Guest Posted February 21, 2019 Share Posted February 21, 2019 (edited) This is the setup envisage, can it be improved? When closed: Batteries: Edited February 21, 2019 by Guest Quote Link to comment Share on other sites More sharing options...
VisN Posted February 21, 2019 Share Posted February 21, 2019 5 hours ago, NigelL said: These diagrams do not look anything like my "MultiGrid-II-48V-3000-35-32". It only has a single set of M6 bolts for attaching the battery cables, and an M8 bolt for chassis ground. I agree. This is my Multi ll. NigelL 1 Quote Link to comment Share on other sites More sharing options...
Guest Posted February 21, 2019 Share Posted February 21, 2019 @VisN and @NigelL - me and Plonk have the Multigrid version, that is the pictures you saw. The Multiplus II reference of the starter battery came from its manual. I don't see the same in its Quick Install manual, as you guys have noted. It is not the best idea to connect the batts as we have deduced. I have had my inverter still powering the loads after I disconnected the batts ... the panels happily providing the power. Scared the dinges out of me after the my awe left the building. Lets focus on the thread's core idea as Phil pointed out: What do we need to jot down for a grid tied Victron 3kva installation that anyone can take this as is and go and buy it. My final paperwork with CoC and engineering report could be submitted to CoCT as early as next week. So I'm using that journey here for the next person to follow so that his/her CoC and sign-off can be easier. Quote Link to comment Share on other sites More sharing options...
VisN Posted February 21, 2019 Share Posted February 21, 2019 2 minutes ago, The Terrible Triplett said: @VisN and @NigelL - me and Plonk have the Multigrid version, that is the pictures you saw. The Multiplus II reference of the starter battery came from its manual. I don't see the same in its Quick Install manual, as you guys have noted. I agree with the thread's cored idea as well and truly welcomed the creation of it. I just wanted to point out that the Victron manual for the Multi ll is a bit sub standard. Apart from the 2 DC output gaffe they make reference to 12V and 24V Multi lls when no such models exist. It has been a source of much confusion for me. Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted February 22, 2019 Share Posted February 22, 2019 3 hours ago, VisN said: I just wanted to point out that the Victron manual for the Multi ll is a bit sub standard. Apart from the 2 DC output gaffe they make reference to 12V and 24V Multi lls when no such models exist. It has been a source of much confusion for me. So to stay on track we are going 48V, and the 3kVA inverter of choice is .......Multiplus II? MultiGrid II? Buying decision needed here > @The Terrible Triplett? Which means X............ ? amount of the virtual budget has been spent.---- Chalk it down, it's bought. Hopefully, this emulates real life, and means we can stay focused in this thread and not be revisiting foundation decisions. Next, we need a PV panel choice as a building block. ( 60 cell, 72 cell 330W, 350W, whatever .....let's hear people's preferences and rationales). We have assumed our panels face true north at optimal tilt, so the typical solar window is what? 4 hrs?, 5hrs? (In the absence of authority, I'll call it 4.5 hrs, .... please assist with a year round average historical figure). To optimize our inverter purchase, shall we aspire that our 3kVA inverter is pumping a full 3kVA for direct usage during the solar window, and our array still has enough capacity to charge our batteries for the desired battery DOD at night?..... thoughts about this assumption anyone, perhaps this is too high an ambition? Once we have this consensus, this will dictate how many kWh we need our array to deliver in the typical daily solar window? ... and the subsequent size of the array required. @The Terrible Triplett evaluates our submissions, buys the the array, we cost it out, and things follow on from there..... Quote Link to comment Share on other sites More sharing options...
___ Posted February 22, 2019 Share Posted February 22, 2019 9 hours ago, The Terrible Triplett said: I have had my inverter still powering the loads after I disconnected the batts ... the panels happily providing the power. It has some seriously big-ass capacitors in there (that is a technical term, yes). What is more, the Multi can operate like a power supply, eg when running with Flow Batteries (like the RedFlow) the Multi can actually power the pumps and things needed to bootstrap the battery even when completely dead. So yeah... not recommended for actual use, but it does work. 4 hours ago, phil.g00 said: Next, we need a PV panel choice as a building block. ( 60 cell, 72 cell 330W, 350W, whatever .....let's hear people's preferences and rationales). I actually want to push for 60-cell modules (if possible), for the simple reason that you can put three in series even in cold climates and still have 10% space at the top (with a 150V MPPT), while running at a good 90V-100V the rest of the time. So that narrows the band of modules you can use and caps the wattage pretty much at 275W. But it is at least something to seriously consider. At this point I have just one other question, which is to ask if the average situation TTT has at his home is really what your typical user wants. I tend to find two kinds of users: One wants the convenience of powering existing circuits in his house from the inverter. The other just wants to power his TV and the WiFi and is willing to use an extension cord. The TTT (tm) setup kinda straddles the middle... it works for him, but is that typical? Quote Link to comment Share on other sites More sharing options...
Guest Posted February 22, 2019 Share Posted February 22, 2019 (edited) @phil.g00 in light of the fact that the Multigrid is not the latest, the better choice is the Multiplus II. With a home the average loads 24/7 is wot about 500w - 1kw with the kitchen's huge peaks. The focus is therefor to lower the average consumption of the house to ensure maximum savings and not spend a lot more to take all the loads off Eskom. The inverter can do a max of 2.4kw continuous and with a 3.5kw array it covers a lot of that with solar for earlier in the day and later in the afternoons with more power on cloudy days. Desired DoD at night / day is 20% as Eskom is cheaper at night and the batteries are there primarily for power failures. Pylontech, which we will come back to later, is for continuous use. For this exercise, the focus is on Eskom failures, so the batts must be kept at a good SOC in case, especially at night, Eskom leave the building. For optimal savings: (One can do a Excel spreadhseet, or one can do it like this:) Reduce the evening loads when everyone is asleep to as low as possible. 2kw 200l geyser is on a timer from 9h00 - 11h00 1.1kw pool pump on a timer from 11h00 - 17h00 - IF one has a poolpump, most don't. It has been mentioned to me that by using NodeRed installed on a VenusGX and Sonof switches that one can add the functionality to start / stop loads based on selected parameters. I..e when the pump / geyser comes on and the panels cannot produce sufficient power, inverter is drawing say i.e. >300w from Eskom, switch off that circuit and every 30min try again, between the hours as stipulated above. Simple and low tech. (We will get to this. ) I recon there are more of me out there than not. Budgetary prices are (seeing as I shop hard):Equipment: Victron MultiPlus II Inverter 48/3000 with MK3-USB Victron BlueSolar MPPT 150/100 with VE.Direct cable (1.8m) VenusGX Carlo Gavazzi with RS485 to USB (5m) BMV712 Smart (has Bluetooth but one can save +-R1k and use a 700)Budget: +-R 36 000.00 Solar Panels - Annual average of 5.5 hours per day of max use: 350w Canadian Kumax solar panels: (using 350w as a baseline) as they are all over, at a good price and good warranties as each panels has a serial number And putting 2 in series and 5 in parallel one stays well within the volts with a lot of potential to add more panels. See below The larger the panel the cheaper the mounting costs. Labour rate of a professional installer R 1 800 per dayBudget: R 1 950.00 x 10 = R 19 500 + R 3 600 = +-R 23 100 Batteries (+-8-10 year life at SOC of 80%) 8 x J200RE 12v 200ah with 48v watering kitBudget: R 45 300 Total: R 104 400.00 Note to keep in mind: Idea is to go full budget with ample room to also opt to halve everything, adding on as one has spare funds. Like take 50% of the panels and 50% of the batteries upfront. I learnt recently that because my +-4 year old T105RE's where always lightly cycled that I could have added 4 more - and then used them harder. With this MPPT you can go rather big on the array with 350w panels ... Edited February 22, 2019 by Guest Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted February 22, 2019 Share Posted February 22, 2019 (edited) So Multiplus II, it is. Bought. The PV seems to be two- faceted issue, which panel choice? And how big an array to build from the chosen panel? I'll argue the panel choice firstly. If our goal is best bang for the buck, @plonkster makes a valid case for 60 cell panels as 72 cell panels have a VOC so close to 50V that the safety margin of a 150V or 250V MPPT equals losing an entire panel. Whereas a 60 cell panel has a VOC of 40V From what I have seen cost/watt is at least equal to a 72 cell panel. Shading of a cell, takes out 20 cell, as opposed to 24. (60 vs 72) I like that that a 72 cell panel is a nice round 2m x 1m form factor. However, overall I think the argument for a 60 cell is compelling. I think with 60 cell we can generalize on 40Voc and 9.5A Isc 280W and a standard form factor of 1m X 1.65m. -- I see R5.60/watt available. Lets hear arguments for a 72 cell panel ...... @The Terrible Triplett can decide. Then we'll tackle the array size, which I can already see is going to be controversial. Edited February 22, 2019 by phil.g00 Juokorow 1 Quote Link to comment Share on other sites More sharing options...
NigelL Posted February 22, 2019 Share Posted February 22, 2019 (edited) I have 3 x 3 strings of JA Solar 330W panels (72 cells) connected to a Victron MPPT 150-70, so may be reasonably close to the voltage limit in cold weather. I think I will still be okay since I am in the Cape Town CBD area, so the lowest temperature I have ever recorded was around 5C. My panels are also oriented roughly North-West so tend to only get direct sun after it has warmed up a bit. So far my highest voltage recorded by the CCGX is 133.85V. I will post updates if I run into any issues. EDIT: The Solar installation company who put in my panels recommended the Victron 150V MPPT in combination with 3 series panels - even when I specifically queried the low-temperature voltage limit. Edited February 22, 2019 by NigelL Quote Link to comment Share on other sites More sharing options...
NigelL Posted February 22, 2019 Share Posted February 22, 2019 (edited) On 2019/02/20 at 9:31 PM, The Terrible Triplett said: Combiner Box: 1 x DB box 3 x NoArk 63A 1000VDC 6ka double pole breaker to break all 6 wires - or 2 x 4 pole NoArks. 6 x PV Fuse Holder with LED light - on all 6 wires 10 x 20amp fuses 1 x Citel Surge Protection DC/PV Type 2 1000VDC (DS50PVS-1000) I opted for 3 x 16A NoArk Double-Pole breakers (one for each PV string) since the breakers apparently have a more accurately controlled trip threshold than fuses. I then have a 40A NoArk Double-Pole breaker as an overall DC disconnect. The nice thing about these breakers is that they do not appear to mind opening or closing them, even under full load. I used the Citel "DS240S-130DC" surge protection which has a maximum DC Operating voltage of 180V. My reasoning was that this would clamp earlier than the 1000V version and hopefully protect more stuff from blowing up in case of a surge Edited February 22, 2019 by NigelL Vosser and Barezzi 2 Quote Link to comment Share on other sites More sharing options...
Guest Posted February 22, 2019 Share Posted February 22, 2019 1 hour ago, phil.g00 said: Lets hear arguments for a 72 cell panel ...... @The Terrible Triplett can decide. The two things I picked up last year, when looking for panels, was that the smaller wattage panels where ever so slowly getting scarcer and more expensive per watt and that MPPT's are slowly all creeping up in voltages. And to my surprise, I saw that >=400w panels are on their way. There are two sides arguing in my head:Side 1: After being been burn twice before when I got panels only to find 2/3 years later that there was none left on the market, makes me lean towards bigger "newer" panels that may very well still be around in 2-5 years from now if I want to add to the array then. Flip side: If one buys now and that is it, then it is wiser to go for better volt to MPPT match, smaller controller and be done with that leg of the install. Note: I have been burnt using this logic more than once before - never say never. And less I forget. I have asked myself: So 100v versus 145v / 240v or even 600v, seeing it is 20m, what is the real cost benefit over 20 years? Keeping in mind that the controller may not last 20 years, that cable costs are much less than a MPPT. Another thought: Does the panel / MPPT matched closely really make that big a difference in the ROI? Personally I don't think voltages makes that big a difference on the ROI as that only time that really comes into play is when the array is preforming at 100% every single day. THEN every little titbit must be very carefully noted. No home runs at max array power all the time. So, the choices are: You are set, pick the array and controller and move on. You want leeway, space to move around, buy the biggest MPPT you can with the most commonly sold panels today making sure you keep tabs on them ito availability. I choose the more flexible option i.e. larger panels for reasons above and due to lower cost of install at the maybe insignificant cost of compromising maybe a teeny weeny bit on the volts. @NigelL - I like your idea, we must discuss it when we get to that level. Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted February 22, 2019 Share Posted February 22, 2019 37 minutes ago, The Terrible Triplett said: I choose the more flexible option i.e. larger panels for reasons above and due to lower cost of install at the maybe insignificant cost of compromising maybe a teeny weeny bit on the volts. Fair enough, you're the boss. So what are the actual panel specs we have to work with: Isc , Voc, wattage and cost/watt? The MPPT choice is not yet on the table until we decide array size. The array size should be typified on what a typical SAn would want from his system. I think this means forgetting your own personal circumstance, and considering the best bang for buck. Realistic criteria to me is achieving maximum bill reduction, and being able to have 2.4kWh x 2hrs load-shedding standby capability. When load-shedding starts it will be every day for a few days, so my system should replenish fully on a daily basis. To my mind this means 2.4kWh x 4.5 ( our solar window) + (2 x 2.4kWh x 1.3) ( load-shedding standby x LA battery losses) = 17.04kWh. And this 17kWh has to be reaped in 4.5 hours, which means I need a 3.8 KWp array.( minimum). Is my assumption of a 4.5hour average solar window realistic? Lets hear... Russell and ___ 2 Quote Link to comment Share on other sites More sharing options...
Guest Posted February 22, 2019 Share Posted February 22, 2019 (edited) 28 minutes ago, phil.g00 said: s my assumption of a 4.5hour average solar window realistic? Been told that for SA it is 5.5 hours per day on average over 12 months. 28 minutes ago, phil.g00 said: Isc , Voc, wattage and cost/watt? 350w panels are R 1 950.00 = R 5.57 per watt. CS3U 350P Nominal Max. Power (Pmax) 350W Opt. Operating Voltage (Vmp) 39.2V Opt. Operating Current (Imp) 8.94A Open Circuit Voltage (Voc) 46.6V Short Circuit Current (Isc) 9.51A Module Efficiency 17.64% Operating Temperature -40°C ~ +85°C Max. Series Fuse Rating 30 A Max. System Voltage 1500V (IEC/UL) or 1000V (IEC/UL) - if ever ones want to go higher volts MPPT TEMPERATURE CHARACTERISTICS Specification Data Temperature Coefficient (Pmax) -0.37 % / °C Temperature Coefficient (Voc) -0.29 % / °C Temperature Coefficient (Isc) 0.05 % / °C Nominal Module Operating Temperature 42 ± 3°C Edited February 22, 2019 by Guest Quote Link to comment Share on other sites More sharing options...
Mstott Posted February 22, 2019 Share Posted February 22, 2019 What are your thoughts on the following ? Rated Power:400 W canadian solar MCS Reference:0 Length:2,108 mm Width:1,048 mm Depth:40 mm VMPP:38.7 V IMPP:10.34 A Voc:47.2 V Temp. Coefficient (Mpp):-0.37 % R2600 ex vat Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted February 22, 2019 Share Posted February 22, 2019 (edited) 2 hours ago, The Terrible Triplett said: Been told that for SA it is 5.5 hours per day on average over 12 months. OK, but just so we are comparing apples with apples, I am talking about a block of time that if we squared start slope and the end slope would represent a full power rectangle. Next, should I be considering the annual average, or should I be considering the winter average, a worst case scenario? 2 hours ago, The Terrible Triplett said: Open Circuit Voltage (Voc) 46.6V @The Terrible TriplettI think we have to accept any panel of this voltage range, will breach 50V in cold weather, somewhere in SA. Bear in mind, you still have to adhere to the recommended MPPT voltage limits. We can't be recommending breaches of warranty. 2 hours ago, Mstott said: Temp. Coefficient (Mpp):-0.37 % I see this as the most important criteria to compare solar panels, especially in warm climates. This is average-ish. 2 hours ago, The Terrible Triplett said: 350w panels are R 1 950.00 = R 5.57 per watt. Good price, --- is it VAT inclusive? I think this is about the sweet spot of price/watt vs panel size. There are probably a few market offerings, that would be within a smidgen of these so I think these are a good work-horse choice. 2 hours ago, Mstott said: R2600 ex vat 2600 x 1.15 = R2990 vat incl. 2990/400 = R7.48/watt Our pretend scheme is not a huge set up, so we didn't put a premium on roof real estate. Which is a realistic assumption to make for a scheme this size. You would only save 1 panel in seven vs the 350W panel at R5.67/watt, but it would be a couple of K more for the six panels. You wouldn't earn this premium back in roof mount savings. To make this exercise realistic the budget is limited, splashing out in one area means going short in another. Edited February 22, 2019 by phil.g00 Quote Link to comment Share on other sites More sharing options...
Guest Posted February 22, 2019 Share Posted February 22, 2019 11 minutes ago, phil.g00 said: breach 50V in cold weather, somewhere in SA. My panel installer, with all his experience, said not a chance in Cape Town for the 350w. HOWEVER, it is best to be cautions. To run the larger 350w and the newer 400w (and even bigger ones coming) two in series - or go 250v MPPT if you must have higher volts. Am pretty sure one of these years you will have very large panels and by fitting two in series they will be a perfect match for the 150v concrete ceiling of the Victron controllers. But lets not deviate. This is a very very good exercise to show the importance of the Temp. Coefficient and the effect of that on MPPT's and warranties. 22 minutes ago, phil.g00 said: ... considering the winter average, a worst case scenario? It is always better to understand and plan the worst case. However please note: There is a trick with Cape Town. It is called winter RAINFALL region with very weak sun. So there is a point where one just sit back and say ... basta this. How many months can I score, for in summer Cape Town delivers again. Cape town has better irradiation than Gauteng over a one year period. But this is a general plan, we plan for the worst case ... noting that winter rainfall areas are the worst of the worst cases. 32 minutes ago, phil.g00 said: 2990/400 = R7.48/watt Shop harder is what I say. 34 minutes ago, phil.g00 said: ... is it VAT inclusive? Yes. Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted February 22, 2019 Share Posted February 22, 2019 30 minutes ago, The Terrible Triplett said: But this is a general plan, we plan for the worst case ... noting that winter rainfall areas are the worst of the worst cases. Well, if the worst case is too extreme, we have to bias towards it, knowing that the ideal is impractical. So if you say winter in Cape Town is the SA worst case scenario, how about a version of the 80/20 principle. Forget about the worst 20% of the year, but ensure you are covered for the other 80%. Because the stats are all in monthly format, that translates to not sizing for the worst 3 months of the year in Cape Town, but sizing according to the solar window of 4th worst month. Then the rest of SA being further North with Summer rainfall, should fair better than the Cape Town extreme case. How does that turn out? What size solar window we have got to work with then? Quote Link to comment Share on other sites More sharing options...
Guest Posted February 22, 2019 Share Posted February 22, 2019 1 hour ago, phil.g00 said: Then the rest of SA being further North with Summer rainfall, should fair better than the Cape Town extreme case. Nope. As I said, general plan as Cape Town is better off than Gauteng for example. Or are we also going to get caught up in the details and cater for Upington too? We should not cater for the worst week / two weeks of Cape Town no. And we should focus on the annual generation and the optimal use of that. ROI is not per month, but calculated more generally per annum / lifetime of the equipment. So switch off that pool pump during winter months in Cape Town and cover the pool ... bylaws says you must cover the pool in any case. Here is some real data: Information from here: http://www.sauran.net/Pta: 2100 - 2200 kWh/m2 per annumCT: 2300 - 2400 kWh/m2 per annum At best CT gets 15% more sun per m2 per annum.Upington: +-3 100 kWh/m2 per annum - 50% more than Pta. Quote Link to comment Share on other sites More sharing options...
___ Posted February 22, 2019 Share Posted February 22, 2019 49 minutes ago, The Terrible Triplett said: Or are we also going to get caught up in the details and cater for Upington too? I did the math on the new 335W Canadian Solar modules that came this week.... and you know what, I made a darn mistake. I thought it was 0.31V for each degree, bit it os 0.31 PERCENT. I will redo it here for the benefit of all, as the numbers do a look a bit better. Start with 45.8V at 25°C. Subtract 0.31% for each degree under that, let's say at °5C, that is (1+(20*0.31)/100)*45.8V = 48.7V. At 0°C it is 49.4V. At -4°C it is 49.9V. Since -4°C is the lowest on record for Cape Town, you're probably okay, even if just barely so. In the two decades or so that I've lived here, 0°C was the lowest I've seen. But you really should design this to work elsewhere in the country too. Like Harrismith for example. Or the Sutherland of Namibia (Seëis, pushing -12°C some winters) where those same panels are going to push 51V. I enjoy what you guys are trying to do here, but I still feel like some fine-tuning will be required Russell 1 Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted February 22, 2019 Share Posted February 22, 2019 21 minutes ago, plonkster said: But you really should design this to work elsewhere in the country too. Like Harrismith for example. Or the Sutherland of Namibia (Seëis, pushing -12°C some winters) where those same panels are going to push 51V. I agree, this must be a system that can be installed anywhere (within reason) in SA. There are areas where performance mileage may vary, but the breaking of certain rules that may lead to equipment failure or safety concerns should be respected absolutely. The end result of this exercise should a nationally capable scheme. With regard to performance criteria, it should be optimized to suit Mr. Average's expectations in a domestic residential setting. I think we have to put ourselves back in our pre-solar mindset. We should be mindful that our scars are everyone else's open wound. 1 hour ago, The Terrible Triplett said: ROI is not per month, but calculated more generally per annum / lifetime of the equipment. I watched the phenomenal numbers of solar-curious unregistered guests on this site during load-shedding, and from that I draw the conclusion that while ROI is a factor, having the capability to be independent of ESKOM during a load-shedding window is even more important to Mr Average. So I submit that Mr Average wants: 2hrs (stage 2 LS) x 2.4 kWh ( Inverter capability) x 1.30 (LA Battery round trip efficiency) to be replenished daily by his solar array first. (And he wants his system to be capable of this in the lowest monthly day average of the year). After that, I grant you, he'll take all the ROI he can eat, but the floor is set in his mind by load-shedding independence. There is a hierarchy of needs and when you're starving that first loaf of power independence bread is worth multiple loafs of subsequent ROI bread once you've eaten. Following on from the theme that Mr Average should represent the collective of people that live elsewhere in SA. Mr Average lives in a town, for which 80% of SA has better irradiance stats and only 20% of SA has worse irradiance stats. If we can agree on Mr Average's criteria, we can move towards the sizing the array. demaniak and ___ 2 Quote Link to comment Share on other sites More sharing options...
Guest Posted February 22, 2019 Share Posted February 22, 2019 (edited) 1 hour ago, plonkster said: I still feel like some fine-tuning will be required Agreed. However. Sometimes we get so bogged down in the nitty gritty that the bigger picture seldom gets clearly defined, or lost in a bunch of posts. We are working A case sample here, sharing the LOGIC we apply to get this sample working so that the next person can apply the same LOGIC where they live, catering with confidence for Harrismith versus London versus Cape Town. 1 hour ago, plonkster said: I made a darn mistake. No problem. We all do. The one rule I apply is the Victron Excel calcs: Don't run on the brink. Just in case. Sound advice for the customers benefit. So the onus is on ME to make SURE I cater for the lowest possible temps in MY area. Truth be told I double check any contentious views with experts I trust who do this every day for a living. Have seen below zero when we lived next to Erinvale Golf Estate in S/West, a few times, never where we live now in 20 years. Know your area's lowest temps! That is on you, the owners shoulders. Edited February 22, 2019 by Guest Quote Link to comment Share on other sites More sharing options...
Guest Posted February 22, 2019 Share Posted February 22, 2019 (edited) 23 minutes ago, phil.g00 said: If we can agree on Mr Average's criteria, we can move towards the sizing the array. It is said, teach a wo[man] to fish, and s[he] will never go hungry. (interesting that the the words indicating a male are 2nd. ) If we use a general sized operational system that is in the process of being signed off, first with a CoC and next with a engineering report, I think we will cover a LOT of bases, together, so that it does not matter what the next person "catches", them knowing that with each point we button down, the baseline rules are noted in bold for that level. The core most fundamental rules ito panels and MPPT's: Rule 1: Check YOUR AREA's lowest possible temps. Rule 2: Don't EVER exceed the "cast in concrete" max VOLTS of YOUR controller. Rule 2: Don't EVER exceed the "cast in stone" max AMPS of YOUR controller. Moving on, we have 350w Canadians ... next point on the agenda? EDIT: I chose the 350w panels for a simple reason: To elicit thought processes. If the 400w panels where available last year, I would have been using them for this exercise. Edited February 22, 2019 by Guest Quote Link to comment Share on other sites More sharing options...
___ Posted February 23, 2019 Share Posted February 23, 2019 9 hours ago, The Terrible Triplett said: Know your area's lowest temps! That is on you, the owners shoulders. The funny thing is that in this area we pretty much use only direct-coupled solar water heating... because supposedly we don't have to worry about it ever freezing I agree with all said so far, and I also know about analysis-paralysis. It's done... the panels are bought then? Quote Link to comment Share on other sites More sharing options...
NigelL Posted February 23, 2019 Share Posted February 23, 2019 9 hours ago, The Terrible Triplett said: Moving on, we have 350w Canadians ... next point on the agenda? Another point, that causes some confusion and debate, is how to configure the "Backup" (AC-OUT1) and "Assisted" (AC-OUT2) connections to the Multi-II. This includes the optional use of an external Energy Meter or external Current Sensor. See the following graphics from Victron that illustrate two approaches to doing this. I opted for the external current sensor, but this required some extra effort with the mains cabling. Quote Link to comment Share on other sites More sharing options...
NigelL Posted February 23, 2019 Share Posted February 23, 2019 (edited) It took some time to work out the pros and cons of each of the above approaches. Option 1: Assisted Loads connected to AC-OUT2. Pros: There is no need for any external current sensor or energy meter. The Multi-II uses it's internal current sensor to limit the Grid-Tied current to the programmed setting (i.e. it compensates for current used on both AC-OUT1 and AC-OUT2). Cons: The total combined current of AC-OUT1 and AC-OUT2 loads is limited to the maximum input current on AC-IN (assuming the battery is very discharged). The recommended maximum input current is 32A. If you have to isolate the input to Multi to do repairs etc, you loose power to the AC-OUT2 loads as well as AC-OUT1 loads. Option 2: Assisted Loads connected to AC-Distribution Box. Pros: The current to the assisted loads is not limited by the Multi-II at all (32A total current limit does not apply). You can isolate the input of the Multi-II without affecting the Assisted loads. The external current sensor has the same performance as the internal current sensor so the system reacts very quickly to changing loads. The external sensor replaces the internal sensor when plugged in - so you only get a single "AC Loads" reading. Cons: You need to purchase an extra current sensor (about R500). The current sensor has a 1m lead, so the Multi-II must be physically close to the current sensing point where the Assisted Loads combine with the AC-IN to the Multi. Victron states that one cannot extend the current sensor lead without running into problems (noise coupling into the low-level current-sensing signal). Edited February 23, 2019 by NigelL Barezzi 1 Quote Link to comment Share on other sites More sharing options...
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