February 7, 20233 yr Greetings all, I have a relatively limited space available / set aside for the mounting of two batteries and 8.8KW SunSynk inverter, along with trunking, isolators, DBs etc. Using some of the SunSynk graphic elements, I'm busy finalising a planning schematic for this setup that needs to use the available wall space efficiently - which will also be very close to the house DB (ie less than 3m). On the layout below, please ignore specific attachment points relative to the hardware components, this is more to illustrate the layout and specs. I may have the DC and AC DBs made up, and want to be certain of correct specification and ensure quality components without any shortcuts here. off the shelf units seem either ridiculously over-priced or the component brands unknown to me. On some aspects I'm rather uncertain - this is generally in green font below (there may well be other glaring errors and I'll update the diagram accordingly. It's also a spec-list of sorts in terms of the requisite components. The battery and inverter specs are listed below, as well as the individual DB components. I'd greatly appreciate input on the specific questions below: (1) My PV will comprise two "sets" of panels, each connected in series, with Voc ratings of just under 300V and 400V respectively. Since I'm not combining any strings into single MPPTs (i.e. I will utilise both of the 2 available MPPTs on the inverter, with panels in an East-West config), am I correct that the DC DB needs to have 2 inputs and 2 outputs? And this is effectively a DC DB rather than a combiner box since no strings get combined here to feed to individual MPPTs (?). (2) With the SunSynk's MPPTs having a 500V max rating, should the SPDs also be 500V rated in the DC box (I've seen 600V rating in another install which is well above the SunSynk's MPPT max)? (3) With the two PV strings respective series Isc at 14A, is the correct fuse rating inside the DC box 15amp? Or should it be 20amp or something higher? (I think the setup will remain 1 string per MPPT goring forward, i.e. no doubling of current) (4) The fused disconnector for the batteries (2 in parallel, combined 10KWh): should the fuses used here be 160amp rated, or higher? Bearing in mind, the SunSynk's max charge/discharge rate is 190amps. I've seen other installations with 10KW battery and same inverter using 160 amp fuses and have been wondering about this. (5) Cable: if using 50mm2 cable from the battery bank back to the Inverter, how does one thread this size cable into the SunSynk battery connectors (I purchased 3 pairs). Or can the cable be connected to the SunSynk battery using appropriate lugs? I'd like to avoid using busbars or doubling up on cables if possible. (6) Earth neutral bridge box: where does this get positioned for layout purposes, bearing in mind limited available working space. Between SunSynk and the Inverter AC DB? (7) AC DB: Are these component specs appropriate to this setup? These specs were copied from another similar installation. (8) The main house DB is in the kitchen. I'd like to install an indicator light which lights on the kitchen DB when there is no grid power, as a warning to ensure family and housekeeper goes easy on household machines during this time when there's perhaps poor solar generation. Is this easily achieved with one of these indicator light plugs that can attach to the DB DIN rail, and does this require a wiring loop back to the Inverter's AC DB? Or a shorter loop back from somewhere else within the main house DB? Sorry, lots of questions! Hopefully many will have short and simple answers. I'll update the graphic to remove any errors or uncertainties. Appreciate any input. Edited February 7, 20233 yr by Kalahari Cruiser updated heading
February 7, 20233 yr 8 minutes ago, Kalahari Cruiser said: Appreciate any input. Still need to read all your text, but offhand you have power feeding from the main db to the inverter db and one pair of cables in the drawing from the inverter db to the inverter, you should draw this more the way it would be, the inverter gets power in by way of the main db and the has its output (UPS) feeding the inverter db for the critical loads, the earth neutral bridging should be done at the output of the inverter (with a relay/contactor controlled by the inverter) in its db before the GFI/Earth Leakage switch... will try and comment on the rest later...
February 7, 20233 yr Author Many thanks @Kalahari Meerkat. I realise the simplistic schematic may hide important detail to help guide positioning of say the earth neutral bridge. I've updated the schematic, and hope that I have understood you correctly here. I should perhaps update the OP with the updated schematic once confirmed. Edited February 7, 20233 yr by Kalahari Cruiser Diagram tweak
February 7, 20233 yr 19 minutes ago, Kalahari Cruiser said: I should perhaps update the OP with the updated schematic once confirmed There probably should be no connection between the main db and the inverter db, else it looks more correct... unless you want to feed the main db from the inverter when commercial power is gone... then you'd need to play a fast shell game, since you'd need a change over in the main db, probably not in the inverter db, but the change over would need to disconnect the grid cable to the inverter, disconnect the eskom side from the main db and connect the inverter db to feed the main db now as well... so then the essential loads db link must stay in place, but would have to be switched in the main db, to not be connected when commercial power is available...
February 7, 20233 yr Author Thank you for your suggestions. I don't want to risk complicating the diagram (i.e. not entirely intended to be technically 100%) but more in terms of broad layout and specs of the various components. But the diagram should also not mislead or end up with red herrings, and essentially address the questions and help with layout planning (my space is limited to around 160cm x 150cm). How can I improve that Mains DB to Inverter AC DB link you refer to, to make it broadly correct without misleading - bearing in mind that the purpose is to help plan the component specs (and possibly source or commission same) and layout given limited 'real estate'. I will not wire this myself but do want to understand the specs - ensure no short-cuts are taken. I do appreciate all of these inputs.
February 7, 20233 yr 6 hours ago, Kalahari Cruiser said: (1) My PV will comprise two "sets" of panels, each connected in series, with Voc ratings of just under 300V and 400V respectively. Since I'm not combining any strings into single MPPTs (i.e. I will utilise both of the 2 available MPPTs on the inverter, with panels in an East-West config), am I correct that the DC DB needs to have 2 inputs and 2 outputs? And this is effectively a DC DB rather than a combiner box since no strings get combined here to feed to individual MPPTs (?). yes, I would have made the strings the same, 7 panels each, but maybe roof space/or wherever they're being put does not allow for this... no combiner, 1 input and one output per string, no connection between them.... 6 hours ago, Kalahari Cruiser said: (2) With the SunSynk's MPPTs having a 500V max rating, should the SPDs also be 500V rated in the DC box (I've seen 600V rating in another install which is well above the SunSynk's MPPT max)? yes, its 500V for the panels, but the MPPT is up to 425V... don't get too close to the edge, else you find out the earth might be flat after all 🙂 and fall of the edge... 500V SPDs are probably the right way to go... 6 hours ago, Kalahari Cruiser said: (3) With the two PV strings respective series Isc at 14A, is the correct fuse rating inside the DC box 15amp? Or should it be 20amp or something higher? (I think the setup will remain 1 string per MPPT goring forward, i.e. no doubling of current) you could even go 40A, I reckon as long as the cables could handle that current even though it should never get there... so size the cable for 20A, *** edited *** then use 15A fuse... since Isc is 14A only... 6 hours ago, Kalahari Cruiser said: (4) The fused disconnector for the batteries (2 in parallel, combined 10KWh): should the fuses used here be 160amp rated, or higher? Bearing in mind, the SunSynk's max charge/discharge rate is 190amps. I've seen other installations with 10KW battery and same inverter using 160 amp fuses and have been wondering about this. ditto, fuse should protect the cable... so size the fuse to match the current carrying capacity of the cable... 50mm^2 can supposedly carry 175A... 6 hours ago, Kalahari Cruiser said: (5) Cable: if using 50mm2 cable from the battery bank back to the Inverter, how does one thread this size cable into the SunSynk battery connectors (I purchased 3 pairs). Or can the cable be connected to the SunSynk battery using appropriate lugs? I'd like to avoid using busbars or doubling up on cables if possible. you should run 50mm^2 between the batteries themselves as well as between the batteries and the inverter, as per your drawing, the fused disconnector should probably be between the 2 batteries... the only other option would be to have a small DC LV db where both batteries each with one fused disconnector feeds into this db and both a batteries combine on the output of this to feed the inverter... either way, on the Sunsynk, I think a larg-ish lug would be the connection method, I don't know the batteries, but I suspect the same applies... lloking at the Sunsynk manual, though, it looks like if you want to cater for the 190A... you'd have to run 2 x 50mm^2 for the positive side, one from each battery and the same for the negative side... maybe a DC LV db just for the batteries and out of it, and into the inverter a 75mm^2 pair and from battery to db 50mm^2 pair each... if you size this db correctly for potential expansion, you could add batteries without panicking about existing cabling, just add fused disconnect, in this case all negative through one fused disconnect and each battery on it own fused disconnect on the positive lead... all combining to feed the inverter... 6 hours ago, Kalahari Cruiser said: (6) Earth neutral bridge box: where does this get positioned for layout purposes, bearing in mind limited available working space. Between SunSynk and the Inverter AC DB? I'd use a contactor inside the inverter ac db, one pair of cables for control coming out of the inverter to drive the relay of the earth-neutral contactor... you should have all you need in the db, otherwise... live from the inverter, neutral from the inverter and earth connected, I'd hope to the houses earth and all the load connections in that db... 6 hours ago, Kalahari Cruiser said: (7) AC DB: Are these component specs appropriate to this setup? These specs were copied from another similar installation. yes and no... the MCB from the inverter should really be a GFI/Earth leakage trip switch with over current protection... whatever its real name is... so an earth leakage trip switch with a rating of 50A, I guess, the same or similar for the main db, to provide power to the Sunsynk from the main db, an isolator/trip switch of 50A would probably be appropriate, why do you want a change over switch? you should run everything you can't live without on the UPS side of the inverter and whatever lives on the input side, will be able to get some power, if not all, fed from the sunsynk, but obviously only when the grid is around... have you ever looked at your energy consumption footprint? do you regularly draw 8kW or more? based on this you can make some decisions... 6 hours ago, Kalahari Cruiser said: (8) The main house DB is in the kitchen. I'd like to install an indicator light which lights on the kitchen DB when there is no grid power, as a warning to ensure family and housekeeper goes easy on household machines during this time when there's perhaps poor solar generation. Is this easily achieved with one of these indicator light plugs that can attach to the DB DIN rail, and does this require a wiring loop back to the Inverter's AC DB? Or a shorter loop back from somewhere else within the main house DB? the light, I'd imagine would require power, so would have to be powered back from the inverter's ac db, it could also be something with a battery, that can indicate that the charging power for the light has gone awol, ie no commercial power, then it would not require power or signalling from the inverter side... since you're probably talking about an LED with minimal draw, let's call it 100mA at 3V, thus 300mW it wouldn't require huge battery capacity even for 4.5hour blackouts... If I misuinderstood/mininterpreted/incorrectly replied to any of the questions, you'd better try again 🙂 also note I am not an electrian so my advice here is given based on what I'd consider doing, with the DC fuses etc. there may be rules/regulations in place, that would put me in the wrong, maybe one of the more qualified dudes around can comment on what may not be kosher or halal in the recommendations... Edited February 7, 20233 yr by Kalahari Meerkat changed my mind about fuse size on panels....
February 8, 20233 yr Author Thanks so much for such a comprehensive reply and input from you @Kalahari Meerkat. That's greatly appreciated. 15 hours ago, Kalahari Meerkat said: yes, I would have made the strings the same, 7 panels each, but maybe roof space/or wherever they're being put does not allow for this... no combiner, 1 input and one output per string, no connection between them.... Yes roof config means 6 "East" possible, and a further 8 "West", albeit the latter in three nearby locations, a bit spread out, but all pointing in exactly the same direction. Chimneys and alcoves interfering a bit. 15 hours ago, Kalahari Meerkat said: 500V SPDs are probably the right way to go What I suspected - I've seen other installs using 600V but since that's way past the inverter's MPPT max, I also thought that 500V must make more sense, but wasn't sure. 15 hours ago, Kalahari Meerkat said: ditto, fuse should protect the cable Noted, so then 160A fuse for the 50mm2 cable, unless it ends up being 75mm2 cable, in which case a higher rated fuse. 15 hours ago, Kalahari Meerkat said: and into the inverter a 75mm^2 pair and from battery to db 50mm^2 pair each Food for thought - just not sure how this would work with the SunSynk battery connectors (capsules into which the cable feeds and which hook onto the battery). I've read somewhere that the supplied cables are 25mm2. My batteries are still boxed. With respect to the battery cable diagrams, was definitely not intending to connect in the way the left diagram shows, but have a closed loop with pos to first battery and neg return from slave battery. I've been told that the connections between the batteries must be same length and spec, but that this is not so relevant to the cables between the inverter and battery (i.e. invariably one is likely to be longer due to a longer run). But to understand you correctly, rather than running cable like the below diagram, one doubles up and basically has the outside return loops as well as both feeding to the first battery + and -. Does only this result in a doubling of the battery's individual capacity of the 100AH batteries to 200AH for the 2-battery bank? Or is the doubling of wires per your diagram merely to cater for the possible current draw of up to 190A (or whatever lower rate one has set)? 15 hours ago, Kalahari Meerkat said: have you ever looked at your energy consumption footprint? do you regularly draw 8kW or more? based on this you can make some decisions... I have, but not so much on a daily basis. I'm prepared to change consumption behaviour though and adapt accordingly. I do have data on an annual basis though, with daily averages, and my consumption patters range from around 16-20KW per day (on a monthly basis) for about half the year (summer), to the highest of 30KW/day in June last year. There would be some travel or holidays inbetween which would lower the average numbers, but it gives me a ball park figure. 15 hours ago, Kalahari Meerkat said: I'd use a contactor inside the inverter ac db, one pair of cables for control coming out of the inverter to drive the relay of the earth-neutral contactor... you should have all you need in the db, otherwise... live from the inverter, neutral from the inverter and earth connected, I'd hope to the houses earth and all the load connections in that db... I was about to order one of those boxes that someone mentioned in another thread (R1.5k) but given space constraints, if this can be incorporated within the AC DB box I'd prefer that option, thank you. Intention is a 12-way AC DB for this, hopefully ample space for this earth-neutral bridge. I'll update the schematic later.
February 8, 20233 yr Hi @Kalahari Cruiser, What I think @Kalahari Meerkat meant by "energy consumption footprint" is more something like this below: Such a picture will give one an idea of how much, what and when are you consuming energy. In my view, the purpose of spending some/lots of Randelas is to maximise one's ROI. (and beat loadshedding, of coarse). The easiest way to do that, is by load shifting (should trademark that :-)). Plan or be prepared to utilise the power your PV's will produce to the maximum. But that requires discipline / Automation or a lot more Randelas for more batteries etc. In the picture above, early mornings PV is used to recharge the 1/2 empty batteries - at a slow rate - to ensure they last up to 10 years. During the day, try and run items like pool pump, washing machine, dishwasher geysers etc. hopefully under control.(and a DB that allows it). Later in the day I run my heatpump to ensure 2 x geysers are up to temp for showers in the evening and next morning. Other larger spikes are just typical kettle boiling/microwave etc. Just have enough left for unplanned load shedding at any time, which is easy enough to implement on a Sunsynk/Deye. Hope this helps in your installation. And no, I'm not changing my handle to Kalahari Snake!
February 8, 20233 yr Author Thank you Sidewinder I agree with all you say and that is very much the intention - although much of my queries relate purely to the electrical setup and specifications, as I have a limited space set aside for this and may be sourcing these items myself. I already have an 8KW sunsynk and 2 batteries (10KWH), still boxed, with the panels arriving very shortly. And yes, beating LS and having a ROI hopefully of less than 10 years is the idea. We already cook with gas, our two geysers are on solar (and only really require some grid in winter), and I'm not running a pool pump. The consumers are a number of fridges and freezers, heated towel rails, TV, coffee machine, toaster, and air fryer. The oven doesn't get used much anymore. Then there's the dish washer and washing machine that run daily and will be moved to times when there's decent power generation from the panels. Where does one obtain such an energy consumption chart you shared (I assume it's from your inverter/battery BMS)? I've only got monthly averages from the municipality, so have an overall picture, but will in time manage my loads accordingly - and focus on the sunny part of the day to run machines. Panels will be a nominal 7,700W. I know I'll soon be adapting the household's energy consumption patterns. No more running dishwashers overnight etc, or ironing last thing in the afternoon... 23 hours ago, Kalahari Meerkat said: I'd use a contactor inside the inverter ac db To understand you correctly, @Kalahari Meerkat, the contactor placed inside the AC DB alongside the inverter would manage this earth neutral bridge (and would save me from having to purchase a stand-alone unit as per in the diagram above). Would you mind letting me know if this contactor spec would be - is it one of these in the list at EM? https://www.em.co.za/search?keywords=contactor Seems a neater and less space occupying solution then, thank you!
February 10, 20233 yr On 2023/02/08 at 4:30 PM, Kalahari Cruiser said: To understand you correctly, @Kalahari Meerkat, the contactor placed inside the AC DB alongside the inverter would manage this earth neutral bridge (and would save me from having to purchase a stand-alone unit as per in the diagram above). Would you mind letting me know if this contactor spec would be - is it one of these in the list at EM? https://www.em.co.za/search?keywords=contactor Seems a neater and less space occupying solution then, thank you! yup, the 1st one on the list would do, you'd only need one of the two contact pairs, since all you'd have is neutral connected to the one switching contact and earth to it NO partner, which, when the inverter switches the contactor, would then bridge earth and neutral...
February 13, 20233 yr Author On 2023/02/10 at 12:15 PM, Kalahari Meerkat said: the 1st one on the list would do Thanks very much, @Kalahari Meerkat. That first one is the "ESC225 CONTACTOR 25A 2NO 230VAC". Much appreciate you checking on that list. Have tweaked the diagram (intended to clarify my understanding and sourcing rather than being a full schematic). Anything that still requires tweaking? Especially around the contents of the AC and DC box contents...?
March 1, 20233 yr Author Can someone with the right knowledge please confirm some remaining lingering questions, please. 🙏 (a) DC isolator? Is a standalone DC isolater switch required between the inverter and the 160A DC Disconnect that runs from the battery bank? Or would the Keto on its own be sufficient (both + and - fused)? If a separate DC isolator is also required, what are the specs for this? (b) AC DB For a 8KW SunSynk setup, is the following the complete list of components for the AC DB between inverter and main DB? 1 x 2-pole Main CB (MCB) - (50A?) 1 x MCB for inverter supply (50A?) 1x Change-over-switch (40A?) 1 x MCB for inverter return (50A?) Indicator lights (for grid and inverter availability - optional) Contactor for earth neutral bridge ? (see below) (c) Neutral Earth bond hardware Are the options either via a Contactor installed inside the AC DB box, or a relay installed installed on the inverter side? -- Contactor (230V / 2NO / 25A?) - example link as confirmed earlier in this thread - otherwise if sourced elsewhere what are the required specs (Amps, 1xNO?, 1 pole?) -- Relay (230V, what specs? Amps and contacts? Could someone post a link to a suitable one? Example (but no stock) I've read numerous threads here on this, and (I think) generally understand the concept around the earth neutral bridge when grid is off and inverter is in islanding mode, but am still confused by the exact hardware requirements. I assume there needs to be a loop from the ATS240 on the inverter to the relay or contactor, that is NO when there's grid available, and closed (bonded) when grid is off. The relay in turn is connected to the load side to neutral and earth, and closes instantly when grid is absent?
March 2, 20233 yr Author 20 hours ago, Kalahari Cruiser said: (a) DC isolator? Is a standalone DC isolater switch required between the inverter and the 160A DC Disconnect that runs from the battery bank? Or would the Keto on its own be sufficient (both + and - fused)? If a separate DC isolator is also required, what are the specs for this? Just answering myself here, am I correct in assuming that if one uses a Keto or similar DC disconnector, there's no need for another DC isolator alongside it. That would only apply if the cables are fused in a way that's missing a disconnector, e.g. like one sees in some automotive applications with their inline fuses. Correct? 20 hours ago, Kalahari Cruiser said: (b) AC DB Anyone able to assist on the AC box contents (and more specifically the amp ratings of 50/40 amps)? I'd like to source quality components like Hager. Perhaps this should be in the components forum...? Edited March 2, 20233 yr by Kalahari Cruiser
March 2, 20233 yr 18 minutes ago, Kalahari Cruiser said: Just answering myself here, am I correct in assuming that if one uses a Keto or similar DC disconnector, there's no need for another DC isolator alongside it. That would only apply if the cables are fused in a way that's missing a disconnector, e.g. like one sees in some automotive applications with their inline fuses. Correct? I'm not a sparky or installer, but I previously had a Keto between my batteries and inverter. Now I have something similar to a Keto. No extra breaker required. If I need to disconnect the batteries and inverter, I just pull the fuse
March 2, 20233 yr Author Thank you very much! And I assume the Keto does just that, when the bar is pulled down, it disconnects the fuses (mine is still boxed).
March 2, 20233 yr 6 minutes ago, Kalahari Cruiser said: And I assume the Keto does just that, when the bar is pulled down, it disconnects the fuses Correct
March 6, 20233 yr Author 2 LiFePo4 batteries in parallel - what is the correct setup and why? The other day a family member had backup power installed - 8KW Deye and 2x Hubble AM5 5kwh batteries in parallel. My understanding was that for correct balance, the batteries must be installed as per the diagram below (note this isn't a Sunsynk graphic, I just used SunSynk graphic elements to mock this up). In the family member's installation (that was initially also missing the neutral earth relay/contactor bond on the backup side, and has the CT clamp installed inside the inverter cavity), the two Hubble batteries were connected as follows: Inverter via DC fuse/isolator -> Battery 1, and then battery 1 -> battery 2 (with equal length cables). Not the neg loop back from the second battery to the fuse/isolator. The installer came back and insisted that this is the correct setup (or at least, is perfectly acceptable). I'm guessing it may have something to do with modern LiFePo4 batteries and their BMS. Please can someone confirm that this is in fact correct (or a perfectly acceptable way, with no long-term harm or uneven degradation), or whether the connection must be as per the mockup below (and why). I've seen the FreedomWon battery manual (?) show the basic inverter -> battery 1 -> battery 2 setup, without the loop from batter 2 neg back to isolator. All the other schematics always show per below. Thanks in advance
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