Replies

1. 
   Steve_Merrette | Apr 14, 2001 06:23am | #1

   *
   1999 NEC Article 300-3.C - 600 Volts, Nominal, or less. 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.

   I hope this helps. basically you should be fine running them together as long as you don't exceed the minimum fill of the conduit.

1. 
   Bill_Hartmann | Apr 14, 2001 05:27pm | #2

   *SteveThat section is designed for multiple POWER circuits.Article 725 covers low voltage circuits. For example 725-26(b) Class 1 Circuits with Power Supply Circuits. Class 1 cirucits and powr supply circuits shall be permitted to occuply the same cable, enclosure, or raceway **ONLY** where the equipment powered is functionaly assoicated.Note there are several different classes and there are exceptions. But the general limitation is to not mix low voltage and 120/240 in the same conduit.The reason being is that if there is a fault all of the "low voltage" equipment can have 120v on it and it is not insulated or installed to be safe if this happens.

1. 
   teresa_greer | Apr 15, 2001 01:51am | #3

   *Steve,,Bill,, Now we are a bit confused with the answers you have posted. Our relays will be dedicated to turning ON one system of lights in each room.Can that qualify as Functionaly Associated? Teresa

1. 
   The_Tennis_Court_Builder_...on_t | Apr 15, 2001 03:57am | #4

   *no...teresa...separate.

1. 
   Steve_Merrette | Apr 16, 2001 03:37am | #5

   *Bill, Article 300 is for general wiring practices and is not limited to power. yes 725 covers low voltage and I assumed she was talking about the same circuits so I didn't differentiate. I shouldn't have made that assumption. When she talked about existing home wiring I guess I wasn't paying attention. I agree that it should be done in separate if they are for different applications.If however they are for the same lighting circuit then you would be fine running them together.Teresa, don't be confused. if you ever saw or read the NEC you would understand that it is a codebook that is very complicated and open to interpretation sometimes (although usually the inspectors interpretation wins)

2. 
   teresa_greer | Apr 16, 2001 05:02am | #6

   *Thanks guys; Your interpretations and quotes have given us a great start on this problem. Thanks again; Teresa G.

3. 
   Bill_Hartmann | Apr 16, 2001 05:31am | #7

   *SteveThere are two problems with refering to section 300. First 300-1(a) ..for all wiring installations UNLESS MODIFIED BY OHTER ARTICLES.And while 300-3(1) does all multiple circuits to be in the same conduit, they ALL have to rated at the voltage of the maximum circuit. IE, 120 volts. And it also specifically refrences 725-54(a)(1).725-54 has some many different exceptions that I am not sure of this, but one approved expection appears to allow the use of CL3 cables for the low voltage wiring in the same conduit with 120 volt circuits. I did a search at Belden and all CL3 cables have separate PVC jacket. One such is 5402UE Multi-Conductor - Security/Alarm Cables, 4 conductor #20 stranded.

4. 
   Art_B | Apr 16, 2001 03:11pm | #8

   *I've 4 miles of low voltage control and data wiring in my house and not ONE INCH is in conduit with power wires. NEC can and has been interpreted 1000 different ways. AJ's one liner is best, "no...teresa...separate."

5. 
   J._Belcher | Apr 16, 2001 04:58pm | #9

   *The insulation rating of the low-V wiring must be at least as high as the voltage of power wiring run with it. (Control wiring is generally 300V rated). If functions are related & max conduit fill is not violated, it's okay.But more to the point, why bother? Your low-voltage stuff doesn't need raceway. (There's a few exceptions, but you shouldn't encounter those in a house).I would separate.

6. 
   Steve_Merrette | Apr 16, 2001 06:10pm | #10

   *J. Belcher, in the initial post Teresa mentions running conduit in block walls. I am (Gulp) assuming that they are running in conduit to protect the cables from the rough block edges. they may however live in an area that requires wiring be done in conduit. Chicago is one that comes to mind.

7. 
   Mike_M. | Apr 18, 2001 05:43am | #11

   *Steve, you sound like you've had a little experience with the joys of the Chicago elecrical code.Theresa, Art and AJ are on the money. The best advice here is to keep them separate. You can find many different ways of interpreting the code, but as a general rule and practice, keep them separated. I've never run across an instance where we've run any LV and HV in the same pipe. Additionally, proximity to HV cabling or sources, particularly if run parallel can create inductance on the LV cable, causing interference with the system(s) being controlled. This is typically more of a problem with communications circuits, but it can create problems with other control devices, as well. If you have any serious doubts, talk it over with the inspector. That's who will let you know what will or will not be acceptable. Mike

8. 
   Steve_Merrette | Apr 18, 2001 06:38pm | #12

   *No Mike no personal experience with it other than some people I've worked with who have. The "inductance" you refer to is commonly known as crosstalk and is generally only an issue with communications or audio as you pointed out. seeing as the low voltage is also the same 60Hz as the power cable it doesn't even raise an issue of frequency interference. Depending on what you're doing yes sometimes it's better to run them separately but as stated before if it's the power and low voltage for the same thing (most typically lighting) it doesn't matter enough to get all worried about.

2. 
   teresa_greer | Apr 18, 2001 06:38pm | #13

   *
   We ran conduit through the block walls on our solar home.Along with the typical home wiring we also planned to run a low voltage relay system in the same conduit.We have now been told that this combination may be a code violation.Can anyone confirm this and/or explain why it might violate?