conduit exposed to sunlight

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bwyllie

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Do the adjustments in Table 310.15(B)(2) apply to just the protion of the feeder that is exposed on the roof or the entire feeder length? For example, if I am installed a feeder from the basement to the roof top unit, does the entire feeder from the basement to roof top unit get derated or just the portion where I penetrate the roof and run the conduit exposed on the roof?
 
The rule applies to conduit, such as RMC. It does not apply to EMT. EMT is not conduit, but both RMC and EMT are raceways. The rule should apply to the conductors, and this may be fixed in the 11 NEC.

The 10% circuit ampacity rule can be used, so keep your exposed conduit less than ten feet or 10% of the total length.
 
tom baker said:
The rule applies to conduit, such as RMC. It does not apply to EMT. EMT is not conduit, but both RMC and EMT are raceways. The rule should apply to the conductors, and this may be fixed in the 11 NEC.

The 10% circuit ampacity rule can be used, so keep your exposed conduit less than ten feet or 10% of the total length.
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I agree, the rule should apply to conductors and not conduits (or raceways). If it applied to conductors it would cover all wiring methods and not just conduits.
 
kwired said:
I agree, the rule should apply to conductors and not conduits (or raceways). If it applied to conductors it would cover all wiring methods and not just conduits.
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I don't think the rule should apply to either until they show some proof that it has caused a safety or fire hazard to run conduits (raceways) on roofs and put electrical wiring into them. A lot of the stuff that gets changed gets so because somebody wants to get his name on a code change. That roof method has been in use since they started writing code books. How many you seen that up and caught fire cause the sun was shining on them? Or got moldy and blew up the raceway cause it rained and a drop of water got into the old compression connector? What this trade needs is a lot more regulatin.... lots and lots more. :mad: ;) :D
 
macmikeman said:
I don't think the rule should apply to either until they show some proof that it has caused a safety or fire hazard to run conduits (raceways) on roofs and put electrical wiring into them. A lot of the stuff that gets changed gets so because somebody wants to get his name on a code change. That roof method has been in use since they started writing code books. How many you seen that up and caught fire cause the sun was shining on them? Or got moldy and blew up the raceway cause it rained and a drop of water got into the old compression connector? What this trade needs is a lot more regulatin.... lots and lots more. :mad: ;) :D
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Did we have a bad day at work today??:)
 
macmikeman said:
I don't think the rule should apply to either until they show some proof that it has caused a safety or fire hazard to run conduits (raceways) on roofs and put electrical wiring into them. A lot of the stuff that gets changed gets so because somebody wants to get his name on a code change. That roof method has been in use since they started writing code books. How many you seen that up and caught fire cause the sun was shining on them? Or got moldy and blew up the raceway cause it rained and a drop of water got into the old compression connector? What this trade needs is a lot more regulatin.... lots and lots more. :mad: ;) :D
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A study was done by the International Association of Electrical inspectors in Las Vegas....the results were in the IAEI journal, leading to the FPN for the 05 NEC and the change in the 08. What I suggest is insead of complaining after the fact, that you get involved with the code process and review/comment on the code changes. I have had several code changes, not to get my name on them, but to improve the code.
 
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macmikeman said:
I don't think the rule should apply to either until they show some proof that it has caused a safety or fire hazard to run conduits (raceways) on roofs and put electrical wiring into them. A lot of the stuff that gets changed gets so because somebody wants to get his name on a code change. That roof method has been in use since they started writing code books. How many you seen that up and caught fire cause the sun was shining on them? Or got moldy and blew up the raceway cause it rained and a drop of water got into the old compression connector? What this trade needs is a lot more regulatin.... lots and lots more. :mad: ;) :D
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You are correct. No rule should apply unless such rule is derived from, including but not limited to the following:
  1. Empirical experience,
  2. Supported by physical - not anecdotal - evidence,
  3. Based on calculations.
I am happy to report that your wishes were granted by the Genie. All conditions of the rule are met.......:grin:
 
tom baker said:
The rule applies to conduit, such as RMC. It does not apply to EMT. EMT is not conduit, but both RMC and EMT are raceways. The rule should apply to the conductors, and this may be fixed in the 11 NEC.

The 10% circuit ampacity rule can be used, so keep your exposed conduit less than ten feet or 10% of the total length.
Click to expand...

Is there a definition for conduit in the NEC? If not, are we not supposed to use conventional definitions [i.e. dictionary] for terms.

The definition for conduit is: A tube or duct for enclosing electric wires or cable....at least in the dictionary I looked in.
 
Gentlemen, not studies, give me the actual data. How many fires. Where and When. By the way Tom, that study done is pretty damn convincing. Good science. But Al Gore quotes well done scientific studies all the time and yet the ocean in front of my house did not rise 10 feet over the last 20 years, I know cause I been here waiting..... :cool:

And thank you for helping to write the code book. You guys have gotten it darn near perfect lately. ;)
 
dana1028 said:
Is there a definition for conduit in the NEC? If not, are we not supposed to use conventional definitions [i.e. dictionary] for terms.

The definition for conduit is: A tube or duct for enclosing electric wires or cable....at least in the dictionary I looked in.
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The NEC typically uses the word 'conduit' as part of a name like 'rigid metal conduit', or 'flexible metal conduit', and not as a general term. There is no definition for 'conduit' in article 100.

The use of the word 'conduit' in 310.15(B)(2)(c) may have been a mistake, it would be more of the NEC style to use the word 'raceway' in this instance. I would like to think if there were a cable installed instead of a raceway that it would be subject to the same temperature and therefore conductors from any wiring method should be included in 310.15(B)(2)(c).
 
iwire said:
So even if we have all found crunchy, brittle conductors on roofs unless there was a fire all was OK.

Got it. :roll::grin:
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You could be right about crunchy brittle conductors on roofs, but I don't remember seeing any myself, at least of late. However take note- Hawaii has the lowest avarage summer temperatures according to the data presented in Toms link, so maybe its just you guys who witness real damage to wiring from running across roofs..... We even beat Anchorage.... by one degree. :grin:
 
kwired said:
The NEC typically uses the word 'conduit' as part of a name like 'rigid metal conduit', or 'flexible metal conduit', and not as a general term. There is no definition for 'conduit' in article 100.

The use of the word 'conduit' in 310.15(B)(2)(c) may have been a mistake, it would be more of the NEC style to use the word 'raceway' in this instance. I would like to think if there were a cable installed instead of a raceway that it would be subject to the same temperature and therefore conductors from any wiring method should be included in 310.15(B)(2)(c).
Click to expand...
I believe that the word conduit was used by the submitter of the proposal because the test was made with conduit and not with EMT or MC cable.
 
dana1028 said:
Is there a definition for conduit in the NEC? If not, are we not supposed to use conventional definitions [i.e. dictionary] for terms.

The definition for conduit is: A tube or duct for enclosing electric wires or cable....at least in the dictionary I looked in.
Click to expand...

don_resqcapt19 said:
I believe that the word conduit was used by the submitter of the proposal because the test was made with conduit and not with EMT or MC cable.
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And the responsible code panel is so intellegent that they figured that only conduit was subjected to the heat and nothing else is:confused:

I know that installers that have been on a roof when it is hot outside have figured out that they themselves are subject to heat as well as everything they touch.
 
kwired said:
The NEC typically uses the word 'conduit' as part of a name like 'rigid metal conduit', or 'flexible metal conduit', and not as a general term. There is no definition for 'conduit' in article 100.

The use of the word 'conduit' in 310.15(B)(2)(c) may have been a mistake, it would be more of the NEC style to use the word 'raceway' in this instance. I would like to think if there were a cable installed instead of a raceway that it would be subject to the same temperature and therefore conductors from any wiring method should be included in 310.15(B)(2)(c).
Click to expand...

Raceway.​
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An enclosed channel of metal or nonmetallic materials designed expressly for holding wires, cables, or busbars, with additional functions as permitted in this Code. Raceways include, but are not limited to, rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight flexible conduit, flexible metallic tubing, flexible metal conduit, electrical nonmetallic tubing, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways, and busways.

Perhaps the available data, based on the tests, was only for conduits, so extending it to all raceways would not have been supported by data. ​

 
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