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stoverr2
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# Posted: 1 Mar 2012 09:06am
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Hello all,
I've searched speaker wire on the site and not seen too much regarding my question. I recently built a 12x20 cabin that will be powered by solar in rural southern Ohio. I'll try and include a pic or two, basically because I'm so dang proud of what we built for less than $5k. Here's my question. I'm about to start in on the electrical and have been pricing components. I was wondering if I could simply use a fairly high gauge speaker wire for my wiring needs?
Here's a link of what I was thinking of using for most of my runs.
http://www.amazon.com/Premium-100ft-Speaker-Wire-Cable/dp/B003YE23JU/ref=sr_1_4?ie=UT F8&qid=1330610396&sr=8-4
I would step up the gauge for the run to the inverter.
Some details that you may find necessary to accurately answer my question:
At the moment, only 45w of collection
Panels are on the roof
Two batteries at the moment
Have a 1000w inverter that will be in the "kitchen" area for my coffee needs.
Will run an RV pump for pulling water in from catch basins.
I hope this provides enough information for you to help me out.
Allen
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SE Ohio
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# Posted: 1 Mar 2012 09:56am
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Allen,
Welcome neighbor! I too have an off-grid place in southern Ohio (Vinton Co). It is wired for 120v by previous owner who used a generator. I too have a 45W solar panel, but only 1 deep cycle battery.
Since the inverter will put out 120V AC, you might consider having regular household Romex wire in the walls between the inverter and the kitchen outlets? For connecting batteries and inverter, you might consider some large gauge jumper cables, fairly cheap and available.
We forego the microwave and coffee maker an instead use a kerosene stove, safe for indoors. In the summer we cook outdoors on a Coleman stove.
We don't use an inverter. We use the 120 wiring for 12 volt. It isn't "optimum", but it gets the lighting job done with 12 v compact fluorescent bulbs (large gauge 12 v wiring would have less voltage drop per foot of wiring, being more efficient).
Another lighting idea is to use a Lowes solar light package. It was designed for outdoors, has a panel with a long wire, and three solar lights with long wires plug into it. The panel can go on the roof and the light wires run indoors. One should add switches for each light. This setup will provide pretty good indoor lighting for about $30, and makes it look like someone is home if you leave the lights connected when you are away.
Having lights on a separate battery from your cooking setup is a nice plus. If one system is discharged, you don't lose all conveniences.
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MtnDon
Member
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# Posted: 1 Mar 2012 10:35am
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There is no advantage to using speaker wire over solid wire, other than the stranded wire is more flexible. In fact depending on the connections that are to be made stranded wire may be detrimental. The gauge of the wire is what is important, along with the amperage to be carried and the length of the wire.
Household receptacles, power centers, etc are all designed for solid wire, not stranded.
Welding cable is better than auto battery cables; the insulation is tougher. BUT welding cable has much finer strands and should be used with connectors designed for fine strand wire.
Choose your wire by the gauge required. Then std Romex is fine for in the wall runs.
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stoverr2
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# Posted: 1 Mar 2012 11:19am
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Standard Romex will be acceptable for use with DC applications?
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Rob_O
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# Posted: 1 Mar 2012 11:44am
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I see your cable is CL2 rated. Per the NEC...
*CL2 circuits are limited to 100VA of power at 30V and up to 0.5VA between 30V and 150V.*
source:http://ecorecables.com/resources/what-is-a-cl2-rated-jacket
If you are running 12V lights the cable is fine, I would not recommend it for 120V usage
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MtnDon
Member
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# Posted: 1 Mar 2012 01:05pm
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Quoting: stoverr2 Standard Romex will be acceptable for use with DC applications?
As long as the romex is used in locations it is meant for, it's fine. Dry indoor locations, not exposed. If it will carry the current it's fine. IF there is a mix of AC and DC wiring they should be well identified and kept separate from each other. The romex also gives you a ground. DC should be grounded but I believe the NEC will let you get away with ungrounded circuits in 12 VDC systems. Not sure of the cut off, but grounds are good.
Solid wire is not used in what would be the most common uses for DC circuits, those being auto and truck wiring plus recreational marine. Those are subject to vibrations and movement that could lead to wire failure with solid wire..
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TomChum
Member
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# Posted: 1 Mar 2012 04:34pm - Edited by: TomChum
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Quoting: stoverr2 At the moment, only 45w of collection Panels are on the roof Two batteries at the moment Have a 1000w inverter that will be in the "kitchen" area for my coffee needs. Will run an RV pump for pulling water in from catch basins.
To answer this you need these details. And more, but this is a good start. For 1&2 if you can choose locations for inverter and the battery that the wires are as short as possible that makes a noticeable difference.
1) How long is the wire from the panel to the battery?
2) How long is the wire from the battery to the inverter?
3) Do you want to size the wire for the option of "90 watts" of solar panel?
4) What is the amp draw of the inverter at full output?
5) What is the amp draw of the RV pump?
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rayyy
Member
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# Posted: 1 Mar 2012 06:31pm
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Your safest bet is to go with 12 guage romex,Color the white wire with red tape or red magic marker for all the red + connections and leave the black wire black for the - ground connections.For sure though,place a 10 amp fuse off your batteries positive side to any circuit wireing.12 volt dead short can easily start a fire.
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stoverr2
Member
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# Posted: 1 Mar 2012 06:44pm - Edited by: stoverr2
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Tom, I'm gathering some of the information you're asking now. The inverter us down at the cabin so I've emailed the manufacturer. I've not yet purchased the pump so I'll research standard ranges and get back to you. The distance from the panels to where we plan on storing the batteries (under the cabin) will be between 20-30 feet. Yes, ideally we will be adding to the solar system in the near future. Either doubling or tripling the gathering capacity.
I hate to be one of those guys that's asks a question and then questions the answer, but I'm seeing Romex being listed as not only a viable option, but perhaps even a preferred one. My understanding has been that DC applications work best with stranded wiring. 95% of the cabin will run on DC, with only the occasional usage of the inverter for AC devices. Have I been approaching the electrical aspect of my build with too narrow of blinders on?
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MtnDon
Member
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# Posted: 1 Mar 2012 07:00pm
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There is much controversy over the proper use of colors in DC circuits. Many folks use the same rules they learned with automobiles. The NEC however takes a different approach. I know not everyone here builds to code and that's up to the individual.
In a home AC circuit the NEC has the neutral wire white and the hot black. Black in never a ground or a neutral. Red is also authorized for use as a hot wire in AC; common to wiring three way switches. The NEC also covers DC circuits. The NEC treats the Negative DC wire the same as the AC neutral wire. They are always white. Always. Following that reasoning, the black wire in DC is always Positive. As in AC the ground wire in DC is always bare or green. No need for colored tape or markers.
If you were building a car or a trailer, go ahead and use red for positive, black for negative. If this is a cabin, I'd suggest using the NEC convention. If a real electrician comes along sometime in the future he should be expecting things to be wired according to the NEC. If you ever do need to wire something to be inspected you will already be doing things the "right" way. To me that makes sense, but that is me. It is just a suggestion.
The inspector in my area is a stickler on colors being correct. But he uses his discretion and permits welding cable for battery cabling, as long as the negatives have 6 inches or more white tape at each end on the usually black cables.
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TomChum
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# Posted: 1 Mar 2012 07:02pm - Edited by: TomChum
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Romex is fine because it's tough and low cost. The only reason I would use stranded wire is if there is movement. For example I have a "battery drawer" under my cabin, and it slides out so I can water my batteries. I use stranded wire there.
For any condition where there is zero movement, solid wire is actually better, it has less surface area to corrode.
As Mtn Don says, the gauge of the wire is the deciding factor.
TO push 12vDC over 30 feet you will need a fairly big wire, a lot bigger than 12-2 Romex. You might be able to use 10-3, where you use White+red for "+" and "Black+Grnd" for neg. There are lots of tables on the internet that will help you size a wire for 12vDC over 30 feet, someone will post one soon.
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MtnDon
Member
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# Posted: 1 Mar 2012 07:32pm - Edited by: MtnDon
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Someone just did 
http://www.nooutage.com/vdrop.htm
http://www.jhlarson.com/ind_tables/volt/calc_voltdrop.htm
http://www.currentsolutions.com/vdrop.php
http://www.csgnetwork.com/voltagedropcalc.html
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ndflicks
Member
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# Posted: 3 Mar 2012 04:04pm - Edited by: ndflicks
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I wouldn't run 14 or 12g for the inverter. #2 should bee good for about 150amps in short runs with low losses.
The wire you linked is copper, but a lot of the speaker wire(especially the heavier stuff) being sold is CCA(copper clad aluminum). I use it with no issue but I run heavier gauge and solder the ends.
Don't forget to fuse everything and put in cut-offs.
Another thing... you only have 45w now, but if you elect to expand later, running a heavier incoming wire will save you some headache/do-over later.
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MtnDon
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# Posted: 3 Mar 2012 05:27pm - Edited by: MtnDon
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I remembered something I wanted to mention, but forgot... when it comes to choosing fuses or circuit breakers watch what they are rated for. Not all breakers or fuses that are rated AC can or should be used on DC current. There is a difference.
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stoverr2
Member
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# Posted: 3 Mar 2012 05:42pm
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When I rebuilt a boat a few years back I used a fuse block made by Blue Sea o think it was. Was thinking about using the same concept for the cabin. Basically a 12 gang block with a negative bus. Worked like a champ in the only other DC application I've done from scratch.
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TomChum
Member
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# Posted: 3 Mar 2012 06:36pm
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Cabin systems are often simple. I'm using automotive fuses.
My entire lighting circuit (20watts of LEDs) runs thru a single 2A automotive fuse. I think I will divide it into two 2A circuits with 2 fuses.
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MtnDon
Member
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# Posted: 3 Mar 2012 06:44pm - Edited by: MtnDon
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That sounds good for the DC branch circuits. For fusing the inverter and as a master system fuse there are some fuse types that are better than others.
Type T are the best and start around 100 amps and go up. They are made so they will not cause an arc so are safe to use near batteries. They are also very fast acting. Type T should be located as close to batteries as possible. A quick acting master fuse becomes more important as more batteries are connected to the system in parallel. See note below...
Class T fuses have an Arc Interrupt Rating (AIR) Current of 20,000 amps D.C. and 200,000 amps A.C. This is much higher than the rating on the other fuses listed below. This is important; see note below. Code installations usually require a Class T fuse.
Don't use a type R fuse, they are time delay. Type ANN can be used for inverter protection if they have sufficient amps; good to 80 VDC maximum. Also type ANL and ANE are suitable in a 12 VDC system.
AIR rating: Batteries under short circuit conditions can deliver immense quantities of current, especially when more than one are connected in parallel. Some circuit breakers and fuses that are suitable for DC use do not have a very high AIR rating. If the rating is too low, a direct short circuit, with power coming from a battery bank, can actually cause the breaker contacts to melt/weld together before the breaker can interrupt the circuit. That renders the breaker useless and something else will burn up. Maybe a wire, maybe the cabin. That's why a Type T fuse should always be the first thing in the positive lead from the battery, and as close as possible to the battery.
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TomChum
Member
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# Posted: 3 Mar 2012 07:17pm - Edited by: TomChum
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Thx for the info, I have not solved that part yet.
I have a Magnum Energy MMS1012, 1000w charger/inverter. Magnum recommends an input overcurrent device of 300A capacity. (*12=3600W) & I have not located one yet.
Anyway this is getting pretty far off the topic of "Speaker Wire for 12v needs?"
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MtnDon
Member
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# Posted: 3 Mar 2012 08:18pm
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300 amp Type T, $20 or $45 with the holder ... holder accepts up to 4/0 cable
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TomChum
Member
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# Posted: 3 Mar 2012 08:23pm - Edited by: TomChum
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Don, that was beautiful, thanks. I ordered it and its on its way.
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stoverr2
Member
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# Posted: 3 Mar 2012 08:40pm
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I reckon I'll be ordering something along those lines as well.
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MtnDon
Member
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# Posted: 3 Mar 2012 10:20pm - Edited by: MtnDon
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Glad to help. They are good folk to deal with too. I've ordered things from them many times. Their inventory isn't always the same, and so it is nice they show their stock levels. They have batches of things as a "once only" thing. I have some very nice DC breakers I bought from them at a super good deal; I use them as disconnects for the PV modules and charge controller plus as a DC system disconnect after the Type T fuse. It's a sure and easy cut off for the inverter. We pull that every time we leave the cabin for more than a day.
Similar to these, but higher amps and volts
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