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Old 10-27-2010, 12:27 AM   #1
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No Romex underground ...


... because of the bare ground wire.

OK, I know that it's a violation of code to run Romex underground in conduit, but I don't understand the why. Apparently it's because of the uninsulated ground wire because Romex is made of THHN wire. The only exception is that in Romex, the ground wire is bare, and apparently could get wet. So, my question is, So What?

What's the safety concern with the bare wire getting wet? Our ground rods are driven in the wet ground, and the bare wire from the Service Panel goes to this rod, and it rains, and there's never any harm.

Please explain this to an apparent dummy DIYer.

Thanks.
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Old 10-27-2010, 01:04 AM   #2
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No Romex underground ...


It has nothing to do with the bare wire getting wet.

THHN is only rated for dry conditions.

Type NM cable is only rated and approved for installation in dry areas. The inside of any conduit that is buried is considered a wet location.
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Old 10-27-2010, 01:19 AM   #3
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No Romex underground ...


kb, I found the following which further confuses me. From WesBell Electronics, at http://electricalwire.biz/Romex/MC_Cable_VS_Romex_Electrical_Wire_Bare_Copper_Grou nd.html:

Quote:
Romex wire is used as an indoor only cable because of the bare copper ground wire. All of our Romex is made with THHN THWN wire (Thermoplastic High heat and Water resistant Nylon coated) which can be used outdoors. However the thin Romex jacket can not stop water or moisture from penetrating and coming in contact with the uninsulated ground wire. As a result Romex can only be used indoors.


So, I'm confused now that you say it has nothing to do with the bare wire getting wet.
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Old 10-27-2010, 01:20 AM   #4
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No Romex underground ...


Quote:
Originally Posted by sirsparksalot View Post
... because of the bare ground wire.
Yes and No depending on which way it will feed to so with UF cable I know it have bare conductor but it good for anything as long it is NOT TO spa or pool that have it own set of codes. { We will discuss that on other topic }

Quote:
OK, I know that it's a violation of code to run Romex underground in conduit, but I don't understand the why. Apparently it's because of the uninsulated ground wire because Romex is made of THHN wire. The only exception is that in Romex, the ground wire is bare, and apparently could get wet. So, my question is, So What?
Et alors ??? I will tell ya the answer the Romex is allready tested at the UL /CSA testing centre and they know what is work and what not and to make it worst the conductor itself is not always be marked as you expected so it is part of cable and the ground wire itself is not THHN/THWN insuating materal at all it is a straght copper conductor.

One of the guys in here which they have direct access to the NEC code book they can quote the numbers in here and you can look it up.



Quote:
What's the safety concern with the bare wire getting wet? Our ground rods are driven in the wet ground, and the bare wire from the Service Panel goes to this rod, and it rains, and there's never any harm.

Please explain this to an apparent dummy DIYer.

Thanks.
Ground rods are listed to handle wet situation no issue per UL testing.,,

Grounding electrode conductor is bare so that is not a issue as long it have proper size.

Now you have to understand that all the underground conduits are treated as wet location even INSIDEthe house if you have slab which you bring the conduit under the slab that is wet location as well.,,

I am sure other members will be more than happy to explain this to you but in their word but once you read thier word it will end up just about the same as I spoke.

Merci.
Marc
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Old 10-27-2010, 01:23 AM   #5
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No Romex underground ...


Quote:
Quote:
Romex wire is used as an indoor only cable because of the bare copper ground wire. All of our Romex is made with THHN THWN wire (Thermoplastic High heat and Water resistant Nylon coated) which can be used outdoors. However the thin Romex jacket can not stop water or moisture from penetrating and coming in contact with the uninsulated ground wire.

As a result Romex can only be used indoors.



So, I'm confused now that you say it has nothing to do with the bare wire getting wet.
I wrote underline that is the key answer why it can NOT use outdoor useage.

Merci.
Marc
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Old 10-27-2010, 01:28 AM   #6
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No Romex underground ...


Marc,

I appreciate your time, truely, in answering. I'm just attempting to understand the consequences. Of course end the end, I always go by the code, but I have several properties and it's a continuing interest to me to understand the theory behind the rules.
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Old 10-27-2010, 01:29 AM   #7
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No Romex underground ...


Quote:
Originally Posted by frenchelectrican View Post
I wrote underline that is the key answer why it can NOT use outdoor useage.

Merci.
Marc
That simply tells me the rule. It doesn't tell me why it would be a bad thing for the bare copper wire to get wet.
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Old 10-27-2010, 01:33 AM   #8
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No Romex underground ...


Quote:
Originally Posted by sirsparksalot View Post
Marc,

I appreciate your time, truely, in answering. I'm just attempting to understand the consequences. Of course end the end, I always go by the code, but I have several properties and it's a continuing interest to me to understand the theory behind the rules.
Ahh ok no problem at all .,

Ok I will tell you couple example which I have ran into allready couple time and it pretty much the same with other Electricians in this forum ran into espcally with conduit.

The last time I pull one out it was pretty much black with the insluating materal is comming apart and it was start to make a high impelanice short circuit there { not high enough to trip the breaker } but it keep the meter running in overdrive mode until I pull that cable out due it was breaking down due the conduit have full of water in there and the water itself is not really clear and I know some case some plastic or rubber can come apart with wet rotting so that why it is not listed to use with underground conduit runs at all.

Merci.
Marc
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Old 10-27-2010, 06:11 AM   #9
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No Romex underground ...


Quote:
Originally Posted by sirsparksalot View Post
That simply tells me the rule. It doesn't tell me why it would be a bad thing for the bare copper wire to get wet.
It is NOT a bad thing.

I hate to be rude, but that site you quoted is crap! They have no clue what they are talking about.
There is NO problem with a bare copper wire getting wet. We can run a bare copper grounding electrode conductor outside to a buried ground rod. I think that has a slight chance of getting wet, don't you?
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Old 10-27-2010, 08:42 AM   #10
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No Romex underground ...


Quote:
Originally Posted by Speedy Petey View Post
It is NOT a bad thing.

I hate to be rude, but that site you quoted is crap! They have no clue what they are talking about.
There is NO problem with a bare copper wire getting wet. We can run a bare copper grounding electrode conductor outside to a buried ground rod. I think that has a slight chance of getting wet, don't you?
Speedy, that is at the crux of my confusion. YES, ABSOLUTELY, I would give the EGC a slightly higher chance of getting wet during rain. And I'm not finding your comments rude, as those quoted aren't my words. However, that's just one of several sites I've found that explains why Romex can't be used outdoors, and they all claim that it's because of the bare copper grounding wire.

Now that that's settled, what is the theory behind NM not being rated for wet conditions? Obviously, there's a good reason, based on safety, why the NEC prohibits underground running of Romex. If the problem is with the outer sheath deteriorating and causing some sort of problem, why can't we simply peel off the outer sheath, run them as individual THHN/THWN, and run them underground, in conduit?

Please don't tell me that it's because the UL and Code says so. Please help me understand WHY the UL and code says so.
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Old 10-27-2010, 08:44 AM   #11
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No Romex underground ...


Quote:
Originally Posted by sirsparksalot View Post
.... Our ground rods are driven in the wet ground, and the bare wire from the Service Panel goes to this rod, and it rains, and there's never any harm.
Quoted for Speedy
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Old 10-27-2010, 09:12 AM   #12
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No Romex underground ...


Quote:
Originally Posted by sirsparksalot View Post
Please don't tell me that it's because the UL and Code says so. Please help me understand WHY the UL and code says so.
The manufacturers did not pay UL to list their product for use outdoors. The code requires that products be installed according to the listing. There really is no need to have another product that can be used outdoors when there are options like UF or conductors in conduit. The additional listing would also add cost to the product that no one wants to pay.

The jacket is not UV rated and breaks down. The conductors inside the sheath are not labeled as to actual type regardless of the one quote above. NM is a cable assembly and is not meant to be stripped out of the sheath.
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Old 10-27-2010, 09:12 AM   #13
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No Romex underground ...


The paper wrapping in NM-B is a factor too, as it can wick water along inside the jacket.
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Old 10-27-2010, 09:38 AM   #14
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No Romex underground ...


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Originally Posted by McSteve View Post
The paper wrapping in NM-B is a factor too, as it can wick water along inside the jacket.
And again, this is bad because ......?
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Old 10-27-2010, 09:40 AM   #15
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No Romex underground ...


OK, let me restate this question. What would happen if we ran 3 individual THHN/THWN and a Bare Ground wire underground in conduit? What are the consequences of allowing the ground wire to get wet?
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