DC voltage wiring in home

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iceworm

Curmudgeon still using printed IEEE Color Books
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North of the 65 parallel
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EE (Field - as little design as possible)
In our aircraft labs, we have 120V 400Hz supplies and 28 VDC power supplies. These 28VDC ones can be huge -- 400A or more. One lab in particular uses QO panels for the 28 VDC distribution. It is has 30A single pole breakers feeding non-locking 120V 30A receptacle because we don't seem to use those receptacles anywhere for anything else. Kind of unwieldy though to have a 30A cord for a device using 5 amps. But the runs can be long and you need the larger wires.

I think the 12-0-12 system has a lot of merit and mirrors the 120V multiwire branch circuit scheme. Finding 12V devices is easy. 24V is less common, but there are some maritime and aircraft items in this range. Automotive items are really things that will operate on 12 to 14V, as the system is typically 12.5V on just the battery and 14.4V when the alternator is running. It would be nice to see some standardization on the 12/24/28 VDC systems with common receptacles configurations and sizes.

I went with 24 because gen house and batteries are located 50' away (I wanted to noise down). And 24V cuts way back on the copper as compared to 12V. Inverter full load is 140A at 24VDC. Yes, the 12V tap is convenient. I put in two power point receptacles for the kid's video player and a 12V input CD player (non-automotive) Interestingly I can't use the inverter to power the video player. It is not close enough to a sinewave and it puts lines on the screen.

Yes, it would be nice if there was some standardization on receptacles.

ice
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
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Electrician
I went with 24 because gen house and batteries are located 50' away (I wanted to noise down). And 24V cuts way back on the copper as compared to 12V. Inverter full load is 140A at 24VDC. Yes, the 12V tap is convenient. I put in two power point receptacles for the kid's video player and a 12V input CD player (non-automotive) Interestingly I can't use the inverter to power the video player. It is not close enough to a sinewave and it puts lines on the screen.

Yes, it would be nice if there was some standardization on receptacles.

ice

It would be more than nice.

I work on emergency radio setups that have 120/240 VAC and 12 VDC in the same trailers, EOC's, etc. The only standards are the ones they decide to use, and they may be different two counties over.

I have a box of 12 VDC adaptors to go from just about every configuration I have seen to another. There's Molex, Anderson, Weatherpak, Packard (yep, like the car. The P in PED connectors stands for Packard) Bosch, cigarette types and OEM T connectors just to mention a few.

What a PITA.
 

GoldDigger

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I went with 24 because gen house and batteries are located 50' away (I wanted to noise down). And 24V cuts way back on the copper as compared to 12V. Inverter full load is 140A at 24VDC. Yes, the 12V tap is convenient. I put in two power point receptacles for the kid's video player and a 12V input CD player (non-automotive) Interestingly I can't use the inverter to power the video player. It is not close enough to a sinewave and it puts lines on the screen.

Yes, it would be nice if there was some standardization on receptacles.

ice

You should consider a small (low power) pure sine wave inverter if you have a lot of sensitive loads that do not all accept 12V DC.
Of course you would then have to identify a separate set of 120AC receptacles :)

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iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
You should consider a small (low power) pure sine wave inverter if you have a lot of sensitive loads that do not all accept 12V DC.
Of course you would then have to identify a separate set of 120AC receptacles :)

Sent from my XT1080 using Tapatalk

I thought about it. But my 15 year old, steped sinewave, 3000W inverter runs the skill saw, little oiless air compressor, chargers for the battery operated tools, and a few lights (not all at the same time). It's pretty bullet-proof, and I don't have to listen to the generator all day.

So far, anything that needs a pure sine wave is at the bottom of the list.

The kid started to complain one day about the power to his video player - battery had died. I put him on the posthole diggers and marked out ten supports for the new walkway. Amazingly the non-working video was never a problem again. He started asking for the SS 22 and went out hunting squirels. And now we have a 12V receptacle and power supply so it is moot.

Hummm ... We do have a 300W inverter for travel - runs the laptop, video, charges phones in the pickup, works great. As I recall, it was pretty inexpensive. I'll take it out next time. I have to be careful about what we leave out there. Three months of -40F occasionally will do in the electronics. I'm really surprised the batteries for the tools live through it - but they do.

ice
 
Has anyone here done any DC wiring in a home with panel and breakers for lighting? Now that renewable energy along with LED lighting is getting way more popular I would think its a matter of time before people start doing something like this.

I disagree with your statement. I live off grid and my place has a 12 volt DC system, but it will be 120V AC soon. With the advent of inexpensive, efficient, pure sin wave inverters, and the low cost of solar modules, going the low voltage DC route is really no longer practical, even for very small systems. I am current using 12VDC CFL's at $20 a pop and each light has a 12-2 homerun. When you figure the cost of these less common low voltage DC components and the extra wire required, you might as well go with an inverter and just get a few more PV modules to make up for the inverter losses. PV is so cheap now, I will be putting in a 3 KW system for my place next summer that will have a 22% voltage drop! Its a 1400 wire run and just buying a few more modules to cover the losses is cheaper than buying larger wire.
 

kwired

Electron manager
Location
NE Nebraska
Yes (to the bolded statement) that is true.

Q: What exactly would be (or not be) acceptable to use exactly where? I can't tell if you are talking about QO panels in boats, or QO panels in dwellings on DC service. I'm not clear why the NEC not applying to watercraft has anything to do with the discussion. Clear me up here.

ice

I wasn't trying to condemn your installation, but was merely trying to point out that NEC would not have applied to that installation. Some people reading may find that information useful to them. The QO panel was likely still a good option to use for that installation.
 

nicknorth

Senior Member
Very interesting to hear everyone's applications of uses and opinions. Ice - on your place that you have wired in 24VDC what type of wire did you use, I think you said NMB but did you use that for everything? I would guess if SQ OD is rated at 48VDC that the other panel hopefully would be too, but this is something that everyone would have to check into beforehand.

I like peoples comments about having standardized devices. What someone was going to create a brand new receptacle for 12VDC and 24VDC how would you configure it? Obviously I think it would have to be way different so there was no chance of something plugging in a 120V device, but I think something with rounded holes (approx 3mm?) to allow round prong style outlets to slide into them. It would be cool if people could post some drawings of what they would create.
 

kwired

Electron manager
Location
NE Nebraska
Very interesting to hear everyone's applications of uses and opinions. Ice - on your place that you have wired in 24VDC what type of wire did you use, I think you said NMB but did you use that for everything? I would guess if SQ OD is rated at 48VDC that the other panel hopefully would be too, but this is something that everyone would have to check into beforehand.

I like peoples comments about having standardized devices. What someone was going to create a brand new receptacle for 12VDC and 24VDC how would you configure it? Obviously I think it would have to be way different so there was no chance of something plugging in a 120V device, but I think something with rounded holes (approx 3mm?) to allow round prong style outlets to slide into them. It would be cool if people could post some drawings of what they would create.

Something tells me there isn't much need for receptacles on the DC circuits as most of what is connected is likely fixed lighting or appliances. Most anything portable will be 120VAC and would not be connected to the DC system or would run through an inverter first then through typical wiring methods used for 120VAC.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Very interesting to hear everyone's applications of uses and opinions. Ice - on your place that you have wired in 24VDC what type of wire did you use, I think you said NMB but did you use that for everything? I would guess if SQ OD is rated at 48VDC that the other panel hopefully would be too, but this is something that everyone would have to check into beforehand.

I like peoples comments about having standardized devices. What someone was going to create a brand new receptacle for 12VDC and 24VDC how would you configure it? Obviously I think it would have to be way different so there was no chance of something plugging in a 120V device, but I think something with rounded holes (approx 3mm?) to allow round prong style outlets to slide into them. It would be cool if people could post some drawings of what they would create.

No need to reinvent the wheel. There are great DC configurations already. All that needs to be done is to chose one over the others for a standard.

In emergency radio set ups, most have chosen Anderson Power Pole connectors. Some are using Molex, but the RS versions, which fit perfectly, often fail under moderate current loads. The radios usually come with an OEM T connector, which is a PED design.

Receptacles (as in 'in wall') are usually the automotive cigar lighter types. One advantage of using them is the plugs can be individually fused. A huge disadvantage is they are often difficult to use as the plugs take a bit of pulling to get out of the receptacle.

We have been battling this for as long as I have been playing with DC stuff, around 45 years. So far, the only problem is the lack of arrival of a consensus, not the lack of a good design.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
... Ice - on your place that you have wired in 24VDC what type of wire did you use, I think you said NMB but did you use that for everything? ...
Yes and yes. 12 wire, 15A circuits 24V - five lights on two circuits, a pump. 12V - two power point (automotive looking). Only a few amps on each ckt.

... I would guess if SQ OD is rated at 48VDC that the other panel hopefully would be too, but this is something that everyone would have to check into beforehand. ...

I don't know if other common residential panels have CBs rated for DC or not - Yes I would definitely check each application.

... I like peoples comments about having standardized devices. What someone was going to create a brand new receptacle for 12VDC and 24VDC how would you configure it? ...
Checking my crystal ball - It's cloudly and really fuzzy. However, I see the next automotive standard as being 42 VDC. The automotive standard will kick start the power point receptacles, equipment ratings, and batteries. The rest of us will tag right along.

So why 42VDC, not 24VDC, or 48VDC?
Well, 48V puts the charging voltage at 54V, above the osha 50V limit.. 42V charges at 47.5. below the 50V limit. As for 24V, we would be looking to upgrade that in a few years. Why not just make the jump to the top? It would be several years before we have to take on the regulatory limits fight.

ice
 
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K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Yes and yes. 12 wire, 15A circuits 24V - five lights on two circuits, a pump. 12V - two power point (automotive looking). Only a few amps on each ckt.



I don't know if other common residential panels have CBs rated for DC or not - Yes I would definitely check each application.


Checking my crystal ball - It's cloudly and really fuzzy. However, I see the next automotive standard as being 42 VDC. The automotive standard will kick start the power point receptacles, equipment ratings, and batteries. The rest of us will tag right along.

So why 42VDC, not 24VDC, or 48VDC?
Well, 48V puts the charging voltage at 54V, above the osha 50V limit.. 42V charges at 47.5. below the 50V limit. As for 24V, we would be looking to upgrade that in a few years. Why not just make the jump to the top? It would be several years before we have to take on the regulatory limits fight.

ice

What is the 'osha 50 volt limit'? As I understand OSHA, it applies only to employees, not to individuals or cars. Am I missing something here?

Ford used to have 110 volts going to their heated windshields. These were on 1974 ish Lincolns and T-Birds. They had special dual voltage alternators.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
What is the 'osha 50 volt limit'? As I understand OSHA, it applies only to employees, not to individuals or cars. Am I missing something here?

Ford used to have 110 volts going to their heated windshields. These were on 1974 ish Lincolns and T-Birds. They had special dual voltage alternators.

Ok
Change it to a "preceived 50V limit
I'm sure you do far better than I (understand osha)
Probably not (missing anything)

And 18KV to 80KV going to the sparks.

That's the best you get when I am crystal ball gazing. And I'm okay with you not agreeing

ice
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Ok
Change it to a "preceived 50V limit
I'm sure you do far better than I (understand osha)
Probably not (missing anything)

And 18KV to 80KV going to the sparks.

That's the best you get when I am crystal ball gazing. And I'm okay with you not agreeing

ice

Here is a picture of a 2011 Ford Lariat with a factory 120 VAC receptacle in the center console.

2011-ford-f-350-super-duty-lariat-rear-seat-vents-120-volt-and-12-volt-power-outlets-photo-351247-s-1280x782.jpg


Your crystal ball needs rewinding.......:D
 

broadgage

Senior Member
Location
London, England
What is the 'osha 50 volt limit'? As I understand OSHA, it applies only to employees, not to individuals or cars. Am I missing something here?

Ford used to have 110 volts going to their heated windshields. These were on 1974 ish Lincolns and T-Birds. They had special dual voltage alternators.

AFAIK, much stricter standards apply to electrical work and equipment over 50 volts, might not apply to an owner driver working on their own vehicle, but would apply to employees in vehicle repair or maintenance facilities, and probably also to employees carrying out basic checks on a company vehicle.

The proposed new vehicle electrical voltage is a 36 volt nominal battery, with 42 volts nominal on float charge with the engine running.

It was proposed to make 24 volts/28 volts the new standard for cars, but a cynic like me suggests that this was rejected because 24/28 volt equipment is already a low priced commodity in widespread use for trucks and buses, no profit there. Something new, different and expensive is needed.
It has been rumoured that the 36 volt nominal battery is to consist of two batteries in series each of 18 volts nominal. 18 volt batteries are not used or useful for anything else so will no doubt be hugely expensive. 3 batteries each of 12 volts generates no "continueing revenue stream" for the vehicle builder.

Rules in other countries differ in detail, especially as regards the cut off voltage, but are similar in principle.
AFAIK the limit in some countries is 42 volts (old lamp catalogs list 42 volt lamps for safety inspection lamps) I once found a German machine for the wet diamond cutting and polishing of concrete floors , this used a 3 wire, 3 phase supply of 42 volts between phases.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
AFAIK, much stricter standards apply to electrical work and equipment over 50 volts, might not apply to an owner driver working on their own vehicle, but would apply to employees in vehicle repair or maintenance facilities, and probably also to employees carrying out basic checks on a company vehicle.

The proposed new vehicle electrical voltage is a 36 volt nominal battery, with 42 volts nominal on float charge with the engine running.

It was proposed to make 24 volts/28 volts the new standard for cars, but a cynic like me suggests that this was rejected because 24/28 volt equipment is already a low priced commodity in widespread use for trucks and buses, no profit there. Something new, different and expensive is needed.
It has been rumoured that the 36 volt nominal battery is to consist of two batteries in series each of 18 volts nominal. 18 volt batteries are not used or useful for anything else so will no doubt be hugely expensive. 3 batteries each of 12 volts generates no "continueing revenue stream" for the vehicle builder.

Rules in other countries differ in detail, especially as regards the cut off voltage, but are similar in principle.
AFAIK the limit in some countries is 42 volts (old lamp catalogs list 42 volt lamps for safety inspection lamps) I once found a German machine for the wet diamond cutting and polishing of concrete floors , this used a 3 wire, 3 phase supply of 42 volts between phases.

I am interested in your source for the new proposal. When I worked for Chrysler the only place the company discussed future systems was in the class room. Ford and GM also guarded their real plans well, too.

We heard lots of stuff that customers thought, but most of the time they were very far from the mark when it came to what was actually going to be produced and sold.

I don't think we will be moving from the 12 volt system for accessories anytime soon. There are just too many out there and still being used.

Higher voltage for the starter may become a reality when the engines have to be restarted hundreds of times per day, but so far, it looks like Prius has stayed with a 12 V system. Remember, you can't jump start a 24 or 36 volt battery with a 12 volt supply.
 

kwired

Electron manager
Location
NE Nebraska
I don't think we will be moving from the 12 volt system for accessories anytime soon. There are just too many out there and still being used.


I could also see using higher voltage, but tapping it so 12 volts is available especially for user accessories, especially for electric driven vehicles - and this probably already does happen on those, I know almost nothing about EV's BTW and don't expect them to be the thing in these parts anytime soon, if people around here want economy and the weather is nice they ride their ATV's.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
I could also see using higher voltage, but tapping it so 12 volts is available especially for user accessories, especially for electric driven vehicles - and this probably already does happen on those, I know almost nothing about EV's BTW and don't expect them to be the thing in these parts anytime soon, if people around here want economy and the weather is nice they ride their ATV's.

They hybrids, at least, have two sets of batteries. One HV set for the drive motor and a 12 volt battery for starting, lights and accessories.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
.... Remember, you can't jump start a 24 or 36 volt battery with a 12 volt supply.
If the swap were made, I think we would get over it - relatively quickly. Cause that sounds exactly like what my granddad said when they switched from 6V to 12V. :roll:

ice
 

GoldDigger

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The Prius starts the engine using the traction battery and traction motor M1, and other high power accessories like A/C are driven by inverters.
If the traction battery is drained, jumping the 12V accessory battery will not help.
But if the accessory battery is down, the controls do not work and you have to jump it.

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