RGS Elbows

A

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Any of you guys ever install pvc conduit underground with RGS elbows? The spec seems to always read the rgs elbows are required when conduit exiting ground. Never understood why just there and not for horizontal bends that remain underground. Isn't the purpose for this to prevent wire from busting through the elbow when pulling? Thanks
 
We use them with PVC embedded in the concrete pour. Never used them underground with PVC because it kind of defeats the purpose of burying PVC in the first place.
 
The companies I worked for up until 2001 did that all the time. Especially if it was a long pull. Did not want the pull rope to cut into the 90. Coated the RGS 90 with that black tar stuff.
 
An unpopular perspective and untested concept, but I like to use RGS on the stub up as it is an elbow and reduces potential for burnout and the steel provides some inductive qualities to the feeder which may reduce the severity of transients
 
I mainly work on waste water treatment plants and lift stations but I use pvc coated rigid elbows for 90% of the underground that I do. String will easily burn through a pvc elbow, especially on longer pulls. I have never see a spec that differentiated between horizontal and vertical elbows.
 
I am in a contrary mood. I see this requirement all the time. I also see foremen/superintendents in my company doing it even when not required. I am an unbeliever. First, with a properly sized rope, you are never going to burn through a PVC elbow using a tugger. The speed and tension just isn't enough to create that friction and heat. That leaves smaller pulls by hand. yes, if a person uses a thin rope or the string and/or pulls too fast you can get burn through. Use a goo 5/8 or 3/4 mule tape for your pulls and I don't believe you will get burn through. If you do, then your problem is mor likely the installation and too many elbows or conduit fill.
 
Strathead said:
I am in a contrary mood. I see this requirement all the time. I also see foremen/superintendents in my company doing it even when not required. I am an unbeliever. First, with a properly sized rope, you are never going to burn through a PVC elbow using a tugger. The speed and tension just isn't enough to create that friction and heat. That leaves smaller pulls by hand. yes, if a person uses a thin rope or the string and/or pulls too fast you can get burn through. Use a goo 5/8 or 3/4 mule tape for your pulls and I don't believe you will get burn through. If you do, then your problem is mor likely the installation and too many elbows or conduit fill.
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I've probably installed 1 stick of PVC for every 1000 sticks of metal conduit but I still agree with you. I think that this burn through issue isn't that big of a problem when you're using the right rope.
 
Strathead said:
I am in a contrary mood. I see this requirement all the time. I also see foremen/superintendents in my company doing it even when not required. I am an unbeliever. First, with a properly sized rope, you are never going to burn through a PVC elbow using a tugger. The speed and tension just isn't enough to create that friction and heat. That leaves smaller pulls by hand. yes, if a person uses a thin rope or the string and/or pulls too fast you can get burn through. Use a goo 5/8 or 3/4 mule tape for your pulls and I don't believe you will get burn through. If you do, then your problem is mor likely the installation and too many elbows or conduit fill.
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I 100% agree it can be avoided by your suggestions but I struggle with the idea of pulling in 3 #12s or a twisted shielded pair in with mule tape because the underground 3/4" run has 3 90s and is longer than your fish tape. Plus there is the issue of getting the mule tape in the conduit to start with, I have always used a vacuum, mouse and string. I guess a Rodder would work on larger conduit but I have never used one on smaller conduit. Plus they sorta dummy proof your underground which is a bonus when it is concrete encased.
 
infinity said:
I've probably installed 1 stick of PVC for every 1000 sticks of metal conduit but I still agree with you. I think that this burn through issue isn't that big of a problem when you're using the right rope.
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Yeah I have never had a problem despite doing my share of tough pulls. I did see it once, got a picture somewhere, but it's like a 3", 36" rad sweep with a rope "hypotenuse" completely cut thru. This was the MV contractor on the solar job we were on and what they were trying to do was ridiculous: it was long and they were trying to go out of the ground ,up and back down a pole all in one shot. It would not have been an issue with a little common sense.
 
I watched the inside radius of a 2" PVC stub up turn a lighter color and then turn translucent enough that you could see the rope moving inside but it didn't burn through. That was the only time. Almost every underground PVC run I've ever done was with PVC elbows. The only time I've used steel elbows was cell sites and government projects and I didn't like it. I've seen more problems with the PVC cracking at the transition to steel than burn through on PVC elbows.
 
Decken said:
I 100% agree it can be avoided by your suggestions but I struggle with the idea of pulling in 3 #12s or a twisted shielded pair in with mule tape because the underground 3/4" run has 3 90s and is longer than your fish tape. Plus there is the issue of getting the mule tape in the conduit to start with, I have always used a vacuum, mouse and string. I guess a Rodder would work on larger conduit but I have never used one on smaller conduit. Plus they sorta dummy proof your underground which is a bonus when it is concrete encased.
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I was typing while thinking of common sense. I use a fiberglass fish tape a lot and I have a rule that I better not catch anyone pulling with it. Even still, a twisted pair would be an exception in most cases. 3-#12 a little different. I 5/8 mule tape will have no problem in a 1/2" conduit all day long though. It is also slick so there is little rope tension. Just a good habit even in EMT, but a must in PVC. Even pulling in the rope one must take extreme care with a nylon pull string.
 
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