Jay:
I use a spreadsheet I created for voltage drop calculations. I have
upgraded it periodically and recently added columns to indicate de-rated
ampacities due to temperature and conduit fill. This spreadsheet is
available at: http://mpandc.com/resources/resources.html
As a caveat, I don't use Excel as my native spreadsheet language, but I
port tools I want to make available to the public to Excel as it is a more
commonly used application. No guarantee is implied on the use of this tool
and I do appreciate any feedback.
William Miller
At 10:37 PM 1/13/2009, you wrote:
Hi Bill,
Who puts this into a spread sheet or computer program?
thanks,
jay
peltz power
On Jan 8, 2009, at 11:56 AM, Bill Brooks wrote:
Peter,
We cannot use load diversity to increase the number of conductors in
a PV
conduit since there generally is little diversity among the
conductors,
particularly on large arrays.
The more traditional conduit adjustment table to use is Table
310.15(B)(2)(a). The value from this table is multiplied by the
temperature
adjustment factor in Table 310.16. The key is what to use as the
ambient
temperature in Table 310.16. We also have the third adjustment of
Table
310.15(B)(2)(c) in the 2008 NEC for conduit close to rooftops. Even
if you
are excused from using the 2008 NEC by a jurisdiction, the 2005 NEC
has
310.10 FPN2 that generally recommends a 17C adder on ambient
temperature.
engineers doing HVAC wiring are just now learning this stuff.
Most inspectors will quickly cite the fact that the ampacity cannot be
greater than the 75C column, so we check to make sure (nearly always
is just
fine).
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