Working as a plans examiner for a large municipality in the Phoenix metro area, what would be the correct approach to determine the most accurate correction factor for (2002 NEC) Table 310.16 to use for outside exposure? Also, in addition to roof or exterior wall locations, when would this correction factor be applied, in attics, direct burial applications, or...???
Correction factor for outside exposures
- Thread starter bgoble
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Correction factor for outside exposures
The Correction Factors are based on ambient temperatures. However, the NEC does not define or explain what is meant by ?ambient.? There have been some interesting discussions, and disagreements, amongst members of this Forum, regarding the meaning of ?ambient.?
The simple answer is that ?ambient temperature? is the temperature of the surrounding area. But that leaves open the question, ?Does this mean the highest temperature seen by the surrounding area at any time throughout the year, or does it mean the year-round average, or does it mean the median (i.e., halfway between highest and lowest), or is there some other and better way to determine the ?ambient temperature?? Is this, in fact, the same question that you are now asking? If so, you will get several different answers.
That is up to the local authority.
The Correction Factors are based on ambient temperatures. However, the NEC does not define or explain what is meant by ?ambient.? There have been some interesting discussions, and disagreements, amongst members of this Forum, regarding the meaning of ?ambient.?
The simple answer is that ?ambient temperature? is the temperature of the surrounding area. But that leaves open the question, ?Does this mean the highest temperature seen by the surrounding area at any time throughout the year, or does it mean the year-round average, or does it mean the median (i.e., halfway between highest and lowest), or is there some other and better way to determine the ?ambient temperature?? Is this, in fact, the same question that you are now asking? If so, you will get several different answers.
charlie
Senior Member
- Location
- Indianapolis
Re: Correction factor for outside exposures
A proposal was made for the 2005 Code but it didn't pass muster. The proposal was to require a 30 degree increase in ambient for outside runs of conduit because of exposure to the sun. Test data was submitted but it was from just one area of the country and was considered flawed because of the way it was done. Without looking anything up, I think a task group was formed to look into it further for the next Code cycle.
A proposal was made for the 2005 Code but it didn't pass muster. The proposal was to require a 30 degree increase in ambient for outside runs of conduit because of exposure to the sun. Test data was submitted but it was from just one area of the country and was considered flawed because of the way it was done. Without looking anything up, I think a task group was formed to look into it further for the next Code cycle.
- Location
- Illinois
- Occupation
- retired electrician
Re: Correction factor for outside exposures
Charlie,
That information did make it into the 2005 code as FPN #2 to 310.10.
Don
Charlie,
That information did make it into the 2005 code as FPN #2 to 310.10.
Don
charlie
Senior Member
- Location
- Indianapolis
Re: Correction factor for outside exposures
UH OH
Well . . . OK . . . but it didn't make it into mandatory language.
I think they are looking into it further. I suspect it will make it into mandatory language in the 2008 edition.
UH OH
Well . . . OK . . . but it didn't make it into mandatory language. I think they are looking into it further. I suspect it will make it into mandatory language in the 2008 edition.
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