I have a nice scrap of #4 aluminum overhead triplex wire ("periwinkle", whatever that means) from an old electrical service I took down. I'm running a new 60A circuit in 3/4" EMT, and this wire is just the right length. Can I untwist it and use the 2 insulated wires? I also have a piece of #6 THHN copper wire long enough to use for the grounded conductor.
I'm not sure if the AL wires from the triplex have an approved covering for use in conduit (or if it matters). All my connectors are approved for AL, and I have a bottle of that black deoxidixer goop.
[Note, I do not have tables at hand. So I can't really even tell you whether 2 #4 Al + 1 #6 Cu in 3/4" EMT is permitted. This is more of an educated guess unless one of the pros comments.]
I don't think you'll get a "code answer". I don't think triplex, as manufactured, is "listed" for (buried?) conduit, because that's not what the "cable" is used _for_.
[I'm even unsure of the code designation for Triplex. If you can identify the code designation for the individual conductors, you may be just fine.]
If it's "everything that isn't expressly allowed is forbidden", you may be stuck.
All that being said, I'd ask the inspector. Aerial-rated insulated conductors in good condition has _gotta_ be good enough for conduit.
Do use cable grease to pull it thru the conduit - the stuff is very stiff, and you don't want to damage the insulation.
Any given conductors' Ampacity rating is a free-air rating. Constricting these conductors to a 3/4" pipe (if you can even get them all thru) will almost certainly de rate the Ampacity.
This may or may not make the cable acceptable for the intended use.
The free-air rating for this cable is 78 or 91 amps, depending on if it's
75C or 90C temperature rating (and I'm not sure which it is). The ampacity for not more than 3 aluminum conductors in a raceway (conduit) is 55/65/75 amps, for 60/75/90C temperature rated wire, respectively. I'm well within the allowable amperage as long as I don't exceed the conduit fill. Two #4 and a #6 is borderline for the conduit fill, and I'll have to measure it and calculate the percent fill to see if it's OK.
I'm just not sure what covering is on this wire, and I don't know if it's flame retardant, etc.
I'll measure the wire diameters and calculate the conduit fill. If it's OK, I'll go ahead and use it. It will be easy to pull it out and replace with #6 copper if the inspector doesn't like it, plus that will give the inspector his token one thing wrong that he can find ;-) He's kind of professionally obligated to look until he finds one violation when the work is being done by a homeowner rather than a tradesman.
Bob You have too many veriable for a inspector to try to look the other way even when he likes you.
First you have triplex and when you peal it out to get the 2 wires the inter coating may not have a rating on it as to stamped on it. If it is stamped on the wire as to size / type / rating by numbers you may be alright but if not he is looking at unrated wire to concider. He will have to like you to pass it by.
Secondly 2 number 4 AL. wire and a # 6 ground / netural will not fit or in suppose to not fit in a 3/4'' conduit. If you can get it through the conduit it will be tightly packed and the inspector will say something as to too much heat build up being so packed in there. The amps will be low at a 60 amp breaker but there is no chart or way for the inspector to rate this set up. He is going to say something here. He better like you !
thirdly A pair of #4 AL. wire and a #6 ground in conduit of 1 1/4" , which it calls for, is rated for 55 amps in conduit. Your 60 amp breaker will carry or wire rating to carry about 48 amps min. wire rating . If the packing of the wire would cause a derating of the wire in some way unknown to me. You have only 7 amp derating before it starts to not be big enough. He is going to have to like you here.
Forthly Hey buy you some # 8 RHH Copper wire and it will be rated for 50 amps in conduit and fit fine in the 3/4" conduit. You can get it for about $.20 a foot or $20.00 a 100 foot roll. If you use the #8 RHW or the # 8 THW it will not be high enought rating to use and it will not fit or Not suppose to use it in 3/4" conduit. Invest $20.00 and be done with it.
You will have the cards stacked against you when the inspector looks at it. He is going have to like you really well to see this set up passing.
Certainly true. I was commenting about the insulation rating _alone_, I didn't have the tables to comment on ampacity/derating/conduit fill.
3/4" pipe is going to be _tight_, and just pulling it could be a real problem. Ie: copious pulling grease.
As a FYI, CEC code permits the use of CSA-rated PE tubing for burial, and reduces required burial depths (versus "unconduited") by 6". You can also lay treated lumber over top and get the same advantage. I don't think NEC permits PE, but I do believe they permit lumber "shields".
If you're burying it, you may get a distinct advantage by _not_ conduiting it. You may only need the conduit at the building entrance points (especially if above ground). Use PVC electrical conduit at the entrances down to the right depth, and then put a half loop of slack in the cable.
If the cable is in good condition, I'm pretty sure you can finesse it past the inspector. But I think the conduit is too small, and you seem to be confirming that too. So, _ask_ first.
If the inspector rejects it, you may find trying to pull the Al out, and restring Cu (or different Al) is a _real_ PITA, _especially_ if he doesn't like the conduit size either.
Sure? I just checked one cable manufacturer, and their 90C #4 Al three conductor triplex is UL rated 125A for direct burial, 90A in "ducts".
formatting link
[IIRC, my garage is 100A direct burial (no conduit except for a PE sleeve under the driveway, and grey PVC "entrance sleeves") #4 (or #3, can't remember for sure) Al. Should go check the chunk I still have]
coating may not have a rating on it as to stamped on
be alright but if not he is looking at unrated wire
Triplex doesn't have an external sheath. Any stamping on it is going to be on the individual conductors.
I had just looked it up in the table in the back of the NEC book to get the
78/91 numbers. But now that you mention it, I looked it up at the manufacturer's web site and "periwinkle" is rated for 125A ampacity in open air. The insulation is .045" XLP (cross-linked polyethylene?) and rated
600V. The wires look in great shape, but I didn't see any markings on them.
I think it would be fine if I were using 1" conduit, but I don't have a bender for 1", and a bender would cost more than the equivalent #6 copper wire. I haven't done those conduit fill calculations for 3/4 yet because I can't find my micrometer :-) If the calculations work out OK, I should probably call the inspector before I pull the wires.
The link above was "Cross-linked PE" and called XLPE. I _suspect_ "XLP" is the same as "XLPE".
A google search for periwinkle& aluminum showed it at 90A via Thomas Register.
[I didn't know they gave different code names for the same cable at different guages... Too bad you didn't have some "Vassar" instead of "Periwinkle". Bizarre. Almost as bizarre as your "penny nail" system.]
My question is - must you use metal conduit? Must you use conduit at all? Why not electrical grey PVC? You can bend that with a hair dryer.
If you insist on metal conduit, you can probably get a pipe bender (check your yellow pages) or electrical supply store to make a couple of bends for less than 10 bucks - just measure carefully.
I have to use metal conduit because this will be a "service mast" for the overhead wiring. The triplex from the house will attach to and be supported by the conduit. The inspector says I can use EMT because the wires are overcurrent protected in the house (I'm not sure why that makes a difference.)
The building is only about 11' 6" where the service drop attaches (12'
2" at the peak, but I can't get to the peak), and the inspector says the point of attachment has to be at least 12'.
So I am coming straight out just below the soffit and at the facia (a
12" overhang) have a 90 degree bend straight up about 16 inches. Then a weatherproof service cap. I have a galvanized clamp to hold the conduit in place 1/2" off the facia board. Inside the building I haven't run the conduit from the service ell to the panel yet. It will have a couple of odd bends (one's about 60 degrees and the other about 20 degrees.) I will finish all that Saturday.
The worst case at this point is I have to buy another $15 or $20 worth of copper #6 wire. I just like the idea of reusing the AL wire I already have rather than wasting it.
Ah, so the triplex you want to reuse and conduit to be installed is mostly _inside_ the house, right?
I thought this wire was to be used outside...
I can see the sense of EMT being okay here, because since it's overcurrent protected in the house, the consequences of a failure aren't anywhere near as bad as a failure in the main feed.
But, they let you use 3/4" conduit (EMT or otherwise) as a "mast"?
Egads. Not a chance under our codes. As one of our code books comments (rather snidely): "the mast & attachment has to be strong enough to pull your wall off if a semi snags your overhead..." ;-)
H'm. If it was ordinary NMD, you'd only need to conduit the mast itself.
I'd consider using a premade mast sections for the eave (likely 1.5" or
2"), and then conduit the rest in plastic (to take the place of the non-existant exterior sheath on triplex).
If the difference is only $15 or $20, why are you bothering us?
This will be such a short vertical section above the support clamp that it probably *will* be strong enough to pull the 2x6" facia off the garage. Have you ever tried bending a 12 inch section of EMT? A 10 foot length will almost bend under its own weight. A one foot length is hard as hell to bend.
At the house, the insulator where the messenger wire attaches is almost
20 feet high.
But if the little EMT mast ever does get torn off or bent, I'll cut it off about 5" long where it sticks out from the wall just under the overhang, put the service cap on the end, and cut the wires off just short enough to make drip loops. I will screw a big insulator into the facia where the clamp used to be and attach the messenger wire to it (11' 5" above the grade) where I wanted it in the first place. I already have the right insulator in my junkbox.
Not that I'm planning to redo it after the inspection or anything...
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.