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Star Harvester

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  1. @JustinSchoeman@Gnome@PowerUser At the risk of raising an old debate from the grave and zombifying this discussion, I found this thread quite interesting and would like to drop my 2 cents worth. While it is obvious that the bigger the cable the better the safety, the less the voltage drops, the lower the temperatures, the higher the efficiency etc. some guys take this a step too far and suffer high financial costs (seeing as copper is not cheap). I saw some cable cross section numbers being dropped on this thread which made me feel like a vienna on a boerewors shelf in Shoprite Checkers.... Like @Leshen I am also running 50mm^2 cable which came pre-fitted to my 10/8 Freedom Won with a Multiplus II 8kVa and have not had any problems. This despite the Multiplus being able to supply short burst peak power of 15kW and the Freedom Won having a 200A continuous and 300A peak discharge current spec. So this lead me to browse around a bit and I came across this table in another thread. As you can see duty cycle plays a role in a cable's current rating. Furthermore, most of you probably know the equation below or a similar equation which can be deduced by looking at electrical resistivity and making use of the old primary school equation V = IR. With copper's resistivity of 1.724 x10-8 as per Google, and taking into account, Victron for instance recommends a voltage drop below 2.5% in Wiring unlimited, you can quite easily see that at 48V, a 50mm^2 cable with a 2m run between inverter and battery (x 2 for the return = 4m) and a target voltage drop of 1%, you can run up to 348 Amps. Please check my equations below as it was done in haste and I cannot guarantee there aren't any errors. Point I'm trying to make is there are many factors such as length, voltage, material, acceptable voltage drop, duty cycle etc. which determine whether a specific cable size is adequate for a specific application. Don't just throw a frankfurter at it if maybe a vienna would have been perfectly reasonable while hurting your pocket less. A = EDIT: Just realized something, fuses only break the circuit well above rated current, sometimes multiples depending on the specific fuse's time current curve. This implies you do need quite a comfortable safety margin on what your cable can handle and it is probably taken into account when these (what may seem like conservative) cable current ratings are calculated. So ignore what I said above, stick to the regulations, and when in doubt throw an anaconda of a cable at it to be sure... if you can afford it.
  2. Awesome thanks @P1000 and also for the explanation regarding the CT. Makes sense. I have everything on AC out 1 and AC out 2 though so not applicable in my case. Good knowledge to have for other installs though
  3. Do you know if an external reverse power flow blocking device is required with a Multiplus II, if it has an NRS097-2-1 certificate ? The way I see it if the South African settings are configured in VE.configure it is compliant in terms of anti-islanding and as long as "grid feed in" is disabled in ESS, reverse power flow is also blocked? Having to add external gadgets to get my system compliant is a headache I hope to avoid, DB real estate is very limited in my install.
  4. My panels look like this 1 week after cleaning.... I am not exactly spiderman and my neighbours are going to think I have gone OCD mad if I jump up and down my roof on a weekly basis. So isn't there a more sustainable solution? Has anyone tried these so called nano ceramic coatings? The information and company details behind these products look a little bit sketchy so I am not sure if it is just a money making gimmick? Kind of makes me think the salesmen behind these proliferate car detailing products which are being hawked at filling stations have simply relabeled some of their product lines as PV coatings. Nevertheless, hoping there is a real McCoy out there someone can recommend
  5. Thanks for this, that answers it then. The multi battery with total kWh > 5 x kVa inverter rating requiring suitable fuse/DC breaker to each inverter is interesting since a short circuit fault in a Victron without the Victron triggering an overload error is something which I haven't ever considered to be honest. Then again, I suppose it is one of those what-ifs which could happen theoretically, especially during installation if the cables/batteries are not handled properly. As a side note, they mention fuse OR DC rated breaker. If a breaker is used it should be bi-directional i.e. non-polarity sensitive. I see many polarity sensitive breakers being used out there which can only operate correctly in one direction where current is always from source to load and wiring must be done accordingly (usually indicated by + and - or arrows on the breaker itself). This is obviously not appropriate between inverter and battery if one considers another what-if of a short on the battery side during charging from grid and an even more unlikely "what-if" of the inverter not triggering an overload to break the fault current.
  6. Just to clarify, if you remove the inverter and connect whatever other load or perhaps another inverter without built-in isolator, in future you no longer have a way of isolating PV without removing fuses or even live cables. Breaking a circuit under load via removal of a fuse/cable is a bad idea, just look at the warning on most DC fuse holders...
  7. I have been wondering the same thing and noticed in the Freedom Won installation manual that a 2 pole breaker is only required in Australia where both the positive and the negative battery cables must be broken. Currently in my situation introduction of an additional fuse on positive from the battery to the busbar in the DC connector box (if installed in the box) only introduces cabling difficulty, additional cost and more unwanted resistance. If I install an additional fuse not in the DC busbar box but closer to the battery I end up having to cut my battery cables really short which I am not keen on as I might move in the next couple of years and might require longer cables when reinstalling. So for me the additional fuse seems redundant and unnecessary when considering the Freedom Won's built in breaker. The only justification ofcourse would be if you want to break both positive and negative since the Freedom Won only breaks live but we are not in Australia and most Victron schematics I have seen only fuses the positive not the negative. The SANS extract you reference above seems to be targeted at the PV side of the system. Here an additional 2 pole isolator makes sense since with the isolator embedded in the inverter, if you remove the inverter for some reason, there is no way of isolating the fuses. Take into account you cannot disconnect fuses under load due to arcing, they have to be isolated first with an appropriate DC isolating device (has to be correctly rated and don't use AC isolators) and then the fuse can be removed/replaced.
  8. Don't know if this has been discussed but what are the banks doing or have they done in preparation for an Eskom doomsday scenario? Do they have offshore back-up servers and other sufficient redundancies so that digital financial records/footprints are all maintained in a country without a functional grid for a prolonged period? I can't really comprehend what happens to our financial system in a grid collapse. Insurance companies have been sending notifications to clients informing damages under grid failure scenario are not covered so they are obviously considering the possibility. That being said, I am also in the camp thinking we won't get to a grid collapse but might see higher stages of load shedding than ever before.
  9. Hi @frivan may I ask your reasons for recommending steel conduit? Arc fault fire protection and protection from the elements?
  10. @Steve87 @CCC Telecom Thank you both for two great posts! Grounding of my PV system has me running around in circles and I simply can't get a clear answer from any of the installers in my area, I've spoken to 5 including 2 bigger "players". Seeing as I am not in a lightning prone area, some are even of the opinion that grounding of the PV frames only introduces unnecessary risks for the following reasons, simply grounding PV frames and having an SPD does not offer direct lightning strike protection anyway and at best some protection against induced surges so grounding for this purpose is relatively moot neither PV- nor PV+ is allowed to be grounded (no system grounding of PV as a source) on a Victron SmartSolar MPPT and fault current is therefore limited, if any, and fuses/breakers won't trip in the combiner box if only 1 PV strings is installed. Even if system grounding was used max fault current is still only Isc and string fuses won't break with 1 string. So here ground means nothing. if no GFPD (Ground Fault Protection Devices) is used it actually creates the risk of an undetected ground fault causing ground currents with a DC voltage on your ground conductor connected to your utility earth which is in turn bonded to AC neutral at the provider's supply. If a transformerless inverter is used you could have a return path via the AC neutral via the inverter, all a bit too complex for me to understand... I just don't see how this DC current running around in unintended circuits can be a good thing. if you install Ground Fault Protection devices such as those in the US markets it breaks equipment ground under fault. Hence why Victron has the sticker on their MPPT's warning that when a ground fault is detected the equipment chassey's must be regarded as unsafe to touch. How is this good, break one fault just to create another safety hazard? Perhaps grounding of the PV rails/frames can offer some protection for an installer doing maintenance on the system but how often after initial installation does someone actually climb on the roof in close vicinity of the panels. Perhaps in bigger commercial installations where regular cleaning takes place this is valid but I am yet to see any traffic on roofs in the residential sector other than initial installation. And there are many installations in my area. Perhaps we are missing something vital and I would really appreciate any insights you can give. But with the limited knowledge I have right now it seems, with the issue of induced lightning surges aside, no grounding and running your PV array in a CLASS II format is the lesser of 2 evils? Also I noticed on Steve's post in the inspection table they actually look at GFP, where does one even get a GFPD in SA if not imported at unaffordable prices from offshore markets?
  11. The topic of grounding has been discussed at length but it still remains a headache for me and hoping to tap into the collective wisdom of this Forum to hopefully reach a state of less uncertainty. As background, most of you probably know grounding of PV systems has been a contentious issue for a long time. See this article from 1994 as an example of how old this topic is article.pdf . According to this article ungrounded Class II PV systems (no system grounding i.e. neither PV cables grounded but frames etc. grounded) seems to be the safest option but it remains a trade-off and there seems to be no clear cut simple answer. Grounding in general even on AC systems is not an easy topic. This widely known long video by Mike Holt (which many of you may have watched) is testimony to what a complicated subject it is. Please note I am not trying to dive into the subject of lightning protection, earth rods etc. in this thread. Nevertheless, for full context regarding my current grounding configuration, I'm not using Earth Rods/Spikes (after watching Mike Holt's video) and simply following the SANS schematic attached with AC utility earth as my main system ground. Lightning is not common where I live and for me safety, equipment grounding and early fault detection is more important than trying to protect against direct lightning strikes where ultimately your only real protection is insurance (if not excluded in the fine print). Unless you spend a lot of money on a proper lightning protection system in Faraday Cage around your house type format, earth mats etc. Induced surges will hopefully be caught by string DB surge protectors and minimized loop cable laying under the PV array. So am only looking at grounding configurations, Ground Fault Protection and safe continuous equipment grounding from a non-isolated Victron MPPT (PV in negative not isolated from Battery out negative) point of view, where Victron explicitly states no system grounding on the PV generator as it will lead to ground currents. This in combination with a Freedom Won Lite 10/8 battery where I can't find any reference in manuals nor any indication on the unit itself that the battery negative should be grounded and I am yet to see an installation with a Freedom Won where the battery negative is explicitly grounded. Yet in Victron's latest Wiring unlimited under "Section 7.7 System Grounding - Grid-connected Energy Storage System (ESS)" it explicitly shows the battery negative as grounded. So my uncertainty/headache lies in these 2 questions, As stated, I am using Victron SmartSolar MPPT's and as such no system grounding i.e. neither of the PV cables are grounded only the frames. I know it is low probability but everything ages and I am not comfortable with the scenario of potential undetected ground faults causing ground currents and would like to add a GFPD device. However, this is complicated by availability and affordability of GFPD's where I live and on top of this the implementation of GFP leads to a break in ground under fault (based on the overseas solutions by Midnite Solar, Earth Guard, Morningstar which I have seen) which in turn creates the problem of compromised equipment grounding on MPPT casing etc. So I am between a rock and a hard place. Most other installations like mine, in my area, simply have non-system grounded PV but frames grounded, no GFPD and a decision to look the other way and "hear no evil see no evil" as far as potential ground faults causing ground currents go. How would a Power Forum "black belt" approach this? In terms of grounding the negative of the Freedom Won. Should or shouldn't this be done? No one in my area, including a Victron Importer/Distributor who also does installations. Secondly, if not grounding the Freedom Won, if I was ever able to get a GFPD would this still work as intended?
  12. As a side note, I guess this is why we have Class II (double insulated), UV stable etc. cable for PV but after seeing how recklessly some installers run this cable, put it under strain, bury it raw under stones on flat roofs and bend it around sharp edges where conduit/trunking was cut etc. the double insulation does not give me much comfort...
  13. _____________________ This is giving me a headache too. I hear what you are both saying and also watched Mike Holt's video (a lot to take in as you said and perhaps I need another watch) but I still don't have clarity regarding the scenario @Chris_S has posed. I am having trouble understanding how a ground fault in the scenario Chris posed gets detected and cleared without the DC equivalent of an AC GFCI. Also don't see how a DC MCB will see enough fault current to clear the fault even if the negative PV cable is bonded to earth (bonded to rails of panels) since PV panels have a limited short circuit current and as per Mike Holt's video the only way to ensure a high enough fault current is via return to the source. Yet as per this article from Fluke's website arcing and ground faults can cause major problems such as the 2009 Bakersfield, California fire . Perhaps I am missing something but this seems to be a major risk with PV installations which is not talked about enough nor has a clear cut solution except for regular insulation tests and open circuit voltage tests as per Fluke's article... honestly who in the residential sector will actually do that apart from people on this forum? https://www.fluke.com/en-us/learn/blog/grounding/dc-ground-faults-pv-systems
  14. Hi Coulomb I have a clone MKS 3kVA 24V Plus which only has a USB port, no RJ45 jack/RS232. Do you know of a WIFI module which might work, either with direct USB port, or otherwise via a USD to serial adaptor cable? Will a setup on my home WIFI with Watchpower be possible or will the WIFI module come with appropriate monitoring software?
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