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Running XLPE From Main House to Guest House (encased in PVC Conduit)

Running XLPE From Main House to Guest House (encased in PVC Conduit)


Old 09-29-15, 01:21 PM
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Join Date: Sep 2015
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Running XLPE From Main House to Guest House (encased in PVC Conduit)

2 WIRES- 4/0

1 WIRE- 2/0 (Neutral with a yellow stripe)
KINGWIRE (can’t read the numbers) SWEETBRIAR 2/0 AWG AL TYPE USE-2 600V SUN-RES XLPE [UL] COREAL 14/12/12 NEUTRAL H.O.

Hello and thank you for taking the time to review my request for help. And I apologize in advance if this topic has been addressed before and I did not see it or if I don’t use the correct terminology in my request for help. I will begin with explaining what I am trying to do, explain how I got to where I am today, and request advice on whether this is safe (NEC compliant) way to do what I am trying to do. If not, what is the danger other than not specified in the NEC.
About June 2014 I began to build a 1,200 sq. ft. guest house (House #2) next to my primary residence (House #1). The guest house and my primary residence are about 60’ apart from each other with a heavy-duty steel overhang (garage-port) in between the two. Both houses face east. House #1 has the electricity service (Smart meter box and Breaker Panel mounted outside the house) in the back of House #1 (facing west). The property is in an unincorporated area of Fort Worth, TX. The service comes from the utility pole about 200 feet west of House #1 and the electricity is run underground. The service provider (Oncor) has visited the site and has confirmed that the wires coming from the service utility pole (underground) to House #1 are sufficiently thick for an electrician to remove the current meter box of House #1 (200 Amps now) and install a two-lug 320 Amp meter box to feed both houses, each with 200 Amp service.
About December 2014, I had about 4 electricians (licensed and bonded) come out to give me estimates on what to do to power the 200 Amp in House #2. All of them advised that I should remove the 200 Amp meter box from House #1 and install a two-lug 320 amp meter box to feed both 200 Amp breaker boxes in House #1 and #2. They also suggested installing a breaker cutoff next to the 320 Amp meter box outside of House #1.
All of them suggested two options for running the wire.
Option A: Run the XPLE wire (without conduit) diagonally (from the back where the 320 Amp meter will be and through the attic of House #1, coming out of the attic at the roof eave and through the heavy-duty steel overhang and into House #2 (House #2 has its breaker box inside the house of an the exterior wall on the side of the overhang used to run the wire). The wire in the overhang lies inside of an exposed red 12” C perlin that supports the sheet metal of the overhang and encased in 2” gray PVC. A liquid tight connector would be used where the wire exits the attic of House #1 through the eave and another liquid tight would be used where it enters House #2, on the wall as it is a 2-story house). Option B: All the same, except run the XPLE along the eave of House #1 in PVC conduit and make the two corners with liquid tight.
Now, I have completed most of House #2 (including the wiring of the electrical panel and receptacles in House #2) and placed the XLPE wire in 2” PVC gray conduit-Option B.
To be on the safe side, I decided to do some research on the wire (XLPE) and found some conflicting information about running the XLPE overhead in conduit, not sure why.
Most of the posts I found on the Internet state that the NEC does not recognize the XLPE and therefore it cannot be used in a dwelling so I decided against running through the attic (with or without conduit). From my understanding, it is because the XLPE is not flame retardant and is a fire hazard to use in dwellings. Another concern I read about is that a rodent could eat through it (it would take a big rat). I am also not sure if it is permissible to encase it in PVC and run it overhead even though the wire states that it is “SUN –RES …UL… USE-2”
After reading various forums on this subject, including this one, I decided to call another Master electrician. He came out and looked at the set up (of both Houses). While he was there I explained my concerns about the XLPE and I asked what he thought. He took down the information on the wire and said he needed to check the “book,” (I assume the NEC book?) While he was there, I asked him if I could not run the XLPE wire through the attic (cased or uncased), if I could encase the XLPE wire in 2” gray PVC and run it under my roof eave supported by steel hangers (I explained there would be four 90 degree turns in the wire). He said he would have to check that out too. He called me back the same day and said that the “book” did not say that I could or couldn’t run the XLPE through the attic, but it was up to me if I wanted him to do that. He said he could not be responsible should there be any problems. I asked about encasing the XLPE in PVC and running it under the house eave. He said he would be more comfortable doing that (under eaves) because the XLPE would not be inside the dwelling (House #1). He did not have any problems with the four 90 degree turns.
PLEASE NOTE: I cannot bury the wire because of the concrete slab that runs along the back of House #1 and the power from the utility pole is also buried below the same slab (burying the wires running perpendicular to each other is too difficult, time-consuming, and expensive to do). Running the wire overhead above the roof line is also not possible because of the roof angle and trees in the area. Also, I already have two service drops from the electrical provider (one to the water well and another to House #1) on this property so I cannot get the utility company to provide another service drop without it costing me a whole lot of money (300’ run underground to House #2).
1. Is the wire that I purchased safe (NEC compliant) to use encased in PVC under roof eaves supported by steel supports and using liquid tight at the angles? Can you provide any citations to any applicable sections of the NEC?
2. Assuming the wire is not safe (NEC Compliant) to run overhead (encased in PVC), is it safe (NEC Compliant) to run it under the eaves of House #1?
3. Are there any issues with the wire having four 90 degree turns?
4. Is it also safe (NEC Compliant) to run the encased XLPE on the steel C perlin (part of carport)?
5. Any other ideas, suggestions, or other unforeseen issues not presented here would be appreciated.
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Old 09-29-15, 02:33 PM
ray2047's Avatar
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You can't use triplex. You need quadplex, two hots, neutral, ground.
Old 09-29-15, 04:12 PM
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Join Date: Jan 2010
Location: USA
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Why go to the expense of buying direct burial wire to go in conduit above ground, makes no sense to me. I'd use aluminum Type XHHW; 2 hots, 1 neutral and 1 ground. If the feeder is for a 200 amp service, I'd use 2 - 4/0s, 1 - 2/0 and 1 #2 ground.
Old 09-29-15, 07:52 PM
Tolyn Ironhand's Avatar
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the wire states that it is “SUN –RES …UL… USE-2
1) It is common for conductor insulation to have multiple ratings. Your wire is marked "USE-2" so that is what wire type you would follow in the code. (Art 338)

2) USE cannot be used for interior wiring so your only option is to run it on the outside of the building. If it is exposed it should be installed in conduit.

3) Code-wise, no. But trying to pull in 2 - 4/0, 2/0, and a #2 will be a HUGE pain IF you can even pull it in. The conduit system is required to be complete before the wire is installed. I would recommend adding some pull boxes or at the very least, some conduit bodies for pull points.

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