[adiabatichottub]

Really depends on what we're talking about. A lot of electrical safety equipment has a DC rating, usually something like 90VDC/300VAC. Also, most DC equipment just isn't going to have the stored energy to generate a big arc. Well, except batteries, and we're already piling them all around us.

[torginus]

I mean it depends, but for dual rated stuff has both a voltage and current limit, both of which are way lower. Like typically a 230V/20A AC switch can switch 24VDC/2A. And the energy is not in the equipment, its in the mains (or batteries like you said, or PV panels)

[adiabatichottub]

Right, but that's why I mentioned safety equipment. Your common DIN-mount UL-489 branch circuit breaker will be rated for the same trip current, same short circuit current rating (SCCR), but lower voltage. So you can use the same wiring and breakers as you might have with AC and your 48V battery bank won't vaporize the $5 hardware store toggle switch that somehow became a shunt.

[torginus]

I mean, most AC circuit breakers use electromagnets to trip on overcurrent (as well as bimetallic strips using thermal methods for sustained high current).

Electromagnets dont work for DC, so your breaker will never trip. For thermal protection, you need current, so that checks out, and it would make sense for it to be rated under 50V as thats considered the highest voltage thats not life threatening on touch.

PV Batteries in general have a very high current (100s of A) at ~50Vish volts, so I dont think there's a major usecase for using household breakers for them.

Im still not getting your point BTW, switches and breakers are two separate things, with different workings, and household (and datacenter) DC would be I think around 400ish V, which is a bit higher than the peak voltage of AC, but still within the arc limits of household wiring (at least in 230V countries).

The advantage of DC is that you use your wiring more efficiently as the mean and peak wattage is the same at all times. Going with 48V would mean high resistive losses.

[adiabatichottub]

> Electromagnets dont work for DC, so your breaker will never trip.

If electromagnets don't work for DC then what am I supposed to do with this pile of DC solenoids and relays? ;)

> PV Batteries in general have a very high current (100s of A) at ~50Vish volts, so I dont think there's a major usecase for using household breakers for them.

That's what the SCCR rating is for. When there's a fault you're going to have a LOT of current flowing until your safety kicks in. Something like the grid or a battery bank will happily provide thousands of amps almost instantaneously. Breakers designed for protecting building wiring are rated for this. Now, most household breakers aren't dual DC/AC rated, but you can actually buy DC rated breakers that fit in a home panel (Square D QO series).

> Im still not getting your point BTW, switches and breakers are two separate things, with different workings, and household (and datacenter) DC would be I think around 400ish V, which is a bit higher than the peak voltage of AC, but still within the arc limits of household wiring (at least in 230V countries).

My point is that there isn't any material reason why DC can't be as safe as AC, all the proper safety equipment already exists. Extinguishing a DC arc during a fault is a solved problem for equipment at household scale.

> The advantage of DC is that you use your wiring more efficiently as the mean and peak wattage is the same at all times. Going with 48V would mean high resistive losses.

I just mentioned 48V because it's a common equipment voltage for household DC systems. 400V would be good for big motors and resistive heating loads.

Regarding DC vs AC and wiring efficiency, talking about mean vs peak wattage just confuses the issue. 1 volt DC is 1 volt RMS. It is an apples-to-apples comparison. If you want to say "we can use 170VDC or 120VAC with the same insulation withstand rating, and at lower current for the same power", then that is absolutely true. But your common 600V THHN building wire won't care if you're using 400V AC or DC, so it's mostly immaterial.