Stubups into a Gutter

[Smart $]

This is exactly what I'm up against. 2' nipples or less above the panels would put me right in the ceiling joist area.
It's going to take 4' min. from the top of the panel to the bottom of the gutter, maybe even a little more.
...

Not getting a good mental picture of your situation...

Ceiling construction (materials, framing, etc.)? How does 2' put you in joist area, yet 4'+ puts you above it?

 

[Smart $]

.... Perhaps I'll write up a proposal...

Submitted...

(2) Selection of Ampacity. Where more than one ampacity applies for a circuit, the lowest value shall be used.​

​

Exception: The second lowest value shall be permitted to be used provided the lowest-value portion length does not exceed 3.0 m (10 ft) or 10 percent of the adjacent portion(s) length, whichever is less.​

Informational Note: See 110.14(C) for conductor temperature limitations due to termination provisions.​

Statement of Problem and Substantiation for Public Input​

Deleted 'given' and 'length' because they are unnecessary.

Changed the Exception wording to cover possibilities that would otherwise be excluded from a literally technical interpretation.

As an example, let's say we have a circuit 50' in length from panelboard branch circuit breaker to load terminals. The wires exit the panelboard enclosure through a conduit 4' in length containing 10 current-carrying conductors, are then routed 2' through a wireway with less than 30 current-carrying conductors, then continue in a conduit by themselves to the load.

The conductor ampacity for the portion exiting the panelboard in conduit would have the lowest value. The Exception can not be applied because the adjacent portion in the wireway is only 2' in length and there is no Code means to determine ampacity in an enclosure regardless of conductor length. Even if we could carry a higher ampacity across more than one adjacent portion, wireway to load is 44', and 10% past the transition at the wireway does not cover the 6' distance to the panelboard.

The circuit ampacity through the Exception, as reworded, is permitted to be that of the wireway or load-end portion of the circuit, whichever is less.​

Comments...?

 

[Smart $]

Decided to change the Exception wording:

Exception: Any portion with a length not exceeding 3.0 m (10 ft) or 10 percent of consecutive adjacent portions length with higher ampacity, whichever is less, shall be permitted to be excluded from determination.

 

[jap]

Not getting a good mental picture of your situation...

Ceiling construction (materials, framing, etc.)? How does 2' put you in joist area, yet 4'+ puts you above it?

The panels are in a space for a future mechanical room. in a metal building. A temporary 12' wall was built with plywood on it so we could go ahead and get the panels mounted and pipes started out. Eventually it will be wood framed and the ceiling in the mechanical room will be 8' not sure of the width of the ceiling joists yet. if the gutter is not high enough it will be sitting on the deck of the mezzanine above it (3/4" Plywood Flooring). to be sure to be at a workable height above the future mezzanine floor, the nipples out of the panel up to the gutter above the mezzanine will have to be more than 2'. don't wan to have to fight through the ceiling joists every time we need to get another run out of the panels. it would be a lot easier to come out of the gutter above with the smaller conduits above, then use the larger chases down to the panel below.hence the gutter above the mezzanine to make things simple.

 

[jap]

Submitted...



Comments...?

I don't know about any one else but by the time I tried to figure out exactly what all this meant, I'd find a way to make the nipple 24" or less so I wouldn't have to worry about it.


JAP>

 

[Smart $]

The panels are in a space for a future mechanical room. in a metal building. A temporary 12' wall was built with plywood on it so we could go ahead and get the panels mounted and pipes started out. Eventually it will be wood framed and the ceiling in the mechanical room will be 8' not sure of the width of the ceiling joists yet. if the gutter is not high enough it will be sitting on the deck of the mezzanine above it (3/4" Plywood Flooring). to be sure to be at a workable height above the future mezzanine floor, the nipples out of the panel up to the gutter above the mezzanine will have to be more than 2'. don't wan to have to fight through the ceiling joists every time we need to get another run out of the panels. it would be a lot easier to come out of the gutter above with the smaller conduits above, then use the larger chases down to the panel below.hence the gutter above the mezzanine to make things simple.

Understand now.

Have you considered putting the gutter top at 8' and running extra stub ups through mezzanine-floor elevation? ...or simply putting two gutters in, one as just mentioned and the other at workable height above mezzanine floor?

 

[jap]

Understand now.

Have you considered putting the gutter top at 8' and running extra stub ups through mezzanine-floor elevation? ...or simply putting two gutters in, one as just mentioned and the other at workable height above mezzanine floor?

I've decided to leave the gutter below the ceiling and just use short nipples into it.
It wouldnt be such a bid deal if they would make loadcenters without knockouts. I priced a CH 42 cir single phase loadcenter without knockouts a while back and it was something like $225.00 for them to make it at the flex center. Cant choke that much. The random KO"s in the loadcenters are made for romex installations not the 3/4" riser racks I'm used to instaling out the panelboards I'm used to working with. Thanks for the info Smart. very interesting stuff.

JAP>

 

[Smart $]

Revised my proposal, again. Hopefully this will be the last revision to this one... :blink:

(2) Selection of Ampacity. Where different ampacity values apply to portions of a circuit, the lowest value shall be used for circuit ampacity.

Exception: Any portion not exceeding the shorter of 3.0 m (10 ft) or 10 percent of consecutive adjacent portions length with higher ampacity shall be permitted to be excluded from circuit ampacity determination.

Informational Note: See 110.14(C) for conductor temperature limitations due to termination provisions.​

Statement of Problem and Substantiation for Public Input

1) Subsection general requirement, as reworded, is just more proper use of grammar and implements no change.

2) Exception wording change provides for additional possibilities excluded under current wording. Portions of the circuit beyond the immediately adjacent portion are excluded for establishing 10% of the higher ampacity length or as the ampacity value permitted to be extended past the transition.

As an example, let's say we have a two-wire circuit 50' in length from panelboard to load. The wires exit the panelboard enclosure through a conduit 4' in length containing 10 current-carrying conductors, are then routed 2' through a wireway with less than 30 current-carrying conductors, then continue in a conduit by themselves to the load but in a higher ambient temperature. The circuit uses the same size and type of conductor throughout.

The conductor ampacity for the portion between panelboard and wireway would likely have the lowest value with 50% factoring for 10 current-carrying conductors. The Exception, as currently worded, can not be applied to this portion because the adjacent portion in the wireway is only 2' in length. Even if we could carry a higher ampacity across more than one adjacent portion, the portion between wireway to load is 44', and 10% past the transition at the wireway does not cover the 6' distance to the panelboard.

Through the Exception, as reworded, the portion between panelboard and wireway can be excluded from circuit ampacity determination because it is less than 10% of the consecutively adjacent portions with higher ampacity. Circuit ampacity is permitted to be that of the load-end portion of the circuit (likely the second lowest ampacity portion, having to be corrected for the higher ambient temperature).

 

[jap]

Revised my proposal, again. Hopefully this will be the last revision to this one... :blink:

I can even understand that.

Another question that may need to be on a different post, is, when dealing with 3 way switching.
if you have 2 3 way switches 100' apart fed with 2 separate circuits,,,, do you need to derate because of the distance and the number of travelers and switchlegs that end up being installed in the conduit?

for instance say there was em lighting that needed to be fed at both ends along with switching for the lighting that required 2 120v 20amp circuits.

(2) Hots, 1 neutral and a ground would travel from the start through the 100' run to the 3 way at the other end, then 4 travelers and 2 switchlegs back 100' to pick up the lights that need to be switched at the beginning . if this was installed in a 3/4" conduit how does one determine the voltage drop or derating?
in the middle you would end up with, 2 hots, 1 neutral, 1 ground, 4 travelers and 2 switchlegs, 10 wires total.
I can see the actual current traveling 100' east on the ungrounded conductors, 100' back west on the travelers, then, 100' back east on the switchleg to the lighting.

 

[GoldDigger]

Only one of each pair of travelers gets counted as a CCC. Beyond that, count everything but the EGC and the neutral of an MWBC.
And yes, the distance for VD calculation can get large.