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rmak
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# Posted: 18 Feb 2014 08:29am
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The thing that lead me away from dc only was that I might want to use ac appliances in the future. However, a plus for dc is that I read you can run computer and charge phones, etc from a cigarette lighter/ubs port like some cars have.
That's my limited viewpoint. Hope more knowledgeable folks respond.
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bldginsp
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# Posted: 18 Feb 2014 08:47am - Edited by: bldginsp
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Quoting: rmak I never saw ground wires, lightning protectors or dc circuit breakers in a system before. Are these needed on a simple set up? Are dc circuit breakers like the ones in cars? How many amp circuit breakers are used?
Ground wires, lightning protection and fuses/breakers are not needed to make the system work, but they are safety features that are required if you are doing a compliant, permitted installation, or if you want to use the safety features agreed upon by the professionals that know much more about all this than me and you.
The amperage of a fuse or circuit breaker is a function of the wire it protects. A 15 amp breaker protects #14 wire, because if you put more than 15 amps into a #14 wire it will overheat. A common mistake is to put #14 wire into a 20 amp breaker by mistake or otherwise. This allows more amperage into the wire than it was designed to take, if the user manages to pull that much amperage thru the circuit. Might never happen, might not happen for a long time, then 10 years from now someone plugs in one too many gadgets, the wire heats up, burns, starts a fire. That's what the Electrical Code was originally created to prevent. The DC fuse installed on the battery positive wire (the hot one) is designed to open the circuit if there is a short circuit on the positive wire, such as worn thru insulation arcing on the negative wire. If the fuse isn't there to open it, the arcing quickly gets worse and makes a fire. You want that fuse to be as small as possible while still allowing normal operation without burning. The size of the fuse is a function of the amperage capacity of the wire it protects.
Yes, automobile DC breakers and fuses do the same thing- prevent wires burning up from overcurrent, be it from a short, fault, or overload.
Each person has to ask themselves what degree of safety they want to incorporate into their installation. Usually, using the standard safety features described above is not a lot more expensive, it's more a function of just arranging the installation in a certain way. It takes a lot of research to do so, particularly with off-grid systems since they differ from standard household systems in several ways. Hiring an experienced pro to, at least, design your system is a good idea but costs additional money.
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rmak
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# Posted: 18 Feb 2014 09:18am
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Thanks bldginsp! I tried to register with that site, but keep getting invalid referrer message. I can't even contact the site administration without getting that message. So thanks for the page.
So, trying to follow MtnDon's drawing it looks like he has two grounding locations, one at the panels and one grounding the charge controller and batteries.
He also shows four circuit breakers throughout the system.
Is that what I should do?
Also, my question was-can I use automotive breakers, or are there special dc breakers for solar applications?
Thanks to all for helping the solar challenged.
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MtnDon
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# Posted: 18 Feb 2014 10:02am
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Quoting: rmak So, trying to follow MtnDon's drawing it looks like he has two grounding locations, one at the panels and one grounding the charge controller and batteries.
One of the dangers of posting "this is how I did it" photos and drawings is that some folks will copy it as being 100% good. I noted above about the exception allowed because of the distance. That schematic does not have a ground wire between the two halves of my system and it has grounding at both ends. If that system could have been built with all components closer together like most systems, then it is wrong. With 20 feet or so between PV panels and charge controller you would only have one set of ground rods PLUS a ground wire connecting the PV end to the CC end.
That is IF it was being built to code or best practices. That is what I try to do.
NOTE on grounding rods. Code only needs one, but if there is one the resistance must be below 25 ohms (or is it 15? My brain can't verify that this morning) BUT, if there are 2 rods more than 8 feet apart, you do not need to meter the resistance. And you can't measure a rods resistance with only one ground anyways. So 2 rods are simpler. BUT there is another BUT... If there are two ground rods they must be connected to the system ground point by one continuous unbroken wire. No splices anywhere in the grounding wire.
Gotta go for now
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Dillio187
Member
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# Posted: 18 Feb 2014 10:20am - Edited by: Dillio187
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I'm a fan of using THESE to protect my 12V circuits in the cabin. They take automotive fuses, look great, and are easy to use. You can get them in various sizes so you don't need to buy a huge one to use a few circuits.
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bldginsp
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# Posted: 18 Feb 2014 10:23am
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Using auto breakers for your solar setup might work from an engineering perspective, if you have all your wire sizes correct, but I rather suspect that the currents you will be encountering in a solar setup will be different. I suggest you investigate the cost of the standard components used in the solar industry. Using auto components certainly wouldn't pass code, because they are made for a different application.
I would reiterate MtDon when he says it's dangerous to copy someone else's design for your own without knowing how to make the necessary alterations for the particulars of your installation. Once you get on that website, I suggest you make single line drawings like those MtDon showed us, show them on the forum, and I think you will find lots of help from very experienced people. Half of understanding solar is knowing what products are available and exactly what they are capable of, the other half is matching up components in your particular instal with the correct wire sizes and protection from hazards. You can kill yourself with deep cell batteries.
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Dillio187
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# Posted: 18 Feb 2014 11:07am - Edited by: Dillio187
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my above comment was for the 12V circuits to feed the cabin, not to protect the solar panels. While it's true that automotive fuses like that will work fine with 12V panels (most fuses like that are rated to 32V), I prefer better protection myself.
Keep in mind you do not need fuse protection until you get over 2 parallel circuits in your solar panels. You merely need to prevent a shorted panel from taking the amperage of the other parallel circuit.
I will 2nd (or 3rd of 4th) the NAWS forum. It has helped me immensely in my solar endeavors.
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rmak
Member
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# Posted: 18 Feb 2014 11:22am - Edited by: rmak
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So...Dillio, It's been recommended to me that I only need two solar panels. I was going to connect the two wires from each together and send those into the charge controller. So, if I read you correctly, I don't need a fuse between the panels and controller. Correct?
Would I need one between the charge controller and battery?
Would I need circuit breaker #3 and #4 in his drawing?
It also sounds like you are suggesting just one ground rod if the panels are close to my cabin, or on my cabin. If that is correct, what gets grounded where?
Again, sorry for paraphrasing. I am a simple man. You are also suggesting that I draw what I intend to do and post it here for review.
Finally, when this drawing is posted, someone will tell me what components from the solar industry I should use.
Is all this right?
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Dillio187
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# Posted: 18 Feb 2014 11:56am - Edited by: Dillio187
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Quoting: rmak So...Dillio, It's been recommended to me that I only need two solar panels. I was going to connect the two wires from each together and send those into the charge controller. So, if I read you correctly, I don't need a fuse between the panels and controller. Correct?
correct as long as the panels are identical. If you have an MPPT controller, you could actually likely series the panels as well, as MPPT controllers will down-convert higher voltage panels to battery voltage.
Would I need one between the charge controller and battery?
Would I need circuit breaker #3 and #4 in his drawing?
absolutely, those are required. EVERY positive lead off of a battery should be fused as close to the battery as possible.
It also sounds like you are suggesting just one ground rod if the panels are close to my cabin, or on my cabin. If that is correct, what gets grounded where?
if the panels are close (or on) your cabin, you can ground everything in the same place. If the panels are away from your cabin a ways, you will want a ground rod there.
Again, sorry for paraphrasing. I am a simple man. You are also suggesting that I draw what I intend to do and post it here for review.
Finally, when this drawing is posted, someone will tell me what components from the solar industry I should use.
Is all this right?
You could draw something up, and probably get several different responses regarding what to buy, how to install it etc.That's why you need to educate yourself on the subject, so you can make the best choices that fit your needs.
I would advise taking several weeks or more and read the various solar forums mentioned here. You will begin to understand how the systems work, and things to watch out for. Then instead of being someone who cannot repair their own system, you are an informed purchaser and repair tech!
Good luck!
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bldginsp
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# Posted: 18 Feb 2014 01:40pm
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I agree with Dillio to research as much as you can to be aware of the particular needs of your system. I would also caution against a newcomer learning just enough to be dangerous. I'm a newcomer to off grid solar even though I have experience with standard utility systems. When I design my off grid system I plan to pay a pro designer to look over my design partly for advice about the best least expensive way to do it, but also to check for safety. If I come to that designer having researched and made a comprehensive plan, it should take a minimum of their time and my money to just review what I've done and fine tune it.
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MtnDon
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# Posted: 18 Feb 2014 02:16pm - Edited by: MtnDon
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Quoting: bldginsp ....research as much as you can..... Quoting: Dillio187 ...advise taking several weeks or more .....
I read, learned, asked questions, etc etc over a period of a year before I bought anything, before I knew with certainty what equipment I needed to do the job I wanted with reliability. In part that was because we had agreed that we were not going to rush into the building of the cabin either. We purposely put ourselves on a slow track. As it worked out that was a great idea, a great plan.
The cabin itself changed size and location on the land. The electrical system grew as we better defined what we wanted, not just what was needed to survive. Alternative energy systems are one of those things that cost less in the end if you do a proper workup of what the electrical needs and wants will be. The power systems for cabins using alternative energy systems don't grow as well as those that are grid connected.
Job#1 is to get down on paper what the electrical needs and wants are; how much power will be consumed and for how long each day. Calculate the watt hours of power used in an average 24 hour period. Then add 10% as a minimum, IMO; power consumption often grows beyond the estimate.
If you are not sure what watt-hours are then learning that is your starting point.
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rmak
Member
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# Posted: 18 Feb 2014 02:24pm - Edited by: rmak
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I'm just figuring five 40W lights (cabin is only 12 X 16). A cell phone dock so we can listen to Pandora, and a laptop that I use for my landscape painting. By the calculator that's around 2040 watts per day.
The guy at Solar Blvd. said two panels, an inverter, controller with meter, connectors and cables.=640.00.
One Trojan battery from another source=171.00
I'm buying the Honda 2000i generator now. It would really help the cabin renovation to use some power and pneumatic tools when needed.
I'm planning on buying in early May, so I have more time to research. Does that sound like a good plan?
They also carry a 240W system with upgraded components for $749. I might just spring for the upgrade.
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MtnDon
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# Posted: 18 Feb 2014 08:58pm - Edited by: MtnDon
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Quoting: rmak By the calculator that's around 2040 watts per day.
Clarify that a tad please. Do you mean 2040 watt-hours per 24 hour day?? Watts by themselves doesn't mean too much. And is that AC watt-hours or DC watt-hours? I ask because if that 2040 number is based on AC power there are inverter losses to take into account. There are also battery losses to account for with both AC and/or DC.
FWIW, 2040 watt-hours a day is not a small amount of power, IMO. There are days when we do not use that much and we have a microwave, TV and DVD as well as lights (120 VAC LED)...
To do some calcs and check on the recommendations from the vendor we would need to know your good usable sun-hours at the worst time of the year you would need power. Or your geographic location if you are not sure on the sun hours. Then also the ball park lowest anticipated temperatures.
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Quoting: rmak Thanks bldginsp! I tried to register with that site, but keep getting invalid referrer message. I can't even contact the site administration without getting that message.
I would go there again and retry. Maybe reboot the computer first; clear your cache / cookies. You will get a lot of very useful info from folks who have been involved in alternative energy solutions for a long time. The forum is sponsored by a vendor, but the forum people are honest and not biased towards what that company sells.
To quote from some of the first replies to bldginsp question on learning...
"The first step in any system design is to know "What do I want this system to do?".
That means you must know your loads. Your peak loads, your average load, the time of day of the loads, and the duration of the peak loads. Once you do that, you can intelligently design on paper a system that will power your loads. Many folks are surprised and disappointed to learn that most of their system is not usable when they need to upgrade their system... it pays to get it right the first time.
After you figure out your loads, come back to the forum and you will get most of your questions answered.
"
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Quoting: rmak I'm planning on buying in early May, so I have more time to research. Does that sound like a good plan?
At this point you can not go wrong with more and more research. It will save money in the long run. Remember an undersized system or a system undersized in even one category like PV panel sizing or battery bank capacity will be an unsatisfactory system and one that will cost more in the long run.
I have watched a few people rush ahead and later watched them buy new charge controllers, new inverters, new batteries...basically a new system, before they had a satisfactory working system.
I understand the process of estimating what the potential power use will be can be frustrating and confusing. But that is more important right now than wondering about what fuses or breakers to use.
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ChuckDynasty
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# Posted: 19 Feb 2014 10:15pm - Edited by: ChuckDynasty
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Quoting: rmak I'm just figuring five 40W lights
40w or 40w equivalent?
My Home Depot have dimmable Cree LED soft white:
60w replacement (uses 9.5w, 800 lumens) $6.97
40w replacement (uses 6w, 450 lumens) $4.97
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rmak
Member
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# Posted: 20 Feb 2014 03:44pm
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Quoting: ChuckDynasty 40w or 40w equivalent?
Chuck, maybe you didn't believe me. I'm new at this game. I saw 40W on the draw calculator and hit it. I thought with such a small sq footage (192 sq ft) I wouldn't need more than five lights.
Where am I going wrong? I'm trying to learn. Thanks.
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MtnDon
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# Posted: 20 Feb 2014 06:46pm
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What kind of lamps do you use at home? Start with that. For example, where you read, what is the type of bulb (incandescent, long tube traditional FL, CFL...)? What is the wattage stamped / printed on the bulb base? Is it bright enough?
Personally I could not get by with a 40 watt incandescent or equivalent. But then I am older than many here; as eyes age they need more light to see as well as when you were younger. We used to use 75 or 100 watt incandescent bulbs. Then 23 watt CFL (real power measure). Now we use the Cree 800 Lumen (60 watt equivalent). BTW, we love those!
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ChuckDynasty
Member
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# Posted: 21 Feb 2014 07:25am
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rmak, I was just trying to point out that different types of bulbs use different amounts of energy. You have three bulb type options.
You were figuring 5 lights @ 40w apiece for a total of 200w of lighting.
This would be incandescent bulbs, but why use this type when a fluorescent bulb that is equivalent (40w equivalent) in the light it gives uses maybe 9w for a total of 45w of lighting or the LED 40w equivalent that uses 6w for a total of 30w of power.
With regard to a small solar setup it's a huge difference to use LED bulbs in your lighting, or at least fluorescent.
As Don says above a 40w many not be suitable for the light you need in all areas.
If your walls and ceilings will be light colored less total wattage will be needed as opposed to darker walls that will absorb the light.
LED bulbs are the most expensive to purchase so when I saw the ones I mentioned in my previous post at HD they were the most inexpensive I've seen.
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creeky
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# Posted: 23 Feb 2014 05:25pm
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holy cow rmak. throw that calculator out! I have a fridge (electric). I watch tv (canada rules olympic hockey!). i listen to my stereo. use lights. computer. phone. live full time off grid. 2kw per day of energy is what I need to be happy. if i'm tight on sun i can get by on 1500. that's inverter use. battery drain. etc...
so something is very wrong with the 2 kw. esp. as your system is sized (2 panels/1 battery) much smaller.
on a technical note:
i do wish that more people would go to wikipedia and look up watts or watts per hour or watt hours ... see "Confusion of watts, watt-hours and watts per hour"
2040 watts per day is exactly the same thing as 2040 watts or 2040 watt hours. don't mistake a different energy use just by changing the time... the amount of energy is 2040 watts.
dillio. that's some good advice. and I'll point rmak to the naws site as well. they have a good selection of reliable info there.
also rmak. don't be afraid to build a smaller system and then expand. it's what most folks who use solar do.
as for your needs, what actual watts are the panels and amps of the battery. a good rule of thumb i have seen from people who actually live off grid and are happy with their systems is 1 watt of panels per 1 amp hr of battery at 12v.
I have 1500 watts panels to 1200 amps at 12v. it works great. awesome. unbelievably well.
but there are soooooo many variables. i mean 1 watt generation to 4 amp storage is lots if you only use the energy every other weekend... and the panels can reload your batteries over a longer period of time. and similar if you only use the system in the summer with the long days. i could use 500 watts of panels if i didn't have to live through long canadian winters.
anyway. imho. 2 cents and all that. good luck.
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