Where can I find a reference to average ambient air temperature for New Hampshire.
Table 310.15(B)(2)(c) Ambient Temperature Adjustment for Conduits Exposed to Sunlight On or Above Rooftops
Temperature Adder
Distance Above Roof to Bottom of Conduit ?C ?F
0 ? 13 mm (? in.) 33 60
Above 13 mm (? in.) ? 90 mm (3? in.) 22 40
Above 90 mm (3? in.) ? 300 mm (12 in.) 17 30
Above 300 mm (12 in.) ? 900 mm (36 in.) 14 25
FPN to Table 310.15(B)(2)(c): The temperature adders in Table 310.15(B)(2)(c) are based on the results of averaging the ambient temperatures.
(c) Conduits Exposed to Sunlight on Rooftops.Where conductors or cables are installed in conduits exposed to direct sunlight on or above rooftops, the adjustments shown in Table 310.15(B)(2)(c) shall be added to the outdoor temperature to determine the applicable ambient temperature for application of the correction factors in Table 310.16 and Table 310.18.
FPN: One source for the average ambient temperatures in various locations is the ASHRAE Handbook ? Fundamentals.
Here's the NEC FPN which sends you to the link that I posted:
3.5 ambient temperature: The temperature of the air or other
medium where the equipment is to be used. [IEV 826-01-04]
NOTE?Ambient air temperature as applied to an enclosure or
housing is the average temperature of the surrounding air that
comes in contact with the enclosure or housing. Ambient air
temperature as applied to a component or device within the
enclosure is the average temperature of the surrounding air that
comes in contact with the component.
Pierre I am missing your point
What ambient temps??? are they talking about......results of averaging the ambient temperatures.
....adjustments shown in Table 310.15(B)(2)(c) shall be added to the outdoor temperature ...
And the temperature at the time at which you install the cables is not the ambient temperature to correct cables too. It is the highest temperature the installation will see over a typical year.
I agree with your thoughts here and I think it is the prudent way to go, but there is nothing in the NEC that makes it that clear.
For what it's worth I am willing to bet your area has days hotter then 95F so you are not even following your own advice. :grin:
My personal feeling is you must use the highest temp the conductors will operate in..
Where can I find a reference to average ambient air temperature for New Hampshire. Need to calculate roof top conductors in GRC.
Need to apply 310.15 (B) factor
I disagree and think this is silly. Your basically saying you have to take the record high ever