Is there or will there ever be a 48VDC outlet standard for homes & buildings?

[tonypsofla]

Should not be a problem of transferring DC voltage the short distances inside a house. (DC is not good for long distance, just ask Edison)

So have the big players come together and agreed on a 48VDC wiring and outlet system?
90% of your electrical stuff would work better with a steady 48VDC than 115 AC as with that it has to down convert, rectify and use huge capacitors to filter out the valleys.

The 20% energy loss of transferring 48v battery to AC and the electronic products change it back to dc is just a waste.

[russ]

Should not be a problem of transferring DC voltage the short distances inside a house. (DC is not good for long distance, just ask Edison)

Boy you sure have that backwards! You are 100% wrong.

[sdold]

48 V DC would still need to be converted to AC and back in the power supplies* to produce the different internal voltages needed to run most electronic equipment. Besides, if you have devices running on 48 V, the wire size needs to be bigger to handle the same power. I don't see any advantage.**

*forgetting for now about series regulators like the LM78xx series.

**except for telco and microwave equipment, which is usually hardwired, but it might be nice to have plugs.

[Sunking]

48 V DC would still need to be converted to AC and back in the power supplies* to produce the different internal voltages needed to run most electronic equipment. Besides, if you have devices running on 48 V, the wire size needs to be bigger to handle the same power. I don't see any advantage.**

You would be correct and the reason you do not see it or ever, or ever will, is low voltage is, well low voltage = low power and expensive wire.

Just how in the heck would you distribute over a network like a whole neighborhood. There is a very good reason we and the world distribute using AC. Only thing we got wrong in the USA because we were first, is too low of a voltage for house currents. We are 240/120 while a majority of the world is just simple 240 for residential services. Higher the voltage the less expensive it becomes with the lowest losses.

But to answer your question there is nothing preventing you from wiring your home with 48, 24, or 12 wiring. All you have to do is follow electrical codes. Now good luck finding gizmos that use 48 vdc and they will not be high powered. Example, a Euro example. A 15 amp 240 volt circuit can power a 2880 watt device continuously on 14 AWG wire for a considerable distance of about 100 feet one-way distance. A 15 amp 48 volt gizmo on 14 AWG can power a 550 watt gizmo for only about 25 feet 1-way.

[sdold]

I assumed he was talking about 48v versions of appliances for off grid use. The market for those would be so small that they would probably just be regular products with inverters added.

[inetdog]

Should not be a problem of transferring DC voltage the short distances inside a house. (DC is not good for long distance, just ask Edison)

So have the big players come together and agreed on a 48VDC wiring and outlet system?
90% of your electrical stuff would work better with a steady 48V than 115 AC as with that it has to down convert, rectify and use huge capacitors to filter out the valleys.

The 15% energy loss of transferring 48v battery to AC and the electronic products change it back to dc is just a waste.

Comparing 48V DC to 120V AC for distribution inside the house, you find that for the 48V you will need to use wire with about three times the cross section. The added cost of ire and larger raceways and more difficult installation keep it from being the obvious choice that you see it as.

If TELCO equipment did not have a long history of 48V DC and a large investment in battery plant, powering equipment from 48V DC would not be an obvious choice for them either.
The exploration of using DC for distribution in large data centers focuses on higher voltages (~300V). That is too high a voltage for safe domestic use, since unplugging live connections can cause serious arcing.

[Sunking]

If TELCO equipment did not have a long history of 48V DC and a large investment in battery plant, powering equipment from 48V DC would not be an obvious choice for them either.
The exploration of using DC for distribution in large data centers focuses on higher voltages (~300V). That is too high a voltage for safe domestic use, since unplugging live connections can cause serious arcing.

Hey Dave data centers do use some some DC, but it is 48 volts.

Now off in a room somewhere you can find some high voltage DC battery banks, but it is used for the UPS. Most equipment in data centers can use either 90 to 270 VAC @ 50 or 60 Hz (208) so it can be used in every country. Large format UPS can use up to 600 VDC on something like a 1 to 2 Mw system. Large format UPS almost all operate at 480 VAC. Then out in the equipment rooms you will find strategically place PDU's (power distribution units) that take the 480 volts, and transform it down to 208/120 for distribution to equipment racks.

[inetdog]

Hey Dave data centers do use some some DC, but it is 48 volts.

Now off in a room somewhere you can find some high voltage DC battery banks, but it is used for the UPS. Most equipment in data centers can use either 90 to 270 VAC @ 50 or 60 Hz (208) so it can be used in every country. Large format UPS can use up to 600 VDC on something like a 1 to 2 Mw system. Large format UPS almost all operate at 480 VAC. Then out in the equipment rooms you will find strategically place PDU's (power distribution units) that take the 480 volts, and transform it down to 208/120 for distribution to equipment racks.

I was not talking about currently used DC systems but rather the "conceptual" DC distribution (center tapped +190/N/-190) described in this paper.

The advantages of higher AC voltages for distribution, as well as some good arguments for capping the voltage at 240VAC can be found in this related paper, which makes your point on specific costs very well.

[Sunking]

I was not talking about currently used DC systems but rather the "conceptual" DC distribution (center tapped +190/N/-190) described in this paper.

Interesting had not read the White Paper from ADC. THX. However that is proposals and not currently in use.

Now in electric utilities at just about every sub station you see will have a 140 VDC battery bank in there that powers all the Relay, Switching, Control, and Telemetry.

[ZoNiE]

We should convert to 240V since it is already wired into the house. A simple large transformer and split bussbar at the panel to make the 240V L1-L2 to line-Neutral. This will leave our L1-L2 appliances alone. Gov't could give out transformer vouchers like they did with the Digital to Analog TV adapters. Power company pays for the big one, Gov't pays for the little ones needed to use existing appliances that cannot take 240. Light bulbs can simply be changed as the socket is the same. The gov't can use this to burn out all the existing leftover incandescent bulbs LOL.

In Brazil, they use an outlet that can have either 110 or 220V. Some outlets are the same as ours, sometimes they wire in european or Swiss outlets. Their "Standard" is a cross between ours and Euro's w/o the ground. They are labeled with the voltage they carry so people will not plug a 110V device into a 220V outlet, but they can. The shape of the outlet allows them to easily import European appliances w/o Change.

It makes sense, as a transitional measure, but how many people would fry electronics and such by not reading the voltage on the appliance?

At least most new (electronic) devices can take 90-240V AC and automatically convert internally, so more likely than not, people would only blow light bulbs and older resistive load appliances. It would be nice to have 240V at the plug. With our wire sizes, we could carry a lot more current.

Euro outlets are usually 7A and 16A to our 15A and 20A. I don't advocate switching to round pins, as they wear out much faster than bladed outlets. Damn plugs always fall out of the wall over there...

British Plugs are absurdly large and are internally fused.

Brazil Plug:
brazilelectric.jpg

I am starting to see universals like the one below in Hotel Rooms overseas, especially Singapore and have seen some on 777 aircraft. I bought a power strip in Malaysia with these and put a US plug on it so anyone who visits can plug in in our conference room.
ef10.jpg

[inetdog]

We should convert to 240V since it is already wired into the house. A simple large transformer and split bussbar at the panel to make the 240V L1-L2 to line-Neutral. This will leave our L1-L2 appliances alone. Gov't could give out transformer vouchers like they did with the Digital to Analog TV adapters. Power company pays for the big one, Gov't pays for the little ones needed to use existing appliances that cannot take 240. Light bulbs can simply be changed as the socket is the same. The gov't can use this to burn out all the existing leftover incandescent bulbs LOL.

It may seem like a small point, but in terms of conversion cost the following actually adds up:
The circuit breakers in a normal US commercial or residential panel for 120/240 or for 208Y/120 three phase are only rated for a voltage of 120V to ground. What you suggest would require replacing all circuit breakers with ones that cost upward of twice as much (and may actually require replacing the breaker panel itself.)
And the insulation inside light fixtures as well as the insulation in switches may well not tolerate a voltage of 240 to ground/neutral.
You would also have to provide two opposite 240V phases (for a difference of 480V) or else rewire every circuit in the building that carries both an L1 circuit and an L2 circuit with a shared neutral wire. (Called a MultiWire Branch Circuit, MWBC, or Edison circuit.)

[russ]

What you suggest would require replacing all circuit breakers with ones that cost upward of twice as much (and may actually require replacing the breaker panel itself.)
And the insulation inside light fixtures as well as the insulation in switches may well not tolerate a voltage of 240 to ground/neutral.
You would also have to provide two opposite 240V phases (for a difference of 480V) or else rewire every circuit in the building that carries both an L1 circuit and an L2 circuit with a shared neutral wire. (Called a MultiWire Branch Circuit, MWBC, or Edison circuit.)

Lots of difference between BSing and doing

[Sunking]

The circuit breakers in a normal US commercial or residential panel for 120/240 or for 208Y/120 three phase are only rated for a voltage of 120V to ground. What you suggest would require replacing all circuit breakers with ones that cost upward of twice as much (and may actually require replacing the breaker panel itself.)

Not entirely accurate. Any breakers that can fit in a single phase breaker box is rated 240 VAC. They have to be in the event you loose your grounded circuit conductor from the utility, and that is a very common occurance most folks have seen at least once in their life. Ever been in a home where some lights are brighter than the others that should be the same intensity? If you do, rush out to your main breaker and turn off power to the house. Immediately call the POCO and tell them the voltage is unbalanced and your fridge is making funny noises. You will hear the POCO's truck breaks squeal outside before you hang up the phone reporting it to them

However it will never happen in the USA, so it is a moot point. Once a standard is in place, almost impossible to change. Problem for the USA was Edison himself and his damn light bulb operating on 110 VDC really screwed us up being first to electrify. Having said that there is nothing to prevent you from wiring your home with 240 VAC Balanced lines. Eliminates all the headaches of a unbalanced 240/120 grounded system. Question is where are you going to get your gizmos? Appliances no problem as most all are made to operate on 208 or 240. Computers no problem as the power supplies are designed to operate from 90 to 275 volts. Many TV's and AV systems can work 90 to 275 volts. The rest? Easy solution though, just install a 2:1 step down transformer. But all unpractical.

As for converting existing home wiring, actually pretty easy to do. You just put Black tape on the ends of all White Conductors, and move them to a circuit breaker. Green wires stay put. Then change out all your receptacles to a 250 NEMA-6-XR. Good luck finding gizmos with the right NEMA-6-XP


nema-plugs-receptacles.gif

[inetdog]

Not entirely accurate. Any breakers that can fit in a single phase breaker box is rated 240 VAC.

Think again Dereck.
The typical breaker found in a 120/240 panel (and essentially all residential breakers) have a voltage rating of "120/240". What that means is that they can withstand and safely interrupt 240 volts between their line and load terminals. And, as you say, in the case of an open neutral the breaker could see L1 voltage on the line terminal and L2 voltage on the load terminal, for a total of 240V across the breaker. That is the 240 part of the 120/240 rating.
But the reason for the "slash rating", with the 120 in front, is that the breaker is only tested and rated for a maximum nominal voltage of 120 volts to ground on any terminal. (Even though ground does not appear as a current carrying wire connected to the breaker.)

One effect of this is that you are not allowed to use a slash rated breaker on the high leg of a 120/240 three phase four wire panel. Nor can you use a slash rated breaker in a corner grounded 240 delta situation, even when the load is between one of the ungrounded lines and the grounded line. Nor can you use a two pole slash rated breaker for a line to line load of 240V in a corner grounded delta configuration.

The fully rated 240V breakers are generally used in three phase delta panels, and cost a lot more than slash rated breakers.

[Sunking]

Think again Dereck

You are welcome

.

The typical breaker found in a 120/240 panel (and essentially all residential breakers) have a voltage rating of "120/240". What that means is that they can withstand and safely interrupt 240 volts between their line and load terminals. And, as you say, in the case of an open neutral the breaker could see L1 voltage on the line terminal and L2 voltage on the load terminal, for a total of 240V across the breaker. That is the 240 part of the 120/240 rating.
But the reason for the "slash rating", with the 120 in front, is that the breaker is only tested and rated for a maximum nominal voltage of 120 volts to ground on any terminal.

So what has changed that would prevent you from using the exact same Ganged Two-Pole breakers you already have? No requirements have changed on voltages. The system is still Grounded on the secondary of the transformer, you just are not using a Neutral. As for voltage you still have the same 120 to Ground reference. The only change requirement to meet code is you have to get rid of the single pole breakers and replace them with ganged two-pole breakers.