Can I Run 0-10V Control Wires With 277V in Same Conduit?

"Can I run 0-10V control wires with 277V in same conduit"

You CAN do anything you like. But SHOULD you? In my opinion, no, on several levels.

1. Even with 600V rated insulation and excellent shielding, you cannot attenuate all of the potential induced voltage on that signal when it is "trapped" in a metal tube with high current carrying conductors. There is always going to be a little bit of induced voltage. If it's a short distance, you can usually adjust it out but the longer the run, the more induction will take place. 400' is a long long way to go. You are asking for headaches.
2. Voltage control signals, such as 0-10VDC, are particularly susceptible to noise. For the same reasons as above, you will pick up a lot of cumulative noise on that signal, even with shielding.
3. 0-10VDC is also a bad choice for a 400' run even if it has its own conduit. Voltage drop can be a real problem at that distance. I would use 4-20ma myself, even if it means putting a converter at each end.
   

GA JRaef

The only violation of code I can think of that prevents running any additional wire through any conduit is if that exceeds the fill capacity of that conduit. (You cannot pack it tight with wire for many reasons.) But since we don't know how many or the size of the 277V wire, nor the size of the conduit in question, no suggestion on this point cam be made. But you are quite right that a 400' run of 0-10VDC (presumably single ended) is just asking for trouble.

If you absolutely must run the control signals in the same conduit as the power then 10 vdc is definitely the wrong way to go for the reasons JRaef explains.

If it were a short run then running a 4-20 mA signal through shielded twisted pair might work but 400' is an awfully long antenna.

You might try using a V/F converter at the sender, run a variable frequency current through the shielded twisted pair and then do a F/V conversion to get your 0-10V signal back.

Personally for this application I would convert the 10v signal to a fiberoptic signal, run optical fiber in the conduit and then convert back.

I like the fiber idea. Otherwise I would avoid the very thought, you are asking for all kinds of trouble with induced signals.

I see that this is your first post on these forums, so... first... Welcome!!!

Second, I see that you have received a lot of good information here as to why you should NOT attempt this.

However, if we had some additional details related to what the dimmer controller was dimming and/or how critical and precise the dimming reduction has to be at any given state of adjustment, there may be some room there for compromise.

I can presume with the stated limitations this is not a new installation and maybe there is not enough in the budget to run a new conduit. Maybe required crane access prevents an overhead run, maybe the only way to get the wire there, within the stated budget of the job is, to use this conduit.

So, since it is NOT advisable to do this, with some additional information we may be able to suggest some more suitable alternatives.

Since you're new to the forums, you probably were not too sure what to expect. Heck, I've been here awhile, and sometimes they still scare me, haha. But seriously, there are a lot of great members here that love to help people in real need of a solution to a problem. And, the more details we get the better chance of getting a workable solution to your problem.

Good luck and again... welcome to CR4.

JavaHead

Remember it is very easy to induce a voltage and hard to induce a current. Converters to turn the 0-10 VDC to 0-20mA can be had for $120. That will be much more stable...But I do like the fiber optic idea.

http://www.automationdirect.com/adc/Shopping/Catalog/Process_Controls/Signal_Conditioners/FC-33

It's not good practice.

If the dimmer signal is a current signal, then it might be possible to get away from it, as current signals are largely immune to interference. If it is a voltage signal then expect problems, the solution to which may be to segregate the wiring as recommended by others above.

Hi Mariana,

Lots of good advice telling you what not to do and having experienced what used to be called 'hum pick-up' in a similar situation I can appreciate your dilemma.

All is not lost! Your conduit will provide an excellent continuous support for the screened signal circuit(twisted pair with drain possibly) with it being tie wrapped all the way. By adopting this method you will also protect the 0-10V circuit from other stray emfs that abound in these environments.

Warning: If using screened cable only earth the screen at one end, preferably the supply end otherwise you can create the very thing you are trying to avoid! (Tie back and insulate the other end).

Good luck and enjoy the Forum.

Massey.

0-10V is the standard for analogue control of dimmers. The length could be problematic even when segregated, but putting it in the same conduit as the AC supply is a recipe for failure.

There are a variety of serial control systems for lighting on the market which can interface to 0-10V systems and it may be better to use one of these.

For stage lighting DMX-512 is the universal standard. Architectural systems include DALI, Lon or BACnet. Some of these are RS-485 based systems as is Lutron's own system and are well suited for long cable runs.