I have to agree. It may differ depending on your local electrical code, but in most areas, anything having to do with a solar power system should be separate. In my area, all of the conduits for solar have a red reflective sticker on them labeled as "Solar Circuit" every few feet. In case of a fire, they kill your main breaker, but the solar panels could still be putting out a few thousand watts of DC. The safety rules can be pretty strict.
In reality, it is safe, if all of the wire is rated for 600 volt use. But being safe and meeting local codes is not always the same thing.
I did many industrial control installations, and any time we had to run a low voltage control line to a power device, it had to be THHN 600 volt wire, even for a 12 volt relay signal at under 3 watts. Our main wire trough had a dividing wall inside, with high volt on one side, and low volt on the other. As long as nothing exceeded 70 volts, we could use 300 volt wire on the low volt side. And the local inspector had us put labels on the trough door that it was a dual voltage system. "Multiple Circuit Fed system, High and Low Voltage Present" Now in your case, it is DC, but it is still 200 volts. That obviously requires at least 600 volt insulated wire. Most areas also require labels on DC power feeds. It is easy to use a non contact pickup and sense if there is AC power on a wire, but DC cannot be easily detected with a wand like that. A current clamp will only work if a load is drawing current, and even then, they are not fool proof. DC at higher voltage is very dangerous. Just 36 volts DC can kill if it gets a solid connection to you. 200 volts is nasty. Even with a rapid shutdown at the solar panels, it should still be in a conduit or trough that is labeled as a DC solar circuit.
I am also looking up battery and inverter backup feeds, as I think they also need special labeling. Once I have my battery inverter online, I will have 4 circuits in my home that will be live during a power failure, as well as my solar power being live to charge the batteries. I am adding a second disconnect next to my solar one to shut down the inverter from outside my home. We never want to think about a disaster, but if something bad happens, the last thing we want is to have a situation that could injure a first responder. They will know the local codes, and that is what they will look for. I live in an earthquake and wildfire area in Southern California.
