SD Dylan
Member
- Location
- Franklinville, NJ
Recently I've needed to determine the ampacity of a multi-conductor cable and I've found my self going round and round in the code book. I need some help.
I found the Lapp 190 Series, 600V, TC-ER, Power and Control cable that I'd like use everywhere I can for basic power and control signals on the machines we design. Normally I would use Table 12.5.1 and apply the appropriate deratings for temperature and current carrying conductors to determine the ampacity. But then I came across section 12.8 Cords and things got fuzzy. For a 3-Conductor cable using table 12.5.1 I get an ampacity of 40A but table 12.8.2 gives me 35A for a cord.
So I look up how NFPA 79 defines cable and cord and things get worse.
3.3.12* Cable. A combination of conductors insulated from one another with a common covering that is not a cord.
- 3.3.12.1* Cable with Flexible Properties. A cable or special cable that is malleable but without flexing or constant flexing properties.- 3.3.12.2* Flexible Cable. A cable or special cable manufactured with flexing or constant flexing properties.
- 3.3.12.3* Special Cable. A cable intended for specific limited purposes.
3.3.27 Cord. Two or more flexible insulated conductors enclosed in a flexible covering that provides mechanical protection.
My interpretation is that pretty much any "Cable" is actually a cord. But the 12.8 Cords section seems to be fairly explicitly about S type service cords and not intended for power and control cable.
How should this be interpreted and what's a good way to think about this so it makes sense?
I went deeper down the rabbit hole and found NFPA 79 A.3.3.12 that was supposed to further explain cables but just pointed me to chapter 3 of the NEC where I found NEC Art 336 Power and Control Tray Cables.
In NEC 336.80 it says TC cable with conductors >14AWG use Table 310.15(B)(16) and Table 310.15(B)(18) which are pretty much NFPA 79 Table 12.5.1.
In NEC 336.80 it also says for conductors 16 & 18AWG use section 402.5 if installed in a cable tray and 310.15 if installed in a raceway. 402.5 references fixture wire and has 18AWG @ 6A and 16AWG @ 8A. 310.15 gets me back to Tables 310.15(B).
When we run these cable, we may have >14AWG for power or 18AWG for signals. The cables are also installed in various conditions: wiring duct, cabled tied along machine frame, flexible C-Track, somethings a little of all.
What best applies to cables being installed within a machine, connecting different components and enclosures? Is there a simpler way to think about this? I get stuck in serious analysis paralysis trying to do things by this book :?
Thanks All
I found the Lapp 190 Series, 600V, TC-ER, Power and Control cable that I'd like use everywhere I can for basic power and control signals on the machines we design. Normally I would use Table 12.5.1 and apply the appropriate deratings for temperature and current carrying conductors to determine the ampacity. But then I came across section 12.8 Cords and things got fuzzy. For a 3-Conductor cable using table 12.5.1 I get an ampacity of 40A but table 12.8.2 gives me 35A for a cord.
So I look up how NFPA 79 defines cable and cord and things get worse.
3.3.12* Cable. A combination of conductors insulated from one another with a common covering that is not a cord.
- 3.3.12.1* Cable with Flexible Properties. A cable or special cable that is malleable but without flexing or constant flexing properties.- 3.3.12.2* Flexible Cable. A cable or special cable manufactured with flexing or constant flexing properties.
- 3.3.12.3* Special Cable. A cable intended for specific limited purposes.
3.3.27 Cord. Two or more flexible insulated conductors enclosed in a flexible covering that provides mechanical protection.
My interpretation is that pretty much any "Cable" is actually a cord. But the 12.8 Cords section seems to be fairly explicitly about S type service cords and not intended for power and control cable.
How should this be interpreted and what's a good way to think about this so it makes sense?
I went deeper down the rabbit hole and found NFPA 79 A.3.3.12 that was supposed to further explain cables but just pointed me to chapter 3 of the NEC where I found NEC Art 336 Power and Control Tray Cables.
In NEC 336.80 it says TC cable with conductors >14AWG use Table 310.15(B)(16) and Table 310.15(B)(18) which are pretty much NFPA 79 Table 12.5.1.
In NEC 336.80 it also says for conductors 16 & 18AWG use section 402.5 if installed in a cable tray and 310.15 if installed in a raceway. 402.5 references fixture wire and has 18AWG @ 6A and 16AWG @ 8A. 310.15 gets me back to Tables 310.15(B).
When we run these cable, we may have >14AWG for power or 18AWG for signals. The cables are also installed in various conditions: wiring duct, cabled tied along machine frame, flexible C-Track, somethings a little of all.
What best applies to cables being installed within a machine, connecting different components and enclosures? Is there a simpler way to think about this? I get stuck in serious analysis paralysis trying to do things by this book :?
Thanks All
