Learn me: 12VDC house wiring

So, I've cooked up this crazy idea. Solar panels to power all of my installed lighting. Everything would be LED, possibly even home-brew. I know that this isn't a difficult install, no more difficult than fishing any other wire, but do current codes jive with this sort of installation?

These are always the sort of ideas I brew up when I can't call the codes people downtown, and you guys always have another pound to add to my notes.

The end goal here is to allow me to have plenty of lighting available, even when the power is out. In an area with plenty of bad weather, being able to light my house, and a few other key things, from solar or battery backup would be a nice bit of insurance to have.

ive nothing to add other than i like the idea. subscribed.

-J0N

Derick Freese wrote: The end goal here is to allow me to have plenty of lighting available, even when the power is out.

In that case, I would think a cheap generator would do better and cost you less.

I'd rather not have to go wait in line at the gas station after everyone else's generators have run out of fuel. That's why local power generation is part of the plan.

It seems that I can make the lighting system more efficient if I don't have to step down from 120VAC at every fixture, instead of stepping to 3 volts and PWM dimming the lights.

For a cheap generator solution for the worst case scenario and the sun stops shining, I could always put an alternator on my lawn tractor. No need to have an inverter, since it would only be running DC. All it should need is some power regulation, which should be taken care of with the same one used for the solar cells.

Possible OSHW project, too.

I have to admit, I like this notion in many ways. Separately from a backup generator. OK, here's my musings.

I've already got old car batteries. While they won't kick over a starter motor, they will power bulbs. Wiring them in parallel increases my capacity. Just leave it 12 volts.

Cheapie solar charger from Harbor Freight or the like. I'd also include something 110, like a Battery Tender, to help maintain the battery pile. The solar charger would be there to help support the battery pile when the power is out.

I'd be inclined to run wires and sockets, not hard wiring 12 volt LED lights. I'd use sockets distinctly different than 110v sockets to prevent confusion. I'd run it discretely, like along baseboards. I'd have lamp assemblies with leads to be plugged in when power goes not. Run the wiring radially or as a loop. Since it's 12 volt dc, powering led lights, it wouldn't much matter as the load would be minimal.

All this would provide lighting, and perhaps the likes of chargers for my cell phone and such. Quite nice.

This still leaves things like furnace fans, furnace ignitors, well pumps, sump pumps, refrigerators and such unpowered. These things all take 110V a/c current. You really cannot make them work on 12 volt dc, or just about any other dc power for that matter.

So, you likely will still need a generator to live comfortably without power for an extended period of time.

For about $100 you can buy a ~900 watt 2 stroke generator that will run almost all day on a gallon gas. Won't power your refrigerator, but it will run a well pump and such.

For about $300 you can buy a ~3,000 watt generator that will run all day on a few gallons of gas. If you're the type who stores 5-10 gallons of gasoline in the shed, you'll be good to go for a week or more if you're carefull. A generator of this size will power your furnace, a refrigerator and most other things in your house. Just not all at the same time.

You might want to also look at some of the passive solar heaters, and a solar oven just for fun. Can save on your heating bills, and are interesting to learn how to make and use.

Everything would be installed as a separate system to my current 120VAC electrical system. For now, I'm looking to power my lighting, my home network, my security cameras, and maybe a couple of attic fans.

A solar water heater is in its first stage of parts gathering. After replacing my last electric heater, I think I can do far better if I home brew hot water.

Lamps and such will stay 120VAC, at least for now. The change to LED there has already started.

The real savings will come when I install a geothermal heat pump, but that's another thread.

So many different ways to go! Most of the LED lights I have are the puck lights that have a transformer to step it down from 110V AC to 12V DC, don't know if this is common or standard or what, but they don't cover the majority of my lighting.

Sounds like you want solar as the primary source, battery as the secondary and grid as the tertiary...possible generator as 4th (quaternary? sounds good). Switching and wiring is just a circuit design, but capacity is going to be the hard decision.

Are you looking to keep from kicking the furniture should the grid fail or are you looking to keep a normal lifestyle for a week with no utility power?

I do find it sad that the first question we must ask is how to please the government.

Bruce

Well, all of my lights will be able to be dimmed via PWM. My goal is to keep my security system, home network, and reasonable lighting up should my lights go out. The cell towers have generators and my phone can be used as a modem. Depending on how much power I can make and store, I can change my ceiling fans over to DC. It would be really nice to have those off the grid during a hurricane outage.

You had me until you said attic fans.

A single attic fan will use more power in 2 hours than your LED lighting will in a week.

The home theater guys have options for speaker wiring in wall that should work and meet legal requirements for in wall low voltage. While speaker terminals aren't ideal for hooking up cords and phone chargers and the like you could do a lot worse.

Trolling motors use a 2-wire receptacle and plug that would be a good start too. Bonus for usually having a water proof or resistant cover, perfect for hooking up solar panels on the roof and the like.

FYI: low voltage (less than 50V) wiring is covered in the NEC: Article 720, as well as other articles in the Code covering other aspects (batteries, for instance).

In a nutshell - the wiring for what you want to do is essentially the same as standard 120V wiring. You CANNOT use speaker wire for power.

We use solar panels with (4) deep cycle 6 volt batteries. Each ways something like 100 lbs, heavy. We also have an inverter for 120V AC but we have a bunch of separate 12VDC LED lights too. [REDACTED]

One of the reasons they use high voltage to distribute electricity is because of voltage drop along long conductors. If you run 12VDC over long distances and it drops to 10 VDC, you might not be able to turn on your LED light anymore. So wiring size can be important for the longer runs.

Our controller for our system is a Morning Star brand and we are happy with it. I'm not sure if I'd stay away from the cheap HF controllers or not as I don't have any experience with them.

RossD wrote: One of the reasons they use high voltage to distribute electricity is because of voltage drop along long conductors.

RossD wrote: similar to furnace thermostat wiring (usually 12 or 24 volts) or door bell wiring (usually 12 or 24 volts, again).

NO. Check the Code referenced above. #12AWG minimum for low voltage power wiring. The rules are NOT the same as low voltage control wiring.

In reply to Ian F:

I edited my early response because I thought that was right but I'm not an electrical engineer or electrician.

Amps are amps, regardless of the voltage, so you need to scale the wire gauge for that.

Ian F wrote: FYI: low voltage (less than 50V) wiring is covered in the NEC: Article 720, as well as other articles in the Code covering other aspects (batteries, for instance). In a nutshell - the wiring for what you want to do is essentially the same as standard 120V wiring. You CANNOT use speaker wire for power.

You also are on sketchy ground if you run in in the same conduit or into the same boxes, and there are no set standards for switches and or outlets last time I checked.

That was why I recommended hom theatre stuff; they have piggyback boxes that maintain the two sets of wires in separate cavities but will let a single cover plate cover both. That way if you used regular home light switches for the low voltage stuff from the outside of the wall all anyone would see is a regular switch plate with two switches, one for led area lighting and the other for task lamps.

For wire are talking about fractions of an amp, so voltage drop would be minimal. Code might require a certain size but if s it's only because the code hasn't caught up to LED lights yet.

I've been planning the same project in my own house as well, but for a wind generator instead of solar panels.

I've actually started this same project on a small scale. I've done two LED projects in the house to test in a small scale, and currently am ramping up to a larger scale. In my garage. I am going to run all my lighting with LED strips and power those off two 12V batteries and a wind turbine. There are HUGE differences in light output with different LEDs. What are you using?

with the current (sorry) output of LEDs.. it is quite reasonable to run everything but your HVAC and appliances on 12v. If I were you, I would look into boats, they run on 12v or 24v and most everything you need is quite available there

I would also consider a small wind generator for those times that the sun is not shining

Ian F wrote: FYI: low voltage (less than 50V) wiring is covered in the NEC: Article 720, as well as other articles in the Code covering other aspects (batteries, for instance). In a nutshell - the wiring for what you want to do is essentially the same as standard 120V wiring. You CANNOT use speaker wire for power.

Oh crud, those requirements kill all the redneck fun.

I can't find a way to read them for free, but there's something different under that for lighting systems using less than 30 volts. Still not redneck engineering compatable.

What I've found with the inexpensive LEDs, they are bright, but they don't throw the light very far. Great for task lighting, maybe not soo great for area lighting. I have been waiting for the weather to break so I can install by first area lighting fixture in the garage. I expect to do this tomorrow. I'll report back.
I don't remember if I posted my other two experiments here yet, so here's what I've done so far.
We moved stuff around in our boy's room, putting both dressers under a bunk bed. It was dark, could hardly see in the drawers. So, I made a very simple frame and put about 6' of LEDs on it. I wired it through a Radio Shack project box and a 12V wall wart power supply. It works great.
Before:

Building:

After:

I don't have a before pic of my second product, but I put 3 16" LED strips in my daughters closet, wired through a normally closed, momentary-contact switch, and a similar 12V wall wart.

I need to order some LEDs and build a fixture for my kitchen. For now, I can install the power supply there until I have a few others installed. That gives me time to gather more batteries and maybe score some damaged solar panels on the cheap.

Hell, they make LED strips that fit right into a t8 socket and put out almost as much light at about half the draw. I want something a bit more sophisticated than that.

Have you priced those T8 bulbs? Jay Leno talked about those. I think they were really expensive, but knowing Jay (yeah, we go way back :what the: ) he got the most expensive ones possible. But I was impressed with them. Keep us updated, I want to see how it goes.

In reply to foxtrapper:

I try to dig into again on Monday at work (where my NEC book is).

That closet lighting looks good Dr.

I noticed this morning they retrofitted all of the street light bulbs in my neighborhood with LED. The damn things are bright. The light across the street from me used to barely put out enough light for me to see to my front door. Now the thing lights up my entire front yard. I'm glad my bedroom is in the back of the house...

Most of our clients are full-bore LED, except in a few instances. They can deal with the upfront cost when they're saving 50% in energy and even more in the labor for bulb maintenance.

I was in a client office last week where they had some of those T8 retrofit LEDs. Amazing. Had to really look at them to see it wasn't a fluorescent. Here's an example for $30/bulb:

http://www.bulbs.com/espec.aspx?ID=23896&cm_mmc=GooglePLA--NonBrand--none-_-&AffID=6&device={device}&network={network}&matchtype={matchtype}&gclid=CIDQuZTupL0CFcg7OgodKy4A7w

These aren't the ones I saw, which were a different type that replaced the ballast as well and probably cost more.

I totally get what you are trying to accomplish. LEDs have come a long ways, and will continue to get better. I am about to graduate with an EE degree with an emphasis on renewable energy technology. After years of doing homework, lab projects, and lecture on all manner of this stuff I will say don't bother. Short version is the lighting isn't a very large part of the load and is also the easiest to fix problem with outages (candles anyone?). Return on investment it will not pencil out. Generator is your friend. Just store an extra 20 gallons of fuel and save yourself all the work you are talking about. J