PVC Expansion Coupling

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A/A Fuel GTX

A/A Fuel GTX

Senior Member
Location
WI & AZ
Occupation
Electrician
Situation:

West Central Wisconsin with winter temperatures down to 30 below. Direct burial POCO service lateral. Meter socket 5' OC above finish grade with 2" Schedule 80 running vertically from the bottom of the socket to 18" below grade. Expansion coupling necessary?
 
A/A Fuel GTX said:
Situation:

West Central Wisconsin with winter temperatures down to 30 below. Direct burial POCO service lateral. Meter socket 5' OC above finish grade with 2" Schedule 80 running vertically from the bottom of the socket to 18" below grade. Expansion coupling necessary?
Click to expand...

If your job was solidly-piped I'd probably say that an expansion sleeve would take care of frost movement, but with just that one conduit going into the ground 18", I would think an "S" formed with the conductors below grade would be more effective. Just my HO, though.:smile:
 
With such cold temperatures, I would think the frost heave/depth of frost would be great enough that an expansion coupling would be more effective.

Fred is from the northern portion of NYS, so he may have more valuable experience than what I have just offered.
 
Pierre C Belarge said:
With such cold temperatures, I would think the frost heave/depth of frost would be great enough that an expansion coupling would be more effective.
Click to expand...

In the POCO's meter manual, they show expansion couplings but don't enforce their use. The situation described is very typical of a residential service in my area. I don't use an expansion coupling in the described install however if there were a 90 below grade I would use one. I feel the 90 would give the earth more gripping power if there were any heaving.
 
My impression was if the service was in conduit its total length
then a slip coupler was necessary.I fail to see its benefits if the
meter was mounted to a home or structure with a foundation or
frost wall.When I go to a pad mount or pole then I use one.
Just my take..BTW Fred is south of me :grin: much warmer!
 
A/A Fuel GTX said:
Situation:

West Central Wisconsin with winter temperatures down to 30 below. Direct burial POCO service lateral. Meter socket 5' OC above finish grade with 2" Schedule 80 running vertically from the bottom of the socket to 18" below grade. Expansion coupling necessary?
Click to expand...

Your conduit is acting like a chase not a raceway, therefore no expansion coupling should be necessary. Does your POCO call for expansion couplings on vertical chases or just on complete raceways or those that include 90's?

Frost heave directly against a foundation is not normally a problem as the heat loss from the building usually prevents frost getting any closer than a few inches to the building. Frost heave is more of an issue as you move away from the building (hence the problem with 90's). Normally, with direct burial cable, we see several feet left in a S shape in the bottom of the trench.
 
jim dungar said:
Does your POCO call for expansion couplings on vertical chases or just on complete raceways or those that include 90's?
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The manual shows the use of expansion couplings but doesn't differentiate their use in a chase versus a raceway. I have never seen the local POCO use a raceway for laterals including primaries to pad mount transformers. If there was a problem, I guess they would enforce their use since it's their wires that are coming up into the meter via this chase. For now I'll just continue on with the "elbow" rule......If there is a 90 below grade, I'll include an expansion coupler.
 
For "severe frost heave" my WPS meter manual suggests, but does not list as required, a slip joint for 400/600A underground services. They show a homemade slip joint of 6" PVC coming down from the meter base with a piece of 4" PVC slipped into it (6" overlap) and going into the ground.
 
I used to live in Alaska and have seen a few installs where the PVC was pushed up into the meter damaging it due to frost heave.
They made a local amendment to use fnmc for bottom entries.
 
Last edited:
aksparky said:
I used to live in Alaska and have seen a few installs where the PVC was pushed up into the meter damaging it due to frost heave.
They made a local amendment to use fnmc for bottom entries.
Click to expand...

Was there a full conduit run underground all the way up to the meter or was it a direct burial lateral with a 45 or 90 below grade as part of the sleeve?
 
What size is your service?
Most of the POCOs in central WI want open bottom pedestal mount meter sockets for their direct burial installations 200A and smaller.
 
jim dungar said:
What size is your service?
Most of the POCOs in central WI want open bottom pedestal mount meter sockets for their direct burial installations 200A and smaller.
Click to expand...

Typical residential is 200A. I see the pedestal services out in the country where we must run the feeders into the house but the city environment is still with the meter socket attached to the house with the POCO lateral coming up to it. Our main source here is Xcel Energy.
 
According to the on-line version of Xcel's service manual (my emphasis):

"Ground Movement ? Slip sleeves (expansion joints) will be furnished and installed by the Company on all new underground residential meter installations in Colorado. An 18" length of 2?" Schedule 40 or 3" Schedule 80 PVC conduit shall be installed at the bottom of the underground riser. Refer to 2005 NEC? Article 300.5(J) (FPN), or as may be amended and to the Illustrations Section, Drawings SC-30, SC-40, SC-50, SC-90 and TR-10 for typical slip sleeve installations."

 
jim dungar said:
According to the on-line version of Xcel's service manual (my emphasis):

"Ground Movement ? Slip sleeves (expansion joints) will be furnished and installed by the Company on all new underground residential meter installations in Colorado.

Click to expand...

Interesting....I guess Wisconsin earth is more stable:D
 
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