Class 2 & 3 Conduit Fill

Status
Not open for further replies.

spur60

Member
Location
South Dakota
This question is somewhat specific to Minnesota Power Limited installation and inspection. Currently, we have some inspectors stating that class 2 and class 3 low voltage wiring does not need to follow pipe fill requirements because the conductors are generating little to no heat,and class 2 & 3 have no specific code mentions regarding conduit fill. On the other hand, we have an inspector or two that has stated we must follow chapter 9 table 1 because of 725.3.
725.3 states that we are to follow 300.17. 300.17 does not specifically state we have to follow any specific tables or % fills.
for example, we might require 32, 18 gauge conductors from a control panel to an air handler. these conductors would be installed in the form of 8 conductor cables. Some may have 0-10VDC or 4-20mA signaling, some may be resistance signaling from temperature sensors, and some may carry 24VAC to power actuators. We also may have communication cables, either RS-485 twisted shielded 1 pair or CAT 5/6. I know I'm good pulling four 18/8 cables in a 3/4 based on the manufacturer's cable diameter and calculating for 40% pipe fill.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
While I agree that 300.17 stops short of requiring compliance with the wire fill rule, there in nothing in Article 725 that modifies the wire fill requirements that are found in the .22 sections of the raceway articles. Since Article 725 is not stand alone like the Chapter 8 articles, the raceway fill rules apply to Article 725 applications.
 

spur60

Member
Location
South Dakota
That's how I interpret as well.
The one inspector I talked with who supported the idea that no pipe fill calculations were need stated "there is no mention of number of conductors in raceways in 725 part III class 2 & 3 circuits." When I asked him about 725.3, he stated "does 300.17 tell you to go to a specific pipe fill requirement?" That's what got me thinking that I could argue against calculating pipe fill with the inspector that stated we needed to follow chapter 9 table 1.
Just another in a long line of issues with MN's inspectors really having no idea what they are looking at when it comes to HVAC controls and/or how to correctly interpret what the state wants them to even inspect.
 
Status
Not open for further replies.
Top