Wet locations, PVC and RX cable

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goldstar

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
K8MHZ said:
Could someone please tell me what RX cable is?
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Sorry. I guess I'm carbon dating myself. I'm just so used to going into the supply house and asking for a coil of 12/2 RX cable and they still know what I'm talking about. If I asked for a coil of NM I don't think they would know what it is (at least in my area). BTW, I still ask for MCM as opposed to kcmills. That's why I stop in here so often - I need to learn how to speak all over again.:)
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
goldstar said:
Sorry. I guess I'm carbon dating myself. I'm just so used to going into the supply house and asking for a coil of 12/2 RX cable and they still know what I'm talking about. If I asked for a coil of NM I don't think they would know what it is (at least in my area). BTW, I still ask for MCM as opposed to kcmills. That's why I stop in here so often - I need to learn how to speak all over again.:)
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That's OK, you carbon dated Bob, too.

I'll bet you remember when Chicago Benders were actually made in Chicago!

:lol:


(I actually own one made there before Lidseen moved.)
 
goldstar

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
kwired said:
If there is temperature difference at each end of raceway condensation is very likely. The more humidity exists the more likely it becomes. Warm moist air is going to condense if the temperature drops. In many areas we see this almost daily every morning with the dew on the grass. The overnight cooling was enough the air could no longer contain the moisture it was holding and it is given up as condensation. This happens in nearly every outdoor raceway. It happens in cold climates when a raceway enters a building, you have warm moist air inside and cold air outside. Migration of that warm moist air through the raceway condenses as it is cooled. Same thing with a raceway entering a refrigerated space.

This is nothing new, you just have never noticed or had it pointed out to you.

You ever seen conductors entering an outdoor enclosure from directly above a main breaker, and the terminals look like they have had water on them? It was from condensation running down the raceway and following conductors to the terminals. Avoiding having conductors run straight to terminals helps prevent this. Give the conductors a "drip loop" if possible. Sealing the raceway doesn't help much as any condensation is still going to accumulate at bottom and likely make it through the seal eventually. Sealing a raceway that enters a building does prevent two different temperatures on opposite ends of the raceway from causing condensation though.
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I was thinking about this yesterday so please bear with me because I'm trying to see it your way. If what you're implying is correct then the same condensation theory would apply to SEU cable. The sheath of the SEU cable serves the same purpose as a PVC conduit. So, let's say you have a service installed with 20' of SEU cable, a weatherhead properly installed at the top and a properly sealed w/p SEU connector into the top of the meter enclosure. The sun is out during the day and heats up the cable. At night it gets cool or even rains and the cable cools and forms condensation inside the sheath. That condensation would then travel down the conductors and pour down onto the jaws inside the meter enclosure and corrode them in a short amount of time.

Somehow I don't see that happening to the degree you point out but here's where we get back to the wire manufacturer and marking of the conductors. The SEU cable assembly has markings on the jacket indicating the rating of that cable. We all know that the insulated conductors on the inside of that cable are XHHW but are not individually marked. We terminate directly to the top jaws of the meter enclosure (no drip loop obviously), so far so good. Now, we decide to come out of the bottom or back of the meter enclosure and instead of using SEU we decide to go with PVC and go directly to the breaker panel. We strip the sheath off the extra SEU that we have and install it inside the PVC. We're now in violation because those conductors are not individually marked.

My point to all of this is that wire manufacturers should be printing the insulation ratings on individual conductors within cable assemblies so we don't have to buy additional wire or give inspectors chicken $#*t reasons to fail an inspection. Stop making NM cable with paper wrapping and start using plastic like they do with MC cable. If NM is installed inside PVC, outdoors and in a straight vertical run, any condensation would first have to form inside the PVC and then inside the jacket of the NM. Somehow I don't see that happening IMHO.
 
kwired

kwired

Electron manager
Location
NE Nebraska
goldstar said:
I was thinking about this yesterday so please bear with me because I'm trying to see it your way. If what you're implying is correct then the same condensation theory would apply to SEU cable. The sheath of the SEU cable serves the same purpose as a PVC conduit. So, let's say you have a service installed with 20' of SEU cable, a weatherhead properly installed at the top and a properly sealed w/p SEU connector into the top of the meter enclosure. The sun is out during the day and heats up the cable. At night it gets cool or even rains and the cable cools and forms condensation inside the sheath. That condensation would then travel down the conductors and pour down onto the jaws inside the meter enclosure and corrode them in a short amount of time.

Somehow I don't see that happening to the degree you point out but here's where we get back to the wire manufacturer and marking of the conductors. The SEU cable assembly has markings on the jacket indicating the rating of that cable. We all know that the insulated conductors on the inside of that cable are XHHW but are not individually marked. We terminate directly to the top jaws of the meter enclosure (no drip loop obviously), so far so good. Now, we decide to come out of the bottom or back of the meter enclosure and instead of using SEU we decide to go with PVC and go directly to the breaker panel. We strip the sheath off the extra SEU that we have and install it inside the PVC. We're now in violation because those conductors are not individually marked.

My point to all of this is that wire manufacturers should be printing the insulation ratings on individual conductors within cable assemblies so we don't have to buy additional wire or give inspectors chicken $#*t reasons to fail an inspection. Stop making NM cable with paper wrapping and start using plastic like they do with MC cable. If NM is installed inside PVC, outdoors and in a straight vertical run, any condensation would first have to form inside the PVC and then inside the jacket of the NM. Somehow I don't see that happening IMHO.
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How much free space is inside the jacket of the SE cable as compared to a raceway we are only allowe to fill to 40%?

Less free space means less air to contain moisture that can condense.

Is there condensation in the SE cable? Probably, but it yields much less condensate, may not even drain all the way to the bottom before the next day when it is heated and vaporized again.
 
goldstar

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
I stand corrected for something I said in my previous post. I repaired a 100 amp service today and installed new SEU cable and a meter enclosure. When I stripped the jacket off the SEU cable the individual conductors were clearly marked # 2-XHHW. Cable was made by Southwire. My sincere apologies to any wire manufacturer I may have offended.;) Now let's work on the NM cable.
 
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