Wise to use the DC?

[mjchee]

 We know that any inverter can turn DC to AC, but what I want to know is instead of running an inverter to light the house, would it be a good idea to run all the lights on the direct current? Would I be saving power from my battery bank since I won't be using the inverter? Let's say the inverter is a 750 watt. If it is possible, I would like to set up my system for lights to DC. What do you think?

[dinges]

You would be cutting the inverter losses (my guess, efficiency of an inverter is about 85%). But, at 12VDC, the resistance of your lines has some impact on loss too: lower voltage means higher currents (for the same amount of power, say, 750W). It depends on how long & thick your 12V lines are. If they are thin & long, it might be wiser to switch to 120/240V by means of an inverter.

So, in short, it depends

Peter.

[John II]

A lot of people use DC lights and or appliances for these reasons.

(1) Removing the inverter makes less items that can fail, so the reliability is increased. If your inverter fails... then all lights wired to it will fail. But running directly from a battery bank, that is not a problem. So you have much higher reliability with DC lights.

(2) As mentioned above, if you have proper wire sizing your efficiency will be increased, because all inverters are lossy.

Check out any A.E. ( alternative energy ) catalog on the net.... most all dealers sell DC lamps for most standard A.E. voltages.

John II

[mjchee]

 Thanks for the input and it sounds like it really will be wise to wire some of the lights to DC, besides we live in a small house. It might be a good idea to hook up the restroom for DC. I run a 750 watt vector inverter which I purchased from Wal-Mart and it seems to be working quite well. I wired the off and on switch into the house so I can turn off the inverter when I need to. So far, it's been doing fairly well. Since me and my wife work all day,and the kids are at school, I usually turn off the inverter to save as much power I can. I used to have it on all the time, but it seems more convenient to just turn it off. I don't mind and I will check in to the DC lights very soon. If anyone has other suggestions, please let me know.

[ghurd]

Call me Grumpy, but the inverter efficiency will only be about that high with a high load (90% load?).

A 750W inverter with only a 7W night light, or cell phone charger, will be a very low efficiency. Or with no load, just turned on (for that model) uses some power.

Call me Stupid, but I would wire for both 12VDC and 120VAC.

An 11W 12VDC CFL ($) will use less power than just the inverter without any load.

An #1156 tail light bulb in the bathroom, closet, (where ever) or some other low hour use may be good. Cheap and the inverter will not need turned on before the light is turned on.

Call me Doc, but if the inverter fails, the DC stuff still works.

Call me Sleepy, but its late.  

G-

[John II]

Considering your lifestyle and the very small house, you may be as well off just to have a second backup inverter setting in a box incase lightning or other problems should kill your current inverter ? This might be a simpler redundancy backup method for your particular application.

Some of it is up to personal taste. Myself... I like DC lighting because of it's reliability : )

Be sure to be ultra cautious and not mix ac voltages with dc voltages accidently. It pays to terminate all of your DC wiring in a DC fuse Box... or at the very least don't do any connections in your current master ac fuse box.

I also prefer to use a different outlet and plug for DC voltages. I use the AC outlets where one plug is turned sideways so that I won't accidently plug an AC item into a DC outlet or a DC item into an AC outlet. These I mount in the walls like you would a standard AC outlet. These are available in a double outlet just like your standard outlets.

If you live in Europe, the above tips won't be of any value to you, and you'll have to come up with some other method to prevent accidently plugging a DC device into an AC outlet.

This may sound un-safe or strange to some... but after living nearly 20 years with my DC system, I have also experimented with a lot of DC power strips and have settled on a method that I'm very pleased with and has worked flawlessly for many years. I connect a cord to the above mentioned DC plug. On the other end of the cord, I connect a small box with about (quantity 5) 1/4 inch phono jacks and one fuse holder.

Then on most of my table light fixtures or DC appliances such as boom boxes and other small current devices I put the highest quality 1/4 inch phono plugs I can find. Mouser Electronics sells ultra high quality Red phono plugs which I like. I find this power strip can handle at least 15 to 20 amps without any problems and is much more durable then even the best power jacks that I have come across.

On higher current devices like a DC ultra high efficiency refrigerator, I plug directly into the wall outlet that uses the sideways slots.

John II

[mjchee]

Thank you for your reply and I will check into your ideas. It sounds reasonable to me and saving as much power we can is all that matters. Thanks again!

[WXYZCIENCE]

1...The current required to supply 750 watts at 12 volts is aprox. 58.8 amps.
2...Most houses are wired with 14/2 which is rated at 300 volt 15 amps. Connections to the inverters are usually very short and are rated at the current required.    
My advice as an electrician. The losses from 12v dc wiring would  aprox. equal the losses from the modern inverters. It can be done yes. Check you local code for requirements. Joe              

[mjchee]

Thanks John for your intricate input. I'll make sure that I have an extra inverter on the side. You are right to have another inverter, in case the first one goes out or something like that. I would like to invest in a trace or a similiar inverter for a 12 volt system, but for now I just manage to keep turning off my inverter. At least the switch is just inside the house and that makes it even more convenient. But thanks for the input, I really appreciate it!

[ghurd]

The phono plugs. I did that too!  But for a small boat.

A .50 cal ammo can, motorcycle battery, phono plugs, slide switches...

The sonar, lights, etc had phono ends.

Worked great, except for cheap slide switches.

Then it got tipped over in the garage and nobody noticed.

G-

[dinges]

I used phono-plugs too. Once.

Got a nice short-circuit when plugging or unplugging a small TV on the boat. These connectors aren't meant for that kind of use, so it would be wise not to use them for that.

There are reasons for the enormous variety of plugs that exist (my catalog has 100s of pages full of them).

Peter.

[ghurd]

The RCA phono type? I don't think most of the ones I have used are very shortable.

[dinges]

Now I'm doubting;

If you are talking about cinch-plugs, they're hard to short.

If you mean 6.3mm stereo plugs (which I thought you meant), when inserting or removing the plug they can (in my cause: did) cause a short.

Peter.

[John II]

I should have mentioned I use Mono Phono plugs... Stereo plugs would be much to fragile. Also the high quality ones. Close to 20 yrs or continuous usage and I have never had a short... they are ultra durable... something you can solder lamp zip cord into with ease. I convert table and desk lamps by clipping off the ac plug and soldering in a heavy duty mono phono jack..

Those cheepie mono plugs out on the market have hollow barrels and are so flimsy, you will be lucky to even get a larger wire attached to them without them coming apart. The heavy duty higher quality ones I use are solid barrels and put together right... so they stay together.

And yes they are not RCA jacks... those things are way to light for this application.

I have yet to find a DC Power plug that can match them for larger items, or the ease at which the jacks can be installed with a single drill bit.

I get quite a few electronics parts catalogs myself such as Mouser, Newark, Jameco, Parts Express, Electronix Express, Circuit Specialist, Edlie's, Hosfelt and many others.

Could you give us the name of your catalog so I can add it to the list Peter ? Thanks in advance.

John II

[alterfuels]

I believe a mix is the best then you can get cheap 110 florecents and still have lights on after your inverter crashes after voltage gets low so you can make it to the back up generator!

[dinges]

It's from Farnell.

www.farnell.com

Peter.

[wooferhound]

Just a note on Terminology

The 1/4 inch plug that ya'll are talking about is called a -Phone Plug-

The little connectors that hook up the DVD player to a TV or stereo is called a Phono Plug, or RCA connector

I work providing Sound systems for live events and you have to know your terms to communicate with others on the subject

So now you know the difference between a Phone Plug and a Phono Plug. This will help you if you are searching about it.

The best 1/4 inch Phone plugs are made by Switchcraft or Neutrik . . .

[John II]

Thanks wooferhound:

Now if I can just remember that for any length of time! I had always just called one "phono" and the other "RCA" and never realized that I should have been saying "Phone". A very subtle difference but an important one I surmise : )

Thanks for the info...

John II

[thirteen]

what size wire should be used for 12 v lighting

[ghurd]

http://www.windsun.com/Hardware/Wire_Table.htm

[willem]

Opening normal household equipment, you'll find that almost everything is low voltage DC, with a build in transformer. The very PC you are reading this on, has 12, 5 and 3 volt DC.

Your vacuumcleaner probably contains a 12V motor, there are many reasons to switch to 12V DC if you have the choice.

Use thick wiring! Due to the low voltage you loose substantial voltage in thin wires.

And don't forget to use fuses. You can take them out of any car!

You won't get fried by 12 volt, but you could be fried by the fire starting because something goes wrong inside your equipment.

Another thing, make shure that you have a + and - on the plugs you use.

Go to a boat shop to buy 12 volt bulbs that use only 7 watt, they have it all.

I'm fine with the 12 volt installation I'm building.

[cyplesma]

Just my $.02

I haven't started (not sure I'm going to) using any DC supply in the house yet.

But my plans are to use multiple 200W (kids) - 400W (master) inverters, basically one per each bedroom, and as I continue on building my system (just getting started) I plan on using 1200W inverters for each fridge/freezer, (stove is LP gas for now, boy has that gone up lately, wife may not let me go electric on the stove).

but my plan is to leave the big brother power household wiring in place, use it when batteries are offline. Use a switch in each room to switch back and forth from big brother power to my own power.

So I'll only really have 120vac going through the house.

I'm not doing this in a cabin, I'd have to think about how I would handle that situtaion, I don't know if I'd do it any different. But this is my plan so far.

I think for a cabin, I'd get the DC power jacks that fit on universal connector (in us right now Radio Shack has a whole series of ac/dc convertors and jack that are interchangable, i'd have a dc outlet with say 2/4/6 pair (+ & -) wires coming out of it that also fit into holes for storage, each pair of wires are fused.

only problem with this is your small electric toys don't always give the voltage required or the polarity that the connector needs (stating now, so no one else has too) 8 )

but this too is a learnable thing that takes time, reading those polarity and voltage icons are no different from reading the battery position diagrams, of course your dc outlet would need to have a voltage switch also.

so you'd have to match the voltage, polarity, and jack for each device, and yes I realize that many people (let's face it any nongadget person) would have problems with this for a year or so, but they know how to read a battery position diagram today.

If it was just me in the house, I'd probably just bury a multifuel generator and call it a day and keep everything 120vac that way. maybe even change it to a mr fusion machine. (sorry just spent a lot of time on some delorean sites)

[ghurd]

A possible partial DC solution?

PA/ microphone/ XLR jacks?  They can handle quite a few amps, and are available with a lot of pins. Allowing for multiple voltages in the same socket, while minimizing the possibility of improper connection.

It would almost require several voltage supplies to be active 24/7, but that would not take a lot of effort, money or relative waste.  Google 7805, 7809, and bypass transistor...

G-