Rigid installed on top of concrete floor?

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hardworkingstiff

Senior Member
Location
Wilmington, NC
Well

Well

Well, I went by the AHJ today and the assistant chief inspector at first said no. We then looked at the code and he said the inspector checking it might want me to provide a document from the conduit manufacturer that said the conduit could support the weight of the vehicle driving over it. So basically he decided he couldn't stop it, but would make it difficult.
 
Well, I went by the AHJ today and the assistant chief inspector at first said no. We then looked at the code and he said the inspector checking it might want me to provide a document from the conduit manufacturer that said the conduit could support the weight of the vehicle driving over it. So basically he decided he couldn't stop it, but would make it difficult.
I don't think there is much question as to whether or not the conduit could support the weight of the vehicle. The question is can it remain in shape after years of repeated stress.

In theory, I would say it likely would, as I have seen how much abuse rigid can take. I have seen people use it on dirt track race cars and although I have seen it kinked, I have never seen it collapsed.

Considering a 4000 lb. vehicle, that's 1000 per tire. Figuring a 7 inch tire, that's only 143 lbs. per linear inch.

However......

I wouldn't do it. No matter what the math says, I would still not surface mount any type of conduit knowing vehicles were going to run over it, and skid and spin over it, too. The math never takes into consideration people's stupidity or lack of driving skills. Granted, the pipe has little chance of collapsing, but what about other unforeseen damage? Like being ripped from it's supports by a snow plow. It's not that much effort to cut a groove, chip it out and lay the conduit in the groove and cover it.
 

ceb58

Senior Member
Location
Raeford, NC
Well, I went by the AHJ today and the assistant chief inspector at first said no. We then looked at the code and he said the inspector checking it might want me to provide a document from the conduit manufacturer that said the conduit could support the weight of the vehicle driving over it. So basically he decided he couldn't stop it, but would make it difficult.
I dont see a problem with the install. To help cover your self why not install a piece of 3'' channel iron over the conduit. You could drill the ends of the channel and anchor it on the ends where the tires would not run over the anchors.
 

jusme123

Senior Member
Location
NY
Tell me where the term "SECURELY supported" is used in the NEC.
What you are trying to do is read something into the NEC that doesn't exist.
With that said, "securing" and "supporting" are two different requirements and the word support is defined as
The concrete floor had better be able to support to RMC or as I said earlier, we have a bigger problem than the discussion at hand.
What you are trying to argue for is the securing issue, this could be handled a number of ways.
It is normal to automatically think something isn't allowed because it is not seen everyday but, in this case, there is nothing in the NEC that would prohibit it and we are discussing this in the NEC forum.
If we had a "What would you like the NEC to say" forum we could go with the "it ain't allowed" mind set.;):D

Roger
Roger, the point I was trying to make is that the conduit is adequately supported (its sitting on a concrete floor), however, it is not securely supported adequately. Can a 4" RGS conduit be installed with the same scenario?
 

jusme123

Senior Member
Location
NY
I just don't understand how something that is resting on a concrete surface is not securely supported.

I would have no issue with this size conduit being used in this application. It will provide plenty of protection for the installed conductors.
the conduit has to be secured AND supported ( a strap secures, the concrete floor supports)
would 3/4" be ok? what about 1 1/4" ? 2"? 3 1/2"?
 

macmikeman

Senior Member
With all the amazing things I have learned here and been exposed to over the years, I can't believe not one of the usual darn near genius members has not (and I'm not referring to myself by any means) pointed out that automobile tires are filled with air, a gas, which compresses, and is contained in a rubber (synthetic) casing which also will flex and bend around the obstruction to the degree it will barely affect the conduit to any degree. I would know this because of the fact that while I am a member of the forum, I am no genius.... I have allowed a car tire to roll over my foot before and hardly knew it happened. Didn't even hurt. Now a vehicle traveling at +60 miles an hour down a three lane highway could easily dislodge a conduit strapped to the surface by the friction of the impact imposed on the conduit, but as I said earlier, thats another story not connected to this thread by my friend Hardworkingstiff.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
With all the amazing things I have learned here and been exposed to over the years, I can't believe not one of the usual darn near genius members has not (and I'm not referring to myself by any means) pointed out that automobile tires are filled with air, a gas, which compresses, and is contained in a rubber (synthetic) casing which also will flex and bend around the obstruction to the degree it will barely affect the conduit to any degree. I would know this because of the fact that while I am a member of the forum, I am no genius.... I have allowed a car tire to roll over my foot before and hardly knew it happened. Didn't even hurt. Now a vehicle traveling at +60 miles an hour down a three lane highway could easily dislodge a conduit strapped to the surface by the friction of the impact imposed on the conduit, but as I said earlier, thats another story not connected to this thread by my friend Hardworkingstiff.
Mike, I addressed this (in different words) in post #34. ;)

Roger
 

jusme123

Senior Member
Location
NY
With all the amazing things I have learned here and been exposed to over the years, I can't believe not one of the usual darn near genius members has not (and I'm not referring to myself by any means) pointed out that automobile tires are filled with air, a gas, which compresses, and is contained in a rubber (synthetic) casing which also will flex and bend around the obstruction to the degree it will barely affect the conduit to any degree. I would know this because of the fact that while I am a member of the forum, I am no genius.... I have allowed a car tire to roll over my foot before and hardly knew it happened. Didn't even hurt. Now a vehicle traveling at +60 miles an hour down a three lane highway could easily dislodge a conduit strapped to the surface by the friction of the impact imposed on the conduit, but as I said earlier, thats another story not connected to this thread by my friend Hardworkingstiff.
Mike, I understand what you are saying, but you are talking about running over an electrical conduit with a car on a daily basis, for a permanent installation that should last decades. What will that conduit look like 30 years from now? With regard to the three lane highway scenario, ok, what about running a lighting conduit across the roadway in a parking lot and placing the conduit on the front edge of a speed bump- would this be code compliant?
 
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Well, I went by the AHJ today and the assistant chief inspector at first said no. We then looked at the code and he said the inspector checking it might want me to provide a document from the conduit manufacturer that said the conduit could support the weight of the vehicle driving over it. So basically he decided he couldn't stop it, but would make it difficult.

The more 'seasoned' gentlemen here (I use that term generously :D) have learned to try not and have "knee jerk reactions" to code issues.

Show me the code section the prohibits this installation??? I have not seen it posted in this thread.
Physical damage is not defined in the NEC. Therefore some judgement has to be made. That judgement is hard to make over the internet and is easier to make when one can physically visit the jobsite to see all of the conditions that help in making a decision.

The poster who is using the highway example is way off base, as that is not a realistic installation.

Listen to the simple way that Roger and Iwire are discussing the realisic example hardworkingstiff is citing. Even though this seems like a bad type of installation, maybe it really is not. Remember to try and keep opinions, dislikes and inexperience out of the final judgement. Like Roger brought up earlier, on construction sites I have seen RMC stand up to some pretty rigorous punishment.


My response to this based solely on this thread, and acting as an inspector who tries to use good judgement and the NEC as my basis for decisions would be to say: "I do not like it, but I cannot find a code section or enough judgement to say no."

Remember, as an inspector our job is to serve the consumer, help keep the job moving and support the contractors/electricians in the field.
 
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Mike, I understand what you are saying, but you are talking about running over an electrical conduit with a car on a daily basis, for a permanent installation that should last decades. What will that conduit look like 30 years from now?

The cars will not be at high speed, they have rubber tires, and maybe a couple of cars a day, which means two sets of wheels possibly 4 times or less a day. I think it is very realistic that the placement may be such, that this install could work, as outrageous as that may sound.


I say make the installation so we can answer your question in 30 years. ;)
 

jusme123

Senior Member
Location
NY
The cars will not be at high speed, they have rubber tires, and maybe a couple of cars a day, which means two sets of wheels possibly 4 times or less a day. I think it is very realistic that the placement may be such, that this install could work, as outrageous as that may sound.


I say make the installation so we can answer your question in 30 years. ;)
Pierre, if this was the only possible installation I would tend to agree with the above posters, but its not. The conduit can be embedded in concrete or brought in over head,so why risk damage to a conduit in the name of saving money.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Pierre, if this was the only possible installation I would tend to agree with the above posters, but its not. The conduit can be embedded in concrete or brought in over head,so why risk damage to a conduit in the name of saving money.
The cost enters into the choices that are made every day in the design and or installation of anything.

I don't see a real risk of damage to the conduit even over years of use in the installation described in the original post.
 

jusme123

Senior Member
Location
NY
The cost enters into the choices that are made every day in the design and or installation of anything.

I don't see a real risk of damage to the conduit even over years of use in the installation described in the original post.
Don, that is your opinion and I respect that. IMHO, I feel it is not to code (failure to protect conductors and the secured fastening is inadequate).
 

hotwire1955

Senior Member
Location
nj
With all the amazing things I have learned here and been exposed to over the years, I can't believe not one of the usual darn near genius members has not (and I'm not referring to myself by any means) pointed out that automobile tires are filled with air, a gas, which compresses, and is contained in a rubber (synthetic) casing which also will flex and bend around the obstruction to the degree it will barely affect the conduit to any degree. I would know this because of the fact that while I am a member of the forum, I am no genius.... I have allowed a car tire to roll over my foot before and hardly knew it happened. Didn't even hurt. Now a vehicle traveling at +60 miles an hour down a three lane highway could easily dislodge a conduit strapped to the surface by the friction of the impact imposed on the conduit, but as I said earlier, thats another story not connected to this thread by my friend Hardworkingstiff.
I think you are a genius :)
 

sweetcav

Member
Location
Central Pa
The conduit would probably be fine but what about the added trip factor for the Mechanic working around this lift. My father has been a Mechanic for 29 years and I have seen first hand what goes on in a shop. Moving trannsmission jacks and welders, torch sets all sorts of equipment it seems to me that the shop owner might have other problems
 
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