, especially for PVC, putting in an expansion joint in the pipe does not relieve you of the duty to accomodate the conductors too. Maybe more so with frost heave than for thermal expansion.
 
So in are area we don’t use them when emerging from ground. Never get called and never seen an expansion joint ever around the coast. Is it just something that gets overlooked or does geographical location play an effect.
(Going to look in amended code maybe it’s removed and just never noticed)
 
GoldDigger said:
Thanks for reminding us that, especially for PVC, putting in an expansion joint in the pipe does not relieve you of the duty to accomodate the conductors too. Maybe more so with frost heave than for thermal expansion.
Click to expand...
Yes, on risers coming out of the earth to a typical enclosure, there is almost never enough temperature differential to require an expansion fitting for the thermal movement. It is almost always for earth movement of some type.

I really don't know how you accommodate the conductors in a raceway installation going to things like a meter can where there is not enough space in the can to leave extra conductor so that when the conduit settles, the conductors do not pull out of the lugs.
 
One thing that comes to mind is bending the wires into a wavy curve or spiral inside the conduit for some distance back.
Worst case you would have to install a box or gutter just for bending space.

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300.5J is the section that may require an expansion fitting for a stub up into a box even if it’s a short length. It’s not always required because not every area of the country has the same amount of frost. There have been efforts to put it into the code to require it at all times — most of those being public inputs from people who live in colder areas of the country. So far those have not been accepted.

I knew of a project in the Southern Midwest that was engineered by someone from the Northeast who specified expansion fittings for all stub ups. The electricians didn’t know how to install them for that application because there’s no major frost in that area. So they installed them 100% compressed.
 
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