James Cormican's posts

different modules OF THE SAME NOMINAL VOLTAGE may be wired in parallel using a combiner box as long as you are going to a PWM or SHUNT type controller. 

if i understand correctly, in your case 3 kyo 40w (12v nominal) and 1 kyocera 135w (12v nominal) are all to be wired to a 12v nominal system.  if this is the case a 30 to 60a, 12v, pwm controller should work.  each of the modules will have its own circuit breaker in the combiner with an ampere rating as mentioned on the module label (max series fuse).

 the combiner box should go by the array and allow for leaving the array in conduit.  if you enter a building, the conduit should be metallic until the point of the first disconnecting means.

hope that helps,

james
altE staff

james:

they make something for paralleling stings of pv modules.  it is called a combiner box.  it is listed for the application, and intended to go right next to the array to allow for changing wire type and leaving the area of the array in conduit.  each string goes through an appropriately sized circuit breaker on the ungrounded (positive) while each of the grounded conductors (negative) goes on the negative busbar.  you can pull the combined output to your pv disconnect, then an appropriately sized charge controller.

good luck

james - altE staff

hi friends on the forum.  prove me right on the "field of dreams" theory. . .  if you build it, they will come.

http://www.altestore.com/store/killawatt/

we created this database and just put it online.  I encourage you guys out there to use it and let it grow.  use your kill a watt or watts up meter and see if we can't fill this thing out. 

thanks all for your continued participation in our community.

cheers,

james

i hesitate to speak for john here, but i believe what he meant by saying
 "you have the meter connected across the battery"

is that by connecting your meter to terminals connected to the battery pos and neg busbars, essentially and electrically it is the same thing as measuring voltage across the battery bank posts themselves.  the only difference is the addition of the resistance of the conductors, which for your purposes is irrelevant.

notes for caution!!  rather than disconnect the lead from the dc enclosure with it still attached to the battery post, if you have any series connections in your battery bank, i would remove those and leave the other connections put. 

to put it another way, remove one series link from each series string you have, while leaving the connections in the dc load center alone.  then measure voltage at the terminals in the dc load center and in the battery bank where the conductors go from the battery posts to the load center.  since you would have removed one series connection from each string, you should have an open circuit both in the load center and in the battery box.  of course when you do this, have your appropriate ppe, and make sure your meter is set to dc voltage.

when you are all done with your wiring, while leaving all disconnects off, then replace the series connections (with your ppe on).

for what it is worth, i would suggest bringing in a pro if at all possible.  its not that i mind at all answering the questions, but batteries (and most electricity for that matter) can kill you with 1 mistake, and the question while good for theory, gives me some pause to know that it represents the lack of understanding that may put you in danger.  be careful

james
altE staff

good question, lets go socratic method.

if you reply, tell us which load center is in use, and i can provide more detail.

"I have the disconnect breaker wired on the top going to the positive inverter connection and on the bottom to the positive battery bank terminal and the positive pv output breaker"

Q: so, where is the bottom of the breaker connected to?
A: "and on the bottom to the positive battery bank terminal"

Q: so . . . if the bottom of the inverter disconnect circuit breaker is connected to the positive terminal on the battery bank can it ever be off?

A: no, because it is opening the circuit between the battery terminal and the inverter, not the battery and the box, or more specifically the bottom of the breaker.

Q: does the same hold true for the negative busbar?

A: yep, the busbars (and bottom of inverter disconnect either holding one or acting like one) are extensions of the battery bank terminals.  they are always live, as you cant turn the batteries off.

because the busbars in a DC load center are always energized by the battery bank, it is very important that safety gear (appropriate ppe) and precautions are used when operating inside one.  the disconnects (pv, controller, inverter, loads) all
disconnect each other from sources.  with pv and batteries, it is important to remember that opening a disconnect may stop current flow after that disconnect, but there is no stopping the potential for voltage (and current in the event of a short) from a source before that disconnect. 

you would expect voltage across the postive and negative busbars in a dc load center.  they are merely an extension of the terminals inside a box, to facilitate connecting all those disconnects and branch circuits.  should you try to measure current (WHICH YOU SHOULD NOT) you may have an explosion as you would short the battery bank.

hope that helps,

james
altE staff

hi james,

we are hoping to be running classes in the midwest next year, but I would also suggest that you check out the midwest renewable energy association.  they having been doing RE training for over 20 years i think. 

james
altE staff

no problem.  just to clarify, always use the polarity that is indicated on the module, not the extension.  tape the conductor of the extension to match the color/polarity of the module end it is attached to.

if you would have wired in reverse polarity, it likely would have been the charge controller, not the modules that would have been destroyed.  either way, something to avoid.

the other thing i did not mention is to test voltage with a multimeter at the combiner (set it to 200vdc which is common on $30 multimeters)  Make sure it is set to voltage!!.  with respect to the multimeter, with red as positive, and black as negative, you should see a positive voltage when connected to the red and white respectively when measuring from the bottom of the breaker(s) (on most combiners) to the negative busbar.  if you see a negative voltage that means you have reverse polarity and should check all connections before turning on any disconnects.

james
altE staff

no problem, this happens all the time.

1. watch this video
http://www.altestore.com/video/video-MC-Connector-Extensions-Primer-v6/

2.  leave all breakers in the off position, and leave the series connections for LAST

2. land the bare wire ends to the combiner FIRST so you are not dealing with live current.

3.  use RED tape on the MODULE end MC CONNECTOR with the positive embossed on it.  ANYTHING connected to it that is NOT a series connection MUST ALSO BE LABLED RED.  the connector that will mate to that red end will have a negative on it, but it is the only end that will plug in.  REMEMBER to relable this RED right behind the connector, and also on the outside and inside of the combiner box for the bare end.

4. do the same with the negative end of the series string.  label the connector on the module with white tape, and label right behind the connector extension that connects to it with white tape.  do the same labeling for outside and inside of the combiner. when you do this, put the wire through the stain relief on the combiner first, then relabel with tape on outside and inside, otherwise the tape often gets stuck in the strain relief.

if possible cover the modules with the most opaque thing you can find (the boxes may come in handy here).  remember to leave all circuit breakers off.  make your series connection  last, do the extensions first, so that the last connection you make at the array is the final series connection, with all other breakers in the system off.

if everything checks  at the array and where the balance of system stuff is,you can remove the covering then you can turn on the combiner breakers (if you have any), so long as your PV disconnect breaker is OFF.  if you do not have a combiner, then you must leave the pv to controller breaker off for now. 

if you have a battery based system, turn on the charge controller disconnect, that connects the batteries to the charge controller. 

then turn on the pv to controller breaker, and the controller should wake up and show charging current.

james
altE staff

for folks doing 12v wiring, here are the most common units that they use.  both enclosures are listed to meet code.

depending on the size of the conductors, you may have trouble getting anything above 2awg into the breakers or potentially busbars.  these are the most popular choices, but not necessarily the best for your situation.

http://www.altestore.com/store/Enclosures-Electrical-and-Safety/Electrical-Enclosures/DisconnectLoad-Enclosures/AC-andor-DC/Square-D-QO612L100RB-Square-D-QO-Load-Center/p2579/

square D qo gear is rated for 12vdc as well as 120/240.  I believe that to use this enclosure for 6 circuits, you have to jumper over from what would have been two separate legs of 120.

http://www.altestore.com/store/Enclosures-Electrical-and-Safety/Electrical-Enclosures/DisconnectLoad-Enclosures/Dc/Outback-FlexWare-FW500-DC-breaker-enclosure/p5576/

with 8 small breaker slots, the outback enclosure is larger and more flexible in its implementation.  you will have to add a positive busbar, as i believe that it comes without one, assuming a jumper from the bottom of the large inverter disconnect circuit breaker that is used in typical off grid systems because of 2/0 and larger conductors and their 3/8ths lugs.

12v wiring is not that common anymore as a permanent code compliant solution.  issues such as voltage drop, large conductor sizes, listed equipment (light switches are a nightmare to find), and ability to have anybody but the installer work on it easily are the biggest challenges.

generally, I have found that by the time the time and expense of doing things correctly (code compliant) at the 12v dc level, the costs in time, money, effort, and efficiency, are more than made up for in creating a standard AC system with an inverter.  the wiring instantly becomes smaller, more standardized, and the ability of an electrician to work on the system in the installers absence increases substantially.  only in the smallest of systems (this one may apply) do we find that the 12v systems are the absolute win win.

hope that helps,

james
altE staff

hi roy,

there are not a lot of solar space heating kits because the variables start to pile up. 

as always step 1 is know your loads, and step 2 is to reduce them.

after that, solar thermal is likely the next most cost effective way to go.  a few on our staff are teaching a class right now on solar thermal, but if you call the phone line, and press the directory for solar thermal, somebody should be able to help you with the design elements.

otherwise there are some good books on the subject here.

http://www.altestore.com/store/Books-Classes-Educational-Videos/Solar-Hot-Water-Systems/c453/

and here is a free web video that is somewhat basic but useful.

http://www.altestore.com/store/Books-Classes-Educational-Videos/Educational-Videos/Educational-Video-Solar-Water-Heating-Basics/p6726/

good luck,

james
altE staff

danny,

to harvest that amount of energy, you are looking at an array very roughly between 12kw and 20kw, depending on the variables. 

you can play around with various numbers here:

http://www.altestore.com/store/calculators/on_grid_calculator/


hope that helps,

james
altE store

what size breakers do you have to wire to?
what size conductors are you planning to use?
i have no beef with soldering, but i am notoriously lazy.  i prefer an appropriate listed lug, with appropriate crimper.

we already carry such things for 10awg, and i plan on adding more (larger awg solutions) to the site as a "make it do-able" project for just such an occasion.

http://www.altestore.com/store/Cables-Wiring/Cable-Wire-Tools/Burndy-Products-MR15-Crimp-Tool/p7106/

http://www.altestore.com/store/Cables-Wiring/Wiring-For-Solar-Panels/Grounding-and-Wiring-Accessories/Burndy-Products-TP10-14-Ring-Terminal-QTY1/p7388/

if you answer the above questions, i can point you in the direction of appropriate ring terminals and perhaps crimpers.
i just wanted to point out that such things are certainly available, though somewhat costly for one-time usage.  given the choice i almost always choose crimping, and or purchase factory pre crimped cables for the bigger stuff.

james
altE staff

here is a link, to what we have here for info,

http://www.altestore.com/howto/HydroPower/c21/

http://www.altestore.com/store/Books-Classes-Educational-Videos/Micro-Hydropower/MicroHydro-Scott-Davis/p4342/

good luck,

james
altE staff

here is what the product management staff had to say:

"The highlights are the modules can now be used for end mounting, the load capacity is higher, and these now come with a 25 year warranty (standard). The only difference in the modules is that the frame is actually .4 inches deeper than the original KD135. "

what this means for practical purposes, is that for unirac systems, now dark F clamps will be used instead of C clamps. 

for ground and pole mount systems, you may have to check closely to make sure none of the mounting holes have changed positions.

the old frames are being phased out, and all kd modules will eventually get the new frames.

to the best of my knowledge the cells and therefor the electrical characteristics have not changed.

james
altE staff

home power issue 132, was the cover story, flat plates v evac tubes.

james
altE staff

regarding the choice of max series fuse size, it has to do with what the internal wiring of the module can handle.  there are numerous examples of modules from back in the day that had 15 or 20a series fuse sizes even though they were 50w. 

off the top of my head, sanyo ba3 and ba19 modules have 15a series fuse sizes even though the isc is below 4a.

so i looked at some old bp 40w modules we had, and sure enough 20a series fuse size. 

these modules could handle higher current so they math sometimes worked that you could cram two strings on one ocpd.  this is very rarely the case anymore, with the sanyo being the only one i can think of; and even the sanyo's dont quite make it for the math with two strings in parallel on one ocpd.

kaneka! they can do it too 7a series fuse, about 1a isc

i need to walk away from the computer . . .; back to class prep for next week.

james
altE staff

so to james,

yes, that is one choice.  if you plan on doubling your array, there is another choice.  switch to an mppt controller that can down convert voltages, (flexmax 60, others ...) and then you can leave each series string of up to 4 (maybe 5) modules on one overcurrent protection breaker.  if you took your current array of 3 kyo 40, and wired them in series instead, you would have that one string feed one 6a breaker in your combiner.  your pv disconnect would be 6a, however, the charge controller disconnect would be at minimum 20a, because by down converting voltage 3 to 1 ratio, your current would go up by that same ratio.

if you went this way, you would leave the combiner box, but have the ability to have your current 3 modules, or 4 modules (1 string of 4 in series), or you could double your array as proposed with 2 strings (in parallel each with ocpd in combiner) of three in series.

--

for mr. schmidt, it is important to remember that in a battery based system, it is not only other strings of modules that can be problematic in fault or component failure situations.  the battery bank has the capability of backfeeding, and the ocpd based on max series fuse size, protects the modules, as well as the system and potentially building from all the unpleasant (though less than likely) happenings.  whenever i reply to posts i do my best to highlight the "should" possibility rather than the "could" possibility.  thanks for your posts on this one



james
altE staff

in addition, to what was mentioned above about double lugging, here is the math behind why its now allowed.

take the isc of one module.  multiply it by 1.56 then by the number of strings you want in parllel.  if this number is over the series fuse rating, you are not allowed to wire them in parallel in a battery based system without series ocpd on each string. 

in your case, i believe their series fuse size is 6a, so you cant put more than one module in parallel without using an ocpd rated at 6a for each, (hence the combiner box located at the site of the array).

james
altE staff

your question is a good one and  highlights why dc load centers are important.  when the combiner is by the array outside(combining) then there is the need for an enclosure that can provide the appropriate busbars to handle pv disconnects, charge controller disconnects, inverter disconnects, equipment grounding conductor, load circuit breakers, etc that is located inside. 

yes bus bars would be the way to go, but not bus bars randomly hanging out readily accessible in a live electrical condition.

depending on the case, sometimes one larger controller makes sense, other times the arrays dictate that two controllers would be a better solution.  as long as the controllers are wired in parallel, there should be no problem with their functionality.

james
altE staff

sunframe has black rails, and is generally used when folks want the close to the roof look for aesthetics.

solarmount is the general workhorse from unirac.  there are light and heavy duty variants, along with just the regular solarmount extrusion.  solarmount can be mounted on L-feet, be mounted on standoffs up to 7 inches, or be connected on adjustable tilt legs.  it has a clear anodization coating.

the have pictures of both types of systems on their site, www.unirac.com

hope that helps,

james
altE staff

everything from tarp, to duct tape, to platic jugs, to aluminum foil,  to custom welded tops, or old coffee cans.

not all of those are necessarily suggested . . .

but something is likely better than nothing

james
altE staff

do you have an existing pv or battery system, or generator?

do you have a pressure tank? 

more details would help,

james
altE staff

unless your top of pole mount was designed to have something in the middle, i would not put something there, as it increases weight and windload.  i have seen folks put plywood that they paint whatever color they like, or pegboard to let the wind through and not add weight, but if it were me, i would leave the pole mount alone.

if you want to add another array to charge the same battery bank on the shed roof, then it does not matter what controller you select, as long as it is appropriate for the job.  it will not interfere with the existing pole mount array.  the new array however, will need its own disconnects and potentially gfp protection.

james
altE staff

the evergreen has 108 cells, 54 in series, whereas the sunwize has 48.  the other issue is then you will have two uneven strings attached to the same controller, and this is more of a problem than if they "match".  one string of three and one string of two will not be useful for your mppt. 

if i were you, and you needed more energy production, i would start a new array on a new controller. 

james
altE staff

in most cases the pole is not used as a grounding electrode.  a separate one is driven in.  usually the poles are encased in large concrete foundation, and this limits its ability to pass current to ground.  when driving ground rods in dry climates, often it takes more than one ground rod to successfully meet the required ohms to ground measurement for a safe ground.  in most cases i suspect that this is the case for the pole, offering too much resistance from the concrete foundation.

i would love to hear from others with experience on this topic

james
altE staff

hello,

this may do the job for you.  both battery banks must be 12v, and the array must be 12v nominal

http://www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/Pwm-Type-Solar-Charge-Contollers/Morningstar-Charge-Controllers-Pwm/Morningstar-Sunsaver-Duo-Dual-Battery-Charger-25A/p5600/

it can charge two banks from one array, and the battery banks can be set independently for flooded or sealed.

james
altE staff

check at a place called lehman's.  they do the country living off grid thing really well.

www.lehmans.com

james
altE staff

no, sorry for the confusion, we dont have a trade in program. 

you could always try to sell it on the forum though.  there are some nice, used equipment loving folks in there from time to time.

james
altE staff

as long as you are connecting them in parallel, and using a pwm controller, there is no problem. only concerns are aesthetics and more wires (quantity) for paralleling.

 the max series fuse sizes may be different for the larger modules, meaning different breakers added to your combiner, and potentially to the disconnects before and after your charge controller.  if you add enough power, you may have to examine your charge controller size as well. 

if your combiner is full, you may upgrade to a unit with more slots, or you could elect to wire modules in series and select an mppt controller that can down convert for you.

lots of choices, good luck and feel free to ask more questions.

james
altE staff

nope not sure, thanks for the reply.  good point, this is out of my normal realm, so all input is welcome. 

that is from 2002 code, correct?, and most of the country has adapted to it.  so what do you do when you find these issues; is it a wild goose chase to find what the issue is?

james
altE staff