Not quite clear on calculating box fill rules. I only have a condensed code book so I cannot reference the actual code sections. According to my book it says that each 14 ga. conductor counts a 2 volumes, so it would seem that a single 14/2 counts as 6. There is also a section that defines volumes. In this section it says "1 Volume...for any number of equipment grounding conductors, basing the volume on the largest equipment grounding conductor in the box." Does this mean that a 14/2 actually counts a 5 ci or do I add another ci for a total of 7.
Box fill question
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jimwalker
Senior Member
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- TAMPA FLORIDA
Re: Box fill question
14 awg = 2 cu inches
12-2 =2.25
device on 14-2=4 cubes
device on 12-2=4.5
count each wire entering box
say you have 1 14-2 and recept= 10 cubes
2 14-2 =14 cubes
3 14-2=18
grounds no matter how many only get counted once
and pigtails and nuts don't count.
This is a stupid rule in that a gfci receptacle is the same cubes as a 48 cent switch
But thats the rules
hope it helped
Assume your at mechanic level,do your self a favor and buy a NEC book ,about $40 bucks ,it is one tool you must have
[ January 11, 2004, 12:52 PM: Message edited by: jimwalker ]
14 awg = 2 cu inches
12-2 =2.25
device on 14-2=4 cubes
device on 12-2=4.5
count each wire entering box
say you have 1 14-2 and recept= 10 cubes
2 14-2 =14 cubes
3 14-2=18
grounds no matter how many only get counted once
and pigtails and nuts don't count.
This is a stupid rule in that a gfci receptacle is the same cubes as a 48 cent switch
But thats the rules
hope it helped
Assume your at mechanic level,do your self a favor and buy a NEC book ,about $40 bucks ,it is one tool you must have
[ January 11, 2004, 12:52 PM: Message edited by: jimwalker ]
- Location
- Massachusetts
Re: Box fill question
1 14/2 NM needs 6 cubic inches.
2 cubic inches for each conductor.
Now have 2 14/2 NMs in a box and you will need 10 cubic inches.
The hots and neutrals all get counted and the ground gets counted once.
Now you must add for an internal wire clamp based on the largest wire in the box
And a double volume allowance shall be made for each yoke or strap based on the largest conductor connected to a device(s) or equipment supported by that yoke or strap.
So in the end a box with 2 14/2 NMs internally clamped and a duplex outlet will need 16 cubic inches.
4 hots and neutrals = 8 cubic inches
"1" ground = 2 cubic inches
1 internal clamp = 2 cubic inches
1 Duplex outlet = 4 cubic inches
Total needed = 16 cubic inches
1 14/2 NM needs 6 cubic inches.
2 cubic inches for each conductor.
Now have 2 14/2 NMs in a box and you will need 10 cubic inches.
The hots and neutrals all get counted and the ground gets counted once.
Now you must add for an internal wire clamp based on the largest wire in the box
And a double volume allowance shall be made for each yoke or strap based on the largest conductor connected to a device(s) or equipment supported by that yoke or strap.
So in the end a box with 2 14/2 NMs internally clamped and a duplex outlet will need 16 cubic inches.
4 hots and neutrals = 8 cubic inches
"1" ground = 2 cubic inches
1 internal clamp = 2 cubic inches
1 Duplex outlet = 4 cubic inches
Total needed = 16 cubic inches
jimwalker
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Re: Box fill question
Bob save that clamp and use plastic
Not to confuse him but why do we change the devices cubes because of wire size?Did the #12 get the receptacle pregnant?
and we could put #14 pigtails on #12
Bob save that clamp and use plastic
Not to confuse him but why do we change the devices cubes because of wire size?Did the #12 get the receptacle pregnant?
and we could put #14 pigtails on #12
- Location
- Massachusetts
Re: Box fill question
means your kidding.
Yes I agree but when explaining the volume calcs it is good to know about counting internal clamps.
LOL No I do not think so, but the bending radius of the larger conductors change and we must have space for them.
Now you are scarring me again, I hope theOriginally posted by jimwalker:
we could put #14 pigtails on #12
means your kidding.jimwalker
Senior Member
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- TAMPA FLORIDA
Re: Box fill question
Would i do it NO WAY
Legal i believe so
Good idea NO
Should each item have a cube rating YES
Will that ever happen NO LIKELY
Would i do it NO WAY
Legal i believe so
Good idea NO
Should each item have a cube rating YES
Will that ever happen NO LIKELY
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Re: Box fill question
The not likely part I agree with you.
The only time you could use 14 AWG pigtails on an outlet connected to 12 AWG would be with a 15 amp breaker.
The not likely part I agree with you.
bill addiss
Senior Member
Re: Box fill question
Jim,
Please point out the Code section that says it would be OK to pigtail #14 to a #12 (assuming 20A circuit)
Bill
[ January 11, 2004, 01:35 PM: Message edited by: bill addiss ]
Jim,
Please point out the Code section that says it would be OK to pigtail #14 to a #12 (assuming 20A circuit)
Bill
[ January 11, 2004, 01:35 PM: Message edited by: bill addiss ]
jimwalker
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- TAMPA FLORIDA
Re: Box fill question
Will look for it.Was told its legal from bosses.That is where a lot of wrong information comes from.Gets hard sometimes to seperate sources,
NEC,others,local codes.
Never would i do that.
What my point was is they use a cube measurement on something that could be small as a single pole switch or as large as a gfci.Don't make since does it ?
Will look for it.Was told its legal from bosses.That is where a lot of wrong information comes from.Gets hard sometimes to seperate sources,
NEC,others,local codes.
Never would i do that.
What my point was is they use a cube measurement on something that could be small as a single pole switch or as large as a gfci.Don't make since does it ?
jimwalker
Senior Member
- Location
- TAMPA FLORIDA
Re: Box fill question
If it helps the plastic boxes usually have it printed inside
If it helps the plastic boxes usually have it printed inside
Re: Box fill question
Well now that you all have explained things, the book now makes sense. I was confused on statements such as this-
"2 Volumes... for each yoke or strap containing switches, receptacles, pilot lights, etc., basing the volume on largest wire size connected to a device on that yoke and then doubling it for two volumes." I now understand this to mean a switch or receptacle on 14awg=4cubes and using 12awg=4.5 cubes.
Another confusing point was this one -
"1 volume...for each wire originating outside the box and terminating or spliced within the box."
Still not sure about this one, does this mean to add another cube in addition to the per conductor volume requirements?
Also, if using lock nut style connector, does the lock nut count as clamp?
Well now that you all have explained things, the book now makes sense. I was confused on statements such as this-
"2 Volumes... for each yoke or strap containing switches, receptacles, pilot lights, etc., basing the volume on largest wire size connected to a device on that yoke and then doubling it for two volumes." I now understand this to mean a switch or receptacle on 14awg=4cubes and using 12awg=4.5 cubes.
Another confusing point was this one -
"1 volume...for each wire originating outside the box and terminating or spliced within the box."
Still not sure about this one, does this mean to add another cube in addition to the per conductor volume requirements?
Also, if using lock nut style connector, does the lock nut count as clamp?
Re: Box fill question
You have the wire to the devices correct.
Lets say you have two 14-2 nm cables coming into the device box that is going to have just a switch .........the 2 neutrals would be spliced and count as 2 conductors, the 2 hot being terminated to the switch count as 2 conductors also, the grounds connected with a pig tail or if you used a" greeny wire" nut would count as 1 conductor.
The external cable connector would not qualify as "conductor fill" like a internally mounted clamp would.
John
If I am understanding you correctly you are confused that you would add a extra conductor volume for a splice or terimation ???
That would not be correct.
[ January 11, 2004, 03:03 PM: Message edited by: drg ]
You have the wire to the devices correct.
Lets say you have two 14-2 nm cables coming into the device box that is going to have just a switch .........the 2 neutrals would be spliced and count as 2 conductors, the 2 hot being terminated to the switch count as 2 conductors also, the grounds connected with a pig tail or if you used a" greeny wire" nut would count as 1 conductor.
The external cable connector would not qualify as "conductor fill" like a internally mounted clamp would.
John
If I am understanding you correctly you are confused that you would add a extra conductor volume for a splice or terimation ???
That would not be correct.
[ January 11, 2004, 03:03 PM: Message edited by: drg ]
jim sutton
Senior Member
Re: Box fill question
this means each wire coming into the box such as the 2 14-2's discussed here. Wires that originate inside the box and do not leave the box ("pigtails") would not be counted
answer= no
this means each wire coming into the box such as the 2 14-2's discussed here. Wires that originate inside the box and do not leave the box ("pigtails") would not be counted
Re: Box fill question
I'm not wanting to throw coal on he fire because I never do it. I've always assumed that I could splice a #14 pigtail onto a 20A general use branch circuit to feed a 15A receptacle if it was all done within the box. If this is wrong, please explain 210.24
steve
I'm not wanting to throw coal on he fire because I never do it. I've always assumed that I could splice a #14 pigtail onto a 20A general use branch circuit to feed a 15A receptacle if it was all done within the box. If this is wrong, please explain 210.24
steve
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