How Long Until Low Volt DC dominates building power distribution?

[JRK_Labs]

Intelligent zoned lighting control with one simplified light switch and all low voltage wiring. It should reduce installation time and is optimized for LEDs. I'm only planning to run 120 VAC for outlets and appliances at this point.

 

[mikeames]

combined with the fact that practically every modern device is taking th AC from outlets and converting it to lower volt DC,

I could certainly see home load centers with designs providing USB power delivery to most common sockets though out the house with a few areas with normal 120/220v ac in Kitchens, wash rooms, and shops. Has anyone seen any info like this on next get load centers?

That the equivalent of saying everybody eventually gets out of a car when they get to the store so everybody should just walk to the store , forget cars. Or why have interstate if all people have at home is driveways.

Devices step it to DC because solid-state requires it and control electronics simply don't require a lot of the power. You don't overhaul the system because of that. You mention USB. How many times has that changed? How many times has the nema 5-15r changed? USB-C is good today what about in 10 years. No way would that stand the test of time. Not to mention them physically wearing out.

Intelligent zoned lighting control with one simplified light switch and all low voltage wiring. It should reduce installation time and is optimized for LEDs. I'm only planning to run 120 VAC for outlets and appliances at this point.

Its already out, you posted about it. BUT BUT BUT...... what powers the POE switch?


There will be an increase in POE powered appliances and devices for various reasons, but the buildings electrical infrastructure has stood the test of time, has been reliable, able to adapt to the increased consumption of power and will continue to meet demands with flexibility for the foreseeable future. I see no reason whatsoever as to why it should be drastically changed at the moment. I am open to re-evaluating in 50-100 years.

 

[mikeames]

There's a very good chance that all lighting and switches will be 24VDC tied to a Loxone home automation system.

There are many who wired "smart" homes in the 80s, 90s, and even early 2000s. Some had whole house diming panels and rand the feeds to lights directly to the diming panel in the basement. Only a low voltage "smart switch" was in the room. Now those system are obsolete and there are better alternatives. Too bad the house is permanently wired for one type of system.

Personally the whole "Smart" home stuff is overblow and over rated. I have used it personally, and installed it, and most of it is whiz bang awh cool stuff that only is used when showing off what it can do. NOT ALL OF IT. People seem to be more interested in putting it all in one app and being able to control it on their phone, than actually being inconvenienced by controlling things manually. Just my opinion but smart homes are not a new thing, they just keep changing.

 

[K8MHZ]

The recent advent of USB3 power deliver protocols delievering varying levels of low Volt DC power options which are delievering enough power to run most computer equipment, lighting, and many appliances combined with the fact that practically every modern device is taking th AC from outlets and converting it to lower volt DC, I am wondering when the fundamental change in load center solutions will begin to charge, particularly on the residential side of things. I can see future load centers doing All of the DC rectification centrally with low Volt USB power delivery lines being distributed thoughout the house. This avoids loads of switching power supplies all over the house from plug in hone chargers to switchng done in 120v/USB power plugs. Such ad hoc power conversion at everywhere endpoint is not efficient and just generally wasteful.

I could certainly see home load centers with designs providing USB power delivery to most common sockets though out the house with a few areas with normal 120/220v ac in Kitchens, wash rooms, and shops. Has anyone seen any info like this on next get load centers?

If you are suggesting that the load centers provide 5 volt DC through a cable to a USB receptacle, what about voltage drop? What size cable would you need to assure 5 volts at the receptacle with 50-100 feet of run length? A quick calculation showed that using #12 for 100 feet of 5 VDC, a 1 amp load would drop over 8 percent. You would need to go up to 10 AWG to maintain less than 5 percent voltage drop. I don't see the advantage over just using 120 VAC at the receptacle to be converted to USB voltages.

Edit to add: 5 amps will drop over 40% at the end of a 100 foot run. To maintain a 5% drop, you would need to run 3AWG.

 

[gadfly56]

If you are suggesting that the load centers provide 5 volt DC through a cable to a USB receptacle, what about voltage drop? What size cable would you need to assure 5 volts at the receptacle with 50-100 feet of run length? A quick calculation showed that using #12 for 100 feet of 5 VDC, a 1 amp load would drop over 8 percent. You would need to go up to 10 AWG to maintain less than 5 percent voltage drop. I don't see the advantage over just using 120 VAC at the receptacle to be converted to USB voltages.

Edit to add: 5 amps will drop over 40% at the end of a 100 foot run. To maintain a 5% drop, you would need to run 3AWG.

Yeah, that'll work well.

 

[gar]

210730-1929 EDT

Way back in the 1870s Tom Edison did some analysis, or had his employees do an analysis on what voltage to use.

First, Edison understood that to make a workable and useable system work that it had to have parallel loads, and a low distribution source resistance. This was in contrast to many others in the electrical field that viewed a power system from the perspective of maximum power transfer. Maximum power transfer occurs when source resistance equals load resistance. I believe that the 110 to 120 V supply voltage was based on what seemed possible in the construction of a light bulb.

Also note that Edison invented the 3 wire distribution system to reduce copper costs. In seems reasonable to call this a two phase DC system.

Besides the basic elements Edison created all the other items necessary to create a complete electrical system.

An AC power system means you can use a simple, rugged, and reliable device ( a transformer ) to get whatever end voltage you want. The 120 V level system is not a bad choice. Also note that with an AC system vs a DC system there is relatively quick arc quenching. Reliability of the basic elements in a 120 V AC system is very good. Note, Edison started with a DC system because that was practical for him at that time to create a whole new system of lighting in just a few years. About 2 years at the very start, and another couple years to fairly high power ( the Pearl St power station ). The DC-AC fight was probably mostly a personality conflict between Edison and Tesla.

For a concept on Edison and Invention see "Working at Invention" a publication by Henry Ford Museum and Greenfield Village by William S Pretzer.

.

 

[kwired]

In 25 words or less, tell us what advantage that has over conventional power, considering that 120 volts will still be needed for appliances, etc.

-Hal

Wood stoves and go back to "ice houses" for storing chunks of ice from the local lake in the winter for use in the summer

Think that was right on 25 words even.

 

[yuhong]

If you are suggesting that the load centers provide 5 volt DC through a cable to a USB receptacle, what about voltage drop? What size cable would you need to assure 5 volts at the receptacle with 50-100 feet of run length? A quick calculation showed that using #12 for 100 feet of 5 VDC, a 1 amp load would drop over 8 percent. You would need to go up to 10 AWG to maintain less than 5 percent voltage drop. I don't see the advantage over just using 120 VAC at the receptacle to be converted to USB voltages.

Edit to add: 5 amps will drop over 40% at the end of a 100 foot run. To maintain a 5% drop, you would need to run 3AWG.

This is not 5V DC. 48V DC is not new.

 

[Besoeker3]

This is not 5V DC. 48V DC is not new.

Quite right. We use 40,Vdc for anodising units. Mind you, those are 40,000A units - maybe not quite what the original poster had in mind.........................

 

[K8MHZ]

This is not 5V DC. 48V DC is not new.

USB is 5 volts. From the OP's first post:

I could certainly see home load centers with designs providing USB power delivery to most common sockets though out the house with a few areas with normal 120/220v ac in Kitchens, wash rooms, and shops. Has anyone seen any info like this on next get load centers?

 

[electrofelon]

There are many who wired "smart" homes in the 80s, 90s, and even early 2000s. Some had whole house diming panels and rand the feeds to lights directly to the diming panel in the basement. Only a low voltage "smart switch" was in the room. Now those system are obsolete and there are better alternatives. Too bad the house is permanently wired for one type of system.
.

Yup, and those are a nightmare to deal with because you can't get parts and very few people know how to work on them. I have a client that bought a house with one. Occasionally they want me to fix or reprogram something and I tell them no, I don't know crap about it and don't want to try and figure it out.

 

[MichaelO13]

I kind of forgot about this thread but I just dug it up after a project I just finished reminding me of it and I read some of the replies. With all due respect, many of the reply authors drip of luddites being scared of change. I strongly support the trades and recommend to kids all the time to look into becoming an electrician instead of college. My father was a commercial plumber and fed and raised me on his salary. I worked with him as a teenager for years and met tons of electricians. I fell in love the engineering and the work electricians do, to my father's chagrin, since he was a plumber - but he supported me making a career out of it. Luckily I learned outdoor work wasn't for me doing plumbing with him before I made that choice. I can deal with the heat but my body shuts down when it gets under 30 and my hands stop working.

So with that being said, yes - I am an IT type. I work in that field as an data center architect. Despite the opinions of some here, I do not think that limits me to understanding the concept of higher amperage circuits requiring thicker gauge wires. I still to this day enjoy electrical work and watch Mike Holt youtube videos on the IEC, and him ranting about the differences between grounding and bonding. I watch these at night as some would watch ordinary TV shows just because I want to learn. I will never be an electrician professionally being 40 now, but I still like to learn just out of love for it. My long winded and probably too long reply thus far is just to highlight I have nothing but love for all of you that do this job, the value it contributes to society, and the engineering science behind it. I have zero reason to try and 'outsmart' or disrespect you and certainly consider your opinions as stated even if they refute my own.

With all that said, I still stand behind my original statements. Low volt DC has a future in construction whether that be direct DC, USB PD, or PoE (hopefully not PoE it has its own problems but I digress). It simply makes no sense to deliver AC power to systems like LED light fixtures that only require tens of watts at max and having a PCB that rectifies AC in every single light bulb and light fixture is wasteful, expensive, and dumb. The only reason its done now is for legacy support and even then they fail 99% of the time well before the LED itself. That same goes to tech and entertainment devices like tablets, laptops, smart phones and some TVs. I am not going to try an say how the upstream solution will be done be it rectification on a panel level in the building, at the pole, or via HV DC transmission - I will leave all that to the linemen and power plant EEs. Also to be clear - AC mains is not going anywhere either, though I can see a future where lighting is strictly LVDC, there are less mains plugs in a room, and panels are smaller in rating. It is simply cheaper if no other argument swings your opinion. It will start with dense apartments and then on to residential homes; Eventually even some commercial sites.

What reminded me of this thread is a project I am working on at home to convert all my old cat3 and cat5 based phone jacks into emergency lighting and USB power sources since I don't use a land line anymore. I put a 12 volt UPS/Power supply combination near my demarc for all my low volt cabling for my house (yes I disconnected it from telco service first!) I have a circuit that turns on when AC is lost for the lighting, and another one that always provides basic USB power. Each line is fused at a few amps. It works great thus far for those interested

 

[tortuga]

I think there are other advantages of AC over DC for house wiring, and I don't think a bridge rectifier in each light is a big deal. It will be interesting to see 10 amp branch circuits in 2023 literally 100 years after they left the code. It will be interesting to see how things pan out.

I am working on at home to convert all my old cat3 and cat5 based phone jacks into emergency lighting and USB power sources since I don't use a land line anymore. I put a 12 volt UPS/Power supply combination near my demarc for all my low volt cabling for my house

I would not use 12 volts DC on 24 awg wiring ever, If I had to do such a system I would use more like -48 like the telco's used or a proper PoE supply.
at 12 volts your limited to about 12 watts or 1 amp on that gauge.
At -48 then at least you could approach 48 watts.

Also I think Hal nailed it in post #40:

In 25 words or less, tell us what advantage that has over conventional power, considering that 120 volts will still be needed for appliances, etc.

-Hal

 

[MichaelO13]

I would not use 12 volts DC on 24 awg wiring ever, If I had to do such a system I would use more like -48 like the telco's used or a proper PoE supply.
at 12 volts your limited to about 12 watts or 1 amp on that gauge.
At -48 then at least you could approach 48 watts.

I am considering using higher voltages for some of the lights for this reason but luckily a lot of my phone jacks in my house were actually run with higher gauge thermostat wire instead of actual cat3. A handful upstairs are 24 gauge cat 5 though and I am thinking about raising the voltage there. The LED lights I have take 12v or 48v though I would need to put a boost converter in the main power source. The runs are short since all the wiring is hub and spoke and converge in the attic and the LEDs only take a few watts running. That said, I may still do as suggested.

 

[zbang]

“Curiously enough, the only thing that went through the mind of the bowl of petunias as it fell was Oh no, not again."
--Hitchhiker's Guide to the Galaxy

 

[tallgirl]

I am considering using higher voltages for some of the lights for this reason but luckily a lot of my phone jacks in my house were actually run with higher gauge thermostat wire instead of actual cat3. A handful upstairs are 24 gauge cat 5 though and I am thinking about raising the voltage there. The LED lights I have take 12v or 48v though I would need to put a boost converter in the main power source. The runs are short since all the wiring is hub and spoke and converge in the attic and the LEDs only take a few watts running. That said, I may still do as suggested.

I used to have this kind of conversation when I still doing off-grid solar. My clients had 24 or 48VDC in abundance and wanted to more of that and less of the inverter output.

AC is nice because you don't need a fat cable to deliver more than a few amps.

That said, I do believe there will be more / better low voltage DC products on the market and things like DC charging ports will be included in more locations with a household. Some company or industry body will have to come out with an entire product line to support whatever the vision of this future is for pure low voltage DC LED-based lighting solutions happens to be. That means, all the connectors, switches, receptacles, power supplies, wiring methods, everything. There's another thread talking about wafer lights and I think they are stupid because they all have proprietary drivers and connectors.

In my lifetime "low voltage charging things" when from USB A/B, to mini USB A/B, to micro USB, to USB C. That's just been the last 30 years or so. My house is 60 years old. I'm very glad it does't have 500mA USB A charging receptacles everywhere. They'd be useless for trying to charge most of my devices. Dittos for PoE, because PoE hasn't stayed put in terms of how much power and how.

 

[garbo]

The recent advent of USB3 power deliver protocols delievering varying levels of low Volt DC power options which are delievering enough power to run most computer equipment, lighting, and many appliances combined with the fact that practically every modern device is taking th AC from outlets and converting it to lower volt DC, I am wondering when the fundamental change in load center solutions will begin to charge, particularly on the residential side of things. I can see future load centers doing All of the DC rectification centrally with low Volt USB power delivery lines being distributed thoughout the house. This avoids loads of switching power supplies all over the house from plug in hone chargers to switchng done in 120v/USB power plugs. Such ad hoc power conversion at everywhere endpoint is not efficient and just generally wasteful.

I could certainly see home load centers with designs providing USB power delivery to most common sockets though out the house with a few areas with normal 120/220v ac in Kitchens, wash rooms, and shops. Has anyone seen any info like this on next get load centers?

The recent advent of USB3 power deliver protocols delievering varying levels of low Volt DC power options which are delievering enough power to run most computer equipment, lighting, and many appliances combined with the fact that practically every modern device is taking th AC from outlets and converting it to lower volt DC, I am wondering when the fundamental change in load center solutions will begin to charge, particularly on the residential side of things. I can see future load centers doing All of the DC rectification centrally with low Volt USB power delivery lines being distributed thoughout the house. This avoids loads of switching power supplies all over the house from plug in hone chargers to switchng done in 120v/USB power plugs. Such ad hoc power conversion at everywhere endpoint is not efficient and just generally wasteful.

I could certainly see home load centers with designs providing USB power delivery to most common sockets though out the house with a few areas with normal 120/220v ac in Kitchens, wash rooms, and shops. Has anyone seen any info like this on next get load centers?

About 5 years ago at an IAEI class they mentioned that Japan is experimenting with installing DC panels in commercial buildings . Said it would save 3 to 5% on energy due to you would not need a transformer or rectifier in vast majority of electronic devices. UPS'S would be cheaper and consume less power. also a reduction in Air Conditioning. I would be very skeptical of having both AC & DC power in homes. Have seen my share of dangerous work by homeowners. Also do not like the idea of running power for exit luminaires on POI.

 

[gadfly56]

To answer the original question, "How Long Until Low Volt DC dominates building power distribution?", that would be never, and that's just an estimate. Others have pointed out the issues, and they are fairly intractable.

 

[drcampbell]

... Don’t forget that although DC won’t kill you outright by causing heart fibrillation, it rips muscle tissue and breaks bones and unlike AC, it does not let go or knock you away. ...

I've heard the opposite, that DC will kill you outright.

There is a classic paper, published about 1952-ish and titled something like Biological Effects of Electric Current, that investigated the effects on various species of livestock. (sorry, I've lost the citation ... can anybody here find it?) One of the interesting things they discovered was that 50-60 Hz is the "optimum" frequency for biological effects (the greatest biological response for a given current) and that both DC and 400 Hz required about twice as much current for the same effects. (with even-higher frequencies requiring gradually more current for the same effect)

... Fuses are twice as big and breakers 4 times larger because an AC circuit goes to zero Volts 120 times a second so it is trivially easy to shut down an AC circuit where with DC you literally have to pull the arc apart while energized. Large DC breakers are genuinely enormous. A 50 A DC breaker is about the size of a 1000 A AC breaker with no way to reduce the size…it’s physics at work. ...

Fuse/breaker design is a fascinating field of inquiry.

Expanding on this a little ... when a fuse blows, there is a period of time when the element has melted, but the current has not shut off. An arc forms inside the fuse (or between the breaker contacts) and the current continues flowing.

With AC, the arc goes out when the supply crosses zero, and will need to be re-ignited for the next half-cycle. With DC, the arc just continues arcing until something makes it go out. This is why it's common to see fuses rated 250vac/32vdc, or to have no DC rating at all.

And the methods of "making it go out" are often quite entertaining. Sometimes something simple, like filling the fuse with sand. Large DC relays and breakers have a powerful permanent magnet to force the arc away from the contacts. Large breakers often use a "puffer" to blow the arc out with cool compressed air, or force the arc into an "arc chute" to split it up into a bunch of smaller pieces, a little like snow drifts through a picket fence.

 

[Besoeker3]

To answer the original question, "How Long Until Low Volt DC dominates building power distribution?", that would be never, and that's just an estimate. Others have pointed out the issues, and they are fairly intractable.

I agree. For residential here in UK there is just 230Vac and that's it. Lighting and power is ac. There is no easy to convert things like cookers, washing machines, dishwashers and electric showers. And no point in doing so.