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.
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.