PVC expansion fittings

[domnic]

On a under ground service with pvc from under ground from poco to meter base ( 4' ) must i use a expansion fitting, 2011 nec. ( 2" PVC ).

 

[augie47]

For thermal expansion rarely but some POCOs require one to address earth settling.

 

[don_resqcapt19]

For thermal expansion rarely but some POCOs require one to address earth settling.

As does the code in 300.5(J).

 

[ggunn]

A common test question that trips up people is that they give a length for the conduit and ask you how many expansion fittings you need. If you just divide the total by the max span you will get one too many because you don't need one at the other end of the run.

 

[ggunn]

So according to the 2011 NEC, when working on an underground service using PVC conduit from underground to the meter base (4'), it is essential to utilize an expansion fitting. This requirement applies specifically to 2" PVC conduit. By incorporating the expansion fitting, you can ensure the integrity and durability of the conduit system, making it to accommodate temperature changes effectively. Safety and compliance are paramount in adhering to NEC regulations.

Is that language still in the later revisions?

 

[wwhitney]

Is that language still in the later revisions?

The post you quoted sounds like a hallucinating chatbot.

Cheers, Wayne

 

[tom baker]

So according to the 2011 NEC, when working on an underground service using PVC conduit from underground to the meter base (4'), it is essential to utilize an expansion fitting. This requirement applies specifically to 2" PVC conduit. By incorporating the expansion fitting, you can ensure the integrity and durability of the conduit system, making it to accommodate temperature changes effectively. Safety and compliance are paramount in adhering to NEC regulations.

Maybe. I have never seen an expansion fitting anywhere in Washington for ug pvc to a meter or disconnect

 

[don_resqcapt19]

Maybe. I have never seen an expansion fitting anywhere in Washington for ug pvc to a meter or disconnect

Our utility will not connect the power unless you have that fitting for an underground conduit system. No fitting required if the conduit is just a sleeve that protects directly buried conductors or cables as they come out of the ground to the meter.

 

[don_resqcapt19]

So according to the 2011 NEC, when working on an underground service using PVC conduit from underground to the meter base (4'), it is essential to utilize an expansion fitting. This requirement applies specifically to 2" PVC conduit. By incorporating the expansion fitting, you can ensure the integrity and durability of the conduit system, making it to accommodate temperature changes effectively. Safety and compliance are paramount in adhering to NEC regulations.

The code does not actually say that. Here is the 2011 code text for this rule.

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.

If you have a conduit system the expansion fitting is probably the only method that the AHJ will approve, however in some areas they will let you make your own "slip fitting" by sliding a larger size raceway over the smaller one coming out of the ground.
The language for this rule has not been changed since the 2011 code and is word for word in the 2023 code.

 

[electrofelon]

, however in some areas they will let you make your own "slip fitting" by sliding a larger size raceway over the smaller one coming out of the ground.

And just to note that there is a fitting called a "slip riser" that is exactly that. It's just a piece of 2-1/2" with one end shrunk down and a 2" TA on it - and you can often see the "2-1/2" schedule 40" label right on it. I usually make my own out of 2-1/2" PVC and a 2 1/2 ta, which is better in my opinion because it is cheaper, has less restriction at the fitting, and gets rid of the concentric KO that is on a lot of the enclosures we use around here.

But yes we use slip risers or expansion couplings around here. IMO they are good practice not just for movement due to ground settling or Frost heaving, they provide more flexibility which helps reduce breakage.

 

[kwired]

And just to note that there is a fitting called a "slip riser" that is exactly that. It's just a piece of 2-1/2" with one end shrunk down and a 2" TA on it - and you can often see the "2-1/2" schedule 40" label right on it. I usually make my own out of 2-1/2" PVC and a 2 1/2 ta, which is better in my opinion because it is cheaper, has less restriction at the fitting, and gets rid of the concentric KO that is on a lot of the enclosures we use around here.

But yes we use slip risers or expansion couplings around here. IMO they are good practice not just for movement due to ground settling or Frost heaving, they provide more flexibility which helps reduce breakage.

Arlington has one that is basically a male TA with 2" male thread but has 2.5" socket to cement in 2.5" Sch 40 and then slip your 2" PVC inside the 2.5" sch 40. What you suggest works and likely is less cost, but a nit picky inspector will probably say it is not listed for that but will accept the Arlington one because it is listed to be used this way.

 

[kwired]

The code does not actually say that. Here is the 2011 code text for this rule.

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.

I agree, NEC does not require an expansion fitting, some POCO's or even local AHJ's might require one even if not really necessary.

Is possible to use one when earth movement is expected - the catch here that never comes up in discussion is it only protects the raceway. If you don't arrange the conductors so they can move they will strain terminations when they try to move. Conductors with ampacity of ~100amps or more don't flex much at all when coming into typical meter sockets without also putting strain on the termination.

Burying underground raceways/conductors as deep as undisturbed soil pretty much eliminates settling problems, or make sure you have compacted whatever has been disturbed pretty well. Burying underground raceways/conductors below frost line and only passing vertically through the frost zone usually helps with the frost heave potential.

 

[don_resqcapt19]

I agree, NEC does not require an expansion fitting, some POCO's or even local AHJ's might require one even if not really necessary.

Is possible to use one when earth movement is expected - the catch here that never comes up in discussion is it only protects the raceway. If you don't arrange the conductors so they can move they will strain terminations when they try to move. Conductors with ampacity of ~100amps or more don't flex much at all when coming into typical meter sockets without also putting strain on the termination.

Burying underground raceways/conductors as deep as undisturbed soil pretty much eliminates settling problems, or make sure you have compacted whatever has been disturbed pretty well. Burying underground raceways/conductors below frost line and only passing vertically through the frost zone usually helps with the frost heave potential.

I don't see any other way to protect from earth movement if there is complete conduit system. We will always require a slip fitting or expansion joint for a complete conduit system where the conduit comes out of the ground and connects to an enclsoure.

 

[letgomywago]

I don't see any other way to protect from earth movement if there is complete conduit system. We will always require a slip fitting or expansion joint for a complete conduit system where the conduit comes out of the ground and connects to an enclsoure.

If you don't have earth movement you're good. Some areas have stable soil others don't. If you were in permafrost would you ever see soil movement? I think this depends on geology of the area. Where I'm at so long as there isn't decomposing mica it isn't an issue and if there is I haven't seen it become one and I do service work and remodels mostly. I have seen frost heave but that was with 12 inch burried stuff for a post lamp not deeper below frost line stuff.

 

[don_resqcapt19]

If you don't have earth movement you're good. Some areas have stable soil others don't. If you were in permafrost would you ever see soil movement? I think this depends on geology of the area. Where I'm at so long as there isn't decomposing mica it isn't an issue and if there is I haven't seen it become one and I do service work and remodels mostly. I have seen frost heave but that was with 12 inch burried stuff for a post lamp not deeper below frost line stuff.

That assumes proper compaction of the trench at the time of installation....something that almost never happens for an electrical installation unless it is under a parking lot.

 

[letgomywago]

That assumes proper compaction of the trench at the time of installation....something that almost never happens for an electrical installation unless it is under a parking lot.

Then that must be what its like here since there aren't large or even small amounts of houses with conduit stopping half an inch bellow their meters.

 

[Frank DuVal]

Here the Co-Op power companies supply the slip riser. And the big power company does everything (for a price of course).

 

[wwhitney]

Then that must be what its like here since there aren't large or even small amounts of houses with conduit stopping half an inch bellow their meters.

It's going to depend on the construction sequence and local frost depth.

If the underground conduit is installed on undisturbed soil, and is below the frost depth, it shouldn't move vertically. Likewise for the house. Where the frost depth is 24" or less, there aren't likely to be basements, and so both of those conditions can easily be satisfied.

In a colder climate with a deeper frost depth, there are often basements. That usually involves disturbing the soil several feet outside of the perimeter of the building. Which means that the sweep where the conduit turns up to the building is running through disturbed soil and may be subject to settlement. And the conduit itself may be subject to frost heave.

Cheers, Wayne

 

[letgomywago]

It's going to depend on the construction sequence and local frost depth.

If the underground conduit is installed on undisturbed soil, and is below the frost depth, it shouldn't move vertically. Likewise for the house. Where the frost depth is 24" or less, there aren't likely to be basements, and so both of those conditions can easily be satisfied.

In a colder climate with a deeper frost depth, there are often basements. That usually involves disturbing the soil several feet outside of the perimeter of the building. Which means that the sweep where the conduit turns up to the building is running through disturbed soil and may be subject to settlement. And the conduit itself may be subject to frost heave.

Cheers, Wayne

Makes sense. We have lots of basements here but you're looking at minimum 3 ft for our local utility requirements. Usually it's 4 feet down and then they are only cutting back 2 or 3 ft for their basement forms. Everything here is new or old not new in old locations if that makes sense. All the old stuff is overhead also.

 

[garbo]

On a under ground service with pvc from under ground from poco to meter base ( 4' ) must i use a expansion fitting, 2011 nec. ( 2" PVC ).

At an continuing education class the inspector told us that he requires an expansion joint on all PVC conduit feeding meter cans. He said it's not for the expansion & contraction from cold winters to hot summers but to make up for ground settlement. Iny area have came across a few 2" PVC that pulled out of male adapter .