Rewire older array at high voltage -- safe?

I'm changing an old system from off-grid to grid-tied. The solar array had been wired in 10 parallel strings of 4 panels each, to feed fairly low voltage (82 Voc) to a charge controller for a 48v battery bank. To feed the new SMA sunnyboy 3.0 i need higher voltage. I'm all set to rewire into 2 strings of 20 panels each (410 Voc), and it just occurred to me that the panels may not be safe at that higher voltage. Without thinking about it i suppose that i'd been assuming that a system voltage up to 600v would be fine, but I don't know if that's true of these old panels.

The panels are Photocomm, Inc Power Value PV-65 modules. I have a spec sheet that lists OC and MP voltages and current ratings, but there is no mention of max system voltage. The company doesn't appear to be around anymore. Should i be concerned about wiring these panels into 410v strings? Are there differences in newer modules that make them capable of higher voltages than older panels?

Comments

  • littleharbor2littleharbor2 Posts: 979Solar Expert ✭✭✭✭
     The panels should have Maximum system voltage stats listed on the label. My guess ,it will be 600 volts. If you decide to do this you really should closely inspect every bit of the wiring. I suspect there will be fully accessible junction boxes on the modules. This would allow you to completely rewire the array with fresh wire.

     All that being said, I tried looking up your panels, no luck. Are they 65 watt panels? You really need to see if they are on the power company's list of approved equipment.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • BB.BB. Posts: 27,681Super Moderators admin
    That old of panel is probably not UL Listed or Listed for 600 volt operations.

    Safety wise, buying new panels (200 Watts or greater) is probably safer, less issues with insurance and building code, and fewer wiring connections (1x 260 Watt panel vs 4x 65 Watt panels).

    Sell the old system or keep it for backup power.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • TroySmith80TroySmith80 Posts: 10Registered Users ✭✭
    Thanks for the responses... i have to admit, not what i was hoping to hear, as far as replacing wire or replacing the whole panels. Sometimes good advice isn't easy to take though.

    The panels are pretty difficult to access, they're on a 45 degree metal roof, way up on a tall 2 story house. The junction box is inside the house, in a loft space, so i can do all the wiring changes there and can complete the whole project without having to get up on that roof. Maybe i can get up there and try to get a look at a label. Replacing the system is not really in the budget, the reason for this change is partly because batteries are too expensive. It's not my house, i'm helping with the project.

    I'm a bit confused/surprised by the recommendation to replace the wires, littleharbor. If it had originally been configured as high voltage, and was now the same age, would your recommend replacing the wires even if nothing else was changing in the system? That's a lot of extra labor and expense.

    Of course it's easy to say that it's safer or simpler to just dump the whole system and replace with all new stuff, but that's a big deal. How can i determine if there's actually any real problem with running this system at higher voltage?
  • littleharbor2littleharbor2 Posts: 979Solar Expert ✭✭✭✭
    Critters love chewing on wire insulation.  Exposed non PV wire can have the insulation dried and cracked by the sun. Sounds like accessing the array is going to be a difficult task. 

    Your bigger issue I believe is determining whether or not these panels are even eligible to be used in a grid tie fashion. 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • EstragonEstragon Posts: 2,593Registered Users ✭✭✭✭
    You have two "actual, real" problems. The first is whether the insulation used on conductors in the panels and wiring is physically able to carry the higher voltage safely. Both should be marked with ratings. It/they may or may not be physically safe at higher voltage, and absent labelling showing higher voltage rating, you would have to assume not. Even if so rated, you would want to examine carefully to be sure the rating is still applicable (no chew marks, chafe, brittle insulation, discolored areas on panels, etc).

    As LH2 notes, the second and maybe bigger issue is whether the system will be permitted and pass inspection. With no way of demonstrating high voltage design, and reusing parts and wiring of uncertain age, it may be a problem. I'd try to run it by the inspector before spending a lot of time looking for labels and wire markings though. Depending on local AHJ, it may be moot if they're going to make you replace it all anyway.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • PhotowhitPhotowhit Posts: 4,660Solar Expert ✭✭✭✭
    Thanks for the responses... i have to admit, not what i was hoping to hear, as far as replacing wire or replacing the whole panels. Sometimes good advice isn't easy to take though.
    From what little research I found that Photocomm was 1 of the first to send panels to UL for testing. 1 of the first 5 companies to have UL listed panels back in 1996, pretty amazing, I was wondering it the Home power article had sat on the shelf for a while. Might be worth doing a bit more research, perhaps the panels were of the same series before they were tested.

    If free standing and outside, and your power company doesn't care about anything on your side of the inverter, I might go ahead and put them in series. Perhaps not if you are in an area prone to long dry spells... Don't think there is anywhere for a fire to go on glass and aluminum panels. 

    Of course you may find that you have a bad panel or 2 in 40 - 25 year old panels. Your insurance company would likely not appreciate it either. 

    Seems like people are always looking for 12 volt nominal panels, bet you could find a home for them and buy 10 new 72 cell panels and not get hurt too bad.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • BB.BB. Posts: 27,681Super Moderators admin
    Note that animals can bring nesting materials under panels--So there may be stuff that can fuel a fire (besides the plastic backing and insulation of panels and wiring).

    Metal buildings and roofs have their own fire issues (steel is relatively easy to deform, >~450F, and not a good fire barrier--For example steel beams need thermal insulation to better withstand the heat). Plus any embers from a fire can spread to other parts of the property/landscape.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • TroySmith80TroySmith80 Posts: 10Registered Users ✭✭
    There's no building code or inspections in the area i live in, which is part of why i live here. We still try to follow code, as best practices, most of the time... but not always. We're also part of a sort of sub-grid which already feeds 30kW or so back to the grid through two service drops. So adding the new backfeed from this system is just adding a little more power to our sub-grid which already has a bunch of different production sources and sends the combined output to the service drop.

    All that to say that i don't think there's much concern for the panels meeting code, passing inspection or being on any lists. I don't want to be reckless though.
  • PhotowhitPhotowhit Posts: 4,660Solar Expert ✭✭✭✭
    FWIW- Looks like Photocomm, became Golden Genesis Co and then merged or was bought out by Kyocera in 1999;

    https://www.buildinggreen.com/newsbrief/kyocera-buys-golden-genesis-pv-merger

    Looks like Kyocera either continued the line or perhaps sold the remaining supply under their name. I never found where it was tested/listed by UL;

    https://www.kyocerasolar.com/dealers/product-center/archives/spec-sheets/PV65-PV75.pdf
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • EstragonEstragon Posts: 2,593Registered Users ✭✭✭✭
    If that's the case, you're left with the issue of whether the old panels and wiring are physically capable of handling the higher voltage safely.

    With no apparent labelling to indicate if either/both were originally designed for the higher voltage, and absent a thorough inspection for subsequent damage, it's a real crap shoot.

    Only the home owner can decide if it's worth the risk. IMHO, the risk of catastrophic failure is low-ish (but certainly not zero), assuming reasonable distance to combustibles, etc. A failure is more likely to burn a panel or wire weak point and open the circuit with relatively limited damage, but this is purely a guess. There is a real risk of something much worse, and no good way of quantifying that risk.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Posts: 27,681Super Moderators admin
    edited April 11 #12
    If you can find the old data sheets, or look into the j-box on the rear of one of the panels... Do these panels have "bypass diodes"?

    https://www.solar-electric.com/learning-center/general-solar-information/solar-power-technical-tips.html

    For single and parallel panels, bypass diodes are not needed.

    However, if the panels are placed in series, then by-pass diodes are definitely needed to send current "around" shaded cells, bird droppings, etc. If not, the entire string will try to over voltage and break down the shaded photo cell (cells go "high resistance" in the dark--And at >~12 volts, the diode junctions--solar cells--can be damaged--or possibly start a fire).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • TroySmith80TroySmith80 Posts: 10Registered Users ✭✭
    Well, good news. I got some help on the roof and someone was able to read a label that stated max system voltage at 600v! Posting for resolution and future reference for anyone else searching, photocomm pv-65e panels (at least the ones we have) are rated for 600v. I sure wish that information had been on the spec sheet that was with the system documentation!

    We also checked out wire condition and other aspects, things looked a little weathered, but still very much intact and confidence inspiring. 
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