cu in fill in panel

kwired

Electron manager
Location
NE Nebraska
There isn't the same requirement there is for a device/junction box for small conductor fill.

There is still the wiring space beside breakers that is treated much like a wireway or gutter. IIRC you can fill cross section of that space 20% with conductors and 75% with splices/tap devices and or other allowed items in that space.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
There isn't the same requirement there is for a device/junction box for small conductor fill.

There is still the wiring space beside breakers that is treated much like a wireway or gutter. IIRC you can fill cross section of that space 20% with conductors and 75% with splices/tap devices and or other allowed items in that space.
And I expect that is the basis of the question.
It is 40% for the wireway fill in a panel, but I have never seen anything to tell me the area of the wireway so I can do a fill calculation.

Yes, you can measure the area, but exactly what do you measure? This info should be provided by the manufacturer, but if it is, I have never found it.
 

kwired

Electron manager
Location
NE Nebraska
And I expect that is the basis of the question.
It is 40% for the wireway fill in a panel, but I have never seen anything to tell me the area of the wireway so I can do a fill calculation.

Yes, you can measure the area, but exactly what do you measure? This info should be provided by the manufacturer, but if it is, I have never found it.
20 inch wide cabinet and a panel feeding 100 amp and less branch circuits, generally you will never come close enough to have to worry about much.

"Loadcenter" panels have tighter quarters, and then if you throw in some GFCI or AFCI breakers you really get limited in cross section compared to standard breakers.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
20 inch wide cabinet and a panel feeding 100 amp and less branch circuits, generally you will never come close enough to have to worry about much.

"Loadcenter" panels have tighter quarters, and then if you throw in some GFCI or AFCI breakers you really get limited in cross section compared to standard breakers.
And that goes to my point as to how you measure the square area of the wireway?

I agree, that it would be a rare case that it would be an issue, but I think since the code specifies that maximum percentage of the wireway area that can be used for wire fill, that there should be some guidance as to determining the total wireway area.
 

Chamuit

Senior Member
Location
Texas
Aren't you, in a sense, limited by the number of devices the panel will accommodate by design? An 100A, 8/16 space panel is designed for that use. So, it should be able to handle the typical wiring that would be brought into it. ....Of course, there will be some person and some panel some where that defies sensibility.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Aren't you, in a sense, limited by the number of devices the panel will accommodate by design? An 100A, 8/16 space panel is designed for that use. So, it should be able to handle the typical wiring that would be brought into it. ....Of course, there will be some person and some panel some where that defies sensibility.
The rule in question talks about conductor splices and conductors that pass through the panel.
 

kwired

Electron manager
Location
NE Nebraska
The rule in question talks about conductor splices and conductors that pass through the panel.
But it also includes those that land in the panel doesn't it?

Aren't you, in a sense, limited by the number of devices the panel will accommodate by design? An 100A, 8/16 space panel is designed for that use. So, it should be able to handle the typical wiring that would be brought into it. ....Of course, there will be some person and some panel some where that defies sensibility.
How about if you had one of those QO series 8/16 space panels and used 8 tandem breakers but because of long circuit length and voltage drop you ran sixteen ungrounded and sixteen grounded 6 AWG conductors? Then on top of that those tandems only take 8AWG IIRC so you would need more space to reduce the conductor before you can land it on the breaker lug.

May or may not overfill the space, but definitely will be crowded:blink:
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Yes, it does include the conductors that land in the panel, but it would be difficult to exceed 40% with just those conductors. Even a 2x2 wireway could hold 120 #12s or 19 #4s without exceeding 40%....
 

Julius Right

Senior Member
The O.P.inquire could be interpreted as:
a) (f)cu infill[ in panel] or
b) cu[bic] in[ch] fill in [a] panel [allowable?].
For b option, in my opinion ,you may calculate the permissible area and multiply by actual length.
312.8 Switch and Overcurrent Device Enclosures with Splices, Taps, and Feed-Through Conductors.
(1) The total of all conductors installed at any cross section of the wiring space does not exceed 40 percent of the cross-sectional area of that space.
(2) The total area of all conductors, splices, and taps installed at any cross section of the wiring space does not exceed 75 percent of the cross-sectional area of that space.
 

kwired

Electron manager
Location
NE Nebraska
The O.P.inquire could be interpreted as:
a) (f)cu infill[ in panel] or
b) cu[bic] in[ch] fill in [a] panel [allowable?].
For b option, in my opinion ,you may calculate the permissible area and multiply by actual length.
312.8 Switch and Overcurrent Device Enclosures with Splices, Taps, and Feed-Through Conductors.
(1) The total of all conductors installed at any cross section of the wiring space does not exceed 40 percent of the cross-sectional area of that space.
(2) The total area of all conductors, splices, and taps installed at any cross section of the wiring space does not exceed 75 percent of the cross-sectional area of that space.
I agree, some are challenging just how to determine the volume since there are irregular shape to that volume at times. My thoughts are start with a basic width times depth that includes all obvious free space, if you are under 40/75 on that you don't have a problem if there is extra space that is more difficult to measure. Then if you have GFCI/AFCI's in certain areas you may need to look at that area separately. Most of the time GFCI/AFCI won't be a problem other then for splices in that area or maybe if there is conductors of a large feeder run through that area.
 

Chamuit

Senior Member
Location
Texas
But it also includes those that land in the panel doesn't it?



How about if you had one of those QO series 8/16 space panels and used 8 tandem breakers but because of long circuit length and voltage drop you ran sixteen ungrounded and sixteen grounded 6 AWG conductors? Then on top of that those tandems only take 8AWG IIRC so you would need more space to reduce the conductor before you can land it on the breaker lug.

May or may not overfill the space, but definitely will be crowded:blink:
I did qualify my statement with the word "typical' ....FWIW.

As usual on this forum, extremes are always used. ;)
 
Top