Underground Services/expansion couplings

[eljefetaco]

We live in an area in NJ where there are many underground services and extreme climate changes. Has it ever been proposed to make a PVC expansion coupling mandatory at all meters attached to a house. I see alot of meters being ripped off of houses do to the expansion and contraction of the earth during the climate changes. Should this be an abient temperature correction issue based on temperature range. A entire new code area to develop. IMO

 

[raider1]

Take a look at 300.5(J).

(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.
FPN: 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.

Chris

 

[Volta]

It is a jurisdiction question first. Here the AHJ's resposibility starts at the meter. Though NEC 300.5(J) can be used to enforce an expansion coupling, I don't see it happen much, I just see the damaged laterals.

It is less the contraction of the PVC, usually, and more a settling of the earth in the original trench. Hard to use 352.44 for that directly.

 

[kwired]

One local POCO here requires PVC expansion below meter sockets or CT cabinets on the raceway containing their service lateral. But not necessarily for thermal expansion. I have been told by many of the POCO employees that it is for frost heave or trench settling. I can not convince them this is pointless.

The expansion fitting is for thermal expansion. If you have earth movement the expansion fitting may save the raceway from damage but the conductor within does not expand or contract with the raceway. It will be either pulled or pushed and put strain on the meter terminals and possibly even break something.

 

[Volta]

One local POCO here requires PVC expansion below meter sockets or CT cabinets on the raceway containing their service lateral. But not necessarily for thermal expansion. I have been told by many of the POCO employees that it is for frost heave or trench settling. I can not convince them this is pointless.

The expansion fitting is for thermal expansion. If you have earth movement the expansion fitting may save the raceway from damage but the conductor within does not expand or contract with the raceway. It will be either pulled or pushed and put strain on the meter terminals and possibly even break something.

It is true that the conductors will settle along with the horizontal portion of the conduit. It is often an amount that will separate the pipe, bend the enclosure, or both, but usually not so much that internal components become damaged, if installed in such a manner that the conductors make a wide arc to the terminals. It may not save every installation, but it is not pointless either.

Every lateral load end I've repaired so far from this has had sufficient conductor to use, the internal clamps and clips were fine, and the only damage that occured was from the tension on the male terminal adapter.

 

[kwired]

It is true that the conductors will settle along with the horizontal portion of the conduit. It is often an amount that will separate the pipe, bend the enclosure, or both, but usually not so much that internal components become damaged, if installed in such a manner that the conductors make a wide arc to the terminals. It may not save every installation, but it is not pointless either.

Every lateral load end I've repaired so far from this has had sufficient conductor to use, the internal clamps and clips were fine, and the only damage that occured was from the tension on the male terminal adapter.

You are not getting my point.

Assume we have a PVC raceway connected to a meter socket and then has an expansion fitting. Then runs straight down into the ground and then elbows horizontal at say 3 feet deep and runs whatever distance at that depth. This raceway contains 200 amp conductors.

If the trench settles and pulls the raceway below the expansion fitting down the expansion fitting protects the raceway (until settling beyond the length of the fitting). The portion above the expansion fitting are supposed to be secured to the surface it is mounted on so it does not move. Now the 200 amp conductors are not a part of any of the other equipmnet but are just contained by it, and attached within the meter socket. Where are they going to go? They will be pulled on and if pulled hard enough (200 amp conductors do not flex very easily even if excess conductor is left in the meter enclosure) will break the terminal it is attached to.

If there is free unsecured conductor at the other end of the raceway it may be able to slide within the moving raceway. If the conductors are secured on the other end it can not allow for settling without straining something somewhere.

 

[hardworkingstiff]

You are not getting my point.

Assume we have a PVC raceway connected to a meter socket and then has an expansion fitting. Then runs straight down into the ground and then elbows horizontal at say 3 feet deep and runs whatever distance at that depth. This raceway contains 200 amp conductors.

If the trench settles and pulls the raceway below the expansion fitting down the expansion fitting protects the raceway (until settling beyond the length of the fitting). The portion above the expansion fitting are supposed to be secured to the surface it is mounted on so it does not move. Now the 200 amp conductors are not a part of any of the other equipmnet but are just contained by it, and attached within the meter socket. Where are they going to go? They will be pulled on and if pulled hard enough (200 amp conductors do not flex very easily even if excess conductor is left in the meter enclosure) will break the terminal it is attached to.

If there is free unsecured conductor at the other end of the raceway it may be able to slide within the moving raceway. If the conductors are secured on the other end it can not allow for settling without straining something somewhere.

I get your point and would like to add that the majority of settling can be traced to improper compaction prior to conductor installation. This is why I really don't care for trenchers (as compared to a backhoe ditch). Trenchers leave quite a bit of "fluffy" material below the conductors. This material will settle, plus, you can't see if you just scraped across the top of another conduit or pipe causing damage but having it filled with fluffy material prior to being viewed by the operator.

 

[Volta]

You are not getting my point. . .

I also see your point, and don't disagree with the basic premise. But it takes only a fraction of an inch of settlement to damage the raceway or enclosure, and often that much conductor is available inside. Not always, sure, but sometimes, absolutely. It can save the installation. Not pointless.

 

[infinity]

Since on the pole end of the conductors are just exiting the conduit it is possible that some slack can be pulled into the conduit when the expansion fitting moves on the meter enclosure end.

 

[Volta]

True, but can be a tough pull sometimes.

In this area, it is not always a 'raceway', but sometimes a sleeve for the directly-buried conductors. It would extend 20' or so away from the building to allow replacement or the conductors without disturbing the not-yet existing patio or similar.

The enclosure experiences the downward tension just the same that way, but no chance of the conductors being drawn toward the load end.

 

[infinity]

True, but can be a tough pull sometimes.

In this area, it is not always a 'raceway', but sometimes a sleeve for the directly-buried conductors. It would extend 20' or so away from the building to allow replacement or the conductors without disturbing the not-yet existing patio or similar.

The enclosure experiences the downward tension just the same that way, but no chance of the conductors being drawn toward the load end.

I agree. I was just thinking of some of the easier pulls for a residential 200 amp service. In some cases we can almost push the conductors in so they would move after the installation.

 

[kwired]

I get your point and would like to add that the majority of settling can be traced to improper compaction prior to conductor installation. This is why I really don't care for trenchers (as compared to a backhoe ditch). Trenchers leave quite a bit of "fluffy" material below the conductors. This material will settle, plus, you can't see if you just scraped across the top of another conduit or pipe causing damage but having it filled with fluffy material prior to being viewed by the operator.

The problem I see most of the time is not settling of the trench but settling of the backfill around the new building that the raceway passes through.

The electrician better dig all the way down to where the original excavation was and install his line there or else dig it out and properly compact it up to the depth where he wishes to install his raceway.

 

[wawireguy]

I haven't seen any damage in my neck of the woods from PVC expansion. We get cold winters here also.