Can Tray Cable (TC) be installed in a residential attic (outside of raceway) and then transitioned to exterior buried PVC conduit?

N

Nukem

New User
Location
Louisiana
Occupation
Electrical Engineer
I'm having a pool / spa installed. Due to my wide driveway, I plan to run the main feeder (100A) to the pool panel / power center (AquaLink) from my meter service entrance panel, up into and across my (attached) garage attic, down the opposite exterior wall, and then LB down into a short run of buried PVC conduit over to the pool pump / heater skid. My electrician has proposed using Tray Cable.

Per NEC 2023, 336.10(9):

Type TC-ER-JP cable containing conductors for both power and control circuits shall be permitted for branch circuits and feeders. Type TC-ER-JP cable used as interior wiring shall be installed per the requirements of Part II of Article 334 and, where installed as exterior wiring, shall be installed per the requirements of Part II of Article 340.
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My application has only power conductors; no control circuits. Does that prohibit me from using TC-ER-JP cable as I describe above? Or is this simply poorly worded, and therefore TC-ER-JP cables containing solely power conductors are allowed (i.e., without a raceway in my attic)? I see no reason why the absence of control circuitry in the cable would somehow yield an inferior installation in terms of safety.
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Since you have to pipe up to the attic and down again why not just run the pvc thru the attic and use thwn-2 conductors ll the way
 
augie47

augie47

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Location
Tennessee
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State Electrical Inspector (Retired)
Dennis Alwon said:
I don't understand why either but it does appear to forbid that install. Why don't you just use ser cable?
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SER would not be allowed for the underground portion, correct ?

OP:
I don't know if there were any changes in 2023 that would allow your TC install due to the lack of control wires.
As I recall, the original change was pushed by the generator manufacturers for their product.
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Nukem said:
I'm having a pool / spa installed. Due to my wide driveway, I plan to run the main feeder (100A) to the pool panel / power center (AquaLink) from my meter service entrance panel, up into and across my (attached) garage attic, down the opposite exterior wall, and then LB down into a short run of buried PVC conduit over to the pool pump / heater skid. My electrician has proposed using Tray Cable.

Per NEC 2023, 336.10(9):



My application has only power conductors; no control circuits. Does that prohibit me from using TC-ER-JP cable as I describe above? Or is this simply poorly worded, and therefore TC-ER-JP cables containing solely power conductors are allowed (i.e., without a raceway in my attic)? I see no reason why the absence of control circuitry in the cable would somehow yield an inferior installation in terms of safety.
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There isn't, but originally that cable was custom made for one generator manufacture and when they submitted a Public Input they only asked for the code to include a cable with both power and control conductors.
Note, the code language only requires that the control conductors be part of the cable, but there is no requirement that you actually use those conductors for anything.
 
Dennis Alwon

Dennis Alwon

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Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
don_resqcapt19 said:
There isn't, but originally that cable was custom made for one generator manufacture and when they submitted a Public Input they only asked for the code to include a cable with both power and control conductors.
Note, the code language only requires that the control conductors be part of the cable, but there is no requirement that you actually use those conductors for anything.
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So doesn't that technically require the control conductors to be in the cable? Sounds really crazy to not allow it, IMO however I still see no reason to use it in this case

@augie47 , yes the underground portion could not be ser.... that is why I suggest pipe all the way.
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Dennis Alwon said:
So doesn't that technically require the control conductors to be in the cable? Sounds really crazy to not allow it, IMO however I still see no reason to use it in this case

@augie47 , yes the underground portion could not be ser.... that is why I suggest pipe all the way.
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It requires the control conductors to be in the cable, but it does not require that the control conductors be connected and used.
 
B

Birken Vogt

Senior Member
Location
Grass Valley, Ca
For installations like this, I have used MC (sometimes cheaper than SER) and removed the outer covering to reveal XHHW conductors (labeled) including an insulated ground. The thing is that bare aluminum ground cannot be run underground, otherwise this trick *usually* works. You will want to be sure the individual conductors are marked. You will have to compare costs to individual conductors vs the SER or MC or TC-ER for that matter.
 
L

letgomywago

Senior Member
Location
Washington state and Oregon coast
Occupation
residential electrician
Birken Vogt said:
Where do you order your PVC jacketed MC? Seems to be a regional thing.
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Online is very available. They sell it in shorter lengths on wire and cable your way but I've seen dozens of sellers online. My supplier only stocks 12 2 and 12 3 in it but like I said it's available. Just make sure you get the wet rated connector when using it outside. The inside portion can use an indoor mc connector. The wet rated connectors cost a lot but the labor savings are insane.
 
B

Birken Vogt

Senior Member
Location
Grass Valley, Ca
don_resqcapt19 said:
This was a huge step in right direction...there is not any technical reason why TC cannot be used everywhere NM is used.
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I agree with you completely. I was just pointing out that the current allowable case for TC-ER-JP was obviously cut and paste from a particular mfr, with a bunch of things that do not apply to safety (control conductors included)
 
don_resqcapt19

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
Birken Vogt said:
I agree with you completely. I was just pointing out that the current allowable case for TC-ER-JP was obviously cut and paste from a particular mfr, with a bunch of things that do not apply to safety (control conductors included)
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I don't think that the ER-JP had anything to do with the original proposal...those are requirements in the product standard. The original proposal was for a TC cable that had both the generator feeder conductors and the generator control conductors in the same cable. Since the proposal was submitted by a company that makes generators and transfer switches, their proposal was only to make sure that you could use that cable that was originally only available from that generator manufacturer. The CMP should have expanded the permitted use when they accepted the proposal.
 
L

letgomywago

Senior Member
Location
Washington state and Oregon coast
Occupation
residential electrician
Birken Vogt said:
Let's say I wanted 3Cu or 1Al. Can you give me an example? I have tried to find something reasonable many times but failed each time.
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