operating temperature tables

[Wire-Smith]

Maybe need to search for ROP's back whenever this allowance was first introduced into code or for any times it has had changes to it to better understand why it is there. Yes they more recently removed the table that had been there for a long time and went to the 83% figure - but only thing that really did was made it more clear to applying adjustments like ambient temp or number of conductors in a raceway. without any adjustments you still run same size conductor you did using the old table.

What they have or more like how it applies it is not a demand factor. It also isn't an adjustment factor it is basically allowing us to use a different starting conductor ampacity in the situations described. How they come up with the 83% I don't know.

83% is 120% up-rating

120% is used in other areas of the code


i agree what they have is not a demand factor, but i think your interpretation is in line with a demand factor. (load diversification so we probably won't ever see that high of current)


again, thank you for your time and thoughts

 

[Wire-Smith]

i emailed nfpa library, i'll let you know if i find anything interesting.

 

[kwired]

83% is 120% up-rating

120% is used in other areas of the code


i agree what they have is not a demand factor, but i think your interpretation is in line with a demand factor. (load diversification so we probably won't ever see that high of current)


again, thank you for your time and thoughts

Actually 125% is one of the most popular "up-rating" used in the code, but I see what you are getting at. Again about only way to know why they have what they have is to see what is on ROP's when this was introduced or had changes made to it.

The fact that it is in 310 seems to suggest more focus was on conductor ampacity then on load calculation.

 

[Wire-Smith]

Actually 125% is one of the most popular "up-rating" used in the code, but I see what you are getting at. Again about only way to know why they have what they have is to see what is on ROP's when this was introduced or had changes made to it.

The fact that it is in 310 seems to suggest more focus was on conductor ampacity then on load calculation.

i agree with everything you say in this post, if i haven't been clear on that


that's why I've been saying the interpretation about load diversification would be in 220, to me there's no logic to up-rate wire because of load diversification, why not just add another demand factor in 220 instead?


i'll see what the library sends me and dig through it when i get time. i asked for 1998 (for 99' code)

2001 roc (i found online) doesn't discuss it much, i'm looking at 04' now

 

[roger]

it appears this was put in in 99' does that sound right to everyone? i'm going to try to find the panel discussions on it.

Well before that, it was in the 68 cycle (as far as I go back without going to the NFPA website) as a note to table 310-14 and in that length of time I haven't heard of mass fires attributed to the rule so I would say it's a safe bet that there are bigger fish to fry.

Roger

 

[Wire-Smith]

Well before that, it was in the 68 cycle (as far as I go back without going to the NFPA website) as a note to table 310-14 and in that length of time I haven't heard of mass fires attributed to the rule so I would say it's a safe bet that there are bigger fish to fry.

Roger

i agree i am knit picking here(i'm an electrician, it's kind of what a lot of us do), definitely bigger fish to fry, i was just asked about this lately so i wanted to ask about it. i'm not losing sleep over it. i'm not trying to sound an alarm, just trying to have a discussion and learn something.


thanks for the 68' reference, going back that far it would probably take a lot of digging to figure out the original intent


do you think i'm way off base telling people i respectfully disagree with there interpretation on this?


thanks,

 

[Wire-Smith]

NFPA70
a98ROC


6- 55 - (Article 310, Notes to Ampacity Tables of 0-2000Volts, .
Note 3). Reject

SUBMrITER: Dan Leaf, Palmdale, CA

COMMENT ON PROPOSAL NO: 6-77

RECOMMENDATION: Accept proposal.

SUBSTANTIATION: I agree with the pro[poser'ssubstantiation.

I would venture to say the majority of dwelling unitswith a

minimum 100-ampere service seldom approach the computed

load current much less the service conductor ampacity.

PANEL ACTION: Reject.

PANEL STATEMENT: The data developed for Note 3 was from

actual utility company data for 120/240V 33wire dwellingunitS. It

established that the conductors specified could be usedon a

calculated dwelling unit of the load shown. It does not

reestablish conductor ampacity. Byeliminating the 120/240V

requirement,the proposal adds additional heating to the $-wire

circuit becausethe common conductor now carries

approximatelythe same current as the other phases. In a

240Vapplication the third conductor carries only the

imbalance. Thesame issue is true for the expansion of the Note

to three-phaseapplications. The fact that an additional current

carryingconductor will be in the conduit or cable is not

contemplated bythe values or loading permitted presently by the

Note.

NUMBER OF PANEL MEMBERS ELIGIBLE TO VOTE:

11

VOTE ON PANEL

ACTION:

AFFIRMATIVE: 11

 

[Wire-Smith]

i'm still looking for more. i'm not saying that makes my point, i'm not convinced it does.