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#69070 - 08/26/06 12:36 PM Bundle Temperatures  
ehill  Offline
Member
Joined: Aug 2006
Posts: 27
Interesting report...
http://www.copper.org/applications/electrical/building/pdf/bundle_evaluation_report.pdf

I've been wondering about this recently.

Eric

[This message has been edited by ehill (edited 08-26-2006).]


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#69071 - 08/26/06 12:53 PM Re: Bundle Temperatures  
jwhite  Offline
Member
Joined: Dec 2005
Posts: 64
Trenton, NC, USA
Wow. I never knew that using a butt load of smaller holes, like do was actually a better wiring method. I always thought that I was just too cheep to buy a larger drill bit.


#69072 - 08/26/06 01:12 PM Re: Bundle Temperatures  
BigJohn  Offline
Member
Joined: Mar 2004
Posts: 391
Boston, MA
That's darn interesting. I have to admit, having never personally witnessed the adverse effects of bundling Romex, and having seen it ignored by almost every local "authority" in residential electrical construction, I was darn skeptical about what threat bunlding posed.

Obviously, the bundling does have a serious impact on heat generation.

However, I would have liked the study to address several things: What was the average temperature rise for a single cable carrying the same load as identical bundled cables?

And speaking from personal experience I can say that in a lot of resi. construction cables are regularly bundled for distances far in excess of 24". They may not be packed together in a hole and fire-stopped, so their is certainly more heat dissipation, but by how much? What happens when that same bundle is covered with ten inches of blow-in fiberglass?

I think I'll be a lot more cautious about how I route cables now after seeing this.

-John


#69073 - 08/26/06 02:00 PM Re: Bundle Temperatures  
ehill  Offline
Member
Joined: Aug 2006
Posts: 27
I question their test method, though... To have the bundle pass through the top plate, and then back down the top plate? That's not a "real-world" situation. (Maybe I'm missing something.)

Seems like with all they went through in their test scenario, they could have simulated the "real world" a little better.

Still, the report is interesting.

Eric


#69074 - 08/26/06 02:04 PM Re: Bundle Temperatures  
ehill  Offline
Member
Joined: Aug 2006
Posts: 27
You know, John, I think there's a lot of factors involved, too... I mean... South facing walls without shade in Las Vegas are going to get a lot hotter than a north facing wall in colder places of the county.

OT, a little, we sometimes balk at local code, but I think that's exactly why local codes should exist. Local needs might be complete overkill for other parts of the country.

Eric


#69075 - 08/26/06 02:13 PM Re: Bundle Temperatures  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
I am not as concerned by the routing of the cables in the test but the loading is IMO unrealistic in dwelling units.

Quote
in combination with 73% loading of all the cables


I find it extremely unlikely you would find a bundle of NMs (6) in a dwelling all loaded to 73% or any combination that averages out to 73% at the same time.

How would that happen in any modern dwelling construction?

Even the simultaneous 60% loading of six two wire circuits in a dwelling unit seems remote to me.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#69076 - 08/26/06 02:18 PM Re: Bundle Temperatures  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
Used to be that inspectors here required only one cable per hole, but in the last few years they realized that this turned the framing into swiss cheese, and now allow two only. (Allowing two 12/2/2's) In the guiese of not exceeding 9 current carrying, as you would in conduit, same for stacker and other bundles. Taking a large bundle of cables, like some would above a panel into a single connector isnt allowed for these same reasons.

That said, if I go a few cities over, where bundling is ignored, you can tell the difference. You really can feel the difference in warmth in the bundles. And on occassion see a slight discoloration of romex sheathes in stuff installed around ten years ago.


Mark Heller
"Well - I oughta....." -Jackie Gleason

#69077 - 08/26/06 02:32 PM Re: Bundle Temperatures  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
Quote
Even the simultaneous 60% loading of six two wire circuits in a dwelling unit seems remote to me.


Any building with base-board heat, or AC...


Mark Heller
"Well - I oughta....." -Jackie Gleason

#69078 - 08/26/06 03:23 PM Re: Bundle Temperatures  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Both of those examples are non-continuous loads.

If you had the six circuits all supplying electric heat circuits it would be unusual for all six circuits to have each of their zones all needing heat at the same time.

I take, as I am sure you do many current readings.

It is unusual for many circuits to be at 60% load in a dwelling unit.

Proof of this is the fact you may have 500 amps worth of breakers in a 200 amp panel.

Anything is possible but we regularly assume certain loading characteristics, most of Article 220 is based on assumptions.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#69079 - 08/26/06 03:25 PM Re: Bundle Temperatures  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
And besides all that.

It's the copper org bringing us the message, more copper less heat. [Linked Image]


Bob Badger
Construction & Maintenance Electrician
Massachusetts

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