Q. Bundling house wires?

[SCBO1]

Have you seen this before?

Garage with panel, house circuit wires run across the top of the ceiling and enter the main house structure, zip tied and taped. Is this a common practice? I have seen plumbing J-hooks used to cradle circuit runs before and seen the circuit the runs raying in a fur-down cover duct work in a garage ceiling.

Any code section that prohibits this?

 

[steveray]

Have you seen this before?

Garage with panel, house circuit wires run across the top of the ceiling and enter the main house structure, zip tied and taped. Is this a common practice? I have seen plumbing J-hooks used to cradle circuit runs before and seen the circuit the runs raying in a fur-down cover duct work in a garage ceiling.

Any code section that prohibits this?

View attachment 14086

Yes...Especially buried in insulation....Derating.....Do you use IRC or NEC? A lack of running board could be another issue....

 

[SCBO1]

We use the IRC and yes a running board should have been used IMO.

 

[BN4537]

It's based on E3705.3 in the IRC, 310.15(C) in the NEC.

Basically, you can have up to four white or yellow Romex cables bundled together before the derating (ampacity adjustment) kicks in. The bigger the conductors, the faster you will reach the point where your ampacity adjustment makes a difference. Without getting too precise, once you get above 10 gauge you are pretty much out of luck if you bundle them.

Being buried in insulation definitely makes it a lot worse.

 

[ICE]

Bundling and more than three conductors in a raceway are pretty much ignored in residential applications. I made it a practice to enforce the code on both and I was an outlier qt LA County DPW. I can say that I have never heard of a fire because of bundling or crowded raceways in residential.

Knowing that 85% of all construction here in SoCal is either not inspected or poorly inspected I leave you to draw your own conclusion.

 

[ICE]

Basically, you can have up to four white or yellow Romex cables bundled together before the derating (ampacity adjustment) kicks in.

Is that an IRC code? Could that be copied and pasted here?

 

[steveray]

E3705.3​

Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are stacked or bundled for distances greater than 24 inches (610 mm) without maintaining spacing and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table E3705.3. [310.15(C)(1)]

 

[steveray]

 

[SCBO1]

Looking at the bundle in the photo, would you say its pushing the 41 and above on the amount of conductors? There's 16 runs leaving the panel so a rough calculation would be 16 x 3 = 48 and I picked up a #8ga wire to add.

 

[steveray]

Looking at the bundle in the photo, would you say its pushing the 41 and above on the amount of conductors? There's 16 runs leaving the panel so a rough calculation would be 16 x 3 = 48 and I picked up a #8ga wire to add.

I don't think you count the EGC's there....So maybe 32....?

 

[BN4537]

Is that an IRC code? Could that be copied and pasted here?

It's not a code section, it's just the result of doing the calculations. Both 12 and 14 gauge wires can be reduced to 70 percent of their 90 degree C value without dropping below the value of the breaker they are installed on.

14 gauge wire is 25 amps at 90 degrees C, and 70% of 25 is 17.5 amps, so it's still ok on a 15 amp breaker. That means per the table that you can have between 7-9 conductors bundled and it is ok. If you go more than that, you have to go at a 50% ampacity and it won't work because 50% of 25 is 12.5, so you can't protect it on a 15 amp breaker.

That means that you can have four 14/2s and 14/3s together, because each cable only has two conductors. The ground wire doesn't count, and the neutral only counts if you aren't using the both hots at the same time. If you are using both hots at the same time, you probably aren't using the neutral for anything but the unbalanced load, so it doesn't count.

12 gauge wires are 30 amps at 90 degrees C, 70 percent of 30 is 21 amps which still works on a 20 amp breaker, 50% of 30 is 15 amps and will not work on a 20 amp breaker. Therefore, you can have 4 NM cables together of the 12/2 or a 12/3 persuasion.

 

[wwhitney]

14 gauge wire is 25 amps at 90 degrees C, and 70% of 25 is 17.5 amps, so it's still ok on a 15 amp breaker. That means per the table that you can have between 7-9 conductors bundled and it is ok. If you go more than that, you have to go at a 50% ampacity and it won't work because 50% of 25 is 12.5, so you can't protect it on a 15 amp breaker.

That last sentence is correct for a circuit that supplies more than one receptacle. But if it's some other circuit, say a lighting circuit, and the calculated load on the circuit is 12.5A or less, then it's fine to protect a 12.5A ampacity conductor at 15A per 240.4(B).

Cheers, Wayne