James Cormican's posts

Posted by James Cormican on Jun 4, 2009 11:39 am

#91 -  Renewable Energy > Technical Discussion: Other > Re: Solar Panel Maintenance
do you mean pv or solar thermal?

altE staff


Posted by James Cormican on Jun 3, 2009 08:45 pm

#92 -  Renewable Energy > Technical Discussion: Other > Re: need advice for a secondhand solar panel that draws 18-19v without a load

get a $30 multimeter that can measure at least 50v dc and 10adc and you can figure out what it is.  if your voc is around 20, it is likely a 12v nominal module.

watch this video, tell us the results. 


(2nd one down)

if you dont go that route, with other info, we can play guess that module, and then help with the rest of the components for battery charging if that is what you are after.

guess that module is one of my favorite games!!

mr. schmidt is correct, any info helps in guess that module, including:

color, size, # of cells, size of cells, color of frame, color of backing material, does it have a junction box on the back, where is the j box, how big is the j box, does it have glass on the front or something else . . .

altE staff

Posted by James Cormican on Apr 29, 2009 08:56 am

#93 -  Renewable Energy > Technical Discussion: Other > Re: Cadmium Teluride Solar Panels
here is what their website says.� I dont know more than that.�  I only know one person with cdte modules.� in the states they are only with that ppa company out west, or for large commercial projects.



altE staff

Posted by James Cormican on Apr 28, 2009 03:51 pm

#94 -  Renewable Energy > Technical Discussion: Other > Re: Solar for RV
you can wire the two modules in series.  the controller (the blue sky mppt you mentioned) will down convert it for you.  it will save you on voltage drop.  that would be the way i would do it.  there is no advantage in your case to wire them in parallel.

altE staff

Posted by James Cormican on Apr 27, 2009 05:23 pm

#95 -  Renewable Energy > RE General Discussion > Re: Batteries / Off-Grid
you bring up a good point.  perhaps i was unclear.  nec 690.7 provides multiplication factors in addition to VOC for poly and monocrystalline modules.  so by taking this factor, the voltage as it pertains to the code and other equipment would be higher.

on the subject of language, you mention 72v panel.  for clarity do you mean "panel" as
a. 1 photovoltaic module
b. 2 or more photovoltaic modules wired in series; commonly referred to as a series string, but described in the code as a panel (figure 690.1a)

operating under the assumption of "a", i would assume that the module in your example is a thin film silicon type, or perhaps other type of thin film.  if i had to guess i would say bp millenia.  that being said, if it had a vmp at either 70 or 90v, you are right, even in cold temps, it would likely not make it over the 150v damage threshold of many modern mppt controllers. also, 690.7 would not apply, and you would use the manufacturer's given temp coefficient of voltage to calculate max cold temp VOC.  If  i guessed right and it is the millenia or other thin film module, if you have more than one of those modules, they would all be wired in parallel to prevent the over-voltage (150) that you dont want going to your controller. 

i misused the term derate for 690.7, as it implies lower.  the voltage is not lower, but it corrects voltage higher, thus limiting number of modules per series string in mppt sizing.  that is why i refer to it as derating, lowering the available high end string possibilities.

thanks for participating in the forum, and helping me keep my terminology clear.

altE staff

Posted by James Cormican on Apr 27, 2009 12:13 pm

#96 -  Renewable Energy > Technical Discussion: Other > Re: Solar for RV
2 130 will be too much for the sunsaver mppt.

any controller 30a or higher should be fine on that array.

kyo 135 will have the connectors to wire up in series nicely, but you will have to buy an extension. something like this, that gets cut in half by the user. 


if you go with the 130's, make sure you get appropriate wire and fittings for solar applications, such as pv wire or use-2/rhw-2, strain reliefs and fork terminals rated for the temp and voltage. 

we have that stuff here


and here

ask if you have other questions,  good luck with your project

altE staff

Posted by James Cormican on Apr 26, 2009 03:44 pm

#97 -  Renewable Energy > RE General Discussion > Re: Batteries / Off-Grid
off grid equipment is generally not found above 48v nominal because of this:

nec 690.71b

storage batteries for dwellings shall have cells connected so as to operate at less than 50 volts nominal.


as regards to controllers down converting from 72v, that is true, but in most cases not 72v nominal, where 690.7 cold temp deration in colder climates will prevent 72v nominal pv input to most mppt controllers that have max vdc of 150.  48 and 60v nominal array inputs are fairly common though.

enjoy the sunny weekend,

altE staff

Posted by James Cormican on Apr 23, 2009 08:45 am

#98 -  Renewable Energy > Technical Discussion: Other > Re: MX-60 question
yes, bad idea.

8 is about all you are good for.  fuses okay is input ocpd, and you should have one on the output as well sized for 80. 

if you choose to make improvements to your system, this is where i would go


with these for the inverters


and these for before and after the controller




altE staff

Posted by James Cormican on Apr 18, 2009 03:06 pm

#99 -  Renewable Energy > RE General Discussion > Re: solar panels facing both south and west
just a few points

when you say fuse, just for those reading, if you mean supplementary overcurrent for series strings in the combiner, those fuses cant be disconnected safely under load.  hopefully you opened the circuit with the pv disconnect before any fuse pulling, or you meant din rail breakers in the combiner.

regarding that you ran one "line" did you mean wires or conduit run?.  many combiners can have two outputs, such as a flexware pv8, so even if it was one conduit run, a future two controller solution may be possible if you so desired.  In order to do that, you would have to do conduit fill calcs, and perhaps do a new wire run from combiner to dc load center.  if you used a conduit size larger than 1/2in, it is likely that you could have the setup for two controllers without ripping out the conduit if you wanted it.  if not, no big deal, as we discussed, it is a performance issue, not a safety one.  and the discussion is fun for the forum, and fun as a design challenge.  as always, thanks for writing in.

altE staff

Posted by James Cormican on Apr 17, 2009 08:50 am

#100 -  Renewable Energy > RE General Discussion > Re: solar panels facing both south and west

how were you monitoring the wattage of each group separately?
penta metric or something?  if you were measuring instantaneous wattage, did you measure cumulative energy such as watt hours generated per section?

I am glad that it went up okay and you had fun with the data, but i think the two mppt controller solution would provide optimum energy harvest.


altE staff

Posted by James Cormican on Apr 15, 2009 04:30 pm

#101 -  Renewable Energy > Technical Discussion: Other > Re: Load controller function
if you don't have a dc load (such as a dc light bulb) then there is no reason you must use those terminals.  most people do not use the load terminals on charge controllers with that functionality.

leave them empty unless you were already planning on running a dc load less than 25a from the battery bank (that you would prefer the load not drain the batteries in the event of lack of charging).

altE staff

Posted by James Cormican on Apr 14, 2009 01:31 pm

#102 -  Renewable Energy > Technical Discussion: Other > Re: What size Solar panel do I need to maintain unused 70 Amp Car battery in car?
found this at lunch,

may be correct part number


altE staff

Posted by James Cormican on Apr 14, 2009 12:42 pm

#103 -  Renewable Energy > Technical Discussion: Other > Re: What size Solar panel do I need to maintain unused 70 Amp Car battery in car?
talk to your dealer, vw had a specific part number for a pv module with suction cups for the windscreen to keep cars on dealer lots charged.  i dont know if it is still valid, but you can ask your dealer and then check google or ebay.  i would go that route first to avoid warranty and other complications.


altE staff

Posted by James Cormican on Apr 8, 2009 10:54 am

#104 -  Renewable Energy > Technical Discussion: Other > Re: One diversion controller for Wind and Solar
i will dive into this one.  this to me is a case of can and should.

can you use a diversion controller for both solar and wind? yes.  it would go after battery and only control based on voltage.  it is likely that solar and wind together could easily go over what one diversion load controller would handle.  it is also likely that installing all those blocking diodes would be a pain, and, would increase voltage drop.  the code will require duplicate controllers in case of failure when controlling in a diversion fashion.

the reason that controlling them differently makes sense because they are different in how they operate.  the other advantage is that many solar controllers are very efficient these days, and besides being able to come in at higher voltage than the battery bank (mppt), just about all of them can prevent reverse current, which removes the need for external blocking diodes that increase voltage drop.  even a pwm controller will outperform a module wired straight to the battery.

hope that helps,

altE staff

 other than saving the few hundred bucks reason, i would not use a one controller solution.  I think that a two controller solution would provide better controlling and save the hassle of hardwiring blocking diodes. 


Posted by James Cormican on Apr 4, 2009 08:03 pm

#105 -  Renewable Energy > RE General Discussion > Re: NEC 2008 code manual
I strongly recommend the handbook edition.  it is the light blue one that is hardcover.  it is usually around $110, but worth it to me as it has color pics and notes and explanations not found in the other editions.  if you are studying solar, i can give you other links to very useful code documents from john wiles. 

altE staff

Posted by James Cormican on Mar 31, 2009 02:15 pm

#106 -  Renewable Energy > Technical Discussion: Other > Re: Newbie needs help!
If you have 5 evergreen modules you will not be able to run a 24v system with that controller.

in order to make it work you will need to wire 2 evergreens in series (connect one module's negative to its partners positive {the closest ones if they are side by side}).  you will take the output of those two modules (voltage open circuit should be about 45 ish) and you will bring their output to a combiner box. positive goes through 20a din rail circuit breaker, negative goes to negative bus bar.  you will need an mc connector solarline 2 extension to go from your series connected pair to the combiner box. 

the other two will do the same thing. 

the output of the combiner box (the combiner should be right next to the array)  will be one positive, one negative, one equipment grounding conductor. 

that feeds into your dc load center.  your positive should go through a circuit breaker before the controller's pv + input.  between the controller's battery + output and the battery + busbar should be another circuit breaker.

the negative from the combiner goes to the pv negative on the controller. 

here is a list of products you will likely need to wire the components you have correctly.

http://store.altestore.com/Cables-Wiring/Wiring-For-Solar-Panels/30-MC2-Connector-10-AWG-MaleFemale/p5982/   x2


http://store.altestore.com/Enclosures-Electrical-and-Safety/Overcurrent-Devices-Fuses-Breakers/Circuit-Breakers/Outback-20-Amp-Din-Rail-Mount-Breaker/p5806/     x2

http://store.altestore.com/Enclosures-Electrical-and-Safety/Overcurrent-Devices-Fuses-Breakers/Circuit-Breakers/Xantrex-60A-160VDC-Panel-Mount-Breaker-for-XW/p6159/  x2 (to fit into your xandc175)

please call us if you need help, we would be glad to help with design and safe implementation advice for your components.

altE staff


Posted by James Cormican on Mar 23, 2009 03:55 pm

#107 -  Renewable Energy > Technical Discussion: Other > Re: mixing solar panel voltages within a single solar array
hi dave,

yep, i didnt want to go too far down this road, but there is the min vdc, and min mppt vdc. so 139 is absolute minimum, whereas 150v is where the mppt kicks in.


sma has it in the string sizer, no problem.�  see link above.

sma does not list strings of 5 on its sizer, but maybe on a pole or ground mount (cooler modules) it could work most of the time.�  the trouble is in summertime, that vmp will drop and you would not want to waste the sunny summer months with 10 modules in 2 strings of 5 and the inverter saying "solar voltage too low"�  or in SMA german it might say "VDC BFR" (nein solar Wink) when you could have 7 working modules.

hope that helps,

altE staff

Posted by James Cormican on Mar 23, 2009 02:44 pm

#108 -  Renewable Energy > Technical Discussion: Other > Re: mixing solar panel voltages within a single solar array
the low end voltage is the vmp in hottest conditions. the high end voltage is voc in coldest conditions.

i would not recommend wiring modules at different voltages in series.

per the string sizing tool, it looks as though 1 string of 7 modules in series is the best you can do.  you can do 1 string of 6 as well.

you said you dont have enough for two "arrays" but i think you meant series strings, and if that is the case, that is what the sma tool says as well.  the good news is that it should run the inverter.  the bad news is that because of the quirks of the inverter and your modules, you will have three extra modules to sit on.

being the curious type, i checked and saw that assuming you had the money, inclination, and room in your service panel,
you could do one string of 6 mods at 24v on the 1800u, and you could run 1 string of four mods at 24v on the sma 700u inverter on the middle setting.  this would utilize all your modules, but cost you another inverter.


altE staff

Posted by James Cormican on Mar 17, 2009 12:17 pm

#109 -  Renewable Energy > Technical Discussion: Other > Re: Combining Sharp 224w panels
do you want to wire them in series, (voltage additive to make 36v nominal)

do you want to wire them in parallel (voltage stays at 18 nominal, current adds)


do you intend to grow the system with more modules in the future?

altE staff

Posted by James Cormican on Mar 17, 2009 12:10 pm

#110 -  Renewable Energy > Technical Discussion: Other > Re: Lorentz vs. Grundofs Pumps
they are both good pumps. 

the grundfos has added versatility in that the sq flex series can run on dc pv direct in a wide voltage window, or from a generator on AC. 

the lorentz with ps600 and 1200 can pump from deeper sources. but runs on a narrow voltage window for the pv.

as with most renewable energy applications, there is no "best".  take into account the requirements of the site and compare them to the features of both.

altE store

Posted by James Cormican on Mar 17, 2009 12:04 pm

#111 -  Renewable Energy > RE General Discussion > Re: Morning Star Tristar-45 charger
PWM charge controllers often buzz, humm, or click.  the tristar is 45 or 60a, how much pv do you have??

also with pwm controllers, emi can be problematic for television sets, radios and such.

the common solution to avoid these is to use a shunt type controller.  the ones from specialty concepts are popular, but there are others as well.  they dont make any that go to 45a, so the question comes back to what the array is.

altE staff

Posted by James Cormican on Mar 17, 2009 11:56 am

#112 -  Renewable Energy > Technical Discussion: Other > Re: Connecting two solar panels to a single charge controller
yes, you can connect two modules (of the same nominal voltage) in parallel to one controller.

no, blocking diodes will not be necesary.�  the charge controller will provide that function, and the series overcurrent protection in the combiner box will further protect the modules, provided the overcurrent protection is sized appropriately to the max series fuse size of each module.

to do it properly, a combiner box with appropriate series string protection would be the way to go.�  this box would go next to the modules and allow you to leave the array with one positive (ungrounded-red-), one negative (grounded-white-), and one equipment grounding (green) that would go to your pv disconnect then charge controller.

here is a schematic from a package of a system that is likely similar to yours (at least the array with two modules in parallel).�  to see the schematic, scroll down to a picture of a cabin and click on it.



altE staff

Posted by James Cormican on Mar 9, 2009 11:14 am

#113 -  Renewable Energy > RE General Discussion > Re: Solar Panels for RV's
the first thing is always to know your loads.
if you can tell somebody your watt-hours per day they can help you.

here is a good place to start.




altE staff


Posted by James Cormican on Mar 9, 2009 11:04 am

#114 -  Renewable Energy > Technical Discussion: Other > Re: Hot breakers
hi everyone, please let us/me know when you suspect problems with any of the calculators.  I will be looking into the wire size one this week, as i did not know who wrote it or when.

the other note i should mention, is that the din rail circuit breakers from cbi (midnite and outback) are both rated to 150vdc now, but they can only take 6awg as far as i know.


altE staff


Posted by James Cormican on Feb 19, 2009 11:05 am

#115 -  Renewable Energy > Technical Discussion: Other > Re: Tracker vs. MPPT controller
the best way to compare this is to look at tmy data for the area the array is to be implemented.

it should have the sun hours listed at different latitude tilts as well as have data for single and dual axis trackers.

you can find that data online, or in the back of this book.


by memory i think the 1 axis tracker change from fixed is a 30% increase.  what the owner has to weigh is

a.  is it cheaper to buy the same percentage increase in performance by purchasing more pv or a tracker

b.  am i willing to take something solid state and introduce movement and the potential for maintenance

c.  is it just so cool that a and b dont matter


altE staff


Posted by James Cormican on Feb 9, 2009 11:00 am

#116 -  Renewable Energy > RE General Discussion > Re: off to on grid

if i had a nickel for "how much pv for x square footage of living space",  i might have a new vw.  it is not that it is an unreasonable question, it is just that there is no straight answer.  the amount of electricity usage generally is not that tightly correlated with size of living space.  your apartment is a prime example.  in 800sq feet, i never went above 350kwh/month (with an old frig) because i had gas heat and no a/c.

the issue is not the space, it is the energy usage.  you mentioned your high kwh usage for a small apartment.  the issue is not the space itself, but the loads within it, likely lead by the air conditioner.

to give you an idea, the mean electric usage is roughly 900kwh per household.  during your warm months you are using about double that.  if you do get a house, even though i love pv, i would suggest making the first $5k (that could be used for a pv array) on a set of hardcore efficient appliances, and or insulation and windows.

here are the main determining factors used for determining grid tie systems

1. budget - pv equipment is still pretty expensive

2. loads or % of loads - most folks dont get near 100%

3. space available for pv modules

here is the grid tie calculator link.  as of right now, it assumes a central high voltage dc to ac inverter.



altE staff

Posted by James Cormican on Feb 6, 2009 10:35 am

#117 -  Renewable Energy > RE General Discussion > Re: MPPT based charger options needed
here is one of the more common options for smaller arrays.


here is a whole section full of them if you choose to explore on your own.



altE staff

Posted by James Cormican on Feb 5, 2009 12:10 pm

#118 -  Renewable Energy > Technical Discussion: Other > Re: Mis-matched batteries
leaving aside the ideal as requested, this is in the direction i might go.


i would not hook the batteries up together.

depending on inverter size, something like this could work, and again, not ideal.


although i think blue seas has one without the both selection.

do you mean 300 watt hours per day, or 300w max instantaneous load?

given your parameters, that is just my opinion/ stab at the problem.

altE staff

Posted by James Cormican on Feb 5, 2009 11:08 am

#119 -  Renewable Energy > RE General Discussion > Re: off to on grid
It seems that a person starting out should build an off grid system and then keep adding more panels until there is enough kwatts to make it worth while to tie into the grid.
What do you suggents?

to be clearer, i have no beef with batteries or off grid systems.  the parts i was responding to were in the quote above.  that is, the concept that if the end purpose is grid tie anyway, that a person SHOULD start by building an off grid system until it meets some "worthwhile" threshold.

I do not subscribe to that concept.  obviously batteries have their place and if the load/need/want requires a battery based solution, then great. 

i do not think however that it is a linear progression from off grid to grid tie (operating under the assumption that distributed generation policy in your area makes grid tie possible).  if a grid tied system is the ultimate goal, there is not a need due to technology or cost to require pieces from an off-grid setup for a ramping up period. 

whether that small scale grid tie system (for roughly the same investment as the off grid equipment)  is meaningful or worthwhile  is in the eye of the beholder.

with higher voltage modules and approved listed inverters with low voltage windows, the cost of the minimum grid tie system is decreasing relative to the past.

good discussion

altE staff

Posted by James Cormican on Feb 4, 2009 02:01 pm

#120 -  Renewable Energy > RE General Discussion > Re: off to on grid
I dont think that is the case.  like all renewable energy it depends on the demand or load and the specific resources available (sun and budget). 

i am not sure why it is worth while to spend money and inefficiencies on batteries when the ultimate goal is grid tie.  figure out what the goal is.  If it is fun with a small off grid system, then great, but that should not be confused with the grid tie system goal as just about all of the components will not transfer over.

i would suggest knowing your energy usage first.  second i would set a goal for potential energy usage and possible energy production.  third implement the plan for conservation and efficiency.  fourth, site analysis for renewables.  fifth renewable energy system design, purchase, installation.

if the goal is ultimately grid tie, then i see no reason to bother with setting up a small off grid system first.  dont get me wrong, small off grid systems when installed safely are lots of fun, and a great learning experience.  that learning experience does not necessarily have anything to do with the goal of the grid tie system.  you can get into a grid tie system for less than $5k.

my question to the forum is what is "worth while" to tie to the grid?  for me the mere completion of the project no matter the wattage is walking the talk and setting the example for friends and neighbors.  any code compliant safe system to me is worth while.  what do you think?

thanks for writing in.

altE staff

Disclaimer and Disclosure

The Alternative Energy Store, Inc reserves the right, within its sole discretion, to refuse or delete any posting or portion thereof, or terminate or block the access to this forum.

The opinions and statements posted on this forum are the opinions and statements of the person posting same, and do not constitute the opinion or act of the Alternative Energy Store, Inc (AltE). The Alternative Energy Store, Inc does not endorse or subscribe to any particular posting. No posting shall be construed as the act or opinion of the Alternative Energy Store, Inc.

Click here for BBB Business Review

McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams
Desktop Website | Mobile Website


Click on an icon to share! If you don't see the method you want, hover over the orange "+".


What can we do to help you?

Please enter a summary
Sorry, the copyright must be in the template.
Please notify this forum's administrator that this site is using an ILLEGAL copy of SMF!
Copyright removed!!