Conduit Fill

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This question comes up a lot. For some reason people find this confusing. I've heard from electricians regarding fill that "grounds don't count", "grounds only count as one", etc. If you think about why conduits are limited to a certain fill percentage you'll know that all conductors in the raceway count.

Chapter 9, Notes to Tables:
(3) Equipment grounding or bonding conductors, where installed, shall be included when calculating conduit or tubing fill. The actual dimensions of the equipment grounding or bonding conductor (insulated or bare) shall be used in the calculation
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infinity said:
This question comes up a lot. For some reason people find this confusing. I've heard from electricians regarding fill that "grounds don't count", "grounds only count as one", etc. If you think about why conduits are limited to a certain fill percentage you'll know that all conductors in the raceway count.
Click to expand...
Where I have a moment is for an LB, which has a listed fill, 4-3/0 for example. So what if I have 4-3/0 and a #6 ground? I assume no, but if so, why don't they merely provide the overall conductor area and let us do the math.
 
infinity said:
This question comes up a lot. For some reason people find this confusing. I've heard from electricians regarding fill that "grounds don't count", "grounds only count as one", etc. If you think about why conduits are limited to a certain fill percentage you'll know that all conductors in the raceway count.
Click to expand...
Grounds only count as 1 in box fill no matter how many there are. Not sure if that's per awg size or 1no matter how many sizes in the box..
 
Strathead said:
Where I have a moment is for an LB, which has a listed fill, 4-3/0 for example. So what if I have 4-3/0 and a #6 ground? I assume no, but if so, why don't they merely provide the overall conductor area and let us do the math.
Click to expand...
They tried somewhat with the added wording in the '17 Code.
Not sure how successful the effort
For other conductor sizes and combinations, the total cross-sectional area of the fill shall not exceed the crosssectional area of the conductors specified in the marking, based on the type of conductor identified as part of the product listing.
 
I have found that it is not uncommon for "electricians" to confuse the conduit fill requirement with the requirements for counting the neutral as a current-carrying-conductor.
 
qcroanoke said:
Grounds only count as 1 in box fill no matter how many there are. Not sure if that's per awg size or 1no matter how many sizes in the box..
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The 2020 code changed that. Up to 4 egc's count as 1based on the largest egc.
Then, a 1/4 volume allowance shall be made for each additional egc.

Ron
 
Strathead said:
Where I have a moment is for an LB, which has a listed fill, 4-3/0 for example. So what if I have 4-3/0 and a #6 ground? I assume no, but if so, why don't they merely provide the overall conductor area and let us do the math.
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As Augie stated you can now do your own calculation which makes sense. In your example you still could not use the #6 EGC with the 4-#3/0's.
 
infinity said:
This question comes up a lot. For some reason people find this confusing. I've heard from electricians regarding fill that "grounds don't count", "grounds only count as one", etc. If you think about why conduits are limited to a certain fill percentage you'll know that all conductors in the raceway count.
Click to expand...
It's probably because they are confabulating conductor count for conduit fill with that for ampacity derating in a conduit.
 
infinity said:
This question comes up a lot. For some reason people find this confusing. I've heard from electricians regarding fill that "grounds don't count", "grounds only count as one", etc. If you think about why conduits are limited to a certain fill percentage you'll know that all conductors in the raceway count.
Click to expand...
Yep, you are right, this often comes up in my circles as well. Not sure why, but conduit fill is just that-all conductors take up space. A variation I get is, if it is uninsulated does it count? Of course it does. I think some confuse this with box fill.
 
augie47 said:
They tried somewhat with the added wording in the '17 Code.
Not sure how successful the effort
For other conductor sizes and combinations, the total cross-sectional area of the fill shall not exceed the crosssectional area of the conductors specified in the marking, based on the type of conductor identified as part of the product listing.
Click to expand...
augie47 said:
They tried somewhat with the added wording in the '17 Code.
Not sure how successful the effort
For other conductor sizes and combinations, the total cross-sectional area of the fill shall not exceed the crosssectional area of the conductors specified in the marking, based on the type of conductor identified as part of the product listing.
Click to expand...

Hello, Augie 47. I get this kind of question quite often from students.
The Code calls an LB a conduit body. See Article 100 Conduit Body and 314.16(C) (1) Conduit Bodies. It says it...........
".....mentions an area not less than twice the cross sectional area of the largest conduit or tubing to which they can be attached." The maximum number of conductors permitted shall be the maximum number permitted by T.1 of Chapter 9 for the conduit or tubing (EMT) to which it is attached."
The number of conductors in the raceway should not exceed the number of conductors in the conduit body.

314.16 (2) Splice(s) may be permitted if only when the conduit body (LB) is marked by the manufacturer with their [cubic inch] volume.
314.16 (C) (3) Short Radius Conduit Bodies. Also, known as "Jake Ells" [a slang term] .....they shall not contain splices, taps or devices......"

See 110.3 B Installation and Use. If equipment is listed ,labeled, or both for use shall be installed and used in accordance with any instructions included in the listing, labeling, or identification. I know we don't normally get instructions with LBs or LLs still it's our responsibility as licensed electricians to follow the Code rules for installation. Check the language in 90.5 Mandatory Rules, Permissive Rules, and Explanatory Material. (A) Mandatory Rules. (B) Permissive Rules. Pretty straight forward rules.

The conduit body may contain splice(s) if the MFG. has engraved the cubic inch capacity there on the conduit body or engraved with the maximum size conductor(s) that may be installed.

As mentioned above in the second sentence, "...not less than twice the cross sectional area..."
Here's an example:
Assume a 3/4 inch EMT raceway. Chapter 9 T.4 Article 358- Electrical Metallic Tubing (EMT) In the right hand column under the Total Area 100% column inch square, and trade size 3/4 find 0.533 in the Total Area column you find 0.533 sq in.

Now, the second sentence (at the top) said "twice" so multiply 0.533 x 2 = 1.066.
Now, let's go back to 314.16(C)(1) and read the last sentence, about "The maximum number permitted by T.1 of Chapter 9........"

Thanks for reading
TX MASTER #4544
 
TX+ MASTER#4544 said:
Hello, Augie 47. I get this kind of question quite often from students.
The Code calls an LB a conduit body. See Article 100 Conduit Body and 314.16(C) (1) Conduit Bodies. It says it...........
".....mentions an area not less than twice the cross sectional area of the largest conduit or tubing to which they can be attached." The maximum number of conductors permitted shall be the maximum number permitted by T.1 of Chapter 9 for the conduit or tubing (EMT) to which it is attached."
The number of conductors in the raceway should not exceed the number of conductors in the conduit body.

314.16 (2) Splice(s) may be permitted if only when the conduit body (LB) is marked by the manufacturer with their [cubic inch] volume.
314.16 (C) (3) Short Radius Conduit Bodies. Also, known as "Jake Ells" [a slang term] .....they shall not contain splices, taps or devices......"

See 110.3 B Installation and Use. If equipment is listed ,labeled, or both for use shall be installed and used in accordance with any instructions included in the listing, labeling, or identification. I know we don't normally get instructions with LBs or LLs still it's our responsibility as licensed electricians to follow the Code rules for installation. Check the language in 90.5 Mandatory Rules, Permissive Rules, and Explanatory Material. (A) Mandatory Rules. (B) Permissive Rules. Pretty straight forward rules.

The conduit body may contain splice(s) if the MFG. has engraved the cubic inch capacity there on the conduit body or engraved with the maximum size conductor(s) that may be installed.

As mentioned above in the second sentence, "...not less than twice the cross sectional area..."
Here's an example:
Assume a 3/4 inch EMT raceway. Chapter 9 T.4 Article 358- Electrical Metallic Tubing (EMT) In the right hand column under the Total Area 100% column inch square, and trade size 3/4 find 0.533 in the Total Area column you find 0.533 sq in.

Now, the second sentence (at the top) said "twice" so multiply 0.533 x 2 = 1.066.
Now, let's go back to 314.16(C)(1) and read the last sentence, about "The maximum number permitted by T.1 of Chapter 9........"

Thanks for reading
TX MASTER #4544
Click to expand...
Can you clarify how does this relate to what Augie said about calculating the number of conductors in the LB? Augie correctly stated that when applying the 6X rule (for a conduit body with conductors larger than #6) for conductor combinations other than those stamped on the conduit body you can do your own calculation. And your quote of 314.16(C)(1) left out the part that says "Conduit bodies enclosing 6 AWG conductors or smaller," the conductors in question from post #5 are #3/0.
 
TX+ MASTER#4544 said:
Hello, Augie 47. I get this kind of question quite often from students.
The Code calls an LB a conduit body. See Article 100 Conduit Body and 314.16(C) (1) Conduit Bodies. It says it...........
".....mentions an area not less than twice the cross sectional area of the largest conduit or tubing to which they can be attached." The maximum number of conductors permitted shall be the maximum number permitted by T.1 of Chapter 9 for the conduit or tubing (EMT) to which it is attached."
The number of conductors in the raceway should not exceed the number of conductors in the conduit body.

314.16 (2) Splice(s) may be permitted if only when the conduit body (LB) is marked by the manufacturer with their [cubic inch] volume.
314.16 (C) (3) Short Radius Conduit Bodies. Also, known as "Jake Ells" [a slang term] .....they shall not contain splices, taps or devices......"

See 110.3 B Installation and Use. If equipment is listed ,labeled, or both for use shall be installed and used in accordance with any instructions included in the listing, labeling, or identification. I know we don't normally get instructions with LBs or LLs still it's our responsibility as licensed electricians to follow the Code rules for installation. Check the language in 90.5 Mandatory Rules, Permissive Rules, and Explanatory Material. (A) Mandatory Rules. (B) Permissive Rules. Pretty straight forward rules.

The conduit body may contain splice(s) if the MFG. has engraved the cubic inch capacity there on the conduit body or engraved with the maximum size conductor(s) that may be installed.

As mentioned above in the second sentence, "...not less than twice the cross sectional area..."
Here's an example:
Assume a 3/4 inch EMT raceway. Chapter 9 T.4 Article 358- Electrical Metallic Tubing (EMT) In the right hand column under the Total Area 100% column inch square, and trade size 3/4 find 0.533 in the Total Area column you find 0.533 sq in.

Now, the second sentence (at the top) said "twice" so multiply 0.533 x 2 = 1.066.
Now, let's go back to 314.16(C)(1) and read the last sentence, about "The maximum number permitted by T.1 of Chapter 9........"

Thanks for reading
TX MASTER #4544
Click to expand...
Note that all of that applies only where the conductors are 6 AWG and smaller. You have to go to 314.28 where you have conductors 4 AWG and larger.
 
don_resqcapt19 said:
Note that all of that applies only where the conductors are 6 AWG and smaller. You have to go to 314.28 where you have conductors 4 AWG and larger.
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Augie 47.......314.16(C) (1) mentions the "twice" rule if making splices therein the conduit body. And size 6 AWG is the largest conductor that may be permitted for that reason, larger size conductors installed in a conduit body must adhere to the cubic inch volume as set forth by the MFG, or if no cubic inch volume is noted then the conduit body should be same size as the raceway.

My opinion is that I would not try to make a splice with any size conductor other than a 6 AWG; which would be a size 4 AWG.
Section 314.28 Pull and Junction Boxes and Conduit Bodies. Here we find wire sizes to be 4 AWG or larger. And specific rules for them such as straight pulls, Sect. 314.28 (A) (1) and (2) for angle pulls or u-pulls.

This is where raceways are used and not conductor sizing to determine the size of the conduit bodies used as pull or junction boxes. This is somewhat time consuming and requires more time to arrive at the correct size of the pull box based on raceway sizes and not conductor sizes.

When sizing conduit bodies think of them as if they were raceways. Same rules apply when sizing raceways based on approximate area square inch per conductor as found in Chapter 9, Tables 5. So, you could use a smaller conduit (raceway) but the conduit body must be sized "twice" the cross section area of the largest conduit or, larger than the raceway. In which case you would use reducing fittings installed inside the conduit body.

You will be applying Chapter 9 and Table 5 and Table 314.16 (B) (1).Conductors allowed in a conduit body and conductors allowed in a raceway when determing square inch per wire size and a table from Chapter 9 for various raceways.
 
TX+ MASTER#4544 said:
Augie 47.......314.16(C) (1) mentions the "twice" rule if making splices therein the conduit body. And size 6 AWG is the largest conductor that may be permitted for that reason, larger size conductors installed in a conduit body must adhere to the cubic inch volume as set forth by the MFG, or if no cubic inch volume is noted then the conduit body should be same size as the raceway.

My opinion is that I would not try to make a splice with any size conductor other than a 6 AWG; which would be a size 4 AWG.
Section 314.28 Pull and Junction Boxes and Conduit Bodies. Here we find wire sizes to be 4 AWG or larger. And specific rules for them such as straight pulls, Sect. 314.28 (A) (1) and (2) for angle pulls or u-pulls.

This is where raceways are used and not conductor sizing to determine the size of the conduit bodies used as pull or junction boxes. This is somewhat time consuming and requires more time to arrive at the correct size of the pull box based on raceway sizes and not conductor sizes.

When sizing conduit bodies think of them as if they were raceways. Same rules apply when sizing raceways based on approximate area square inch per conductor as found in Chapter 9, Tables 5. So, you could use a smaller conduit (raceway) but the conduit body must be sized "twice" the cross section area of the largest conduit or, larger than the raceway. In which case you would use reducing fittings installed inside the conduit body.

You will be applying Chapter 9 and Table 5 and Table 314.16 (B) (1).Conductors allowed in a conduit body and conductors allowed in a raceway when determing square inch per wire size and a table from Chapter 9 for various raceways.
Click to expand...
Aren't you glad Don pointed you to 314.28?
 
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