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I have three devices that I need connected. They are about 30 m away. Conduit space is limited so I want to try to get a single, multi core cable through for all of this.

What I need to run:

  1. 220 V from point A to B (110 V per cable): to power an ATS switch that requires 220 V (two 110 VAC lines) to power the switch. (not sure of the power draw during the switch, but it's < 50ms and should be almost zero draw when idle.)

  2. 110 V from point B back to point A: One of the first leads will run through a switch to return the current to a contactor in point A (total of 60 m). The contactor will be NO, but almost always closed. Tech docs say rated coil consumption = 41 mA (Finder 22.64.0.120.4310 https://www.alliedelec.com/m/d/b42d7d884ebd43b9b8adf24d963c352e.pdf)

  3. Three lines from an Arcel power meter. One is groups so I assume I can just ground it locally on both point A and B, and the docs say 30 mA and even an ethernet cable will work. But maybe if the cables are all together it might cause interference? (http://net.acrel-electric.com/download/common/upload/2020/10/23/10943xy.pdf)

If I can use a single ethernet cable (22 AWG?) or a 5 or 6 lead 18 AWG cable, that would be perfect, I'm just not sure if there is any concern. I'd put a 1 A breaker on both the four leads leaving point A.

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  • \$\begingroup\$ Use a cable that has the correct voltage rating and is suitably designed for the environment it is to be fitted. I'd definitely consider using fuses and RCBs too. Check your local electrical codes. \$\endgroup\$
    – Andy aka
    Jan 13, 2023 at 21:46
  • \$\begingroup\$ I'm a bit confused. It seems like you are asking two questions: 1) Whether 22 AWG will work for the distance, voltage, and current of the relay; and 2) whether other wiring will interfere? \$\endgroup\$
    – JYelton
    Jan 13, 2023 at 21:48
  • \$\begingroup\$ @JYelton Yeah, I guess it's two questions. One is just "will it work under these conditions" \$\endgroup\$
    – DAB
    Jan 13, 2023 at 22:08
  • \$\begingroup\$ @Andyaka i'm not concerned with codes for this, i'm just concerned about melting wires. i have some "heavy insulated UV" cat 6 that's intended for outdoors. it's 23AWG but seems that they don't print voltage, but wikipedia says cat5 has a max of 120VDC. would AC be the same? en.wikipedia.org/wiki/Category_5_cable \$\endgroup\$
    – DAB
    Jan 13, 2023 at 22:11
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    \$\begingroup\$ Home fires can start long before wires melt. You might not need to have an inspection to meet code, but you should definitely consider wiring code anyway. :) \$\endgroup\$
    – JYelton
    Jan 13, 2023 at 22:21

2 Answers 2

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22 AWG copper wire has about 53 mΩ per meter1. With 60 meters, the total resistance will be 3.18 Ω. (I'm taking it that you are powering the relay with 110 V, but its contacts are rated for 240 V.) If the relay current is 41 mA at 120 V, the 22 AWG wire will have a 130mV voltage drop (\$0.041 \times 3.18\$) and dissipate about 5.3 mW.

This is well below the recommended maximum current (920 mA in bundles/conduit) for 22 AWG. The relay will "see" about 107 volts instead of 110, which doesn't strike me as a problem. (If you're running an ethernet cable solely for this purpose, you could combine conductors to decrease the resistance and have a larger effective gauge.)

I'm not sure what you mean by "three lines from the power meter." Re-reading your question, I'm reading that you want to run 110 V and these power meter data wires all inside a single ethernet cable? (If you're in the US with split-phase residential wiring, no single conductor will have 220 V potential, so I'm assuming you're just talking about using multiple 110 V conductors.)

While some Cat-6 ethernet cable I'm familiar with has a 300 V rating, I don't think I would run anything more than PoE (48 V) on it due to wiring code. Anyone in the future working with your wiring installation might assume the ethernet cable is only carrying low voltage and be in for a nasty surprise. You'll have to check your local codes to see what's allowed (as Andy commented).

There are multi-conductor "hybrid" cables which are made to carry power and data together, but they can be expensive. I would recommend using separate cables so that it's (hopefully) obvious to anyone what they are for. I agree completely that adding fuse protection is a good idea.

Any time AC power is ran in parallel to data cables, it can induce noise and interference. Typically this is where you would want a shielded data cable to minimize interference. If your electric meter is using a low-speed data interface, or a differential signal it might not be a problem.

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No, I don't think it is safe to place two 110VAC lines and data lines into one single Ethernet cable, because both components would be used outside design specification. Power meter's datasheet clearly indicates NFPA 70 wire methods should be used. Also Ethernet wire gauge varies and can be smaller than 22AWG.

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