Box fill calculation

[Brian Baker]

If you run size 10 wire on a 20 amp recepticle circuit from the main panel to avoid voltage drop on a long run and go in the first box with 10 and leave with 10 but pigtail to the recepticle device with 12 wire is the device value 4.5 or 5 when calculating box fill since only12 is connected to device?This is a theoretical question but would apply to other senarios where the wire may be larger like 8 or 6.

 

[Dennis Alwon]

I think the problem may be whether you can pigtail the device with a #12. Technically you should be able to but I am not certain that is compliant. In either case, I think you need to use 5 as your calculation for the device

 

[infinity]

The pigtail size is irrelevant for box fill since conductors that do not leave the box do not count.

314.16(B)(1) Conductor Fill. Each conductor that originates outsidethe box and terminates or is spliced within the box shall becounted once, and each conductor that passes through thebox without splice or termination shall be counted once.Each loop or coil of unbroken conductor not less than twicethe minimum length required for free conductors in 300.14shall be counted twice. The conductor fill shall be calculatedusing Table 314.16(B). A conductor, no part of whichleaves the box, shall not be counted.

 

[JFletcher]

Welcome to the forum. There is no issue using #12 pigtails to the receptacle if its on a 20A breaker. As far as fill, I'd have to look at the letter of the code to see if the device would be counted 4.5 or 5.

 

[infinity]

Welcome to the forum. There is no issue using #12 pigtails to the receptacle if its on a 20A breaker. As far as fill, I'd have to look at the letter of the code to see if the device would be counted 4.5 or 5.

You might be on to something I believe that the wording says connected to the device.

 

[Dennis Alwon]

Welcome to the forum. There is no issue using #12 pigtails to the receptacle if its on a 20A breaker. As far as fill, I'd have to look at the letter of the code to see if the device would be counted 4.5 or 5.

I agree, I thought he was just pigtailing the equipment grounding conductor with #12.

The code does state the device counts is figured based on the size of the wire attached to the device.

 

[Brian Baker]

I am aware what the code states about pigtails. However as has been pointed out it states connected to device so I feel I have a valid question and hoped someone with a greater code knowlege could answer. Thanks to all who contribute.Also it would be a 15 or 20 amp rec as code pemits on a 20 amp circuit.

 

[Dennis Alwon]

I am aware what the code states about pigtails. However as has been pointed out it states connected to device so I feel I have a valid question and hoped someone with a greater code knowlege could answer. Thanks to all who contribute.Also it would be a 15 or 20 amp rec as code pemits on a 20 amp circuit.

Your question is valid and by the letter of the code you are correct to use 4.5. We are not sure what the intent may be but that should not change your answer.

 

[Brian Baker]

If voltage drop required a larger conductor like 8 or 6 this may impact box size at some point.

 

[Dennis Alwon]

If voltage drop required a larger conductor like 8 or 6 this may impact box size at some point.

You still have to count the #10's for box fill you just use the #12 for the device. Same would be true for #8 or #6

 

[Brian Baker]

You still have to count the #10's for box fill you just use the #12 for the device. Same would be true for #8 or #6

I agree but if the box has two recepticles the values for them with 6 wire would be 20 in³ vs 9 in³ if you could use 12 value. Your clamp value and ground value would be 5 in³ each as well as 5 in³ each for the hots and neutrals it adds up quick and this could affect box size in a tight spot. I like knowing the right way to calculate these things because we all have had situations where we could have saved time and money had we known that one what seemed like a small thing beforehand.

 

[JFletcher]

I agree, I thought he was just pigtailing the equipment grounding conductor with #12.

The code does state the device counts is figured based on the size of the wire attached to the device.

:thumbsup: