Any possible exceptions/ways to (code compliant) put communication wire in same EMT as line voltage?

Question

I know generally it’s not allowed to put low voltage signals into the same conduit (EMT) as line power runs. But I am wondering if there are any exceptions or ways to achieve it (code compliant). For example, I know that Romex together with low voltage signals would work.

I have two applications:

1. I need a simple RS485 connection to my EVSE. It’s mounted outside and one EMT runs to it. I do not want to run another conduit
2. I would like to connect my Enphase Envoy (Solar) via Ethernet. It’s also mounted outside and only one thick EMT goes inside. I do not want to run another conduit

I have read that inner tubes could work. What are the exact rules for this? What inner tube must it be and how does it work with conduit fill calculations?

Or is there an exception if no low voltage signals leaves the enclosed raceway components? For example, when I would terminate the RS485 connection via an ESP32 located in a junction box and never bring a low voltage wire out?

Answer 1

Fiber-optic can go in the same conduit, Comms that is not SELV (like comms between condenser and compressor of a split system) can go in there too. some smart lightswitch comms also can go in conduit.

Comms that is SELV like CAT6 networking, loudspeaker wires, 24V thermostats, doorbells, wired intercoms, or POTS cannot go in the conduit.

RS485 to fiber converters exist and are probably the easiest way to comply with the regulatory requirements. RS485 isolators are another option allowing you to interface SELV RS485 outside the conduit with non-SELV RS485 inside it but they may raise some eyebrows.

for the ethernet, use as media conveters and run fibre. or install a wireless bridge. These things usually use a plug in power supply but hard-wired supplies are also available.

Option C run the cable on the outside of the conduit. SELV circuits don't require conduit in most applications.

Answer 2

Data cables CAN be inside - but no in/out privileges.

You're installing an EV using EVEMS/Load Management, and you have a sensor module in the panel to tell the EV station the service load, so it can either prevent panel overload or capture solar you would otherwise export to the grid, etc. etc.

OK, there's what I call an "envelope" of NEC Chapter 3 wiring methods. Conduits, raceways, gutters, enclosures, junction boxes, a limited list of cable types (MC, NM, UF, SE, USE, etc.) All AC mains power wires must stay inside that envelope.

And, data cables cannot cross in and out of that envelope. This is often distorted into "data cables cannot be inside that envelope", because of course, 99% of the time people want to be outside the envelope at their router, enter "the envelope" to access an electrical conduit to the shed, then exit "the envelope" to connect to a switch at the shed. And we have to scold them not to do that. That is a network which must stay entirely outside the AC power Chapter 3 wiring method envelope.

But contrast with a case where someone has 0-10V dimming going to a bank of fluorescent lights. That entire network only connects the dimmer to the lights, so it's not hard to stay entirely within the conduits and boxes. That's fine.

Or a large campus has a bunch of conduits to carry power for HVAC equipment. They toss an Ethernet line in there for the SCADA system whose jacks are inside the AC wiring enclosures. Again that's fine because it stays entirely within Chapter 3 wiring methods.

And that's what happens with a typical EVEMS data cable.

So you're fine. Don't get psyched by that "data cables can't be inside" nonsense, that's just what we tell the IT department ;) They can be inside if they entirely stay inside and don't leave.

So if you just gotta gotta gotta go in/out, what do you do? One word. Fiber.

P.S. If you're running RS485, you're not running Ethernet. RS485 is like Spanish and Ethernet is like German. They're different languages that could run on the same telephone wire. When you say "ethernet" you probably mean "Cat 5E cable", that's the "telephone wire". That's important because Ethernet bridges e.g. to fiber aren't going to work for you, because it isn't Ethernet. No comprende.

Answer 3

power line ethernet might do the job. This adds a modulation signal to the power line itself without requiring a separate conductor.

Answer 4

For the EV comms cable, since it never leaves the enclosed system, you may have some options:

• Maybe you could use a couple of loose #14 THHN wires? Maybe not? You are supposed to use twisted pair cable but the comms speed/error requirements are probably not very taxing. If the pull isn't too far, try it.
• if you can find twisted pair cable that is 300V rated, is at least 18 gauge, is pullable and has twistiness sufficient to meet your performance needs, that would work. This stuff exists but is expensive and specialized. It's not "ethernet" cable.
• If that's too expensive, you could go back to the #14 and .... twist them ... it's not rocket science and you're not building a 10Gb backbone. You're in EMT so outside noise is excluded anyway, you're just eliminating the 60Hz noise.