New install questions

My first post. I know I am asking alot but, could any of you read my post from another forum and if any answers to any of the questions I ask spark your interest, could you answer them for me?
I know that I should break it down to smaller bits. If you are willing to answer any part I would be thankfull.

http://www.fieldlines.com/index.php/topic,147188.0.html

You are welcome to point out where I am stupid also.
Thanks
gww
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Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions

    From the link:
    I am trying to learn but willing to take a short cut. I am trying to figure the right way to wire my system and not have to change it if I ever have it inspected which I don't plan on doing but figure if it would pass I would have no troubles no matter what happens. I have been looking into nec requirements but will probly show my ignorance with this post.

    I have an outback system, 48 volts. Two inverters for 240 volt power. I am going to buy 16 sams club batteries. I would like to use the smallest wire I can and still be safe. Things I hope to learn by posting here.
    1. The out back manual says to run the house AC power to the inverter from a 60 amp breaker. Would 12/3 gage house wire work for this or do I need to go bigger and if so how big?

    2. For the dc wire coming from the solar. 3300 watts is the max for the mx 60 charge controller for a 48 volt battery bank. My intention is to run this about 200' to my house from a ground mounted aray. I am going to have about a 90 volt 3300 watt solar aray.
    a. what size wire?
    b. Does the combiner box need fused or just a buss bar?
    c. Will the dc breaker panel work as the dc shut off contoller? My inclination is it wont as it is inside the house. If the dc panel won't work does the dc shut off have to be fused?
    d. Fuses were provide with the dc panel, what size does the fuse have to be to be safe?
    e. Is conduit required for exsposed wire runs.

    3. Batteries,
    a. Inside my basement or outside along my house, inside an inclosure?
    b. What size wires?
    c. Will the dc panel be enough fuseing of the batteries.
    d. What size wire should I use to and from and to interconnect the batteries?

    4. Pre hot water heater powered through the inverters out sub-panels at 240 volts ac, using an ssr as the trigger.
    a. What wire should I use?
    b. What wire should I use from the charge controller to the ssr? ssr is 4-34 volts dc. The wire will probly be 50 to 60 feet long.

    I am looking and trying to figure the 125% rule or the 157% rule and what goes where but it would be nice to have good starting points so I could start gethering some of this stuff. Some of you guys and/or girls have built simular stuff and have some of these answers floating around with out even having to think of the math. I will take what you are willing to give even if it is critical of some misconception I might be showing that I have.
    Thanks
    gww
    Also I could put the inverter in a detatched garage and run power to the house but I would have to buy even another sup-panel for my basement and not use the one on the outback mounting plate. I would also have to run the dc wire under ground to the ssr.

    Would this still be a better ideal?
    thanks
    gww

    -Bill "will read/reply a bit later" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    I have been reading this site and it has helped alot. I'm still here and will be anticipating your help. And thanking you the whole way.
    gww
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions

    Thank you for posting again GWW--I got distracted. Squirrel! :blush:
    I have an outback system, 48 volts. Two inverters for 240 volt power. I am going to buy 16 sams club batteries. I would like to use the smallest wire I can and still be safe. Things I hope to learn by posting here.
    1. The out back manual says to run the house AC power to the inverter from a 60 amp breaker. Would 12/3 gage house wire work for this or do I need to go bigger and if so how big?

    On the forum here--We are a cheap but practical bunch here. However, we try to ensure that things are done safely above all. You can get away with a lot of short cuts--But remember these systems are powering your home/cabin/RV and many times will be unattended. It is one thing to "play" with stuff on a work bench--It is another to bury wiring in your walls out of sight/out of mind.

    Remember that heating is Power=I2R. If you double the current, the heating effect is 4x worse. So, just being a "little" over the rated current is actually "squared' in terms of heating.

    The manuals are usually written with the NEC (national electric code) in mind. Which was a response to electrical fires when electricity was being introduced to the world at large. Getting a copy of the NEC Book is usually a good idea. I don't always agree with the NEC and how they do thing (and will tell you when I don't), but in general it is a good starting point that gives you a safe system.

    So--For example the 60 amp breaker for your AC Mains/Inverter branch circuit. I don't know the Wattage/model of your inverters, so lets assume the 60 amps is appropriate. First, the NEC assumes that everything is rated 1.25x larger than the max. continuous load expected on an electrical circuit. In this case 60amps/1.25=48amps max continuous load on wiring. Note that circuit breakers and fuses if operated at max current will eventually trip (i.e., 60 amp breaker/fuse will open in minutes to hours at 60amp, but never should at 48 volts).

    Next, the NEC has deratings for wire diameter, insulation types, conduit fill factor, etc. So, you will see a table like this one:

    Wire Current
    Ampacities NEC Table 310-16


    Assuming copper wire (highly recommended--Aluminum has lots of safety issues if not done correctly). Depending on the type of insulation, abient temperatures (in home, on roof, etc.), you will see that 60 amps will require 6 awg to 4 awg (note, for every 3 AWG steps in wire gauge, that is a doubling of cross-sectional area and a doubling in cost of wire). And there is another derating table for conduit type/size/fill factor (NEC assumes that all wires in conduit are carrying maximum rated current--worse case self heating).

    You will see other tables, for example boating, that would let you use less copper for carrying current. Many times the wiring is exposed (better ventilation, wire can be cooler) and you will see that they say 10 AWG can carry 60 amp. maximum. And to carry 45 amps, you could even use 12 AWG.

    Note that this table does not address conduit, temperatures, insulation type, etc...

    Also note that electrical power is "dear" for solar user. More or less, power is "free" in a small boat/car/RV when driving. However, for solar, very roughly power costs around $1 to $2+ per kWH, or about 10x what commercial grid power costs. So "wasting" a lot of heat in wiring (I2R heating) gets very expensive very quickly in lost power. So, that is another reason we limit our voltage drop in "high voltage" (solar array wiring, 120/240 VAC circuits) to ~1-3% voltage drop.

    You can use a generic voltage drop calculator to estimate the drops. For example, a 48 amp 240 VAC circuit with 3% voltage drop, the one way wiring trip (electrical current always takes the round trip--some calcs use one way, like this one, other require round trip length):
    • 48 amps, 3% drop max, 240 VAC, 4 awg wire -> 250 feet @ 3% / 7.2 volts wiring drop
    • 45 amps, 3% drop max, 240 VAC, 12 awg wire -> 39 feet @ 3% / 7.2 volts wiring drop

    So, there is our next limitation--Wire length and votlage drop... When you get down to 12 VDC wiring, many times you are using much heavier wire to keep voltage drop very low--For example, a 12 volt circuit should have about 0.5 volt maximum drop so everything will function. And for charger to battery, the voltage drop should be around 0.10 to 0.05 volt drop so charger will accurately measure battery voltage under load.
    2. For the dc wire coming from the solar. 3300 watts is the max for the mx 60 charge controller for a 48 volt battery bank. My intention is to run this about 200' to my house from a ground mounted aray. I am going to have about a 90 volt 3300 watt solar aray.
    a. what size wire?
    So, using above voltage drop calculator and the 1% to 3% drop maximum (90 volts, that would be 0.9/2.7 volt drop maximum), the wire awg required to support (3,300w/90v=) 37 amps would be:
    • 2 AWG @ 37 amps will give you 2.8 volt drop
    • 3/O @ 37 amps will give you 1.1 volt drop

    That is expensive copper... If you use the right connectors and crimplng tools, there are copper to aluminum connectors (UL approved, used by power companies to home connections) that work well... In alumimum your numbers would be:
    • 1/O would be 3.2 volt drop
    • 4/O aluminum would be ~1.3 volt drop

    Ouch--That is a long distance and a lot of wire costs... One option would be to install your battery bank/charge controller at the array, and send the power as 120/240 VAC instead--That could reduce wiring costs somewhat (depending on your load requirements and design--say the well is next to the array and the home is 200' away--and your maximuim power is used for pumping).

    Also, large diameter wires are difficult to source and hard to work with... You may want to keep the solar strings separate until they get near the battery shed/controller before compinging to one large diameter wire.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions

    The 5,000 character limit is a bit of a pain with long posts--Anyway, to continue:
    b. Does the combiner box need fused or just a buss bar?

    It depends on the Isc (shorted current rating) and series fuse rating for your solar panels... Most panels need a fuse/breaker when you have 3 or more parallel strings (the two, or more, other strings feed a shorted single string--and need a fuse/breaker to protect the wiring in the shorted string).

    So, assuming you have 4 parallel strings or so--Yes, you will need a combiner box for the + wiring (and bus bar for the -/return wiring).

    Note that NEC requires your wiring rating to be sized for Isc*1.25(NEC derating)*1.25(Solar derating) for maximum current. In most cases, the voltage drop requirements force a larger diameter wire vs current limits.

    Also, you are using an Outback series MPPT charge controller. There are now higher voltage MPPT charge controllers out there. Midnite (same folks that started Outback years ago) now have controllers with upwards of 290 VDC max input rating (or almost 200 VDC Vmp rating, depending on how cold it gets in your area--cold panel produce higher voltages/and more power).
    c. Will the dc breaker panel work as the dc shut off controller? My inclination is it wont as it is inside the house. If the dc panel won't work does the dc shut off have to be fused?

    I am not an NEC code guy--But as I remember, NEC requires conduit into the home up to the disconnect/breaker box. So, in theory you can put the combiner box inside the home as long as you have rated conduit bringing the power in. Note that you can use Combiner Box Breakers as a disconnect, but you cannot use touch safe fuse holders (they can arc/catch fire if you pop the fuse holder under load).
    d. Fuses were provide with the dc panel, what size does the fuse have to be to be safe?

    Look at the data sheet for your solar panels--There should be a series fuse rating (not all spec. sheets say--you may have to call to find out). It is usually ~2x Isc rating of the panel (usually around 15 amps for medium sized panels).
    e. Is conduit required for exposed wire runs.

    Outside, sun/weather is very hard one wiring--As are squirrels (nesting under arrays and chewed wiring is a common service call out here). If you do not have gnawing animals and use UV rated wiring, you can have exposed wiring around the array. And, of course, you can use exposed wiring for the run back to the house/building (just like the utility does).

    Buried/conduit/buried conduit is always a good idea for long term installations (20+ years?). Less change of damage, better visuals. But power poles from array to building is not a code problem (just like your utility). Some folks are on granite shield--It would take explosives to dig a ditch--Fun, but perhaps not the best idea.
    3. Batteries,
    a. Inside my basement or outside along my house, inside an enclosure?

    Batteries and gensets are both significant sources of fire hazards. Gensets and fuel should have their own building away from other structures (we had one person here that lost his entire solar power system when a generator caught fire).

    Batteries, are amazing current sources... A largish battery bank can output >10,000 amps into a dead short. That is more current than available for a pole mounted utility transformer outside your home. When you get to battery wiring, using fuses/breakers (high current, rated for application) is very important for fire safety.

    Also, flooded cell batteries out-gas hydrogen and a bit of electrolyte mist. Keeping them in a ventilated enclosure is a good idea too. Even AGM/Sealed batteries can vent (especially if over charged and/or near end of life), so being aware/careful is still a good idea with sealed batteries too.

    Another is temperatures... Charged lead acid batteries require something like -70F or colder to freeze. Near dead batteries can freezer at 32F. Below freezing, batteries lose significant capacity (while cold).

    Hot batteries lose significant life (for every 10C/18F increase in temperature, batteries will age ~2x faster). If you have temperature extremes in your installation, basement, buried in hole, in berm insulated structure, insulated box/shed can help keep batteries in the 40F to 80F range. Battery heaters are only needed if you have a winter cabin, extreme cold temperatures, and non-use. Use genset and battery heaters to bring batteries above freezing, then normal battery cycling and insulated box/structure can keep batteries warm after than (assuming installed in serious arctic conditions).

    If you have temperature extremes, get the remote battery temperature monitor option for your controller (good idea anyway).
    b. What size wires?

    What size inverter/AC/DC loads?

    What will be your battery bank series/parallel organization?

    Nominally, I like to recommend one series string of batteries/cells (large AH cells/batteries). If you have to parallel strings, I would recommend 2-3 strings maximum.

    Some reading:

    batteries, series-parallel, balancing, help me understand

    About to buy new Batteries - not sure if my set up is correct to start with
    c. Will the dc panel be enough fuseing of the batteries.

    Gets back to load requirements--It is not unusual to have 150-300 amp fusing/breakers on a battery bank for main power.
    d. What size wire should I use to and from and to interconnect the batteries?

    Battery bank organization/size/loads/charging sources, etc...
    4. Pre hot water heater powered through the inverters out sub-panels at 240 volts ac, using an ssr as the trigger.
    a. What wire should I use?
    b. What wire should I use from the charge controller to the ssr? ssr is 4-34 volts dc. The wire will probly be 50 to 60 feet long.

    Need the current in the SSR input... But probably 16-18 awg wire would work (twisted pair to avoid electrical fields getting into wiring and causing weird switching issues). Keep signal wiring away from heavy AC/DC cables, Only cross large/high amperage cables at 90 degree angle, etc.

    Make sure SSR is well heat sinked (can fail from overheating).

    Will you have a lot of "extra power"? Also, if you are using electricity for hot water because of cost/availability of fuel--The "new" hybrid water heaters can be an interesting option for even solar power systems. They are 2-3x as efficient as resistance hot water heaters (use heap pump) as long as the temperatures are above ~55F. Don't use a lot of power (~600 watts maximum????) if the resistance backup heaters are turned off. A bit slow to heat water--but if your needs are not great--may even be cost effective when compared with solar thermal water heating (and much less plumbing issues) or even propane hot water.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    Wow a helpfull post. I now have my homework assignment. I will read everything 5 or ten times and get maby a third of the content.

    I can tell you are a little more organized in passing on imformation. I won't have that talent but will do my best in responding to what you have posted.

    Your questions to me;
    1. Will I have a lot of extra power.
    a. My house probly uses 30 kwhs per day. I have no loads assigned to the sub-panel. I did It backwards. I was bored so I built 2000 watts solar panels. Then I built two hugh piggot 8' turbines. Then I bought a used outback dual inverter GVFX3648 with all the bells and whistles. I only got one mx60 cc with this. Then I bought 2800 watts solar panels cause I don't think my home made ones are going to last that long. When I get it together I will start assigning loads to match.

    b. The ssr and pre-hot water heater. I want to do this for two reasons. 1. I will have the turbines hooked to the batteries with no cc. and may need to put the power some where if there is lots of wind. 2. during the day when the batteries get full I didn't want the solar to be shut down by the cc.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    The post that I just did was about a quarter of what I typed and when I tried to post it I was made to log in again and the rest was lost. I will have to try again tomorrow.
    Thanks
    gww
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Continue, your questions to me;

    2. Loads, I have assigned no loads. My house uses about 30 kwhs per day and I am in another state while building all this stuff. My ideal is to make sure I have enough charging ability for my battery bank and then to assign loads that fit my system with the hot water keeping me from wasting the panel output when my loads don't keep the system buisy. Say put maby 1000 watts of whatever in the sub panel. Preferibly more daytime loads then night and then adjust up or down to try and get the system to work seamlessly. I can relie on the grid when I screw up.

    3. batteries, two series strings of eight 6 volt wired parelel. 416 amp hour battery bank.

    4. ssr current. I couldn't find anything but the voltage on the dc side. 4 to 32 volts. The mx 60 cc is 12 volts and 200ma on it auxzillry out put which is what I hope to use to control it. the ac side is 600 volts and 25 amps.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    I couldn't get your hot water heater link to work.

    Did you see my drawing and the outback diagram?

    When I changes my panel runs from 6 awg to 2/0 I did it based on outbacks manual stating 1/0. I went up due to the distance. I like your wire sizes better. It is hard to decide if wire loss or panel loss is most exspensive.

    The manual says 8awg for the ac connect.

    My questions.

    1. The out back diagram shows a ground at the pv aray. I thought that was changed and I was required to run the ground with the panel wire and connect it to the house ground.

    2. If I have two pv arays and I was going to run four big wires from them. Could I only run three since the neutral is connected to the same block and only the positive is fused, would this work?

    3. I need four 15 amp and six 6 to 8 amp breakers to protect my panels. could you tell me which combiner box at the midnite solar store would do this. Or any where else.
    a. also I need to reverse the polarity of the breakers If I want to protect the panel arays. Is this correct?

    I will know at deer season how long my actual wire runs will be as I will be back home "Missouri" and will measure. If I can decide where I am going to put the inverters. Does 120 ac run that much better then say 87 volts dc?
    If you never answer another question I am still thankfull for what you have already answered.
    Thanks
    gww
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions

    The water heater link goes to the GE GeoSpring water heater... Works on my phone here.

    I will reply later from home to the rest of your posts.

    I did not see your drawings--But that may just be my phone.

    Regarding grounding, there is local grounding of the solar panel frames and the metal mounting. For lightning and safety grounding if there are shorts. Do not connect your DC wiring to the remote grounding/grounding rods--Only connect it in one place, typically near your main panel/entrance to your home/ground rod.

    DC grounding of your negative battery terminal to a ground rod near your main panel... In just one place. Do not ground your DC power more than one location.

    -Bill

    You should have a grounded AC neutral (if you have grid/utility power). You normally tie the DC green wire ground to the same ground rod as the AC ground (again, just one ground connection).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: New install questions

    link works for me too. i am using firefox for the record.
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions
    gww1 wrote: »
    Your questions to me;
    1. Will I have a lot of extra power.
    a. My house probly uses 30 kwhs per day. I have no loads assigned to the sub-panel. I did It backwards. I was bored so I built 2000 watts solar panels. Then I built two hugh piggot 8' turbines. Then I bought a used outback dual inverter GVFX3648 with all the bells and whistles. I only got one mx60 cc with this. Then I bought 2800 watts solar panels cause I don't think my home made ones are going to last that long. When I get it together I will start assigning loads to match.

    Dump loads are great/usually required for HAWT (horizontal axis wind turbines) so you can keep them loaded in heavy wind (and prevent over-speed/destruction).

    The issue is that you have a limit of how much power you can dump into a water heater before it overheats/pops the PTR valve (pressure/temperature relief valve).

    Will you have other methods to load the turbines/shut them down safely in high wind if/when the water heater is "hot enough"?
    b. The ssr and pre-hot water heater. I want to do this for two reasons. 1. I will have the turbines hooked to the batteries with no cc. and may need to put the power some where if there is lots of wind. 2. during the day when the batteries get full I didn't want the solar to be shut down by the cc.

    At least the solar electric panels can be shut down "safely" by just "turning off" the switch (i.e., controller shuts down current flow from array).

    In the end trying to figure out how to use all available power during the day (batteries full, no major loads) is always an interest to many people. Using the extra programmable output on the Outback charge controller to turn on loads when the battery bank is in float (heating hot water, pumping to water storage tank, irrigation, etc.) is something that many people have done over time.

    I agree that it is very difficult to build a solar array that will be safe and reliable vs those you can buy today for ~$2 a watt (plus or minus). We have seen our share of home built/dubious source solar panels fail and even catch fire.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions
    gww1 wrote: »
    Bill
    I couldn't get your hot water heater link to work.

    Here is the link again:

    http://www.geappliances.com/heat-pump-hot-water-heater/
    Did you see my drawing and the outback diagram?

    I saw the photos in the Fieldlines thread.
    When I changes my panel runs from 6 awg to 2/0 I did it based on outbacks manual stating 1/0. I went up due to the distance. I like your wire sizes better. It is hard to decide if wire loss or panel loss is most expensive.

    Off grid solar power costs around $1 to $2+ per kWH--So conservation (turning stuff off, using efficient appliances, etc.) is all a big help.

    Looking at reducing wiring losses kind of fits into that too... You can pretty quickly figure out how much energy you are losing:

    Power = V*I

    So, if you have 3 volt drop at 50 amps, that is 150 watts of loss.

    Say that is about 4 hours per day, 365 days per week:

    150 watts * 4 hours per day * 365 days per year * 1kW/Watt = 219 kWH per year loss

    At $1-$2 per kWH, that is $219 to $438 worth of "lost power" per year. (very rough numbers).
    My questions.

    1. The out back diagram shows a ground at the pv aray. I thought that was changed and I was required to run the ground with the panel wire and connect it to the house ground.

    I am not sure I can see a ground at the PV Array--But my normal assumption is that the Solar Panel Aluminum frames and the metal mounting structure are all connected to 6 AWG wire (single uncut length daisy changed from each panel frame to metal mounting to ground rod next to array). This ground should not be connected to the DC power lines.

    I believe you should run a 6 awg minimum copper ground wire from the remote ground stake back to the main ground rod at the home/power shed. You want any short circuits at the array to eventually return back to the main power area (so you can trip fuses/breakers with a complete circuit).

    If you have lightning in your area--You will need to think about grounding very carefully. Both from a code point of view and a practical safety point of view (note solar/NEC code is not always safe).

    There is also a NEC requirement for "DC Ground Fault" detection circuit. The current method puts a 1 amp fuse (or breaker) between safety ground and earth ground. If there is a hot to ground short it pops the fuse or opens the breaker which turns off charge controller(s). Personally, I think this is very unsafe--But, so far, it is still the "law of the land".

    Note this link is fairly "in depth" about grounding/safety philosophies of system design vs the NEC... If your eyes glaze over--Don't worry about it too much. However, I am still adamant that the NEC using a fuse/breaker to "sense" excessive ground current, then opening, is hugely unsafe.

    Ground Fault Protection
    2. If I have two pv arays and I was going to run four big wires from them. Could I only run three since the neutral is connected to the same block and only the positive is fused, would this work?

    Note sure that I understand what you are typing... There is no "Neutral" in DC power... There is "Hot" and "Return" (+/- in typical installations).

    In 120/240 split phase AC systems, you have the Black Hot and Red Hot and White Neutral. Hot to Neutral is 120 VAC, Hot to Hot is 240 VAC. In center tap transformer circuits, the Hot to Neutral to Hot connections will "zero out" current in the Neutral if the current in the Red/Black wires are equal.

    There is no such analog in DC Power Systems as we use them here (that I can fit with your statement).
    3. I need four 15 amp and six 6 to 8 amp breakers to protect my panels. could you tell me which combiner box at the midnite solar store would do this. Or any where else.
    a. also I need to reverse the polarity of the breakers If I want to protect the panel arays. Is this correct?

    Our host Northern Arizona Wind & Sun can help--Or Midnite can too (they have a forum--See my Ground Fault Protection link). None of us Moderators are connected with NAWS or the solar business here... We are just volunteers to help control spam and answer the questions that we can.

    Yes, many DC breakers have polarity and should "face" the high source of current (typically the battery bank), but in this case the Bus Bar for the Array + common connection point. I believe the Midnite forum has one or more discussions about this (I do not know if the Midnite breakers are polarity sensitive or not).
    I will know at deer season how long my actual wire runs will be as I will be back home "Missouri" and will measure. If I can decide where I am going to put the inverters. Does 120 ac run that much better then say 87 volts dc?

    It depends on how far you want to go... But a doubling of the working voltage is a very significant change (for the same power, it means 1/2 the current, 1/4 the power dissipation, and usually an increase in allowed voltage drop).

    My usual recommendation is to do a paper design around several different options (battery bank at array, sending AC power; vs a "standard" MPPT controller or a "higher input voltage" MPPT controller, etc.). Until you actually try to do the designs, you won't trip over the 4/O wiring requirement, or that you want 120/240 VAC split phase power for a well pump, etc...

    Also, I find it much easier to discuss specifics (an actual paper design) vs a lot of "hand waving" and general rules of thumb. There is a lot of detail require to design a safe and reliable off grid power system.
    If you never answer another question I am still thankfull for what you have already answered.
    Thanks
    gww

    You are very welcome--Hope we all have helped here.

    Obviously I did not get 14,000+ posts by not replying. :p:blush:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    2. If I have two pv arays and I was going to run four big wires from them. Could I only run three since the neutral is connected to the same block and only the positive is fused, would this work?

    I wish I would have said negative wire insted of neutral. same question though.

    You have helped so much though. I am going to study.
    thanks
    gww

    I am going to have to go over you grounding responce several times to understand.

    The combiner boxes. I have been to this sites store and tried to look at the boxes but I don't understand what I am seeing which is why I ask which one would work. when a box says three pole, does that mean three arays or just three wires? does my question make sence?

    Dump loads, I have a morningstar ts 60 that I was originally going to hook to the batteries before I come up to the hot water sceem. I could still use this to control a dump load for the turbines.

    My homemade panels are dubiously built. They will be on ground mounts (200' ?) from the house.
    Thanks again
    gww
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions
    gww1 wrote: »
    I wish I would have said negative wire instead of neutral. same question though.
    Not a problem. We try to be very clear as we are doing this all by written response and don't want to have people make any unsafe mistakes--If we can help it.
    I am going to have to go over you grounding response several times to understand.

    Feel free to ask more questions--grounding can be complex when you have multiple power sources (grid, generator, solar power, etc.)... There are the NEC requirements, and then there are what is practical and safe. Not always the same thing.
    The combiner boxes. I have been to this sites store and tried to look at the boxes but I don't understand what I am seeing which is why I ask which one would work. when a box says three pole, does that mean three arrays or just three wires? does my question make sense?

    It will have three breakers (or fuses) for three circuits. One to each series string of solar panels. And a common bus bar that goes back to the battery shed/charge controller (assuming negative grounded battery bank, you would put the three + wires, one into each breaker, and the - wires go into the bus bar).

    Please feel free to add links to any equipment you have questions about. You can do it by "six pole breaker box" or just pasting the link as below:

    http://www.solar-electric.com/misomnsoarco.html

    Dump loads, I have a morningstar ts 60 that I was originally going to hook to the batteries before I come up to the hot water scheme. I could still use this to control a dump load for the turbines.
    My homemade panels are dubiously built. They will be on ground mounts (200' ?) from the house.

    That is a pretty long distance. You can try several configurations with a generic voltage drop calculator. Try 100 VDC (typical max voltage for cold climate with 150 VDC max vs 290 Voc input rating for controllers):
    >200', ~30 amps, 3% voltage drop at 100 volts (3 volt max)=> 3 awg gives 2.9 volt drop
    >200', ~30 amps, 3% voltage drop at 290 volts (8.7 volt max) => 6 awg gives 5.7 volt drop

    And yes, you can mount the combiner box at the array (shield from rain/full sun) and run a single pair of wires (plus 6 awg ground recommended) or run three strings of smaller pairs of wire (plus ground) to a combiner box at your battery shed (remember, this is safety ground wire from array ground rod to main panel ground rod, not talking about DC grounding here).

    I may be wrong, but I do not see any issue if you run three small gage + wires and one heavy gage ground wire back to the battery shed/combiner box (you would "combine" the three return wires at the array but the three + wires back at the remote mounted combiner box--your choice).
    >200', ~10 amps, 3% voltage drop at 100 volts (3 volt max)=> 8 awg gives 3.0 volt drop
    >200', ~10 amps, 3% voltage drop at 290 volts (8.7 volt max) => 12 awg gives 7.7 volt drop

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    What the outback system diagram shows is pv arays grounded at the arays. I am guessing it means the frames of the solar panels. There is no ground coming to the ps2dc100 breaker box from the solar panels. The House breaker panel, the sub-panel, the dc panel, batteries, charge controllers and inverters are all grounded through connection on the mounting plate and buss bars in the respective breaker boxes. The diagram has a note that says " all gnds are bonded to the back plate thru the mounting screws." Can I do it this way?

    Is welding wire a no no?

    Does the combiner box you showed have a bus bar for a ground?

    I will have more questions later but need to research first and try to digest your previous answers.

    I am slow and hope I don't wear you out. As you are a volunteer you can always quit on me. It makes your help much more giving and I thank you again.
    gww
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: New install questions
    gww1 wrote: »

    Is welding wire a no no?

    Other than the suitability of the insulation on the welding wire for high voltages if you use a series string of panels, the main objection I have seen to welding wire is that terminal lugs and screw fittings which are designed for standard stranded wire will not work properly with the very fine strands used to make welding wire more flexible.
    SMA SB 3000, old BP panels.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    inetdog
    Does welding wire violate code in most places?
    Thank
    gww
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: New install questions
    gww1 wrote: »
    inetdog
    Does welding wire violate code in most places?
    Thank
    gww

    It definitely violates the NEC if you use it with terminal blocks or connector lugs which are not specifically rated by their manufacturer for that fine strand construction. Note that there are some lugs which WILL accept welding wire, although only if used with the manufacturer's specified crimping tool.

    It will also violate the code if the insulation does not meet the code (again typically NEC) requirement for the application it is being used for. I have no knowledge about the insulation type of typical welding wire.

    Whether any individual inspector will care is, of course, subject to chance. :-)
    SMA SB 3000, old BP panels.
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions

    This is from our host NAWS:
    Note: We are currently transitioning from using welding cable to using MTW UL listed cable for all of our battery/inverter wiring. Many solar companies sell welding cable for use with batteries and inverters. There's no safety issue when using welding cable, but it can cause problems with some electrical inspectors. Technically, welding cable is only meant to be used on welding machines. When welding cable is used on anything but welders, it violates the national electric code (NEC). This is why we've started using MTW listed cables. MTW stands for "Machine Tool Wire" and it's essentially the same thing as welding cable, but with a more versatile electrical listing. This means it's approved for many more uses than standard welding cable. If you would like to learn more about cable and wire listing and use, please read this article entitled "Clarifying Confusing Cables" from Home Power Magazine. All other cables are welding cable, unless otherwise specified.

    NEC and UL/NRTL's use a "traceability" system for material/components... For example, the plastic mfg. has a cert. for their raw plastic (tested by UL/NRTL, follow up inspections), then the wire mfg. buys plastic from the mfg. and gets a "red tag" that is filed with the documentation for every shipment. The cable mfg. then builds the cable as document/tested by NRTL, and ships a red tag to the next step in the supply chain, etc. (and the cable mfg. permanently marks the cable with name, type number, etc. per their listing requirements, etc.).

    If you buy welding cable, it may not come with a "history" of traceability (and insulation has not been tested/rated for conduit/wet locations/etc.).

    My big issue was what inetdog said... Very fine wire is difficult to find crimp connectors and tooling that will properly (safely, rated tools/parts) because the fine wire has more "air space" and is larger diameter than normal electrical wiring (I needed high flex cable for a computer system I designed--Was very difficult to find all the right parts to make UL, and me, happy).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions
    Inetdog, Bill, and Host, thank you for your responses.

    I am a little behind in my research cause I tried to download the spell check and it screwed up my computer for a bit so I took some time to get rid of it.
    Bill
    What the outback system diagram shows is pv arays grounded at the arays. I am guessing it means the frames of the solar panels. There is no ground coming to the ps2dc100 breaker box from the solar panels. The House breaker panel, the sub-panel, the dc panel, batteries, charge controllers and inverters are all grounded through connection on the mounting plate and buss bars in the respective breaker boxes. The diagram has a note that says " all gnds are bonded to the back plate thru the mounting screws." Can I do it this way?

    above from quote me, below quote from you.

    I am not sure I can see a ground at the PV Array--But my normal assumption is that the Solar Panel Aluminum frames and the metal mounting structure are all connected to 6 AWG wire (single uncut length daisy changed from each panel frame to metal mounting to ground rod next to array). This ground should not be connected to the DC power lines.

    I believe you should run a 6 awg minimum copper ground wire from the remote ground stake back to the main ground rod at the home/power shed. You want any short circuits at the array to eventually return back to the main power area (so you can trip fuses/breakers with a complete circuit).

    I am not sure I understand. If I hook the pv frames to a pv ground rod and then run a 6 awg wire from there to the house rod and then the way my quote is wiring the stuff doesn't that in efect tye the pv ground and the dc ground together. Also wouldn't this require two 6 awg wires from the pv. My quoted configureation has no ground from the pv to the house. Grounding is hard.
    Thanks
    gww
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions

    Grounding is usually done for several reasons...

    Simply grounding the solar array frame/metal mounts to earth--Get rid of static electricity and energy from lightning strikes.

    The other, if a power lead from the array shorts to the metal framework, you don't want the metal to become energized relative to other metal/pipes/etc. in the area.

    However, earth grounding by itself is not a low resistance ground. And if you get a short, it is still possible to energize the structure relative (for example) a water faucet.

    So--Sending a ground wire from the array back to the building ground/DC ground provides a solid return path to trip a breaker, etc. (and why you run a ground wire from the battery bank to the common ground rod too--to provide that common return path that can sink enough current to pop a fuse or breaker. --That does get into the whole question of a 300 amp fuse on a battery bank to run a large inverter--and the required size of the green wire from DC to earth bonding).

    You really do not "need" to run a 6 awg cable from the remote ground to the local ground--And if all you have at the solar array is the DC power connections to the solar array--you probably are not getting much extra safety with connecting the two grounds together.

    There is a secondary reason for grounding, even with DC/solar power... It is possible to energize the array ground relative to the local ground (ground rod, water pipes, gas pipes, etc.). And depending on the polarity, you can create galvanic corrosion. If the ground is negative and there is a positive fault to (for example) a water/gas pipe, you will corrode holes into the piping pretty quickly.

    http://en.wikipedia.org/wiki/Cathodic_protection

    These become sort of secondary/tertiary issues--But if it is your metal structure, metal piping, or rebar in concrete that fails--It matters.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    I am never going to get it. If you don't mind I would like to give you two wiring sequences and If one of them would meet code just tell me and I will wire it like that.

    Both depend on the combiner box having a ground lug. I think the one you showed has one top left of the breakers. It also looks "to me" that the outback dc breaker box does fuse the ground.

    1. take one continuos ground to the panel frames and run it to a ground rod at the pv panels. take a different wire from the combiner box to the ground lug in the dc breaker box near the inverter.

    2. Take one continuos wire from the pv frames to a ground rod at the pv panels to the combiner box to the ground lug in the dc breaker box near the inverter.

    3. you can say none of the above, even though I hope one of the above works.

    Combiner boxes and fusing.

    1. Even though I did the cold weather voltage on my planed pv series connection and it came to about 139 volts. Do you think I will be good with the 150 volt breakers?

    2. Can buss bars be added to the combiner box if you wanted to have wires going to two charge controllers? In other words is the six breaker box you have pictured able to be configured for two seperate arays?

    3. If the answer to question two is no then I asume if I bought the 12 breaker one I would be regulated to 6 fuses per aray not 4 breakers to on aray and 8 breakers to the other.

    4. If you only need to fuse pv series if they are wired 3 or more in paralel due to two arays being able to over load one (something that can't happen with just two) Could a guy put two series on each breaker insted of just one?

    I ask these questions because on the one aray I will need 4 breakers for 2800 watts. On the other aray I will need six breakers for only 1800 watts. On this aray their is room for expantion without overloading most charge controllers. If I can double up the series to two I can make the 12 breaker combiner work and still exspand depending on the charge controller I use.
    Thank you.
    gww

    PS It is not your explinations on grounding that are bad. I have read every thing including on this site on grounding and on lightning protection and I am never going to understand. so all I want to do is put the wires right so they will please people who do care and can do something about it.

    Also I will never be inspected unless I really get tired of batteries and go grid tie. The only thing that really would worry me then would be needing different long wire runs. If I bury I don't want to dig up. I just figure if I stay close to code I will be safer and it will probly work better. I am not anal about it cause some of my solar and my turbines will never be ul aproved cause they are home made.

    Also I did read you link on cathodic protection but I am a highschool drop out. Maby I can figure how to use a 9 volt solar panel for protection. I have about 66 of them. I get the concept but not the prosses.
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    I am going to try this combiner box. I haven't ordered it yet but intend to soon.
    http://www.solar-electric.com/misomnsoarco2.html

    I am going to take a chance and wire it in the below quoted fasion.
    1. take one continuos ground to the panel frames and run it to a ground rod at the pv panels. take a different wire from the combiner box to the ground lug in the dc breaker box near the inverter.

    This is for two seperate arays for two charge controllers.

    I am about to pull the trigger so if I am messing up would some one tell me.

    Thanks
    gww

    ps If the above is correct enough, I believe I have the wiring part wupped except deciding on component placement and whether wet rated wiring buried or wire in conduit or on a pole.

    Bill
    Great stuff on twisting the wire to the ssr and making sure the small wire crosses large wire at 90 degrees. I have read the whole post a couple of times. Everybody That answered had helpful info!
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions
    gww1 wrote: »
    Bill
    I am never going to get it. If you don't mind I would like to give you two wiring sequences and If one of them would meet code just tell me and I will wire it like that.

    I will try--But you need to confirm with code book/inspectors (if you will be pulling permits) or a local electrician. I am not the expert by any means.
    Both depend on the combiner box having a ground lug. I think the one you showed has one top left of the breakers. It also looks "to me" that the outback dc breaker box does fuse the ground.

    The fuse between safety ground and earth ground is a NEC "#$*$&^). I think it is horribly unsafe. But it is possible your local inspectors will still require it... You can bypass the "current sense 1 amp breaker" with a piece of 6 AWG (or appropriate wire for current) and the whole thing turns into a manual DC disconnect.
    1. take one continuous ground to the panel frames and run it to a ground rod at the pv panels. take a different wire from the combiner box to the ground lug in the dc breaker box near the inverter.

    I want to be really clear... There is Earth/Safety Ground (wire from panel frames/metal structure to earth ground rod). And there is DC Return (and typically the negative battery post is tied to local ground rod).

    So, in the combiner box, are you typing about the the insulated negative bus bar, or are you referencing a green wire ground connection to the metal box?

    The metal box ground (safety ground) would be connected to the local ground rod (at least).

    The DC power wiring will connect to breaker/fuses and to the insulated return bus bar (negative). There will be no other connections from the solar panels power leads to any local ground/ground rod/safety ground).
    2. Take one continuous wire from the pv frames to a ground rod at the pv panels to the combiner box to the ground lug in the dc breaker box near the inverter.

    If this is a ground lug attached to the metal combiner box--Yes. You could also take a second copper wire from the combiner box and run it straight to the local ground rod. It does not have to be one piece copper wire with the solar panel frame ground.
    3. you can say none of the above, even though I hope one of the above works.

    The question is whether or not to run a 6 awg from the array ground rod to the home's local ground rod. I think it is a good idea (all metal structures with electrical power connected to the same "master ground rod" at the home.

    If you have lightning in the area, you have to really do some research on how best to do all this--It is not obvious and sometimes the requirements for "safety ground" and "lightning grounds" conflict.
    Combiner boxes and fusing.

    1. Even though I did the cold weather voltage on my planed pv series connection and it came to about 139 volts. Do you think I will be good with the 150 volt breakers?

    Yep, you are fine. (breakers will not "blow up" at 151 volts). However, many of the charge controllers will log >150 Volt input voltage and void their warranties.
    2. Can buss bars be added to the combiner box if you wanted to have wires going to two charge controllers? In other words is the six breaker box you have pictured able to be configured for two separate arrays?

    I don't know--You may have to buy extra insulated and breaker bus bars to do this--But as long as the total current does not exceed the Listing value (do not jam 200 amps of current into a 100 amp rated box), you should be fine. You may need to buy some extra bus bars to make up all the connections properly:

    Midnite Solar Breakers, Bus Bars, Ground Bars
    3. If the answer to question two is no then I assume if I bought the 12 breaker one I would be regulated to 6 fuses per aray not 4 breakers to on array and 8 breakers to the other.

    If you can get a 4 bus and 8 breaker bus that will fit the box, I don't see why not.
    4. If you only need two fuse pv series if they are wired 3 or more in parallel due to two arrays being able to over load one (something that can't happen with just two) Could a guy put two series on each breaker instead of just one?

    Probably--But I do not believe it is "legal" to put two wires into one breaker--You may have to use a wire nut to bring two wires to one, then connect to breaker.
    I ask these questions because on the one array I will need 4 breakers for 2800 watts. On the other array I will need six breakers for only 1800 watts. On this aray their is room for expansion without overloading most charge controllers. If I can double up the series to two I can make the 12 breaker combiner work and still expand depending on the charge controller I use.
    Thank you.
    gww

    I will say that planing for later expansion is always a bit difficult. Panel and charge controllers come and go. You many times will have to install a new array, box, controller to get everything to play together well.

    I do believe in oversize/extra conduit with extra pull ropes/wire if you are trenching to your array--That you only need to do once--and you can use the extra conduit for communications, AC wiring, etc. if needed later.
    PS It is not your explinations on grounding that are bad. I have read every thing including on this site on grounding and on lightning protection and I am never going to understand. so all I want to do is put the wires right so they will please people who do care and can do something about it.

    Grounding is very tough to do correctly with solar (and wind) power. Everyone one has their own ideas and mixing grounding ideas is sometimes even worse.
    Also I will never be inspected unless I really get tired of batteries and go grid tie. The only thing that really would worry me then would be needing different long wire runs. If I bury I don't want to dig up. I just figure if I stay close to code I will be safer and it will probly work better. I am not anal about it cause some of my solar and my turbines will never be ul aproved cause they are home made.

    And why it is important to have the wiring/breaker/fuses done right--They will reduce the chance of fire/shock. However--Wiring done right will never protect the source or the loads if they are not done "right" (fuses/breakers are to protect the wiring, not the devices connected to the wiring).
    Also I did read you link on cathodic protection but I am a highschool drop out. Maby I can figure how to use a 9 volt solar panel for protection. I have about 66 of them. I get the concept but not the prosses.

    Just read and absorb... Basically, what you don't want to do is "energize" water pipes, conduit, mounting structures in such a way that the electrical voltage/current flow makes rusting/corrosion faster.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    Can't thank you enough. I was reading post today on grounding. 2011 nec had some changes. I still didn't understand it. The part that keeps throwing me from the very beginning is the ground rod at the pv. I have read in several places that two or more ground rods can cause circular currents. One thing is clear in the 2011 nec is that all grounding needs to go to the house main ground. Nobody is going to look and I will need no permits. I believe I will attatch the solar panel frames to the solar combiner ground bar to the ground bar at the inverters. I am going to studie more to decide if I need a gound rod at the pv. If it is a must due to the distance I will put it between the pv and combiner box and will run it to the dc panel at the inverter.

    Is the ground rod at the pv a needed thing?

    I read one other interesting thing today also. Is running the ground wire in the same conduit laying length wise for a long distance a good ideal? Something about interferance? Can't remember exactly what I read.

    I am ordering the above mentioned combiner box today and the respective breakers I need.

    Is their a formula using the width or crossectional of a wire to decide conduit size for the number of wires in it to come up with your 40% fill. I have tried to figure out what size conduit would be needed for four 2/0 wires and one 6awg bare wire. I used .400 Inche times 4 equals 1.6 inches devided by 4" pvc comes up to 40% fill.
    This wire is actualy .420 inch wide with no insulation. So, 4" is probly not big enough if I am even close to doing it right.

    Do I need to count the isulation on the wire? Am I caculating correctly. If I buy wet wire do I need conduit for the underground wire?

    I am going to buy one shut off switch for my turbines also. It will mean I will have to shut off both turbines at the same time if I need it but it also means my turbines will be fused from the batteries. I know there are cheaper ways to accomplish this but at least it will be done. My rectifiers are at the turbine so unless I used more voltage robbing diodes I would have to run lots of extra wires in the pole. No question here just felt like adding a little info.

    Thanks
    gww

    $307.40 today and its just a start. Oww.
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions
    gww1 wrote: »
    Bill
    Can't thank you enough. I was reading post today on grounding. 2011 nec had some changes. I still didn't understand it. The part that keeps throwing me from the very beginning is the ground rod at the pv.

    There are two reasons for ground rods... One is to keep the metal structure at the same voltage level as "the ground". This helps reduce the chance of shock/electrocution (bare "hot" wire touches metal frame work/mounting--You walk up in wet grass and touch the frame work--And zap).

    The other is for lightning. If you get a strike, you want the energy to go somewhere--Preferably not into your home/power system. Shunting the current to earth ground is one way of addressing the issue.
    I have read in several places that two or more ground rods can cause circular currents.

    Probably "circulating current"... If the grounds are working correctly (and something is shorted)--Two ground rods connected to two different power sources (say AC mains and DC backup battery) can "energize" the ground itself. Put 120/240 VAC on two rods 10 feet a part will inject 1-20 amps or so into the ground itself. Not enough to pop a breaker, but enough to create current flow between two ground rods.

    Sticking another metal rod/water pipe in there--You now have voltage between the ground rods and other metal items. And can get a shock.

    I used to help at a marine park and put two ground rods ~100' apart into the soil. Got a shock when I went to wire them up (~60 VAC reading). Large water circulation park, on saltwater/bay fill--was a mess.

    Also, it is possible to have parallel current paths (neutral bonded to safety ground in gackup genset and bonded to safety ground in main panel for home). Now you have the neutral and earth ground carrying something like 1/2 the current each--You never want to carry current from normal operation in a safety ground. You could have a neutral break--and not even know it because the earth ground is still carrying current.

    And for AC/DC systems--The DC current may be 10x that of the AC current (10 amps @ 120 VAC = 100 amps @ 12 VDC = 1,200 Watts). You could cause high DC current to flow through a smaller gauge AC ground wire if you have multiple DC to safety ground connections--Why we always say "one ground connection".

    The normal way to connect a ground (say you have rocky soil and need more ground rods). You drive one ground rod (call it the master). All green wire safety connections (AC ground, DC ground, Telephone/Cable grounds, etc.) are connected to that one rod.

    If you need more grounding rods, you then drive more ground rods around the master rod, and connect the wire from the new rods back to the master rod. That way, you cannot get circulating currents through the earth.

    One person (was it a poster here?) found a bad Neutral/miss-wired connection on his home because the snow was melting around his ground rod.
    One thing is clear in the 2011 nec is that all grounding needs to go to the house main ground. Nobody is going to look and I will need no permits.

    You still wan to do it right--Especially if you have lightning in your area.
    I believe I will attach the solar panel frames to the solar combiner ground bar to the ground bar at the inverters. I am going to study more to decide if I need a ground rod at the pv. If it is a must due to the distance I will put it between the pv and combiner box and will run it to the dc panel at the inverter.

    I really do not understand "I will attach the solar panel frames to the solar combiner ground bar to the ground bar at the inverters".

    I would be a bit surprised if there was a Green Wire/Safety Ground ground bus/bar in the combiner box.

    The usual bus bar should be an insulated (from metal box) bar that is used to collect the "return" (negative wiring) from the solar array and combine it into one large diameter wire to the charge controller.

    You should never attach solar panel frame+safety ground to the DC Return Bus bar in the combiner box... That just "injects" energy from nearby/direct strikes into your power system and home--You do not want that.

    For Lightning--I am not sure of code, but any structures more than 10-20 feet away from each other should have their own ground rod (long wires do not carry lightning current well--it is an AC inductance thing).
    Is the ground rod at the pv a needed thing?

    It won't hurt (metal frames/mountings attached to ground rod)--And if you have lightning in the area, it is a good thing. And it reduces the chances of shock/electrocution if "something goes wrong".
    BB. wrote: »
    A couple threads about Lightning:

    Off Grid Grounding Technique?
    Another Question, this time about Lightning

    Note, the above are discussions, not a do A, B, and C--and you will be "safe". There probably is no such thing with lightning. Several different techniques are discussed--and a few of those posters even have experience with lightning. :cool:

    And our host's consolidated FAQ page:

    www.windsun.com
    Lightning Protection for PV Systems

    From other past posts here, Windsun (admin/owner of NAWS), he said that most of lighting induced failures he saw were in the Inverters' AC output section.

    Towards the end of this thread is a very nice discussion of proper generator grounding.
    I read one other interesting thing today also. Is running the ground wire in the same conduit laying length wise for a long distance a good ideal? Something about interference? Can't remember exactly what I read.

    Nominally, ground wires should not carry any current unless something "goes wrong". So in normal operation, there should be no interference issues (unless you are working with radio gear or something).

    Many people like to bury the 6 AWG bare wire next to the buried plastic conduit--This creates a better connection to earth ground.

    I am ordering the above mentioned combiner box today and the respective breakers I need.
    Is their a formula using the width or cross-sectional of a wire to decide conduit size for the number of wires in it to come up with your 40% fill. I have tried to figure out what size conduit would be needed for four 2/0 wires and one 6awg bare wire. I used .400 Inch times 4 equals 1.6 inches divided by 4" pvc comes up to 40% fill.
    This wire is actually .420 inch wide with no insulation. So, 4" is probably not big enough if I am even close to doing it right.

    It has been too many decades since I had to deal with NEC Code... I would guess there is a table/formula somewhere in the handbook--but I do not know.

    Remember, you are working with significant voltages/current/power. If this is your first time, it would not hurt to do the design (and possible install) with a licensed electrician.

    You may get yourself into trouble if you have never done this type of work before. It is impossible for me reading your posts to be sure of everything you are doing--And I am no expert anyway.
    Do I need to count the isulation on the wire? Am I caculating correctly. If I buy wet wire do I need conduit for the underground wire?

    Read the code book--But there is a difference between Wet/Direct Burial/Armored insulation/cables.
    I am going to buy one shut off switch for my turbines also. It will mean I will have to shut off both turbines at the same time if I need it but it also means my turbines will be fused from the batteries. I know there are cheaper ways to accomplish this but at least it will be done. My rectifiers are at the turbine so unless I used more voltage robbing diodes I would have to run lots of extra wires in the pole. No question here just felt like adding a little info.

    Will the turbines over-speed if you turn off the power? If so, you might look at a double throw type switch... In position A, the turbines are connected to the battery bank. In position B, the turbine is shorted to itself (the typical method of "turning off" a small wind turbine is to short its output which loads the alternator and should stall the blades). Check the manuals for your devices (or if you built them--decide how you will handle disconnected turbines in high wind).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Solar Expert Posts: 963 ✭✭
    Re: New install questions

    Bill
    Thanks for answering. again I studied more ground postings today. For example;
    http://forum.solar-electric.com/showthread.php?14288-Drawing-review-please!/page3
    With these post writen there.
    btw, the implementing of another ground rod is not advisable as there normally should only be 1 and that should be for the main service box. also, the main service box should be the only point where the neutral and ground are tied together.
    and
    Thanks for your feedback. I've changed the design once again! My AHJ suggested that I don't add any new ground rods so they were deleted from my design

    I read another post that said the same thing. I believe you are saying something simular.

    I am going to wire without sinking a ground rod at the pv and just run it all to my house ground rod. Maby attach lightning arresters. I am answering before reading the links on lightning that you provide. I will read them.

    As I mentioned earlyer, Unlike you (compliment), I don't communicate my questions very well and may seem to be repeating them at times.

    The combiner box seems to have a green wire safety buss bar.
    http://lib.store.yahoo.net/lib/wind-sun/PVcombiners-explained.pdf

    I also found a conduit fill calculator and the conduit ended up being one and one half inch for four 2/0 gage wire in pvc 40. If I add the ground wire I know I will be fine with two inch pvc. 40% fill rate. I have no ideal how to figure it myself though.

    I am hoping the wind turbine shut off shorts the turbines. I payed 63 bucks and looked at the wiring of it and I believe I bought the right thing. Would have bought two of the $35 toggle switch ones and fused them but it spicifically said not for nec installs.

    If you see anything wrong please point it out.
    thanks
    gww

    Ps I would say I get plenty of lightning. I have lost lots of computer modems and one time it blew a whole in a copper ice maker feed line took out all my phones and vcrs and froze my tv to one picture untill I turned it off, then it was ok.

    Also I read that if you make sharp 90 dergee bends at the beginning of your combiner exit wires that it helps as high voltage does not like to make the bends.
  • BB.BB. Super Moderators, Administrators Posts: 30,642 admin
    Re: New install questions
    gww1 wrote: »
    Bill
    Thanks for answering. again I studied more ground postings today. For example;
    http://forum.solar-electric.com/showthread.php?14288-Drawing-review-please!/page3
    With these post written there.

    The issue with that--They were adding a new AC ground rod elsewhere at the house (garage, etc.)...

    When you place two ground rods XX feet apart in the ground--And then have a lightning strike nearby--That creates a "voltage gradient or field" and you can get several thousand volts (or more) between the two ground rods. That takes one portion of the home's AC wiring/grounding to hundreds-thousands of between the two rods.

    Instead, run a ground wire from the new GT inverter to the main ground rod... That way, a lightning strike does not create a voltage differential inside the home.

    That is different than the ground rod from the panel frames/mountings (say on a roof top). That ground, you want to run straight from the roof top array to the earth ground rod on the outside wall of the house (do not bring the lightning ground inside the building--bad things can happen as lightning does not always follow the wiring and tends to want to travel on the "outside" of the home/envelope).
    I am going to wire without sinking a ground rod at the pv and just run it all to my house ground rod. Maybe attach lightning arresters. I am answering before reading the links on lightning that you provide. I will read them.

    You still should drive a 8-10 foot ground rod at the base of the array and wire the frames and structure to that ground. You don't want to bring the lightning into your power system/home.
    As I mentioned earlier, Unlike you (compliment), I don't communicate my questions very well and may seem to be repeating them at times.

    I am really poor at English (my only language) and using terms correctly.
    The combiner box seems to have a green wire safety buss bar.
    http://lib.store.yahoo.net/lib/wind-sun/PVcombiners-explained.pdf

    Yes, you are correct. There is a green wire/safety ground bus inside the box.
    Ps I would say I get plenty of lightning. I have lost lots of computer modems and one time it blew a whole in a copper ice maker feed line took out all my phones and vcrs and froze my tv to one picture until I turned it off, then it was ok.

    Read the lightning links I provide earlier... There are several ways of "addressing" the problem. Some people prefer one or another.

    But, my guess, is your fried modems/water line/phones/vcr issues are all a result of poor grounding practices.

    My homes (over 50 years old) did not even have a ground rod (just used copper water line--and did not even ground the natural gas or hot water piping).

    There have been articles about commercial radio transmitters that always had "bad luck" of being knocked off the air when lightning was nearby... But when everything was "properly" grounded (whatever than means :p), the problems "went away".
    Also I read that if you make sharp 90 degree bends at the beginning of your combiner exit wires that it helps as high voltage does not like to make the bends.

    Yes--you should make "sweeping" bends for lightning grounds.

    And--to be clear, it is not the lightning "voltage" that does not like turns--It is the fact that lightning has high frequency current (around 7.5kHz maximum if I recall correctly). It is the "impedance" of the wire runs/turns (and "skin effect") physics that lightning follows.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: New install questions
    BB. wrote: »
    Need the current in the SSR input... But probably 16-18 awg wire would work (twisted pair to avoid electrical fields getting into wiring and causing weird switching issues). Keep signal wiring away from heavy AC/DC cables, Only cross large/high amperage cables at 90 degree angle, etc.

    I'm sure this comes from my water heating setup, driving a SSR with AUX2 on a Classic to power a 240 volt water heater using Waste Not Hi mode. Standard 4,500 watt 240V elements pull 19 amps when they're cold. I use a 25 amp single pole SSR switching one leg of the split phase with 2,000 watt elements, and it works well.

    At any rate, on a 50-60 foot run 10 gauge wire and 30 amp breakers are recommended for electric water heaters.

    The wiring from the controller to the SSR input is very small - the Classics' AUX terminals only accept AWG 18.
    --
    Chris
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: New install questions
    gww1 wrote: »

    Is their a formula using the width or crossectional of a wire to decide conduit size for the number of wires in it to come up with your 40% fill. I have tried to figure out what size conduit would be needed for four 2/0 wires and one 6awg bare wire. I used .400 Inche times 4 equals 1.6 inches devided by 4" pvc comes up to 40% fill.
    This wire is actualy .420 inch wide with no insulation. So, 4" is probly not big enough if I am even close to doing it right.

    Do I need to count the isulation on the wire? Am I caculating correctly.

    What you are looking for is Table(s) C.x in the back pages of the NEC. There is different table for each type of conduit and sections for each type of wire in all the common gauges. Yes, absolutely you need to consider the type and thickness of the insulation, and these tables take that into account. This is much easier than trying to calculate conduit fill by hand.
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