Energy meter data cable in same trunking as inverter AC feed

I’m about to add an ET112 energy meter to the main DB, and I’ve got to route the RS485 communications cable to the Cerbo on the other side of the room. The least invasive route would be to put it in the same trunking as the AC cables going to the inverter. Is this allowable, or will I need to put the network cable in flexible trunking inside the AC trunking?

Here’s what SANS says on the topic:

Does the network cable for the energy meter fall under (b)?

I’ve got the Cat5 communications cable between the Cerbo and inverter running in the same trunking as the battery cables, and now I’m wondering that if the above is not allowed, whether this will be red-flagged as well:


In my experience in industrial automation this was not acceptible.
This was due to the interference of the mains cables.

The run is only a couple of metres. I don’t know how robust RS485 is against interference, but I trust (hope) it will not be an issue. I’m most worried about the regulatory aspect.

Would wrapping the network cable in spiral wrap allow it to pass muster? This stuff:

There’s also the question of the DC side. Will that pass as-is?

RS485 is the brother of RS232 that was created to handle much more interference and also longer cable lengths. So the RS485 should be fine.
If this will pass inspection I cannot say. I’ll leave that to the smart people :slight_smile:


One needs to address what the issue is: Is it noise immunity, physical protection of the data cable or simply regulatory compliance?

As Louis said, it’s RS485 (differential signalling). You should not have noise/interference issues, especially not on a short run.

If you use the Surfix for the AC cabling (the kind that can already be put under plaster without additional protection), then that counts as its own raceway, and makes for an easy workaround.

But with that said, the items you mentioned does not seem to cover this case. You are not using the supplier’s trench, and you are also not hijacking a raceway belonging to Telkom or to the fibre company. I see no reason why you cannot run it alongside the AC cabling. Especially since the meter itself is inside the DB board, where the RS485 cabling also terminates…

Just regulatory compliance. Physical protection is definitely not an issue, and from the other comments here noise immunity won’t be an issue either.

I put in 16mm^2 GP wire in order to make full use of the 50A passthrough current, so no Surfix unfortunately.

I find the SANS wording to be a bit vague. “Signalling circuits” can potentially mean anything other than power cables, including the RS485 data cable.

True. It would seem a bit silly to fault the installation for not separating the data and AC wiring when they both end up in the same DB… but I don’t want to take any chances.

@JacoDeJongh What do you normally do in this situation?

It appears that the industry uses WiFi to communicate between devices so I’m surprised that this energy meter doesn’t have this facility.
Personally I prefer a hard wired data cable (and even better if it’s fibre optic).

Not quite true for the solar industry. Devices used for limiting export or control and monitor import are all hardwired. (At least for the inverter systems i work with) Because of its critical nature I would not use wifi even if the option was available. The closest I go to “Over the air” data for such devices is the use of Zigbee’s.

As for the rest of the components/devices used in the SOLAR industry, they are all hardwired together, the only part that uses WIFI is the monitoring interfaces.

I run mine in the same trunking next to the AC Cables, the cable enter the DB in any case to connect to the bottom of the Carlo. I also run my Network cables in the same trunking as my DC wiring, but not the AC wiring although in a Quattro they connect about 4 cm from each other.


I think the issue the regulators have is if the cabling runs in a shared raceway over long distances where they could conceivably have multiple opportunities to arc across, etc. For an extreme example, see TWA flight 800.

Edit: Just to be clear, I see no issue with this comms cable running your own AC raceway. You are not hijacked someone else’s comms path, and the DC that is in that cable is not the same as the high current DC on the battery side.

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How is this RS485 cable terminated?
Back in the day we used D connectors…

Both ends have an internal 120Ω terminator that you can wire in, should you want to, but at 9600 baud a reflection will be so much faster than the average size of a bit on the wire that you simply don’t have to worry about it. It is common to leave the terminator off, since there is no point in adding a load to the bus if it is not needed :slight_smile:

And what connectors are used??

Please help me out here? I installed a Victron last week. Fitted a 112 in the AC controll box for the Quatro. So if I may not run a coms/signal cable in an AC trunking, how will I connect my RS cable to the ET112 fitted in my AC box? I understand it is writen in SANS but how do I mannage in practice?

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If you are strict on the regulation, it is NOT ALLOWED.
The reason is not because of “noise” but it comes down to insulation levels.

Your comms cables would not be the same voltage level insulation, if you can prove from datasheets the insulation levels are the same or alternatively that no other cables in the same wireway would exceed the insulation of any one of the single cables, then that is a grey area.

The correct way to do this is to completely separate all cables of different insulation levels/voltage levels/ etc.

Sorry @JacoDeJongh , strictly speaking, you have been doing it wrong then… but from an entire compliance point of view you can easily argue “It doesn’t matter” easy enough!

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That makes a lot of sense, thanks.

I ended up running the energy meter cable along (but outside) the AC trunking. Inside the DB it is wrapped in spiral wrap. It was a little bit of extra effort, but I’m now confident it will pass a CoC inspection.

To be honest, you will pass a COC inspection, regardless.

I have very little faith in the general electricians these days… If you get a good one, he will inform you what to do to correct the installation (or just do it if it was small).

If you get a bad one… then you will pass CoC and might go as far as burning your house down! (Okay perhaps I am a bit overdramatic here!)

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A few years ago our house developed strange electrical issues that seemed to gradually worsen over time: Computers would reset when something else in the house was switched on… that type of thing. I suspected it might be the transformer on the street corner, but when a burning smell started emanating form the DB board I realised the problem is probably closer to home. When I opened the DB I found a severely charred earth leakage, caused by the fact that the neutral terminal wasn’t fastened at all. The neutral wire was just dangling there, barely touching the terminal.

This prompted further investigation of the wiring in my house which revealed that the electrician who oversaw the recent renovations (and charged me a fortune) didn’t know what he was doing, didn’t care, or (more likely) both.

So I got myself a copy of SANS 10142 and then rewired pretty much the entire house myself.

It will be hard for me to trust an electrician again.

Screw terminals on the meter itself (like seriously, google it already, the Victron wiring instructions comes up right on top :slight_smile: ). But the meter also has a RJ45 socket on the front, at least the ET112 and ET340 does, the EM24 only allows screw terminals.

If you use the RJ45 socket, then the modbus connection isn’t inside the DB and you can at least in theory have a separate raceway for the cable in a way that they two never meet. As long as the meter itself doesn’t develop a fault of course.

The other end of the cable is a USB plug. That means it can have at most 5V and 2A or so on it. There is a much larger danger of blowing up the GX device, should you accidentally short anything, than the other way round.

But… just use 45 x 25mm trunking with a 20mm conduit inside for the comms cable. Then it is in its own raceway… :slight_smile: