Where to strip multi conductor tray cable before entering conduit?

[NetNathan]

I am running a pair of 4/0 Awg /3 conductor (with #4 ground) tray cables to a piece of equipment using a below ground level covered trench using cable tray (basket style).

I need to come out of the underground tray into conduit to go up about 10 feet.
I want to strip the outer covering from the cable before entering the conduit, so only the insulated wires enter the conduit. This is to reduce the bend radius requirement of the multi conductor cable before entering the conduit.
Is there an NEC code relating to this strip distance?

Cable used:
https://www.wireandcableyourway.com/4-0-3c-thhn-pvc-tray-cable-with-ground.html

Cable Tray used:
http://www.cableorganizer.com/p/wirerun-powder-coated-cable-tray/

 

[iwire]

I am running a pair of 4/0 Awg /3 conductor (with #4 ground) tray cables to a piece of equipment using a below ground level covered trench using cable tray (basket style).

I need to come out of the underground tray into conduit to go up about 10 feet.
I want to strip the outer covering from the cable before entering the conduit, so only the insulated wires enter the conduit. This is to reduce the bend radius requirement of the multi conductor cable before entering the conduit.
Is there an NEC code relating to this strip distance?

Cable used:
https://www.wireandcableyourway.com/4-0-3c-thhn-pvc-tray-cable-with-ground.html

Cable Tray used:
http://www.cableorganizer.com/p/wirerun-powder-coated-cable-tray/

If you are that concerned with the code requirements you should realize that stripping the cable does not change the listed cable into single conductors.

Also if you are really concerned with the bend radius you can't run the unstripped portion through the bend.

How about using a long radius 90 or make your own segmented bend?

 

[NetNathan]

Why do I need this calculation?
The bottom of my 4" deep cable tray is 5" below the trench cover.
I am bending the cable into a 3" EMT waterproof coupling for the vertical run in conduit from the trench cover.


The diameter of the multi-conductor cable (4/0 Awg / 3 cond with #4 ground) is 1.545"'
The bend radius requirement listed for the cable is "5 x diameter".
This means, I would need a bend radius of 7.725" ( 5 x 1.545").

Uh..oh I need 7.725" and I only have 5" to trench cover.
Now...If I strip the multi conductor "jacket" covering from the individual conductors before I bend it...to feed it into the conduit... (and run just the conductors through the 10' section of EMT)..... I can now separate it into individual cables which will be easier to meet the bend radius requirement and feed into the conduit.

Using the same cable specs on the individual insulated conductors (with the overall cover "stripped"):
4/0 THHN is .624"
So I now I only need a bend radius of 3.12" (5 x 3.12").

According to these calculations... I should have plenty of room ( on a 5" deep tray) using the 3.12" sweep requirement to get the conductors in to the conduit.


The reason I originally asked about the stripping distance is ....I plan on stripping the multi conductor tray cable covering back to about 12" before the "arc" of the bend, to be able to have room to bend and feed the individual 4/0 conductors into the 3" conduit (after stripping the covering...This will be about 14' of individual conductors).
I believe that... after I strip the cover off the conductors...they are probably no longer tray rated.....and I will probably have about 8" of conductors that are still horizontal on the tray before the bend lifts them off the tray to go up into the conduit..

 

[Smart $]

If you are that concerned with the code requirements you should realize that stripping the cable does not change the listed cable into single conductors.

Also if you are really concerned with the bend radius you can't run the unstripped portion through the bend.
...

Code section or other reference, please?

 

[Smart $]

What is at the top of the 10' EMT? Is it simply a protection sleeve and cable continues to where it is going in another tray or another raceway such as wireway? Or is it an combination sleeve-raceway that enters the wiring compartment of utilization equipment?

The cable bend radius from tray to EMT is not held to the 4-5" you think it is. You did not allow for the part of the bend that can be in the EMT. Should approach 8". I didn't do the calculation. It will be close.

 

[iwire]

Code section or other reference, please?

110.3(B)

You tell me when you can modify a listed product and make it become a different listed product.

 

[Smart $]

110.3(B)

You tell me when you can modify a listed product and make it become a different listed product.

I'm not saying it is a different listed product. It is still the same product IMO. And we always, always strip off the cable sheath end when we terminate the run... at both ends. What says we can't strip off the amount of sheath that is within a raceway en route and attached to the utilization equipment?

 

[iwire]

What says we can't strip off the amount of sheath that is within a raceway en route and attached to the utilization equipment?

Nothing and that is not what I said.


What I am saying is striped or not striped it remains a listed multi-conductor cable and the bend radius rules still apply. I am not saying they should apply just that they do apply.

I also submit the bend radius rules apply equally to cable installed or being installed or even handled.

So I can't pull 50' of cable through too small of a radius and then continue running that part on the cable tray.

 

[electrofelon]

If you are that concerned with the code requirements you should realize that stripping the cable does not change the listed cable into single conductors.

I am not sure I agree with that. Say I have tray cable with XHHW inners, properly marked per 310......why can't I use them as single conductors? Would cutting them and then splicing them back on be compliant in your view?

 

[NetNathan]

I am not sure I agree with that. Say I have tray cable with XHHW inners, properly marked per 310......why can't I use them as single conductors? Would cutting them and then splicing them back on be compliant in your view?

That will not work. splices not allowed in cable tray.

But I do end up with 3 individual THHN conductors, which should have different bend specs now.

 

[NetNathan]

What is at the top of the 10' EMT? Is it simply a protection sleeve and cable continues to where it is going in another tray or another raceway such as wireway? Or is it an combination sleeve-raceway that enters the wiring compartment of utilization equipment?

At the top of the EMT, there is a 90 deg sweep going into a transformer. The individual conductors ((3) 4/0 and (1) #4) will have plenty of room in the 3" EMT and have no problem in the bend radius of that sweep. I could even use a 3" LB for that.
However....if I could make the bend at the tray to conduit area and run the complete multi conductor cable in the conduit (my original plan)....this sweep radius may also be of concern.

The cable bend radius from tray to EMT is not held to the 4-5" you think it is. You did not allow for the part of the bend that can be in the EMT. Should approach 8". I didn't do the calculation. It will be close.

I do not plan for any of the bend to be in the conduit.
If I use the complete multi conductor tray cable to run through the conduit.....the bend radius minimum is 7.725" according to my calc on the diameter in the previous post (near your approx calc of 8") . That will not work very easily with a distance of 5" from cable tray to cover.
If I strip the outer covering from the individual conductors...the individual conductors now have a bend radius minimum of 3.12"....which should give me the room to bend the individual conductors BEFORE they enter the conduit.

 

[NetNathan]

That will not work. splices not allowed in cable tray.

But I do end up with 3 individual THHN conductors, which should have different bend specs now.

My mistake....splices are allowed in cable tray (392.8).
BUT...I do not want to splice.

 

[Smart $]

... What I am saying is striped or not striped it remains a listed multi-conductor cable and the bend radius rules still apply. I am not saying they should apply just that they do apply....

Can't say I agree with the unsheathed conductors being held to the same bend radius as the sheathed portion. That is, after the cable [sheath] is properly terminated. Do you maintain the required cable bend radius on MC conductors once they enter a panel?

....If I strip the outer covering from the individual conductors...the individual conductors now have a bend radius minimum of 3.12"....which should give me the room to bend the individual conductors BEFORE they enter the conduit.

I can't think of a Code section that says you can't offhand, but you can't strip off the outer covering (i.e. sheath) where the inner individual conductors will not be protected by raceway or enclosure. Cable tray is not a raceway. Does your trench qualify as a raceway?

 

[NetNathan]

Can't say I agree with the unsheathed conductors being held to the same bend radius as the sheathed portion. That is, after the cable [sheath] is properly terminated. Do you maintain the required cable bend radius on MC conductors once they enter a panel?

I have a 6" gutter bringing the power wires from the bottom of a wall mounted distribution panel to the trench. There is enough room in the 6" gutter to support part of the bend radius as the cables lay down on the cable tray.

I can't think of a Code section that says you can't offhand, but you can't strip off the outer covering (i.e. sheath) where the inner individual conductors will not be protected by raceway or enclosure. Cable tray is not a raceway. Does your trench qualify as a raceway?

I have 2 definitions I can work with (or around).
The concrete trench meets the definition of an underfloor raceway.
The cable tray system installed in the trench is rated for above floor or under floor use and I am using all the correct connection components, floor supports and ground connections for an underfloor cable tray system. I would just use cable tray to bring the cables out of the trench, but it is a service area and the customer is concerned about damage to the exposed cable on the tray.

 

[Smart $]

...
The cable tray system installed in the trench is rated for above floor or under floor use and I am using all the correct connection components, floor supports and ground connections for an underfloor cable tray system. I would just use cable tray to bring the cables out of the trench, but it is a service area and the customer is concerned about damage to the exposed cable on the tray.

You keep throwing a pail of paint on my mind's picture of your installation. I was of the impression the EMT extended vertically down to the trench cover. Now I am uncertain how you will be exiting the trench. I was of the impression the cable tray was running horizontally just under the trench cover. Details make or break a Code-compliant installation.

 

[NetNathan]

You keep throwing a pail of paint on my mind's picture of your installation. I was of the impression the EMT extended vertically down to the trench cover. Now I am uncertain how you will be exiting the trench. I was of the impression the cable tray was running horizontally just under the trench cover. Details make or break a Code-compliant installation.

Yes...your impression is correct.

Sorry about throwing you off track with a path that is not an option.

 

[NetNathan]

Cannot strip Multi conductor tray cable (4/0 AWG / 3 Conductor / with #4 ground).
I have found out the #4 ground is not insulated. I do not want to run an un-insulated conductor in the EMT or splice a #4 insulated conductor to the #4 bare wire in the trench.
In am talking to customer about making the trench 4" deeper (luckily it is not finished yet) to support bend of tray cable.

I want to thank everyone for their help....especially Smart $.