wc86
Member
- Location
- Massachusetts
- Occupation
- Electrician
Hello is triplex the same as USE wire? Recently someone told me that 4/0 triplex is good for 240a. But i am unsure what temperature column to use to size it.
Triplex sizing
- Thread starter wc86
- Start date
- Status
ptonsparky
Tom
- Occupation
- EC - retired
I always used it as USE.
Doesn't make it right, just what I did. Never flagged on it.
Doesn't make it right, just what I did. Never flagged on it.
ptonsparky
Tom
- Occupation
- EC - retired
From Priority Cable. Far right two columns are ampacity direct bury and in duct.
Google "URD Ampacity"
- Location
- Illinois
- Occupation
- retired electrician
If this is an NEC application, you can only use the ampacities found in the NEC.
wc86
Member
- Location
- Massachusetts
- Occupation
- Electrician
I am trying to see what amperage 4/0 triplex is good for on a 2-family overhead service thanks
ptonsparky
Tom
- Occupation
- EC - retired
Overhead ...small detail.
Are you supplying it or the POCO?
ptonsparky
Tom
- Occupation
- EC - retired
See Table 310.29
ptonsparky
Tom
- Occupation
- EC - retired
Again from Priority cable.
ptonsparky
Tom
- Occupation
- EC - retired
What is the calculated load?
wc86
Member
- Location
- Massachusetts
- Occupation
- Electrician
The calculated load is 154amps im trying to unerstand if using the triplex 4/0 wire will give a greater amperage than like a 4/0 thwn as it is being suggested to me as some sort of magic wire. I was originally going to use 250kcmil to give room for future circuits add on. My understanding is that 4/0 wire is only good for a calculated load of 180a but we can use 200a break because of next size up rule. Does using 4/0 triplex change this reality?
For NEC application, can't you use table 310.20 for the ampacity of triplex in free air (this is a table for ampacity on a messenger wire, up to 3 current carrying conductors). The ampacity of a conductor depends on many things. The primary one being its insulation temperature rating. But even if it is rated for 90C or 150C or 250C, are your terminations rated for that? And voltage drop will quickly get you too if there is any length to this run.
The ampacity of 4/0 aluminum @ 75C is 224A in table 310.20, 280A in table 310.17, and 180A in table 310.16
The ampacity of 4/0 aluminum @ 75C is 224A in table 310.20, 280A in table 310.17, and 180A in table 310.16
wc86
Member
- Location
- Massachusetts
- Occupation
- Electrician
So regardless of what 4/0 triplex is rated for its still only rated for 180a at 75°c correct?
ptonsparky
Tom
- Occupation
- EC - retired
Depends. We don’t know if the product you are using has insulation listed in the NEC.
- Location
- Illinois
- Occupation
- retired electrician
I don't think that there is any triplex that has an insulation type found in Table 310.4 (310.104 in older codes).
wc86
Member
- Location
- Massachusetts
- Occupation
- Electrician
Is there a situation when using 4/0 triplex in pvc for the vertical portion leading to a weatherhead for a 200a service that the 4/0 wire would be rated for more than 180a?
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I think we need some clarification: Have you been talking about overhead aerial conductors, or conductors in conduit? "Triplex" usually refers to the aerial stuff with a bare messenger. Sometimes people call the underground URD stuff triplex. URD is usually USE but it is possible it's made for the utility market and has no NEC markings.
As to your specific question in this post, three aluminum 4/0 conductors in a conduit would be rated 180 amps and you can next size up to 200. Aerial conductors would be in free air so you would use a different table and the ampacity would be higher.
Seemingly adds more complications. Aerial installations often get by with triplex such as "Portunu" as shown in your Post #8 even though it is not a NEC recognized conductor. The wiring in a vertical riser to your weatherhead on the otherhand is almost always required to be a NEC Art 310.104 recognized conductor. 4/0 XHHW or THWN-2 AL would be rated at 180 amps (75°C) and is often used on 200 amp services
(posted same time as electrofelon)
wc86
Member
- Location
- Massachusetts
- Occupation
- Electrician
So does using any "triplex" wire of any sort vs say XHHW in the vertical riser to the weatherhead have any advantage?
The advantage of most aerial "triplex" is that most have an ACSR bare that serves as the messenger for strength.
There may be one that is dual rated to be used for your riser but I am not aware of one. The advantage if you find one would be that you would not have to transition (splice) where the OH met the riser.
Southwire (and likely other manufacturers) does have a triplex that is also rated RHW but if you are running overhead for any distance you would likely need a messenger cable for support.
www.southwire.com
There may be one that is dual rated to be used for your riser but I am not aware of one. The advantage if you find one would be that you would not have to transition (splice) where the OH met the riser.
Southwire (and likely other manufacturers) does have a triplex that is also rated RHW but if you are running overhead for any distance you would likely need a messenger cable for support.
600VUD Triplex 3E | Southwire
TRIPLE E Aluminum Alloy (AA-8176) Conductors. Cross-Linked Polyethylene (XLP) Insulation.
www.southwire.com
Last edited:
ptonsparky
Tom
- Occupation
- EC - retired
Splice it. Not worth the effort.
- Status