4 minutes ago, Kalahari Meerkat said:

... book spark gap of 1kV/mm should be a reasonable value to sustain a plasma arc...

That is the voltage to establish an arc.  Once an arc is established, the gap is full of ionised particles, which are a good conductor and an arc can be sustained at a much lower voltage.

But otherwise, yes. A DC rated switch (with a higher voltage rating than your working voltage) will be sufficient for the job.

Also, most fuse disconnects are rated for disconnect under load too (but not all, so check the manual!).

Thanks to all the adviceI also thought about the voltage being to low for an arc.

So it would be safe to switch it off.

Thank you. 

Thanks

On 2024/12/04 at 6:39 PM, Stiaan Botha said:

I hope someone can explain the following to me. We have a solar system, and the contractor installed 16A DC fuses on all panels strings positive and negative size. And then again at the combiner box both live and negatives cables had fuses in. He had a bad connections on MC4 connectors and eventually the join box started to burn in total there were 18 strings in this box. After we extinguished the fire none of the fuses at the combiner box and at the panels were blown.

Why?

What's the ampere rating of solar panels?

On 2025/07/17 at 8:18 PM, bilall75 said:

What's the ampere rating of solar panels?

In the case above, a few things to consider

Why was both positive and negative fused on the panel side?

It is a requirement that if you are running your solar wires in the same conduit, they must be fused on the panel side

The fuse rating should be 125% of maximum current. Remember that the fuse is generally to protect the wire, not the panel

Why was there a fire and the fuse didn't blow? Fire was most likely started by a loose/bad connection. This will create heat and start burning. In DC much worse than AC

And when referring to welding, generally in the low 20 volts, so very little volts needed. You can quite successfully weld with 2 car batteries. You will normally have to even put in a resistor like a piece of bloudraad to limit the current.

Don't mix up DC isolaters and DC breakers

Most DC isolaters and even AC isolaters are not rated to isolate under full load. But a DC breakers should be able to isolate under a full load. That's what they are there for

Personally, as I normally run positive and negative in the same conduit, I use inline fuses from the panels. I then use a double pole fuse with a DC surge arrestor in my DC box (not a combiner box unless using Victron) and I use a double pole DC breakers as my isolaters. Can quite easily just switch off the circuit breaker, before going to the panels and disconnecting MC 4 connectors if I am wanting to make any changes.

I don't have to shut down the whole system and remove all loads

This is for the average domestic situation