Bundling Romex into Service Panel

[Karl Knerr]

Rather than use many romex connectors to bring NM cable into a residential service panel I use 2-2 inch sch 40 PVC conduit stubs at top of panel less than 24 inches long with male adapters and bushings. Do I need to support the romex within 8 inches from the top of the conduit and should I strip the romex that is inside the conduit? Also, is there a limit as to how many current carrying conductors can be put inside the PVC counting the nuetral?

Thanks,

Karl

 

[Pierre C Belarge]

Karl
take a look at 312.5(C)Exception. All the information for installation as you have stated is located in the exception.

 

[iwire]

You're method is an NEC violation.

 

[Dennis Alwon]

You're method is an NEC violation.

I don't see it that way. As Pierre pointed out 315.5(C) has the except. As long as those conditions are met it is good to go. Very common around here years ago but no one enforced the 18" rule.

 

[iwire]

I guess I assume flush and you assume surface.

 

[Karl Knerr]

Bob,

Is this a NEC violation because I stripped the outer sheath from the wires inside the PVC?

Pierre,

Thanks for pointing me to the code article.

 

[jumper]

Exception (d) Sealing or plugging:
What do you use to do this? Duct seal putty?

 

[iwire]

I assumed it is a flush mounted panel which would make it a volition.

 

[jumper]

Is this a NEC violation because I stripped the outer sheath from the wires inside the PVC?

Wouldn't that violate 312.5(C) exception(e)

 

[Karl Knerr]

I always kept the length of the PVC at 19 to 23 inches, stripped the jacket off to reduce heat inside and put duct seal around the wires entering the top. Also the panel was a surface mount, and I supported the PVC with a 2 inch strap so the pipe sticks up just inside the floor joist in a basement.

My main question was supporting the wires before entering the conduit and stripping them inside and the exception that Pierre pointed to seems to address this.

Also I think this type of installation makes for a lot more professional looking and user friendly service panel.

Thanks, Karl

 

[macmikeman]

Stripping the outer jacket off the cables before they reach the interior of the panel is a code violation. The jacket needs to be complete inside the box for a minimum of 1/4". Duct seal at the top of the conduit stubs is ok. As Bob points out this is for surface mounted panels only. Better to play carpenter and box in the wiring above and use multiple romex connectors if you were to ask me how I do it, but you didn't so I won't mention it....

 

[Karl Knerr]

Thanks alot everybody. That answers all my questions

Karl

 

[augie47]

Thanks alot everybody. That answers all my questions

Karl

That's good. It only causes me to ask more
(I'm actually just refering to the "why" type questions.. why surface and not flush, etc... ours is not to reason why)

 

[jsharvey]

What about the derating ??

What about the derating ??

Wouldn't dropping your romex from multiple home runs into the panel through a piece of PVC create a situation where you would have to derate for the number of current carrying conductor anyway? It would seem to me that if you had 5, 120V circuits that's 10 current carrying conductors and you'd would have to apply the 50% derate? Am I missing something?

 

[augie47]

In the OP's case he stated his pipe was less than 24", so derating would not apply.

 

[mcclary's electrical]

I always kept the length of the PVC at 19 to 23 inches, stripped the jacket off to reduce heat inside and put duct seal around the wires entering the top. Also the panel was a surface mount, and I supported the PVC with a 2 inch strap so the pipe sticks up just inside the floor joist in a basement.

My main question was supporting the wires before entering the conduit and stripping them inside and the exception that Pierre pointed to seems to address this.

Also I think this type of installation makes for a lot more professional looking and user friendly service panel.

Thanks, Karl

This method violates 334. 30. Also, when using the duct putty, any hole being draft stopped, gets derated according to 310.15 (b) (2) (A)

 

[jsharvey]

In the OP's case he stated his pipe was less than 24", so derating would not apply.

Thanks Augie, I was always told that the length of the conduit didn't matter for the derate on the wires, just the percentage of pipe fill.

 

[augie47]

Take a look at the exceptions to 310.15(B)(2) ('08 pg 146) . There are a few there can come in helpful on occasion.
As an inspector, well, an OLD inspector, I sometime forget them so it;s great if the E/Cs keep them in mind.

 

[don_resqcapt19]

Thanks Augie, I was always told that the length of the conduit didn't matter for the derate on the wires, just the percentage of pipe fill.

The percentage of fill is not involved with the derating...just the total number of current carrying conductors. You can have a 4" conduit with 10 current carrying #12s and have to use a 50% derating factor.

 

[Nium]

The percentage of fill is not involved with the derating...just the total number of current carrying conductors. You can have a 4" conduit with 10 current carrying #12s and have to use a 50% derating factor.

Chapter 9, Notes (4): Where conduit or tubing nipples having a maximum length not to exceed 600 mm (24 in) are installed between boxes, cabinets, and similar enclosures, the nipples shall be permitted to be filled to 60 percent of their total cross-sectional area, and 310.15(B)(2)(a) adjustment factors need not apply to this condition.