# Genset control & Ethernet in same conduit



## melrub480v (Apr 25, 2021)

I working in a commercial building in NYC bad we have a generator (Kohler) with multiple ATS switches in different locations throughout the building. My question is can I run the genset control wires in the same conduit as the Ethernet ( Ethernet is for the ats which goes back to the generator as well) . I'm not sure how many volts the genset control wiring is but wether it's 24v or 240 volts if I get rated wire and cable that's the same voltage rating can I run them in the same conduit. Thank you. Also if there's a code reference please let me know.


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## BillyMac59 (Sep 12, 2019)

It's never a good idea to run ethernet cabling in direct contact with AC voltages. This I've learned from experience and from Prof. Google. As for a code reference....grouped cables must have same voltage rating (or better) as the highest voltage used...


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## Southeast Power (Jan 18, 2009)

melrub480v said:


> I working in a commercial building in NYC bad we have a generator (Kohler) with multiple ATS switches in different locations throughout the building. My question is can I run the genset control wires in the same conduit as the Ethernet ( Ethernet is for the ats which goes back to the generator as well) . I'm not sure how many volts the genset control wiring is but wether it's 24v or 240 volts if I get rated wire and cable that's the same voltage rating can I run them in the same conduit. Thank you. Also if there's a code reference please let me know.


Why don't you use one of those line carrier data units like the Netgear 1000? Do they make them in a commercial version?


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## kb1jb1 (Nov 11, 2017)

I thought you cannot mix different systems in the same conduit. Cause you use it as a sleeve?


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## melrub480v (Apr 25, 2021)

ValeoBill said:


> It's never a good idea to run ethernet cabling in direct contact with AC voltages. This I've learned from experience and from Prof. Google. As for a code reference....grouped cables must have same voltage rating (or better) as the highest voltage used...


Yes i realize that it's never a good idea. And If I wasn't in the situation that I'm in I would definitely separate the two. But I *might* not be able to run a new conduit just for the Ethernet. Again I might not be able to. Hopefully I find a way to get a new conduit through the shaft where the rest of the risers are. If not i'm just going to have to take a long way around. That's all. But I really wanted and hoped that someone would be able to help me with this question. I just wanted a code reference so that maybe i could research it myself. Also Is the genset control wires considered a signaling circuit? Just wondering. Either way thank you.


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## HertzHound (Jan 22, 2019)

I would think the start circuit is a signaling circuit? Probably class 1, but could also be a power circuit? I guess it depends on how the circuit is protected? What makes it ok for luminaire cable to have the 0-10v cable under the same sheath as the circuit conductors? I assume it has something to do with the jacket that’s over the purple & grey wires and then put under the jacket with the power conductors? It creates a “barrier” between the two? I asked at a code update class, but I don’t think the instructor understood the question, based on his answer. My question was because we often put the dimming wires in the same conduit as the power wires when the lighting is all done in conduit. Does the 0-10v purple and grey wire have to be a jacketed cable, or can it be just a purple and grey THHN? I know it has always passed inspection, but I don’t think it has been pointed out to the inspector.

Is the Ethernet cable considered a class 2 or 3 circuit (725) or is it Comunications (800)? They do make shielded Cat5 and Cat6 cable if it was going to be routed near power conductors. 


*725.136 Separation from Electric Light, Power, Class 1, non–Power-Limited Fire Alarm Circuit Conductors, and Medium-Power Network-Powered Broadband Communications Cables.
(A)General.*
Cables and conductors of Class 2 and Class 3 circuits 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 network-powered broadband communications circuits unless permitted by 725.136(B) through (I).


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## VELOCI3 (Aug 15, 2019)

The manufacturer has probably previously addressed this in their spec. 

If there is an electrical engineer involved with this project they address this in the project spec. 

Both those are your best avenues for the answers you are looking for. 


Sent from my iPad using Tapatalk


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## splatz (May 23, 2015)

If the control wires are 24V, and the power supply is marked class two, you have no issue at all. If the controls are 120 or 208 or 240 or even 277 VAC you are probably OK. Everything in the conduit must have insulation greater than the highest voltage in the conduit. The insulation on Cat cables is 300V so the control wiring is probably fine in the same conduit. If you have to run 480 and ethernet together Rockwell makes some comically expensive category cable with 600V insulation.

The current on the control circuits is low so the interference it will generate is low, although if the runs are long it could be an issue. It depends how sensitive the equipment is to the occasional mangled packet.

The harder question is what do you do when the cables exit the conduit in the enclosure? There are rules in article 725 for separation of power and class two in the box, read the rules. One thing you might have to do is sleeve the ethernet in carflex or etc. inside the box. You get some extra lattitude when the class two and power wiring are for the same system, as is the case here. For example there are lighting control panels that have ethernet jacks for the controller right in the panel, right by the insulated bus, all compliant.


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## paulengr (Oct 8, 2017)

Ethernet is communications cable (chapter 8). It has isolation transformers rated to 1500+ V surges at both ends. There is a deep notch at DC extending well past 60 Hz. The cabling is twisted pairs which makes it virtually immune to electrical fields and the baluns make it virtually immune to magnetic ones , to the rune of 30 dub SINR compared to maybe 10 dB for RS-485. This is for UTP. Shielded cable (STP) due to being grounded on both sides creates a ground loop. This reduces magnetic field resistance so that it is a few dab less than UTP in exchange for boosting electrical field resistance to 34 dab SINR. The trouble is that in industrial equipment the magnetic field from open unshielded coils, transformers, motors, etc. (inductive loads) tends to dominate so STP in general is going the wrong way.

On top of that the data signal format itself is designed to avoid low frequencies, partly because of that massive DC notch. For instance with 10 MBps Ethernet (slowest but easiest to describe) a “1” pulse is a negative pulse followed by a positive pulse while a “0” is a positive followed by a negative. It is balanced so no DC and it roughly looks like squarish sine waves so it is naturally more of an AC or RF signal. Compare this to RS-485 which is the underlying signal format for most industrial protocols (Modbus, RS-232 is single ended but same, Profibus). A “1” is a positive voltage pulse and a “0” is a negative voltage pulse. Data signals are centered around DC and definitely in the 60 Hz range.

Prior to AB getting in bed with Cisco when they did their own work they did a lot of electrical testing on Ethernet in general because all the questions being asked here were out there. They were not concerned with Code compliance. They were concerned with the fact that no matter what you tell them, plants are going to run Ethernet, AC, and DC controls together in industrial control panels with rats nests of cables dangling everywhere. But given the undeniable truth that Ethernet is both far faster and very different both electrically and from a signaling format point of view, there were lots of questions. It was designed to allow IT people to dangle it everywhere looped together and wrapped all over power cords yet for the current 10BaseT and better to equal or exceed the performance of “thin” Ethernet, the previous standard using 50 ohm coaxial cable which is again highly immune to just about everything. What they found was that running it strapped to large power cables fed from a VFD for hundreds of feet or running several hundred feet wrapped around cables of a welding robot with UTP had 0.0% packet errors, not one single corrupted 100BaseT packet. They looked for bit level errors (Ethernet has lots of error correction) and again, not one.

So the industrial practices about separation, crossing at right angles, separate ground planes, shielding, etc., are based around +/-10V analog and DC-centered communications protocols, especially RS-232 and RS-485 using straight (not twisted) pair or 3 wire DC referenced cables. The rules apply up to a few kilohertz before radio practices (extensive grounding, shielding, attention to coils in wire, electrically “long” situations) kicks in. Ethernet is an RF signal but it uses special cable that gives the performance of coax. So most of those practices for DC signals are pretty useless.

UL of course just groups everything into broad categories. A communication cable is just that. They don’t get into whether it carries analog phone calls, a servo drive command, or 1GBps Ethernet. It is all treated with the same broad brush. Inside the panel a panel builder is free to just tie wrap everything in one big mass. As stated interference isn’t going to happen even in a “smart” MCC by design. But the moment it leaves that enclosure to meet Code you have to have either all low level signaling or separate raceways and if it’s not clear, separate raceways. One particularly annoying gotcha is that RS-485 works just fine over #14 THHN (but shielding is important!!). Ethernet isn’t baseband...it’s a radio signal on a wire. It cannot work on anything larger than #22. NEC places a minimum of #18 on general wiring (chapter 3) so no matter what, it MUST be separated from chapter 3 wiring. Stupid rule? Yes. Do industrial plants violate it all the time with ZERO consequences? You bet. It’s just not legal to do it unless the AHJ allows it. Industrial plants mostly police themselves and the consequences of ignoring this are on them though.

As to the genny question I hope this makes it obvious that there is no technical reason not to run Ethernet with control wiring. It is highly shielded already despite what it looks like. You better bet any generator controller with Ethernet has been designed with this in mind. As to the Code side as others have stated it comes down to the power limited rules. If you can determine what class the control wiring is you might be able to mix. If not, conduit is cheap. You already need one, just make up 2 of everything. Suck it up buttercup.


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## Yankee77 (Oct 5, 2020)

HertzHound said:


> I would think the start circuit is a signaling circuit? Probably class 1, but could also be a power circuit? I guess it depends on how the circuit is protected? What makes it ok for luminaire cable to have the 0-10v cable under the same sheath as the circuit conductors? I assume it has something to do with the jacket that’s over the purple & grey wires and then put under the jacket with the power conductors? It creates a “barrier” between the two? I asked at a code update class, but I don’t think the instructor understood the question, based on his answer. My question was because we often put the dimming wires in the same conduit as the power wires when the lighting is all done in conduit. *Does the 0-10v purple and grey wire have to be a jacketed cable, or can it be just a purple and grey THHN? *I know it has always passed inspection, but I don’t think it has been pointed out to the inspector.
> 
> Is the Ethernet cable considered a class 2 or 3 circuit (725) or is it Comunications (800)? They do make shielded Cat5 and Cat6 cable if it was going to be routed near power conductors.
> 
> ...


725.136(I)(1)


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## Wessone (Sep 10, 2014)

Yankee77 said:


> 725.136(I)(1)


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## Wessone (Sep 10, 2014)

As a generator installer, coming behind electricians who can't seem to follow instructions, I see this all the time. 

Of course the code can say what the code says-and we all can second guess the manufacturer from now until the cows come home. But, since it is almost guaranteed that the Kohler installation manual says to run it seperately-you run it seperately. Doesn't matter what we "think", or even, frankly what the AHJ thinks-the install manual trumps opinion where I come from. The equipment warranty may well ride on a proper installation.

As far as sheilding, yes it works. However, I rarely see shielded wire installed for anything-unless I unstall it. This, even though the install manual calls for it. Cat 5x et. al., I see, thermostat wire, thhn, thwn, you name it-that I see. Shielded wire is apparently too expensive. 

Additionally, just a thought, but their equipment UL listing is likely based on that particular install configuration, and if this is a life safety install, would you risk your insurance and license to not do it-just because you "think" it will be okay? 

If I were your AHJ-and it were not seperate, and you couldn't show manufacture concurance, you wouldn't pass-just that simple.

Just my two cents.


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