I wonder if there's any future to running both an AC and a DC bus through the house, or if that makes no sense for reasons beyond my basic understanding.
He still has all the original 110 wiring and fixtures in the house, but this battery-backed solar system runs all his lights. It can easily go 2 days without sun before he needs to use the regular lights. Another benefit is that DC LED bulbs are by definition flicker-free, and also low consumption (4-6 watts each) but bright. He calculated he can light each room better than before with 6-8 bulbs, so 40-50 watts, thus only 4-5 Amps (@ 12 VDC) to each room.
All the big appliances in the house still run off of of AC, but he does have a 110 inverter so that he could run a critical appliance such as a fridge during an extended outage.
So this little system replaces 1-2 kWh of incandescent lighting per day (CFC or LEDs on 110 would be less, but not flicker-free), while providing lights during outages. He says it's not cost-effective (the usage displaced by solar and battery usage doesn't cover the cost of the system), but the backup powers is worth it to him.
I guess you could pick whatever voltage you want for your loads and cable runs, but you need to have the appliances you want available (or easily DIY) in that voltage. It would probably be possible to convert down the voltage once, but any more than that and you're introducing loss again.
It is putting more current through each light.
And particularly problematic if each bulb has parallel LEDs and they start burning out: then more and more current is put through the remaining LEDs.
In other words, a 120VAC LED should work just fine on 48VDC with the same output.
It’s also explains why they don’t dim.
(Obviously avoid the dimmable ones in this application!)
You still need PWM to control brightness, no? I'd you're using resistors efficiency goes down a lot.
12 volt wiring in homes isn't terribly efficient as once you get past 6-10 feet you need really expensive (heavy, thick) wires to not have much voltage drop. Most new boats use 24 or 48v for long haul and then local step down to 12v where needed (kitchen, living, sleeping areas etc).
If you transmit the same number of watts at a higher voltage (lower current) rather than at a lower voltage (higher current) through a wire, you will lose less power.
So for moving the power around the house at distances more than around 10 feet (~3 meters), it's more energy-efficient to convert it near the point of use. And if you're already going to convert it, it's probably not worth the expense and complication of running two separate wiring systems.
i think the difference you're looking for is in volume of copper.
The big savings would be in longer lived electronic devices. A sizable portion of digital electronics ultimately fail because the capacitors in their power supplies exceed their designed lifetime. Electrolytic capacitors (ticking time bombs) are cheap and compact for the capacity so they are used for the energy storage required in single phase systems, but if designing a three phase power supply less storage is required and maybe manufacturers wouldn't have to optimize the smaller, capacitors with electrolytics. I've had a 4k TV and a rather expensive musical instrument amp fail for capacitors this year, about $3000 of gear there. Looking back further there are a couple of professional powered sound reinforcement speakers (twice), an iMac G5 (three times). It's probably safe to say over the decades I've had $10k of electronics fail prematurely from electrolytic capacitor failure. These are all items which were not obsolete or worn out. Scale that up from one person to worldwide and it's easily in the hundreds of billions (10⁹) of dollars which could be saved.
The problem is you can't get there from where we are. No one wants to drag more wires to residential houses, no one wants to shell out >$1k for a household phase converter and then rewire their house. You won't convince people to add three phase to a new house because it might be the future. And you won't convince the semiconductor houses to make a line of three phase power supply controller chips just because, well, maybe someone might use it.
We're probably trapped at a suboptimal local maximum.
Edit: In response to atoav's comment I found IEC 60309 and its extra low voltage variant which is a 42mm (1 2.3") 3 phase plug and connector in two compatible sizes good for 1.3kW and 2.6kW. Also, that Germans and Swedes did the engineering first and then built an electrical system and they get 480V 3 phase at 16A to their cooktops and stoves through a plug for a whopping 13kW!
All we are missing is for it to be standard to wire the 3 phase distribution throughout buildings to every outlet (preferably in a backwards compatible manner; in theory converting 3-phase to single phase is just a matter of ignoring a wire. I would assume that a) the grid can handle people doing this and b) doing this with out current 3-phase standard would result in our current single phase standard,
While the appliances are probably approved fo 208V, I doubt they’re drawing more peak current to make up for it.
Edit: and as an aside, why we probably don't do that everywhere: it makes for bigger plugs, and keeping safety standards can be a bit more expensive and space intensive with the potential 400V between phases.
I see the successor to the 16A Perilex connectors you are referencing is IEC 60309 which has an "extra low voltage" version with a smaller, 42mm diameter (1 2/3") plug good for 16A or 32A. 16A devices will fit in a 32A socket, but not the other way around. So that seems to be a 1.3kW and 2.6kW solution. Sign me up!
We don't have three phase (well its not common) but we can heat an oven up to 220c(420f) in 7 minutes. I think its a 3kw oven. its on a 32 amp (isolated) breaker.
Germany is 230v so that would be more like 3kw and 6kw.
I'm in the UK (also 230v) and a standard outlet can do 3kw, I think fuseboard fuses are 32amp so I don't know if 6kw is a practical upper bound though (edit: On 2nd thoughts I'm not even sure this is relevant to 3 phase).
Modern single ovens can also be connected to a standard single phase outlet rather than a dedicated circuit. In my kitchen the induction cooktop is on a 16A three phase circuit, and all the other outlets (fridge/freezer, oven, dishwasher and appliances) are on a 16A single phase circuit.
5:11 from 20°C to 220°C
I've never actually come across anything higher than 3kw, also a 16amp fuse isnt that precise, you could probably get up to 20 amps without it failing. The hotter you run it the quicker it fails though, so if you're regularly running 3.7kw through a 16 amp fuse, you may well find it failing, not through an underlying fault of anything plugged in to it.
Most cables are 16A, so the outlets are 16A as well. Also UK uses 240V, not 230V. 32A circuit breakers would make the cables burn when overloaded.
"Use a 30amp fuse or 32amp MCB for larger radial circuits, ring circuits up to 100m, cookers and electric showers up to 7200W"
>ring circuits up to 100m, cookers and electric showers up to 7200W
Normally those tend to be 3phases.
Of course it's possible to get over 16A on a single phase and a circuit breaker but that's quite a non-standard option. The issue is that if the fuse/circuit breaker is rated for 32A in a standard application (i.e. an outlet) the cables are likely to burn 1st.
I'm talking about the UK here, which I understood to be similar to the rest of Europe(?).
That's a UK website and 3 phase isn't common here. I've just double checked my fuse box, and I have a 32 amp fuse for my socket ring main.
Don't forget for a ring main the current is spread over 2 wires, so if theres 32amps power draw, theres only 16amp on each side of the ring.
Or make power supplies some sort of standard, so you can use your own expensive capacitor power supply instead? Or just shop for things that have separated power supplies?
So as its going to become AC at some point anyway, why not use the existing wiring.
On the other hand, the biggest power users in a house (heater, air conditioner, dryer, stove, refrigerator) seem like they are a different story. In a future home with solar power and a high voltage DC battery pack, I think there is opportunity to make appliances that operate from the raw battery voltage, which is in the 300-500v DC range. That way, there isn't any conversion required at all, and those applications should be able to handle slight variations in voltage as the battery discharges.
High voltage DC is spectacularly more dangerous than high voltage AC.
And no, I never tried lighting one. Hopefully none of them had had an active gas supply in decades.
Given the degree of fire risk in houses that's associated with 230V/10A wiring and devices, I do wonder how much safer it would be to have fewer AC/DC transformers scattered around the house with DC wiring.
If it's just a matter of providing alternative circuitry for low-power devices, presumably you can already improve safety by just using lower-current circuit breakers.
A good point - I guess I'm mostly thinking about the volume of things in the house that don't really need access to even a fraction of the 2.4kW available; having moved from incandescent bulbs to LEDs, I've got a bunch of unnecessary power supply and per-bulb transformers, for example.
The ISS runs 120v DC for this reason...higher efficiency and much less complex since you don’t need inverters and and power supplies.
My burning man camp of 65 people also only has a DC grid that runs on 24v
30kwh daily solar harvest
It’s a thing of beauty :)
I used to have a house built around 1950 which had combination 117/220AC and 25VDC wired throughout the house. The electrical box was sectioned and the 25V had a large transformer. The house had low voltage DC ceiling fixtures that were tricky to source, and everything in the house that was switch controlled was on relays that allowed multi-point control, smart timers, and various other functions. It was a chore to get replacement parts but fortunately the attic had gangways and such so replacing blown relays was not horrific once you had the replacement parts. It was perfect for upgrading to smart control which I did for about half the house before selling it. Here's the thing. Tons of houses back then were wired this way. It was the wiring of the future and they explicitly realized in the 50s that someday they would be able to have computers in the home, perhaps as small as a single room, control everything. So instead of an electrical closet there was an electrical room with enough space for a refrigerator sized computer should such a thing ever come to market. 1950s.
Other companies are working on this (energy sovereignty) issue, my guess it (stand alone affordable systems) will be solved within the next twenty years and be affordable. DC use might be apart of it but I'm doubtful since there is a level of complexity that each device is using different amps/volts/etc that will take new products to solve and the independent grid system still takes a lot of capital.
I would be very surprised if you could find any non-ancient (and I really mean ancient, like, pre-PC, probably even pre-home computers) computer PSU that you couldn't feed with DC. What voltages will work will vary, but as long as you stay below the peak voltage corresponding to the effective voltage printed on the label, you probably won't damage anything.
If you really want to test it, you could measure the resistance at the mains input, if that gives you a non-infinite value that stays at that value (rather than increasing towards infinity), you are dealing with a mains transformer. But you really won't find that in a computer PSU.
It's a hot-swappable 300-1897 (aka X6328A aka Type A217) 1050W Sun PSU. I'm primarily worried about the active PFC I expect in it.
Is there a way to test such a PSU without risking the entire server? (save for taking everything out that isn't needed to post into BIOS)
Active PFC tends to be simply a boost converter at the input stage that boosts the (rectified but still unfiltered) input voltage to (DC) 350 V or more, modulating the current to follow the mains voltage and should generally have no problem with DC input, especially so with wide-range inputs that have to be able to deal with different voltage levels anyway.
I'm particularily worried about confusing that following/regulating circuity. If the 50/60Hz it senses are caused by screen refresh feeding back somehow, it might end up behaving "weird".
But I guess I'll just try, and hope it won't break anything.
The transition is something like: 90-240V AC (50-60Hz) -> DC (1.414*AC) -> AC high frequency ->(transformer) AC low voltage -> DC 12V
Very cheap electronics that use capacitor+resistor voltage drop need AC.
---
To answer the question directly, use a small fuse 1-3A and run the PSU idle. Like advised by sibling, measuring the resistance would be sufficient as well.
https://www.quora.com/Why-do-we-use-AC-but-not-DC-in-househo...
Carrying high voltage DC, comes with its own issues - likely doable though. Many household devices would run perfectly fine on high voltage DC (instead of AC).
The cost for the cables themselves would be lower than copper AC, even.
Think of it something like planning the DC loads on a 55 ft sailboat.
People who do this will usually have one small 300 to 500W sized DC to ac pure sinewave inverter for laptops and chargers of small consumer electronics.
Your fridge is probably running “variable frequency drive”, so instead of being off and on at full blast, it just runs the compressor at 20hz or 30hz or whatever it needs continuously, and dialing that up or down depending on demand.
Your air conditioner too.
For bigger customers, this saves them a fortune in demand charges.
For others, it prolongs life by vastly reducing stop/starts.
tldr: it would make sense for an office building but actually not that much in a residential one.