I cant add panels to existing SMA4000US inverter with plenty of overhead??

Options
Spiffster
Spiffster Registered Users Posts: 23 ✭
in Solar Beginners Corner #1
After getting the run-around trying to add another solar PV system to my house I may need to go a different route. I currently have a 2.94kW system which I want to upgrade. The system is 14 Kyocera 210W (2.94kW) panels tied to an SMA4000US inverter. REC Solar installed this system and for some reason gave me way more inverter than I need. I asked them about adding 5 more panels to the system and they said it could not be done without buying another inverter... umm why?? The SMA spec sheet says max input is 5kW! Why cant i just slap 5 more 210watt panels up there?? That would put me at 3.99kW! I would like them to add to the system because they provide a 10year warranty on the installation and I would not want to void the warranty by adding to the inverter myself (hence the original plan to just add another system).
· Share on Twitter

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    I'm no grid-tie guru but I think you've been given some bad advice (and a poor install). A GT inverter should have maximum panels on it, as the panels don't put out their nameplate rating most of the time. On occasions when they do the inverter will just "clip" the excess power.

    So a 4 kW inverter certainly should have 4 kW of panels on it or possibly more. Most of the companies have on-line string sizing tools that can help you plan exactly what it should be. If I were you, I'd check that out first.

    The main concerns with adding panels to an existing install are that the new panels match the old in terms of Voltage and current so you're not adding a mismatched string, that the orientation is correct so you're not getting different maximum power points, and that the wiring is capable of handling the additional power.

    You seem to have an array undersized by 2 kW. I'd definitely look into the fine details up maximizing it.
    · Share on Twitter
  • Spiffster
    Spiffster Registered Users Posts: 23 ✭
    #3
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??
    Cariboocoot wrote: »
    I'm no grid-tie guru but I think you've been given some bad advice (and a poor install). A GT inverter should have maximum panels on it, as the panels don't put out their nameplate rating most of the time. On occasions when they do the inverter will just "clip" the excess power.

    So a 4 kW inverter certainly should have 4 kW of panels on it or possibly more. Most of the companies have on-line string sizing tools that can help you plan exactly what it should be. If I were you, I'd check that out first.

    The main concerns with adding panels to an existing install are that the new panels match the old in terms of Voltage and current so you're not adding a mismatched string, that the orientation is correct so you're not getting different maximum power points, and that the wiring is capable of handling the additional power.

    You seem to have an array undersized by 2 kW. I'd definitely look into the fine details up maximizing it.


    Thanks for the quick reply Cariboocoot. The SMA4000US will handle 5kW input power from panels. The panels I will order if I can upgrade the system are the same model. One other note is that I am getting my roof's shingles replaced and REC is supposed to come out and remove and re-install all of the panels. Why couldnt they just throw 5 more panels up there while they are at it? I am more than happy to pay for the extra panels... whats with this company :confused:
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    I think I see the problem. You have fourteen 210 Watt panels now, yes? Two strings of seven, perhaps?
    Can't add five more in to that without configuration problems. Possibly you could add another string of seven (21 panels * 210 Watts = 4410 total). However it is configured now, it would need to be a multiple of that. Why they put up that much panel and an over-sized inverter ... :confused: You got me there.
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    Okay I looked up the panels. They're these: http://www.solar-electric.com/kykd210waaop.html Right?
    They have an odd 26.6 Vmp, which means you likely have 14 all in one string: 372.4 Volts out.
    You can't add 5 more to the string because it will put the Voltage over the inverter's input limit @ 500+ Volts. You might get away with four more, but that would add less than 1 kW.

    Two strings of 12 of these panels might have been a better match: 319 Volts @ 15.8 Amps.

    On the whole I'd say it wasn't well thought out. :roll:
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #6
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    You do need to confirm that you can add the panels to meet the Voc/Vmp/Imp/Isc of the SMA inverter...

    It is possible that you cannot add panels in the proper series/parallel configuration such that the new array falls into the "mix" that is supported by that inverter.

    For example, you probably have 14 panels in series (14 total panels).

    Your choices may be to add 2,4,6, etc. ... 2x 8 series strings; 2x 9 series strings, etc.

    Or, add exactly 7 more panel for 3x 7 series panels...

    Or other combinations, for example a 3x 8 string (8 new panels in a strings + 2x 1 each panels added to the two existing strings for a total of 24 panels).

    I don't know the SMA line very well--so my guesses for a 240 VAC home power system (not 208 3 phase power) 4000US:
    MPPT range = 250 – 480 V @ 240 VDC
    Start Voltage = 285 VDC
    Max output power is 4,000 watts
    Kyocera 210 Watt panel KD210GX-LPU:
    Vmp= 26.6 volts
    Imp= 7.9 amps

    It appears that your "valid configurations" would be around:
    • 1x 14 panels = 14 panels
    • 1x 15 panels = 15 panels (may be near Voc-cold max)
    • 1x 16 panels = 16 panels (may be near Voc-cold max)
    • 2x 10 panels = 20 panels (check starting voltage--not sure will work)
    • 2x 11 panels = 22 panels
    • 2x 12 panels = 24 panels (near/over 5kW input limit?)
    The above are my guesses--I do not have the SMA software loaded (or have time to look for the online strings sizing tool).

    So, from what I can gather--they are correct you cannot add "5 panels". It appears you can add (approximately) 1,2,6,8, or 10 panels to your system with the existing inverter.

    A total of 22-24 panels would be the maximum I would recommend from a cost effective point of view (with 24 panels, your system will be limiting output to 4kW for significant amount of time during the middle of the day).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #7
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??
    Spiffster wrote: »
    After getting the run-around trying to add another solar PV system to my house I may need to go a different route. I currently have a 2.94kW system which I want to upgrade. The system is 14 Kyocera 210W (2.94kW) panels tied to an SMA4000US inverter. REC Solar installed this system and for some reason gave me way more inverter than I need. I asked them about adding 5 more panels to the system and they said it could not be done without buying another inverter... umm why?? The SMA spec sheet says max input is 5kW! Why cant i just slap 5 more 210watt panels up there?? That would put me at 3.99kW! I would like them to add to the system because they provide a 10year warranty on the installation and I would not want to void the warranty by adding to the inverter myself (hence the original plan to just add another system).

    Because you can't just "slap" modules on a roof and hook them up without paying attention to string sizing. I have SMA's Sunny Design running, and of course it makes a difference where you are because voltage varies with temperature, but if you were here in Austin, at least, the only configuration in which 14 of those modules would work is a single string of 14 (acceptable strings are from 12 to 16).

    The SB3000 looks like it would have been a better choice of inverter until you look at its input voltage range, which is different from the SB4000. A string of 14 would put an SB3000 in danger of overvoltage on cold days. 13 is the highest you can go.

    Again, string sizing varies with location, but here in Austin you could add 1 or 2 more modules in a single string. The next size up after that would be two strings of 12, which would make 5.88kW. You could do that if you have room on your roof, but the maximum DC power that inverter can accept is 4.24kW, so on cool sunny days the inverter would max out and clip its output.
    · Share on Twitter
  • Spiffster
    Spiffster Registered Users Posts: 23 ✭
    #8
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    Yes'sir, 2 rows of 7 panels. Only room for 5 more of the same panel on that part of the roof because of how the roof is divided. I played with the SMA "Sunny Design" tool (really neat tool BTW) what I came up with for 2 strings doesnt work. See attached. The panels are definitely Kyocera KD210GX-LP panels and the inverter is definitely an SMA4000US and I cannot come up with any string combination with 14 panels that should produce power (Energy Usability Factor 0%) other than 1 string of 14 panels (Energy Usability Factor 100%). So its definitely 1 string of 14... dictated by the minimum PV voltage. And with one string I can go max 16 panels. Anything between 16 and 22 is no-man's land on this inverter with these panels.
    · Share on Twitter
  • Spiffster
    Spiffster Registered Users Posts: 23 ✭
    #9
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??
    ggunn wrote: »
    Because you can't just "slap" modules on a roof and hook them up without paying attention to string sizing. I have SMA's Sunny Design running, and of course it makes a difference where you are because voltage varies with temperature, but if you were here in Austin, at least, the only configuration in which 14 of those modules would work is a single string of 14 (acceptable strings are from 12 to 16).

    The SB3000 looks like it would have been a better choice of inverter until you look at its input voltage range, which is different from the SB4000. A string of 14 would put a n SB3000 in danger of overvoltage on cold days. 13 is the highest you can go.

    Again, string sizing varies with location, but here in Austin you could add 1 or 2 more modules in a single string. The next size up after that would be two strings of 12, which would make 5.88kW. You can do that if you have room on your roof, but the maximum DC power that inverter can accept is 4.24kW, so on cool sunny days the inverter will max out and clip its output.

    Yes, just figured that out. So the SMA4000US wasnt all that bad of a choice by my installer... I would need to add a minimum of 10 (total 24) panels... crap. I learned something today... well back to figuring out how to add another system. Big thanks for the feedback fellas! Sorry I am polluting these forums with so much stupidity.
    · Share on Twitter
  • solarix
    solarix Solar Expert Posts: 713 ✭✭
    #10
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    Now you know why we started using the SolarEdge system which can handle anywhere between 8 and 25 modules in a string and they don't even have to be the same size or brand of module! Plus it can handle shading problems better and is arguably more efficient (well productive) as well.
    We just got of the roof of a 30 module system where we wired one string with 13 and the other with 17 just cause it was easier.
    · Share on Twitter
  • jagec
    jagec Solar Expert Posts: 157 ✭✭
    #11
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??
    Spiffster wrote: »
    Yes, just figured that out. So the SMA4000US wasnt all that bad of a choice by my installer... I would need to add a minimum of 10 (total 24) panels... crap. I learned something today... well back to figuring out how to add another system. Big thanks for the feedback fellas! Sorry I am polluting these forums with so much stupidity.

    You could add 2 more panels...it's not a huge addition, but every bit helps, hmm?
    · Share on Twitter
  • Spiffster
    Spiffster Registered Users Posts: 23 ✭
    #12
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??
    jagec wrote: »
    You could add 2 more panels...it's not a huge addition, but every bit helps, hmm?

    This is true but there is no way REC Solar is gonna come out and just install 2 panels, its just not worth it for them. I could install the panels but then I would probably void the installation warranty.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #13
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    They should be happy to give you a quote. If it is too expensive (permits, utility, drive time, etc.), that is another issue.

    I guess this is reason 405b why slowly growing solar pv systems is not usually a good idea.

    I would get in writing from them that they will not enlarge your system but warranty will be valid if you use a licensed electrician (yea, I can dream).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #14
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??
    Spiffster wrote: »
    This is true but there is no way REC Solar is gonna come out and just install 2 panels, its just not worth it for them. I could install the panels but then I would probably void the installation warranty.
    Nonsense. Anything is worth it if the money is right. It may not be worth it to YOU what they would charge, though... ;)

    It does make me wonder, however, why they designed the system with only 14 modules if there was room on the roof and in the inverter for two more.
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #15
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    They should have sized the inverter and array properly in the first place.
    If the represented this as a 4 kW system they're guilty of fraud, in my opinion.
    · Share on Twitter
  • Spiffster
    Spiffster Registered Users Posts: 23 ✭
    #16
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??
    Cariboocoot wrote: »
    They should have sized the inverter and array properly in the first place.
    If the represented this as a 4 kW system they're guilty of fraud, in my opinion.

    No they said it would be 2.94kW not 4kW. They also told me I could expand the system in the future. Here it is a year later and now they say the only way to go bigger would be to add another inverter. No big deal, I will go with the planned 6 panel (w/ micro-inverters) add-on mentioned in the my thread.
    · Share on Twitter
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #17
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    I wonder if:

    1) installer grabbed wrong inverter from the shop on install day?

    2) no small inverters on hand, and so they grabbed whatever they had a lot of?

    And the front office has no idea of this.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

    · Share on Twitter
  • Spiffster
    Spiffster Registered Users Posts: 23 ✭
    #18
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??
    mike90045 wrote: »
    I wonder if:

    1) installer grabbed wrong inverter from the shop on install day?

    2) no small inverters on hand, and so they grabbed whatever they had a lot of?

    And the front office has no idea of this.

    Looking at the quote, I do see that they had the SMA4000US in there. I remember I had looked at the specs and thought I was kosher with a future upgrade but didnt take into account string and voltage compatibility. Kind of my fault for not doing the research until a year later.
    · Share on Twitter
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #19
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    I ran my setup (see signature) with the assurance of an upgrade from the installer. BOOM they stopped using the original panels hence the Canadian Solar mismatch. I sized my original big enough on the inverter and panels that the 2kW add was a smaller percentage of the max. (only 20% increase)

    Lucky the Canadian Solar panels were a really close match.
    · Share on Twitter
  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #20
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??

    Something else to consider is the maximum amps the service panel can be backfed. Do you have 200 amp service?
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
    · Share on Twitter
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #21
    Options
    Re: I cant add panels to existing SMA4000US inverter with plenty of overhead??
    Spiffster wrote: »
    Looking at the quote, I do see that they had the SMA4000US in there. I remember I had looked at the specs and thought I was kosher with a future upgrade but didnt take into account string and voltage compatibility. Kind of my fault for not doing the research until a year later.
    The SB3000 would not have worked with the 14 Kyoceras; the most it can handle in a string is 13 (caveat: in Austin). 4000W is a bit much inverter for your array, but it will work fine, and it's practically the same price as the 3000. The next size down from the 3000 is 700W, which is way too small, unless you wanted to use 4 of them. For your 14 Kyoceras, the 4000 is really the best choice if the inverter had to be SMA.

    Your installer probably found a deal on SMA inverters and Kyocera 210's, or they were only comfortable designing with them, or both. It's really not that bad a design, given what they were working with. It's just not that easily expandable, and if they told you that it was, they misrepresented the facts. If you just looked at the system and came to that conclusion yourself, well, you learned something, didn't you? ;)
    · Share on Twitter

Categories