The contractor is installing PVC coated GRS conduit. Some of the conduit he is installing is falling down off the concrete walls. Our specifications refer to the NEC for installation requirements. He claims that the NEC allows support to be spaced in general at 10 feet. We claim that the supports should be at 5 feet since this is the support manufacturer's recommendation. He insists that if this is done it will be at extra cost to us since the NEC calls for support spacing to be 10 feet. We contend that the conduit should be securely to the wall using the manufacturer's spacing and that the 10 foot spacing is a maximum, and only comes into play if the conduit is securely fasten to the wall. Are we interpreting the NEC correctly?
Falling GRS Conduit
- Thread starter ksfhigov
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tonyi
Senior Member
Re: Falling GRS Conduit
10' is the NEC minimum. That is not to say you can't support closer if you wanted to (or needed to). You could support every 6 inches if you wanted to and it would be code compliant.
Another issue is the listing and labeling of the supports. If the vendor is stating every 5', then their listing/labeling instructions trump the NEC minimums.
10' is the NEC minimum. That is not to say you can't support closer if you wanted to (or needed to). You could support every 6 inches if you wanted to and it would be code compliant.
Another issue is the listing and labeling of the supports. If the vendor is stating every 5', then their listing/labeling instructions trump the NEC minimums.
russ
Senior Member
- Location
- Burbank IL
Re: Falling GRS Conduit
344.30 requires the conduit to be securly fastened and supported in accordance with 334(A)and (B).
If it's "falling" down off the wall, it is not code compliant.
A manufactures recommendation that aren't part of the listing or labeling are not enforceable.
344.30 requires the conduit to be securly fastened and supported in accordance with 334(A)and (B).
If it's "falling" down off the wall, it is not code compliant.
A manufactures recommendation that aren't part of the listing or labeling are not enforceable.
- Location
- Illinois
- Occupation
- retired electrician
Re: Falling GRS Conduit
The 10' support spacing should not let the conduit fall off the wall. What type of anchors and supports are being used? It appears that the anchors or supports are not of the correct type. The manufacture's "recommendation" is not required to be followed by 110.3(B). Supports closer than the code required 10' would be an "extra", however, the supports being used must securely fasten the conduit. If they don't securely fasten the conduit, then the contractor is not in compliance with the code.
Don
The 10' support spacing should not let the conduit fall off the wall. What type of anchors and supports are being used? It appears that the anchors or supports are not of the correct type. The manufacture's "recommendation" is not required to be followed by 110.3(B). Supports closer than the code required 10' would be an "extra", however, the supports being used must securely fasten the conduit. If they don't securely fasten the conduit, then the contractor is not in compliance with the code.
Don
Re: Falling GRS Conduit
I also agree with Don, if the conduit is falling off the wall, it is probably the anchors. And it also doesn't meet the code if it is falling down.
Are the conduit runs long straight runs? What size conduit? Are there any expansion joints? They may be having a problem with the conduit expanding due to a temp. rise. This time of the year it isn't uncommon to install 10 deg. F conduit one day, and have it reach 40 deg. F the next day.
Steve
Maybe not enforceable per the NEC code, but hopefully somewhere the specifications for the job requires the contractor to follow manufacturer's recommendations.
I also agree with Don, if the conduit is falling off the wall, it is probably the anchors. And it also doesn't meet the code if it is falling down.
Are the conduit runs long straight runs? What size conduit? Are there any expansion joints? They may be having a problem with the conduit expanding due to a temp. rise. This time of the year it isn't uncommon to install 10 deg. F conduit one day, and have it reach 40 deg. F the next day.
Steve
Re: Falling GRS Conduit
Thanks for your opinions. Judging from some of your responses I perhaps did not make my interpretation of the NEC requirements as clear as it should have been.
The way I look at the NEC requirement is: It requires that the conduit be securely fasten. It also requires that the spacing of supports to be no more than 10 feet. For example say a conduit could be securely fastened to a wall by having supports every 20 feet. This would pass the first requirement but in order to be fully compliant it still would need a support every 10 feet.
I do agree that manufacturer's recommendations are not enforceable unless it is part of the contract. We utilized that length only because it is assumed it would provide for a securely fastened conduit. Other lengths would have been acceptable with acceptable justification. Secure support of the conduits are all we are really concerned about, not the spacing, as long as it does not exceed 10 feet. Given the same situation with a different support a 10 foot spacing would be acceptable, if it securely fasten the conduit to the wall.
Thanks for your opinions. Judging from some of your responses I perhaps did not make my interpretation of the NEC requirements as clear as it should have been.
The way I look at the NEC requirement is: It requires that the conduit be securely fasten. It also requires that the spacing of supports to be no more than 10 feet. For example say a conduit could be securely fastened to a wall by having supports every 20 feet. This would pass the first requirement but in order to be fully compliant it still would need a support every 10 feet.
I do agree that manufacturer's recommendations are not enforceable unless it is part of the contract. We utilized that length only because it is assumed it would provide for a securely fastened conduit. Other lengths would have been acceptable with acceptable justification. Secure support of the conduits are all we are really concerned about, not the spacing, as long as it does not exceed 10 feet. Given the same situation with a different support a 10 foot spacing would be acceptable, if it securely fasten the conduit to the wall.
charlie
Senior Member
- Location
- Indianapolis
Re: Falling GRS Conduit
Do not loose sight of what Tonyi and Russ are saying. They are not talking about the manufacturer's recommendations, they are talking about the manufacture's listing/labeling instructions and they are required to be followed by Section 110.3(B).
- Location
- Massachusetts
Re: Falling GRS Conduit
This must be PVC coated RMC as I do not believe there is PVC coated EMT.
IF it is RMC supports every 10' are not always required.
If you meet this requirement
1/2" & 3/4" every 10'
1" every 12'
1 1/4" & 1 1/2" every 14'
2" & 2 1/2" every 16'
3" and larger every 20'
The distance between supports has little to do with the supports falling of the wall.
Use the correct hardware and you can put the supports at the NEC minimum's and still have a strong support.
If the hardware is inadequate then the job fails the NEC not for spacing but as has been said for not being securely fastened in place.
This must be PVC coated RMC as I do not believe there is PVC coated EMT.
IF it is RMC supports every 10' are not always required.
If you meet this requirement
The distances between supports can be increased to the following.
1/2" & 3/4" every 10'
1" every 12'
1 1/4" & 1 1/2" every 14'
2" & 2 1/2" every 16'
3" and larger every 20'
The distance between supports has little to do with the supports falling of the wall.
Use the correct hardware and you can put the supports at the NEC minimum's and still have a strong support.
If the hardware is inadequate then the job fails the NEC not for spacing but as has been said for not being securely fastened in place.
Re: Falling GRS Conduit
what fasteners or fastening system is he using?
If it's falling off the wall, he hasn't complied with the contractual requirements for "neat and workmanlike" which is on any set of specs worth their salt.
I mean if he's supporting the conduit based on NEC minimum spacing, and it's installed using an appropriate strap and fastener(s), we shouldn't be debating this issue
[ January 24, 2004, 01:38 PM: Message edited by: d and o ]
what fasteners or fastening system is he using?
If it's falling off the wall, he hasn't complied with the contractual requirements for "neat and workmanlike" which is on any set of specs worth their salt.
I mean if he's supporting the conduit based on NEC minimum spacing, and it's installed using an appropriate strap and fastener(s), we shouldn't be debating this issue
[ January 24, 2004, 01:38 PM: Message edited by: d and o ]
scott moran
Member
Re: Falling GRS Conduit
Is it truly "falling off the wall" or is it sagging from its own wieght between the supports?? Just curious. One is an issue of safety, and the other is a matter of workmanship being an eyesore.
Is it truly "falling off the wall" or is it sagging from its own wieght between the supports?? Just curious. One is an issue of safety, and the other is a matter of workmanship being an eyesore.
- Location
- Illinois
- Occupation
- retired electrician
Re: Falling GRS Conduit
Then the clamp is not the correct size for that conduit or the screws were never tightened.
Don
Then the clamp is not the correct size for that conduit or the screws were never tightened.
Don
flightline
Senior Member
Re: Falling GRS Conduit
While not disagreeing with Don, let me start out by saying that we have miles of PVC Coated GRC from all of the big 3, [Ocal, PermaCote, & Robroy]. We have standardized on it for all of our exterior locations. We have had this situation, but only in limited amount. Here's what we found; vertically mounted strut, [open ends up and down], with horizontally running conduit, and factory clamps. All components manufactured by the same manufacturer in the area of concern, all of the same line & spec. In a few locations, during the summer, [ warm & things like to expand], in a couple of areas, we have had PROPERLY installed PVC coated hangers slip free from the strut. These areas are adjacent to lightly loaded traffic ramps. In one location, it happened twice over the period of a year. All was installed properly. Our crew was certified by OCAL. We changed strut straps, and all was tight. In one location only, did we find hat it happened a second time, a few months later. We can only surmise that there were differences in the thickness of the coating, between the strut, pipe, and straps. When exposed to prolonged sunlight and warmth, accelerated by road vibrations, these lack of tolerances were different enough to allow for this. All fittings, pipe, and the like were of one manufacturer, and correctly sized. If this is what is happening here, and all has been installed properly, I would contact the manufacturer of the materials, and let them investigate, and possibly pay to have this work redone, should inconsistencies in their system be found. [If that is what Don as intimating, then he would be correct]. We have found them quite forthright on occasion where they were at fault. What is of concern to me is that this seems to be happening in such a widespread fashion in this one area. While there may be additional input added with respect to hanger spacing, a manufacturers' parts must comply with their own published data.
While not disagreeing with Don, let me start out by saying that we have miles of PVC Coated GRC from all of the big 3, [Ocal, PermaCote, & Robroy]. We have standardized on it for all of our exterior locations. We have had this situation, but only in limited amount. Here's what we found; vertically mounted strut, [open ends up and down], with horizontally running conduit, and factory clamps. All components manufactured by the same manufacturer in the area of concern, all of the same line & spec. In a few locations, during the summer, [ warm & things like to expand], in a couple of areas, we have had PROPERLY installed PVC coated hangers slip free from the strut. These areas are adjacent to lightly loaded traffic ramps. In one location, it happened twice over the period of a year. All was installed properly. Our crew was certified by OCAL. We changed strut straps, and all was tight. In one location only, did we find hat it happened a second time, a few months later. We can only surmise that there were differences in the thickness of the coating, between the strut, pipe, and straps. When exposed to prolonged sunlight and warmth, accelerated by road vibrations, these lack of tolerances were different enough to allow for this. All fittings, pipe, and the like were of one manufacturer, and correctly sized. If this is what is happening here, and all has been installed properly, I would contact the manufacturer of the materials, and let them investigate, and possibly pay to have this work redone, should inconsistencies in their system be found. [If that is what Don as intimating, then he would be correct]. We have found them quite forthright on occasion where they were at fault. What is of concern to me is that this seems to be happening in such a widespread fashion in this one area. While there may be additional input added with respect to hanger spacing, a manufacturers' parts must comply with their own published data.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Re: Falling GRS Conduit
...we have had PROPERLY installed PVC coated hangers slip free from the strut.
How the heck does a unistrut strap slip free from the channel?
The solution to this is to simply not mount the channel on the wall. Support it horizontally with a bracket or a trapeze with the pipe on top of the channel. This way, when it loosens, it can't go anywhere.
[ January 26, 2004, 07:25 PM: Message edited by: hbiss ]
...we have had PROPERLY installed PVC coated hangers slip free from the strut.
How the heck does a unistrut strap slip free from the channel?
The solution to this is to simply not mount the channel on the wall. Support it horizontally with a bracket or a trapeze with the pipe on top of the channel. This way, when it loosens, it can't go anywhere.
[ January 26, 2004, 07:25 PM: Message edited by: hbiss ]
flightline
Senior Member
Re: Falling GRS Conduit
In possible answer to hbiss, you're probably correct about the need for more in depth description of how it exactly happened. But having worked with the product from most of the vendors, it CAN be said that on occassion, the strut to clamp bond is not as finite as with uncoated. Hence, my theorization about the un-eveness of the PVC coating being part of the equation holding everything together. your discussion about trapeezing the hangers might be one soloution to this as well.
In possible answer to hbiss, you're probably correct about the need for more in depth description of how it exactly happened. But having worked with the product from most of the vendors, it CAN be said that on occassion, the strut to clamp bond is not as finite as with uncoated. Hence, my theorization about the un-eveness of the PVC coating being part of the equation holding everything together. your discussion about trapeezing the hangers might be one soloution to this as well.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Re: Falling GRS Conduit
...the strut to clamp bond is not as finite as with uncoated.
Don't think that it is the uneveness just that it is soft. If you have to keep tightening that clamp up it's because the PVC gets displaced at the pressure points. Eventually it's going to cut through to the bare steel. Then it won't slip anymore.
Seems to me than that unistrut and clamps in that orientation is not a viable method to hold this stuff. Either bracket a short length of unistrut off the wall or hang a trapeze or rack. Either way the channel is horizontal and gravity won't work against you.
Another option is not to use unistrut at all and go with one or two hole straps.
...the strut to clamp bond is not as finite as with uncoated.
Don't think that it is the uneveness just that it is soft. If you have to keep tightening that clamp up it's because the PVC gets displaced at the pressure points. Eventually it's going to cut through to the bare steel. Then it won't slip anymore.
Seems to me than that unistrut and clamps in that orientation is not a viable method to hold this stuff. Either bracket a short length of unistrut off the wall or hang a trapeze or rack. Either way the channel is horizontal and gravity won't work against you.
Another option is not to use unistrut at all and go with one or two hole straps.
Re: Falling GRS Conduit
Sounds like a bolt (or screw) ran horizonal across the bottom of the strut would stop the clamps from slipping off. Or maybe the unistrut just needs to be longer at the bottom to keep the clamps from sliding off.
It seems like one could find several simple solutions to this problem.
Steve
Sounds like a bolt (or screw) ran horizonal across the bottom of the strut would stop the clamps from slipping off. Or maybe the unistrut just needs to be longer at the bottom to keep the clamps from sliding off.
It seems like one could find several simple solutions to this problem.
Steve
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