I already asked this question in general construction, then realized maybe it should have been in this folder. sorry for the duplicate. (and I got an answer to the first part of the question, but maybe you can shed some light on the why part)
can I pull low-voltage wire for outdoor lighting through the same conduit as UF line?
clients want to bring a low voltage line from their existing transformer into an area which is isolated by hardscape. the only easy way to get there would be to use the existing 1″ conduit which feeds an outdoor plug as a chase.
rustynail informs me this is a no-go. why is that?
thanks for the information/education…
k
Replies
Can be done provided that all the conductors have insulation rated for the highest voltage.
2008 NEC 300.3 (C) Conductors of Different Systems
(1) Conductors of circuits rated 600 volts, nominal, or less, ac circuits, and dc circuits shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.
Edited 12/6/2008 4:57 am ET by England1
So it sounds like the trick is to find low-voltage line with heavier than normal insulation. Hmm... wonder if my local supply house carries that.
thanks,
k
Maybe I'm confused, but wouldn't a typical low-voltage landscape lighting installation be considered "Class 2" (power-limited)?
If it's Class 2, wouldn't article 725.55 apply, particularly "Cable and conductors of Class 2 and Class 3 shall not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, device box, raceway, or similar fitting with conductors of electric light, power, Class 1, non-power-limited fire alarm circuits, and medium power...." unless permitted by 725.55b (separated by barriers)?
Define 'barriers'. There is no 'official' definition of what a barrier is in the NEC. The NEC is a guide for the safe installation and utilization of electricity. It doesn't, nor ever was intended to instruct 'how' to do something.
Real world: The man has a 120 or possibly 240 volt circuit running through a 1" conduit. That circuit must be protected by a GFCI. The case of the low voltage xformer is grounded and presumably bonded. All he needs to do is verify that the insulation on the cables are rated for the highest voltage. More that likely the LV cable is rated for 300 volt which meets the NEC requirement. If it doesn't, then replace the LV with the a pair of single conductors (same wire gauge) with THHN insulation (rated at 600 volt, same as the UF). Clearly identify the conductors at both ends.