table 310.15 (b) (2) (c)

[mistabass]

trying to understand table310.15(b)(2) doing service have to run on top of flat roof @300'

 

[infinity]

Ok so what's the question? That table pertains to the temperature adder for the conductors in a raceway on a roof based on the height above the roof.

 

[mistabass]

so if i'm running thwn-2 i add 40 degres to table310.16

 

[infinity]

so if i'm running thwn-2 i add 40 degres to table310.16

You need to first establish your height above the roof top that the conduit will be run. Since you mentioned 40 degrees are you above 1/2" and below 3 1/2"?

 

[chris kennedy]

so if i'm running thwn-2 i add 40 degres to table310.16

If the conduit is between ?in and 3?in above the roof. The 40? would be add to the design temperature of the install for the area in question. Rhode Island?

 

[mistabass]

yes 3" blocks

 

[chris kennedy]

yes 3" blocks

3 blocks from your house?

 

[iwire]

I am in MA and I figure 92 to 100 F ambient with a 40 F adder which puts me at the 132F to 140F correction factor line of 310.16.

 

[infinity]

If the conduit is between ?in and 3?in above the roof. The 40? would be add to the design temperature of the install for the area in question. Rhode Island?

That is correct. The 2005 ASHRAE handbook will tell you the design temperature. Take that number and add 40 degrees F. Look up the ampacity in 310.16 with the correction factor at the bottom of the table.

 

[mistabass]

massachusetts