Bundling Romex

Status
Not open for further replies.

ERS1129

Member
Location
South Florida
What are the rules as far as bundling Romex i.e How do i figure out how much to derate? This was actually explained to me by an inspector a few years ago when I stated in the trade but time has passed and at the time I had no idea what he was saying anyways.
- Do i use the same table that explains adjustment factors for more then 3 current carrying conductors on a raceway or how do I do this?

-Thanks alot.
 

mcclary's electrical

Senior Member
Location
VA
What are the rules as far as bundling Romex i.e How do i figure out how much to derate? This was actually explained to me by an inspector a few years ago when I stated in the trade but time has passed and at the time I had no idea what he was saying anyways.
- Do i use the same table that explains adjustment factors for more then 3 current carrying conductors on a raceway or how do I do this?

-Thanks alot.



Welcome to the forum, yes you use the same table 310.15 b 2 a,,,,,and bundling occurs when you run the cables together, without maintaining air space (whatever that may be) for 24" or more. Total up your CCC's and consult chart. And keep in mind the same chart applies when cables of NM are passing through bored holes that get fire or draftstopped
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Here is some reading for you

334.80 Ampacity.
The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating. The 90?C (194?F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60?C (140?F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.
Where more than two NM cables containing two or more current-carrying conductors are installed, without maintaining spacing between the cables, through the same opening in wood framing that is to be fire- or draft-stopped using thermal insulation, caulk, or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a) and the provisions of 310.15(A)(2), Exception, shall not apply.
Where more than two NM cables containing two or more current-carrying conductors are installed in contact with thermal insulation without maintaining spacing between cables, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Also don't forget 310.15(A)(2)Exception. There are situations where derating might not apply even if the cables are bundled for more than 24".
 

A/A Fuel GTX

Senior Member
Location
WI & AZ
Occupation
Electrician
and bundling occurs when you run the cables together, without maintaining air space (whatever that may be) for 24" or more

OK........I have a dwelling with 2 X 10's as floor joists. I bore 2 1/2" holes through the joists for the length of the dwelling and place my homeruns through these holes. There may be 10 to 15 homeruns passing through some of these holes. They are not fire blocked. The joists are 2' on center. Is this bundling?
 

mcclary's electrical

Senior Member
Location
VA
OK........I have a dwelling with 2 X 10's as floor joists. I bore 2 1/2" holes through the joists for the length of the dwelling and place my homeruns through these holes. There may be 10 to 15 homeruns passing through some of these holes. They are not fire blocked. The joists are 2' on center. Is this bundling?



Believe it or not, as ugly as it would be, technically an inspector could make you put stackers in between each joist to maintain air space, then back through the bored hole bundled again. Although, I've never had an inspector try it. I've never ran all Hr's through one hole either
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
OK........I have a dwelling with 2 X 10's as floor joists. I bore 2 1/2" holes through the joists for the length of the dwelling and place my homeruns through these holes. There may be 10 to 15 homeruns passing through some of these holes. They are not fire blocked. The joists are 2' on center. Is this bundling?

Unless you do something to seperate them between joists then yes it is bundling. Would been better to have 1 inch holes with maybe 3 per hole. That depends on wire size and what you have after derateing.

Also might be issue with frameing inspector depending on where you place the holes.
 

A/A Fuel GTX

Senior Member
Location
WI & AZ
Occupation
Electrician
Unless you do something to seperate them between joists then yes it is bundling. Would been better to have 1 inch holes with maybe 3 per hole.

Man, that's a lot of holes. FWIW, I see the installation I described done all the time. IMHO, there is enough separation of the conductors between the joists to not cause any issues. The ceiling is not insulated so there is plenty of open space to dissipate any heat build up, which in a dwelling is highly unlikely.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
OK........I have a dwelling with 2 X 10's as floor joists. I bore 2 1/2" holes through the joists for the length of the dwelling and place my homeruns through these holes. There may be 10 to 15 homeruns passing through some of these holes. They are not fire blocked. The joists are 2' on center. Is this bundling?

I also believe it to be bundling but many people don't. 20 years ago I ran about 20 wires in the corner of an attic. I stapled one wire all the way then tie wrapped the rest to it every 4 feet or so. The inspector said it was bundling. When I asked about the install you just mentioned (2"hole with wires) he said it was okay-- I said it's no different--he looked at me puzzled and said- your right but we never turned that down.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
Man, that's a lot of holes. FWIW, I see the installation I described done all the time. IMHO, there is enough separation of the conductors between the joists to not cause any issues. The ceiling is not insulated so there is plenty of open space to dissipate any heat build up, which in a dwelling is highly unlikely.

We can't ignore codes based on how many holes it might take. The fact that inspectors in your area don't enforce all the codes changes nothing. First time you get a new inspector that pushes it you will be crying.
15 wires ran for several feet all going threw the same hole will be touching each other and you know it.

25 years ago we bundled without even thinking twice. As far as i know there were no fires caused from it. Will assume there were some or the rules would not been made.

I totally agree that under normal residential conditions the wires will not get hot enough to care. Code is code and matters not if we agree.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
OK........I have a dwelling with 2 X 10's as floor joists. I bore 2 1/2" holes through the joists for the length of the dwelling and place my homeruns through these holes. There may be 10 to 15 homeruns passing through some of these holes. They are not fire blocked. The joists are 2' on center. Is this bundling?


If the cables are just hanging freely between the joists then IMO they are not bundled. Tie them together and you have a bundle.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
If the cables are just hanging freely between the joists then IMO they are not bundled. Tie them together and you have a bundle.

This is what makes NEC so much fun. They used many words to try and make a rule and it is clear as mud. I can't prove you wrong or right. It is your opinion and if your inspectors share it your fine. Inspectors here will call it bundling. Perhaps we need another pole. What is important is the inspectors opinion as this being gray area it will be his call. Maybe it passes better with a 50 in the panel (just kidding) LOL
 

A/A Fuel GTX

Senior Member
Location
WI & AZ
Occupation
Electrician
If the cables are just hanging freely between the joists then IMO they are not bundled. Tie them together and you have a bundle.

Agree 100%........IMHO, drilling a bunch of extra holes in floor joists is much more degrading to structural integrity than perceived heat generated from MN-B that is installed perpendicular to the aforementioned joists is to the integrity of the insulation.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Agree 100%........IMHO, drilling a bunch of extra holes in floor joists is much more degrading to structural integrity.
If you are away from point supports and point loads (compression zones), then a series of small holes at midheight will be less degrading to structural integrity than a single large hole.

Cheers, Wayne
 
Status
Not open for further replies.
Top