James Cormican's posts

i use the wire size chart in this book all the time.

http://store.altenergystore.com/Books-Classes-Webinars/Solar-Electric-and-Passive-Solar/Photovoltaics-Design-Install-Manual/p481/

in parallel, you would have roughly 30a at 24vdc nominal.  2awg would make it 52 feet for 2% v-drop.

by contrast, if you could wire them at 48v in series parallel with an mppt as david mentions, you would have 15a at 48vdc nominal coming in, which could mean you could use #6 wire for 2% drop for 81 feet.  you can use the #2 from the controller to the battery bank.

also if your system expands by double, you would be okay with #4 or #2 if you were to wire at 48v and have 6 strings of 2 of the same type of modules and an mppt controller such as an mx60.

good luck,

james
altE staff

i think two 12v should work.  i wonder if enphase cares for warranty or anything else.  only issues i see is you would have to add MC solarline 1 connectors, and that may not fit well with the j box and inverter. 2nd issue, if you have two in series, the ends may not reach the inverter forcing somebody to buy or make 3 or 6ft extensions which may get crowded under the modules.

james
altE staff

hey chris,

I talked to the enphase folks in san diego, and they said likely inverter #2 would be for sanyo 96 hybrid cells.

#3 would be 18v modules with likely 54 or 60 cells.  would be right for large kd series kyocera modules.

btw, new evergreen mods 200-210 will have  114 cells, but interesting show the characteristics of a 12v nominal module, vmp 18, voc 22.

I think it is a neat idea, although  AC modules as they were called failed in the 80's.  at 2kw and up, costs seem to even out 1 inverter v multiple, and the higher dc voltage yields lower voltage drop in the favor of the standard string inverter.  under 1kw maybe be a niche, and only the sma 700 lives there now with a tricky voltage window.  like you said, there are not a ton of traditional 24v nominal modules left.

james
altE staff

okay, if you are installing in series, than you will have a 24v array and a 12v battery bank?  that would mean that you have an mppt controller.  is that correct?

by code, once you leave the area of the modules, wiring is required to be in conduit.  once you have the modules connected in series, you would have 1 open positive and 1 open negative on the series string of modules.  you would use something like this
http://store.altenergystore.com/Cables-Wiring/Wiring-For-Solar-Panels/15-MC1-Connector-10-AWG-MaleFemale/p4267/

that would be cut in half with the plug ends going to the array and the bare ends going through a combiner box, or pass thru box like this:

http://store.altenergystore.com/Enclosures-Electrical-and-Safety/Electrical-Enclosures/Combiner-Boxes/Ready-Watt-Pass-Thru-Box/p6045/

this would allow you to leave the "area of the array" in conduit satisfying the code.  once you got to the inside where your charge controller is, you would use bare ends to make the connection to it (hopefully with a disconnect before and after on the positive)

practically, any weather appropriate box you can splice in and leave in conduit will do, and yes you will likely have to have bare ends connecting to your charge controller from your array and from your battery bank.

hope that helps,

james
altE staff

unisolar 64w modules do not come with and plugs on them, they have a junction box.  you may have unisolar 62w modules which came with multicontact solarline 1 connectors.

are you connecting your modules in series or parallel? 24v or 12v array?

what charge controller is it?

how far is it from the modules to the controller, and is it a permanent installation?

you will likely have to strip wires to get into the controller, but i would like to know more about the system first.

james
altE staff

I would not recommend putting a generator through a solar charge controller.

there are small ac chargers if you would rather use the 120vac output of the generator and go through a two or 3 stage ac charger.

perhaps somebody on the forum has done this, but running the generator through a charge controller for solar seems very risky to me.

james
altE staff

yes, that should work.  just be careful on your setpoints so that you dont overcharge the batteries.

the solar charge controller is fine to leave hooked up.  as the voltage of the battery bank goes up or down, the solar controller should react accordingly.

cheers,

james
altE staff

for example, the sma 7000, can do two strings of 14 modules.  1 inverter solution that can do 277 or 208 voltage systems.  you would prob use square d h362rb and du221rb (think those are right part # by memory) for the disconnects to satisfy any inspector [visible, lockable,  . . .]

fronius is great too, but 1 inverter decreases the balance of system gear that you need and also can put you into one backfed breaker instead of 3.

hope that helps,

james
altE staff

what is the voltage? 208? 277? something else?  i am thinking 1 larger inverter may be easier than three small ones.  if we know what the panel voltage is, I can find some inverters that will match.

james
altE staff

3 batteries in series will have the voltage add

in your case 12volts, while amp hours stay the same.

400ah at 12v = 4800wh of storage or 2400wh of usable storage assuming 50% DOD.

based on the numbers, it appears that only if your wind blew 24/7 between 15 and 20mph would the air x be able to keep that battery bank charged if you used it to 50% every day.

if you knew what your loads were you could have a better idea if the air x would keep up. 

hope that helps,

james
altE staff

while that may function, a listed transfer switch would be the appropriate way to provide backup power if need be for the greatest degree of safety to the best of my knowledge.  appropriate listed transfer switches are not that expensive, and most electricians are used to installing generator backup systems that have nothing to do with solar.

cheers,

james
altE staff

I am not aware of any such product.

you correctly point out that anything tied to the grid generally has to meet the ul 1741 and ieee 1547 so as not to send electricity onto a disabled grid.

generally wind turbines and pv modules will output dc electricity that cant be connected to the grid without a grid tie inverter that meets the above standards.

the closest thing to what you describe will be on the market soon and is from a company called enphase energy i believe.  it will allow an individual (with consent of their utility) to grid tie as little as 1 module.  it will meet applicable electric codes to the best of my knowledge.

for more information, please check the university tab and some of the webinars you can watch at your computer.

http://learn.altenergystore.com/

cheers,

james
altE staff

you will need a solar charge controller rated for 1.56 x the short circuit current of you module.

if you need help sizing the module and the battery, you need to find the wattage of the radio and speakers, and you need to decide how long you want to run it each day.

james
altE staff

well, with a variable resource, nothing is 100%.  but that takes in the critical design considerations necessary to enable the system to be more likely to succeed.

remember, batteries will have losses, voltage drop losses, inverter losses, etc . . .

but more power should be way closer to getting the job done

the closer you are to a 1:1 ratio between production and storage, the better.  the absolute minimum for array wattage is a 1:1 ratio between production and load (after derations).

james
altE staff

do you mean a load that draws at 5W that is on 24hrs a day (120W-h/day)?

if so, a 60w array may be a little short in winter depending where you are.

60x .8= 48w  --- 48w x 2 sun hours = 96W-h/day {estimated} (deficit operation)

a 60w array certainly wont hurt, but is by no means overkill for a constant load.

james
altE staff

yeah, that switch that we have is T rated, but not specifically DC rated from what I am finding out.  T rated switches in many cases were dual rated for 5 or 10a dc, but i cant find this rating at least on this switch, i will keep posting as i find info, because this seems to be a common issue.

james
altE staff

dr 1524 and dr 2424 are still available new.  just checked on it, about 2 dozen left from what i can tell if you are in the market for new ones.

cheers,

james
altE staff

i will jump back in here, I spoke with john wiles on the matter, and i am waiting for permission to post his response on the forum.

you can use circuit breakers, and for a cabin that may not be so bad, because they will be rated and listed for the appropriate current and voltage.  in the setups i have seen, they are in the dc load center (like an outback fleware 500).

the other way that some folks go is to use a babybox and din rail breakers.  the breakers are listed for the application so could also meet safety requirements to the best of my knowledge.

james
altE staff

you can put the 15w module with the others, or on the other charge controller.  If you choose to meet electric code, wires leaving the area of the modules should be in conduit.  also, each series string should have its own series fuse or series circuit breaker.  for kyocera 50w, should be 6a.  when multiple units are combined in parallel, a combiner box is used. 

first a link to the module, then a link to a cabin package where you can see a schematic where modules are wired in parallel in a combiner.

http://store.altenergystore.com/Solar-Panels/1-to-50-Watt-Solar-Panels/Kyocera-KC50T-50W-12V-Solar-Panel-with-J-Box/p723/

http://store.altenergystore.com/Kits-and-Package-Deals/Off-Grid-Systems-Cabin-Systems/Off-Grid-Cabin-Special-Pkg-3/p5693/

click on the cabin picture after scrolling down for the schematic.

james
altE staff

no, not worried about questionning the rating, we/I want correct info out there, and myself and the forum appreciate feedback.  i am working on photos for next week, I just wanted to read off what was on the switch for more info.  i found info in the nec in section 404.14, but it is not a certain answer as the switch itself does not say DC on it.

thanks for the help

james
altE staff

here is what it says on the switch itself.

5a-250v-10a-125v-T
CSA, UND LAB INC LIST.

does that help at all?

what other folks have done is use the midnite babybox with dc din rail circuit breakers as switches in simple applications.

james
altE staff

thanks,

i learned something today, i will see what other info i can dig out about the switch we have.

james
altE staff

ahhh, that makes more sense. 

these units can do 50 or 60hz which is cool, but i dont know that it can charge any faster than a CR or DR.  dont remember of the top of my head what size ac charger is in them.

http://store.altenergystore.com/Charge-Controllers/AC-Charge-Controllers/Samlex-12V30A-3STG-AC-BATTERY-CHARGER/p1053/

james
altE staff

yes we have a switch.  i will put the link in.  they are somewhat hard to find.  i think they have to be "t" rated if they are able to do ac and or dc.  usally they click when the switch  is thrown.

http://store.altenergystore.com/Enclosures-Electrical-and-Safety/Miscellaneous-Electrical-Parts/Switches/DC-Switches/DC-Surface-Mount-Switch/p2356/

hope that helps.

james
altE staff

hi chris,

glad everything worked out, wanted to post for others benefit here. 

here is a video of testing a module on our site

http://videos.altenergystore.com/

i would also recommend attaching the charge controller to the batteries first before connecting pv.

connecting pv to the charge controller in the absence of batteries may wreck some charge controllers.  the sunsaver from morningstar has numbers right on the unit to show the order of operations for commissioning the system.

cheers,

james

these links may help you.

http://store.altenergystore.com/Lighting-Fans/Compact-Fluorescent/c495/

http://store.altenergystore.com/Lighting-Fans/LED-Lamps-Fixtures/c578/

i have the c.crane lights all over my house (all but two fixtures).  they shade kinda blue and sorta dim, but they draw at a very low rate (<5w).

james
altE staff

john is right, two inverters to the same bank of batteries is fine, just make sure they are each wired properly, not sharing any wires.

from a functionality standpoint, either way will work.

john makes a good point with two inverters potentially being more efficient.  I prefer one inverter setups because a single inverter with appropriate disconnects will likely be cleaner and safer than multiple dc connections to multiple inverters.  I would take the efficiency loss every time to have a cleaner safer system that any outsider could walk up to and figure out what is going on and how to turn it off.  i tend to be a nervous nancy with those things though.

james
altE staff

what inverter do you have?  I am not aware of any grid tie battery backup inverters at 12v nominal.  just curious?

regarding the batteries and the charger, you batteries probably do not want to be charged faster than a C/10 rate, but if you insisted, you would be looking at something like this

http://store.altenergystore.com/Charge-Controllers/AC-Charge-Controllers/IOTA-Dls-90-90A12V-2Stg-Ac-Charge-Controller/p700/

james
altE staff

hi guys, generally in colder climates, the most 18v modules you can put on an open format mppt controller will be 3 in series, and anywhere from up to 5 or 6 stings depending on the controller.

as far as mixing modules, normally you would not do it.  since these are all essentially the same model or "brothers" you would try to get as close as possible to what you have, so as not to throw off the IV curve for the mppt function.  so 170s and 180s together not a big deal, 170s and 195, will certainly be functional but not the most optimal.

 availability may drive this decision as well.  with the tax credits not being renewed, the market is the craziest i have ever seen it, in terms of supply available to meet the demand.  all installs must be done before jan 1, so installers big and small are buying up everything they can to be eligible for rebates on systems. 

info literally changes daily, so if you or anyone else needs modules, call our staff and we would be glad to help .

cheers,

james
altE staff

the other way that you could go is to use a 12v battery and a dc timer or put it on a manual switch.  in this case, the pump only sees battery voltage, and the module and charge controller take care of the battery.

james
altE staff