Electrical Engineer "it is our opinion"

[Dennis Lassle]

Can an Electrical Engineer disregard the NEC (see below) when it is his opinion that cable that is not UL listed for wet locatins be used in a underground PVC conduit.

The NFPA 130 standard has very strictrequirements on the types of cables that can beused on APM systems.This relates mainly to fire and smoke propagation and requiresthe use of low smoke halogen free (LSHF) cables. lt is our opinion th at the NFPA 130requiremen for LSHF cables is more critical than the need for wet location rated cables.The NFPA 130 a pproved cables that -------- plans to use on this project will handle thesmall amounts of moisture that are likely to occur in the underground conduits due tocondensation and moisture wicking. These cables will not, however withstand beingcompletely submerged in water in a conduit system that is not properly sealed. We areaware of no LSHF cables that would be rated for long term use in a fully water​

submerged application.

 

[Npstewart]

An engineer can require more then code minimum but not less. Otherwise, the person who installed it would be required to install something that was not to code and therefore dangerous. If engineers could design a system that was less then code, then there wouldnt even be a plan review process for signed and sealed drawings.

 

[augie47]

In most of our regional areas, the engineer can appeal to an Appeals Board and if he can show his plan meets or exceeds Code intent, the Board can allow it.
I have seen a lot of "well sealed" PVC conduit runs that are full of water

 

[dhalleron]

I really don't understand why plumbing pipe keeps water in but electric pipe won't keep it out.

That engineer has no hands on experience with electric pipes in the ground or he would have never made that statement. Here in Kentucky, I have never pulled dry wire out of an underground conduit in the 30 years or so I have been doing electrical work. The water I am talking about is not condensation. It is ground water. You don't suck gallons of condensation out of a service conduit while pulling in a mouse with string for your rope.

 

[qcroanoke]

Can an Electrical Engineer disregard the NEC (see below) when it is his opinion that cable that is not UL listed for wet locatins be used in a underground PVC conduit.

The NFPA 130 standard has very strictrequirements on the types of cables that can beused on APM systems.This relates mainly to fire and smoke propagation and requiresthe use of low smoke halogen free (LSHF) cables. lt is our opinion th at the NFPA 130requiremen for LSHF cables is more critical than the need for wet location rated cables.The NFPA 130 a pproved cables that -------- plans to use on this project will handle thesmall amounts of moisture that are likely to occur in the underground conduits due tocondensation and moisture wicking. These cables will not, however withstand beingcompletely submerged in water in a conduit system that is not properly sealed. We areaware of no LSHF cables that would be rated for long term use in a fully water​

submerged application.

If that is the way he typed it with all those errors I don't think I would give him a lot of credit for smarts and his ability to say "I don't have a problem with it because I'm an engineer."

 

[GoldDigger]

If that is the way he typed it with all those errors I don't think I would give him a lot of credit for smarts and his ability to say "I don't have a problem with it because I'm an engineer."

My guess is that the "typos" are almost all the result of pasting a word processor doc int the forum.
If two codes conflict with no other way to resolve the conflict, an appeal is possible but the letter is an input to that appeal, not an end to the discussion.

Maybe he will need to use RGS in concrete instead of PVC?

 

[weressl]

Here in Kentucky, I have never pulled dry wire out of an underground conduit in the 30 years or so I have been doing electrical work. The water I am talking about is not condensation. It is ground water. You don't suck gallons of condensation out of a service conduit while pulling in a mouse with string for your rope.

I bet $ to dougnuts that it COULD be from cummulative condensate. Just as the example made before, it illustrates why does a well sealed water pipe keeps water in an not a sealed conduit. The conduit is not sealed and while it starts with a great condensate surface when it is dry, the evaporative surface becomes less and less.

 

[mbrooke]

In such a case no. There are times where the NEC has "under the supervision of an engineer", but I dont think it will be easy for someone to go outside of where it isnt spesified.

 

[hurk27]

Most of the allowances in the NEC that allows an engineer to allow something that would otherwise not be allowed is calculations on wiring sizes in 310, and manufactures that have UL listed wiring systems that many times are smaller then we are allowed to do (we see this in appliances all the time of undersized conductors), but there are no allowances anywhere in the NEC that would give this permission to allow a non-wet location wiring method to be used in what the NEC clearly defines as a wet location, as it clearly is as anyone who has dealt with underground conduits knows all to well.

Electrical conduit does not have the close tolerances that water pipe does, even RMC couplings are tapped a little larger then water pipe couplings to allow more easier assembly, also these couplings do not have a thread taper as a plumbing fitting does, if it did we would not be able to use running threads even though it is not allowed, if you have ever tried to use one on a water pipe you would notice that it is almost impossible to get a seal even with pipe dope or tape, yes I tried it once when I was in a pinch, this is why the NEC treats all underground raceways as a wet location, also plumbing PVC along with the glue vulcanizes the connection together melting the plastic to form a tight seal which is why you have to use the cleaner to make sure the glue can do its job, electrical PVC does not do this and they are more loose fitting in most cases, if you have ever tried to get a fitting off plumbing PVC you have to break it, but look how many fittings on electrical PVC can be knocked off without damaging it, some times they just pull apart from thermo contraction or ground settling, you never see this with plumbing PVC unless it wasn't installed properly.

But basically there are no allowances in the NEC that allows an engineer to over ride the NEC on this subject, and if the EC were to install it anyways and something happened that caused a person to be injured or damage to equipment, then I would think he would be partly responsible because he should know that the NEC doesn't have this allowance.

Now to the remark that the cable used does not come with a wet location listing, I would say either there are other wiring methods that could be used or the use is not identified as necessary to have a wet location listing as with some low voltage applications?

 

[hurk27]

I bet $ to dougnuts that it COULD be from cumulative condensate. Just as the example made before, it illustrates why does a well sealed water pipe keeps water in an not a sealed conduit. The conduit is not sealed and while it starts with a great condensate surface when it is dry, the evaporative surface becomes less and less.

Actually you can get allot of condensation from air flowing through the conduit when you have a difference of temperature, this is why the NEC requires us to seal any conduit not just service conduits when it will be exposed to a difference of temperature on one end to the other, I even duct seal the openings in my metal receptacles box's mounted on the exterior even if they are flush with the surface to stop any air flow from inside to the outside or visa-versa and never found a rusted out box going back on some of these jobs, but I have installed many feet of conduit embedded to only go back the next day to pull wire and find them full of water because of a high ground water or rain even though the ends of the conduit had been tapped off to prevent sand or dirt from getting into the conduit.

 

[petersonra]

He may be right that there are no suitable cables that can be run UG. That just means he can't run it underground.

In any case if it is UG, why would it need to be a low smoke cable?

 

[kwired]

I really don't understand why plumbing pipe keeps water in but electric pipe won't keep it out.

That engineer has no hands on experience with electric pipes in the ground or he would have never made that statement. Here in Kentucky, I have never pulled dry wire out of an underground conduit in the 30 years or so I have been doing electrical work. The water I am talking about is not condensation. It is ground water. You don't suck gallons of condensation out of a service conduit while pulling in a mouse with string for your rope.

I bet $ to dougnuts that it COULD be from cummulative condensate. Just as the example made before, it illustrates why does a well sealed water pipe keeps water in an not a sealed conduit. The conduit is not sealed and while it starts with a great condensate surface when it is dry, the evaporative surface becomes less and less.

I have to agree with weressl.

Unless you are in the desert where you may not find nearly as much and at times never find any condensation you will have more condensation in those raceways than you may realize.

One hot humid summer day I was burying PVC raceway. It was Friday, there was no excessive ground moisture and it did not rain over the weekend. Monday when I came back to pull conductors my pull rope was moderately wet after pulling through that raceway. Why? condensation. Humid nearly 100 degree air passing through raceway underground that is probably less than 70 degrees is going to condense. True electrical PVC may not seal as well as plumbing PVC but it often seals well enough that it will not drain any accumulated water either. Once it is filled enough to seal any air flow what is there to cause any evaporation?

 

[beanland]

Wire Types

Wire Types

We are missing the critical issue; not the conduit but that some codes are in conflict. If NFPA 130 requires LSHF cable that is not rated for wet areas and the NEC requires cable rated for wet areas, How is that resolved? (I am going to assume that I cannot run overhead.) Maybe the solution is to find a very expensive LSHF cable rated for wet locations; problem solved.

 

[renosteinke]

Opinions are like fingers - everyone has a couple hands full of them!

If you're an electrical contractor, a master electrician, or even perhaps a journeyman, it's YOUR professional opinion that matters. They disagree, let them do the work.

Someone saying "I'm an engineer" or "I'm an inspector" has no more relevance than if they have a certificate in tarot card reading.

It's your wallet, and your reputation. Sometimes folks agree, often they don't. I just went through this last night with a shopkeeper who's doing his own building addition. "I know more than most contractors," he said. Sure he does. I can predict with certainty he'll be fussing with endless issues in a few months, from all the 'code legal' things he did, all the stuff 'the inspector will never see,' all the bad design choices he'll make in his ignorance.

You can take a horse to water, but you can't make him drink.