[RE-wrenches] Wire Sizing

[William Miller]

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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