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jaxbldginspector
02-13-2009, 05:54 PM
Romex 10/2 w/g
Romex 10/3 w/g
Romex 12/2 w/g
Romex 12/3 w/g

jar546
02-13-2009, 07:40 PM
Time to do some derating calculations.

Speedy Petey
02-14-2009, 04:01 AM
Time to do some derating calculations.
Not if they remove that tape. ;)


WTH is all that #10 for???

codeone
02-14-2009, 05:03 PM
Not if they remove that tape. ;)


WTH is all that #10 for???

Check out the 2008 NEC. Removing the tape doesnt matter. Its still considered bundling, you need to derate!

Scuba_Dave
02-14-2009, 05:12 PM
So that's where my flux capicitor went

Speedy Petey
02-14-2009, 05:32 PM
Its still considered bundling,
How do you figure? What would you consider "maintaining spacing"?

codeone
02-14-2009, 06:18 PM
How do you figure? What would you consider "maintaining spacing"?

May be bundling in the sense you are used to is not the correct term I should use. However it would have to be derated per 2008. I personally would still say it is bundled for derating purposes there is no spacing between those conductors and would not pass the job. See below note last two paragraphs.

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 60C (140F)
conductor temperature rating. The 90C (194F) rating
shall be permitted to be used for ampacity derating purposes,
provided the final derated ampacity does not exceed
that for a 60C (1400 P) 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) 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)

Speedy Petey
02-14-2009, 06:24 PM
See below note last two paragraphs.

These cables are neither:

"through the same
opening in wood framing that is to be fire- or draft-stopped
using thermal insulation, caulk, or sealing foam,"

Nor are they:

"installed in contact with thermal
insulation".

So the last two paragraphs do not apply.

If they were, or are to be, then the last two paragraphs apply.

codeone
02-14-2009, 06:28 PM
These cables are neither:

"through the same
opening in wood framing that is to be fire- or draft-stopped
using thermal insulation, caulk, or sealing foam,"

If they were, or are to be, then the last two paragraphs apply.

These cables are going through the draft stopping band of the floor joist as per the building code.
Requiring the holes to be sealed.

Speedy Petey
02-14-2009, 06:38 PM
Since when does a horizontal hole need to be firestopped?

codeone
02-14-2009, 07:06 PM
R502.12 Draftstopping required. When there is usable space
both above and be low the concealed space of a floor/ceiling as -
sembly, draftstops shall be in stalled so that the area of the con
-cealed space does not exceed 1,000 square feet (92.9 m2).
Draftstopping shall divide the concealed space into approxi -
mately equal areas. Where the assembly is enclosed by a floor
membrane above and a ceiling membrane below draftstopping
shall be provided in floor/ceiling assemblies under the fol low -
ing circumstances:
1. Ceiling is suspended under the floor framing.
2. Floor framing is constructed of truss-type open-web or
perforated members.

R502.12.1 Materials. Draftstopping materials shall not be less
than 1/2-inch (12.7 mm) gypsum board, 3/8-inch (9.5 mm) wood
structural panels, 3/8-inch (9.5 mm) Type 2-M-W particleboard
or other approved materials adequately supported.
Draftstopping shall be in stalled parallel to the floor framing
members unless other wise approved by the building of ficial.
The integrity of all draftstops shall be maintained

R502.13 Fireblocking required. Fireblocking shall be pro -
vided in wood-frame floor construction and floor-ceiling as -
semblies in accordance with Section R602.8.

R602.8 Fireblocking re quired. Fireblocking shall be pro -
vided to cut off all concealed draft openings (both vertical and
horizontal) and to form an effective fire barrier between sto -
ries, and between a top story and the roof space. Fireblocking
shall be provided in wood-frame construction in the following
locations.
1. In concealed spaces of stud walls and partitions, includ -
ing furred spaces and parallel rows of studs or staggered
studs; as follows:
1.1. Vertically at the ceiling and floor levels.
1.2. Horizontally at intervals not exceeding 10 feet
(3048 mm).
2. At all interconnections between concealed vertical and
horizontal spaces such as occur at soffits, drop ceilings
and cove ceilings.
3. In concealed spaces be tween stair stringers at the top and
bot tom of the run. En closed spaces under stairs shall
com ply with Section R311.2.2.
4. At openings around vents, pipes, and ducts at ceiling and
floor level, with an approved material to resist the free
pas sage of flame and products of combustion.
5. For the fireblocking of chimneys and fire places, see Sec -
tion R1001.16.
6. Fireblocking of cornices of a two-family dwelling is re -
quired at the line of dwelling unit separation.

codeone
02-14-2009, 07:09 PM
Please note these references are from the 2006 NC Residential Building code based on the 2002 ICC Residential Codes.

codeone
02-14-2009, 07:37 PM
Also if this is a basement thats not going to be finished at this time without a heating system it could be required to be insulated. Then you would have to derate for the thermal insulation also. Another possibility is insulating for sound control also would need to be derated.

codeone
02-14-2009, 07:45 PM
According to 310.15(B)(2)(a) more than 41 current carrying conductors have to be derated by 35% Which means you could not even put a 15A breaker on those #10's. in the first picture on the left if I counted correctly. Hard to see actually how many conductors are there.

TedL
02-15-2009, 06:40 PM
According to 310.15(B)(2)(a) more than 41 current carrying conductors have to be derated by 35% Which means you could not even put a 15A breaker on those #10's. in the first picture on the left if I counted correctly. Hard to see actually how many conductors are there.

Sounds like some bad math.#10 would be 30 amp without derating. 30x.65=19.5 amps, which would allow a 20 amp breaker.

Speedy Petey
02-15-2009, 08:06 PM
You do not derate from the 30A figure. You use the actual temperature rating of the wire, which is the 90 deg C column for new THHN conductor NM cable.

#10 NM cable is derated from 40 amps. And you do not derate by 35%. You derate TO 35%.
Even at a 35% adjustment you CAN use a 15A breaker since we round UP to the nearest standard breaker size.
40 x 35% = 14A = 15A breaker

jwelectric
02-15-2009, 08:09 PM
Sounds like some bad math.#10 would be 30 amp without derating. 30x.65=19.5 amps, which would allow a 20 amp breaker.


It is 35% not 65%

codeone
02-16-2009, 04:21 AM
15A breaker since we round UP to the nearest standard breaker size.
40 x 35% = 14A = 15A breaker

Thanks Speedy Petey that rounding up rule is one I forget once in a while.:o

Still the caculation does come out to less than 15A. I still say the wiring routes taken are very bad practice.

TedL
02-16-2009, 05:32 AM
According to 310.15(B)(2)(a) more than 41 current carrying conductors have to be derated by 35% Which means you could not even put a 15A breaker on those #10's. in the first picture on the left if I counted correctly. Hard to see actually how many conductors are there.

I didn't dig out my copy of the code, but took Codeone's statement "by 35%" at face value. I just did the math check.

I did remember the "next larger standard overcurrent device"
:D.

codeone
02-16-2009, 06:43 AM
Just for debate we need to look at Article 334.80 of the NEC . Looks like it rules out the next highest breaker with two words.

334.80 Ampadty. 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 60C (140F)
conductor temperature rating. The 90C (194F) rating
SHALL be permitted to be used for ampacity derating purposes,
PROVIDED the final derated ampacity does not exceed
that for a 60C (1400 P) rated conductor. The ampacity of
Types NM, NMC, and NMS cable installed in cable tray
shall be determined in accordance with 392.11


Now I'm not saying some AHJ's dont allow this, however it is something to consider. It may be just bad wording to give the intent. That happens sometimes.

hj
02-16-2009, 07:03 AM
There is a BIG difference between derating BY 35% and derating TO 35%, and it appears most of the "mathemeticians" here are derating TO 35%. I might not want them retagging sale merchandise if it is supposed to be 35% OFF the original price, and they tag it as 35% OF the original price.

codeone
02-16-2009, 08:56 AM
English can be hard to follow sometimes.

Heres the derating chart.


Table 310.15(B)(2)(a) Adjustment Factors for More Than
Three Current-Carrying Conductors in a Raceway or Cable
--------------------------------------------------------

Percent of Values in Table
310.16 through 310.19 as
Adjusted for Ambient
Temperature if Necessary

---------------------------------------------------------
4-6 = 80
7-9 = 70
10-20 = 50
21-30 = 45
31-40 = 40
41 and above = 35

TedL
02-16-2009, 10:56 AM
Well, 240.4 would seem to allow it (rounding up to the next larger standard overcurrent device), but I'm working from the 2002 NFPA pocket guide for residential installations.

jwelectric
02-16-2009, 11:09 AM
Notice the title of the table Codeone posted.

"Percent of Values in Tables 310.16 through 310.19 as Adjusted"

It requires the conductors to be reduced to a maximum value OF the percentages found in Tables 310.16 through 310.19

The text of 310.15(A)(2) makes the statement that the lowest ampacity from a calculation is the ampacity of that entire conductor. There is also an exception to this rule if the distance is no more than 10 feet or 10% of the entire run.

We must also look at 334.80 for guidance when installing Non-metallic Cable.
In the last sentence of the second paragraph it clearly states that the exception to 310.15(A)(2) does not apply


41 or more current carrying conductors of 12 American Wire Gauge would have a maximum ampacity of 10.5 amps.

Now without a doubt there are a lot of folks out there that will start screaming about 240.4(B) where an allowance is made to allow the next higher overcurrent device protect a conductor as long as the overcurrent device does not exceed 800 amps.

What these folks forget to do is read the entire section. There are three requirements that this conductor must adhere to in order to be allowed to go to the next higher overcurrent device.
The one which catches my eye and holds my attention is 240.4(B) (1) The conductors being protected are not part of a multioutlet branch circuit supplying receptacles for cord-and-plug-connected portable loads.

So if these #12 are supplying receptacles then There is no conductor in either of these pictures on either thread that can supply receptacles anywhere in that building.

Speedy Petey
02-16-2009, 11:57 AM
The one which catches my eye and holds my attention is 240.4(B) (1) The conductors being protected are not part of a multioutlet branch circuit supplying receptacles for cord-and-plug-connected portable loads.Yup, you are right. I for one was just speaking from memory. I didn't go re-read the section.
To be honest I have never had to apply it in this way so it never occurred to me.

BTW- I was not screaming. :p

Speedy Petey
02-16-2009, 11:59 AM
Just for debate we need to look at Article 334.80 of the NEC . Looks like it rules out the next highest breaker with two words.

334.80 Ampadty. 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 60C (140F)
conductor temperature rating. The 90C (194F) rating
SHALL be permitted to be used for ampacity derating purposes,
PROVIDED the final derated ampacity does not exceed
that for a 60C (1400 P) rated conductor. The ampacity of
Types NM, NMC, and NMS cable installed in cable tray
shall be determined in accordance with 392.11


Now I'm not saying some AHJ's dont allow this, however it is something to consider. It may be just bad wording to give the intent. That happens sometimes.

I have to say, I completely disagree with this interpretation. I don't feel this has any bearing on the situation. The final outcome is LESS that the 60 deg C column, not exceeding it.


Bottom line is JW is right. If these circuits are for receptacle circuits then 240.4(B)(1) rules it out, nothing else.

codeone
02-16-2009, 01:15 PM
I have to say, I completely disagree with this interpretation. I don't feel this has any bearing on the situation. The final outcome is LESS that the 60 deg C column, not exceeding it..

Lets say I have 9 #12's That would be 35A x 70% = 24.5A If by your deff. this exceeds the 60 deg C column.

Now lets say I have 10 #12'S That would be 35A x 50% = 17.5A So this doesnt exceed the 60 deg C column. So can I go to a 20A breaker?

Now lets say I have 41 #12'S That would be 35A x 35% = 12.5A So can I go to a 15A or 20A breaker.

Or in these cases derating is to know weather you need to go to the next bigger wire size to carry the ampacity of your circuit to keep from overheating.

In the case of the #10'S you would still have overheating. And need to go to a #8.
Also exceeding means it will not have the ampacity needed.

Yes JW' s answer seals the case.

jwelectric
02-17-2009, 03:33 AM
Well it doesn't much matter as it all has to come out and be replaced. It should be replaced with MC cable which should have been used in the first place

codeone
02-17-2009, 04:46 AM
Ah yes! Would be the better choice of materials. Derating not as much of a problem. Safer for the public!