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Thursday, June 20, 2019
Question:
Re: CQD answer published June 12 & 13, 2019 - Raceway Fill and Adjustment Factor
1) Charlie; There are a number of useful web sites that will calculate the conduit fill. These will allow one to readily change the number of conductors, insulation type and conduit type and size. There also are a number of apps for smart phones. For a web site, I prefer the Racewayfill Calculator on electrician.com, http://www.electrician2.com/rveltrain05/rf_calculator.html
Unfortunately, the smallest gauge allowed on many web sites is 14 AWG and the few I checked also don't support type TFN insulation. Although it is not stated, I would assume the "dimming" wires are low voltage control wires and they may be Class 1, 2 or 3 circuits. Assuming the "dimming" wires are part of Class 2 or 3 circuits, regardless of the voltage rating of the type TFN insulation, wouldn't mixing low and high voltage wiring in the same conduit be a violation? Andrew H. “Drew” Brejda
2) Hello! Great forum, been following you for years! In response to the answer you gave, shouldn’t 0-10v dimming (I don’t think the electrician specified what classification but I believe most dimming circuits are class 2?) have separation as per 725.136(I)? I really enjoy following every morning! Keep up the great work! Thank you, James Doherty
3) Charlie et all, Thanks for the great service you perform for our industry answering the multitude of questions that are presented. As many of us who interpret the Code, it is sometimes easy to focus on the question and forget about the other issues that each installation can present. In response to CQD on 6/11 & 12/2019 I would like to add that the conductors used for dimming could only be installed in the same raceway if they are considered Class 1 and meet the conditions of NEC 725.48(B)(1) and have adequate voltage ratings. NEC 725.48(B)(1) would limit the Class 1 conductors to only be installed in raceways where the Class 1 circuits and the power-supply circuits are functionally associated. The question implies the installer is interested in “loading up the conduit” to the maximum, which would be acceptable if the Class 1 and power-supply conductors are associated, with no other conductors installed. Class 2 and Class 3 dimming conductors would not be allowed in the same raceway with power and light conductor as indicated in NEC 725.136. Keep up the good work. Bill Neitzel
A
Answer:
Hey Drew, James and Bill thanks for your comments, additional information, and the kind words. You are correct if the dimming conductors are Class 2 circuits as they are defined in 725.2 and supplied by power sources in 725.121, they are not allowed in the same raceway as the power conductors as stated in 725.136(A).