pilotfish

You will need to investigate the grid-tie conditions in your area before heading down this road. In Joburg where I live you will get 42c for feed in, and charged Time Of Use rates for consumption. Based on the 8hr/14hr split, of your 14hr consumption period you would be charged 302c for 3hour, 125c for 3 hr, and 90c for 8 hr. [302 x 3]+[125 x 3]+[90 x 8] = 2000/14 =143c average (we can do this because of the constant load, domestic setup is MUCH more complicated calculation). The ratio of feed in to consumption charge is 143/42 = 3.4 In order to break even on your utility bill under these conditions you will need to produce the following; [4.1 x 8 = 33kWh] + [4.1 x 14 x 3.4 = 195kWh] = 227kWh per day as apposed to the 100kWh per day in the initial proposal. Now you need 45kWp (R375k) and 3x InfiniSolar 3p 10kW in parallel (R150k) 25kWh battery to give you about 3hr backup (R60k) 300m2 structure required for your 150 panels Installation sundries thumb-suck (R60k assuming 300m2 structure mentioned above is already available) That is a budget of R645k, or you could go with 1st proposal (using something other than Axpert of course) and invest the extra R200k to pay for your replacement batteries for the rest of time.

I'm sure he does, my reply was intended as light hearted. A Builders Warehouse gennie capable of the job will cost about R6k. Note that my proposal was a kick-off point because no-one else has responded - I don't doubt that there is much better solutions available , although I don't think that Grid-tie is one of them if the project is in in RSA, because authorities go out of there way to make if uneconomical unless you are prepared to "wind the old clock back" which is a criminal offence.

So when the grid goes down and the fancy Fronius shuts off and all the fish are flopping around gasping for oxygen, with eyes bulging and gills turning purple with moments to go before they die - then the client runs out and buys 100k diesel generator wishing like hell that Clement had sold him a solution with some backup

Note that the Axperts in parallel share 1 common battery bank. The Axpert MKS 5K can charge at up to 80Amps, so 6 in parallel can charge at max 480amps which is over 15% of the 3000Ah bank rating - I would be happy with this scenario. I think the recommendation has to do with charging of some AGM which require a high initial current of 20% of rating, the OPS batteries suggested dont have this requirement so it is a blanket "cover our arse" recommendation in my opinion (but my opinions have been known to be way off on occasion). Also you would set ICC software via your Victron BMV-702 to never discharge beyond 50%, so while you have a 3000Ah bank you would only ever require the charger to recharge 1500Ah.

At 4.1kW total load it wouldn't matter whether it was arranged 1phase or 3phase, because you will have 24kW available if 1phase or 8kW per phase if arranged 3 phase. I would go ahead with 3 phase arrangement and install equipment as follows; Red Phase - 1.1kW air blower White Phase - 1.5kW water pump Blue Phase - 0.75kW air blower + 0.75kW water pump This way you will have nicely balanced phases, plenty capacity to accommodate starting currents, and you can still use a 3phase appliance in future should the need arise - but to do this your grid supply will need to be 3 phase. If not then arrange as 24kW 1phase system - no problem.

4.1kW x 24hr = 98.4kWh per day (ouch!), call it 100kWh so you will need about 20kWp array. So a real cheapo solution would be as follows; 6x Axpert MKS 5k in parallel (for the panel capacity, not for the output power which will be way overkill), about R60k Each Axpert with 10x 315Wp panels = 3.15kWp x6 = 18.9kWp (not quite 20kWp but close enough), about R150k Assume 8hr solar day and 14hr solar night, so your battery bank must carry you for about 14hr's on average. 4.1kW x 14h = 57.4kWh supplied by battery, if you use lead acid and limit it to 50% drain you will need 120kWh battery bank. 120kWh / 48v = 2500Ah battery bank, Ritar make a 2v 1500Ah battery for R4000 - you will need 48 of these for a 3000Ah bank about R192k That's about R402k, plus R48k for installation sundries and R50k for me that's about R500k - sounds like a bargain! Note that this wouldn't be Off-Grid but Grid-Assisted (not grid-tie, you wont be feeding any power back anywhere) so that the Axperts can take power from the grid when needed. You will get probably 80% of your power requirement from the PV system with the grid helping out with the other 20% on them dark and dingy days. If it was me I would want to save R10k a month on the utility bill to make capex worthwhile - I reckon you will save 2500kWh per month so your power cost must be R4/kWh or higher to give this system the green light - if not then just pay the utility bill. Sounds like a blast, have fun

Axpert is a Voltronic product, Must is a knockoff.

They run out at the same time. But in order to run 5kVA of appliances your cables, fuses etc will be MUCH more expensive on the 24v system because you must cater for a maximum of 200 battery amps whereas the 48v system you must cater for100 battery amps

I beg to differ....

Oops, @plonkster beat me to it

No, you would have the same amount of energy stored with 4 batteries; 4 batteries in parallel = 420Ah at 12v = 5.04kWh 2 batt's in series, paralleled with another 2 batt's in series = 210Ah at 24v = 5.04kWh 4 batt's in series = 105Ah at 48v = 5.04kWh You will run the same load for the same amount of time irrespective of whether you are using 12v, 24v or 48v arrangement. The difference is at 48v your current (amps) will be half that of a 24v system and 1/4 that of a 12v system. This is a big advantage because at 48v you will have lower current, therefore lower voltage drop, lower power loss, and you can use thinner and cheaper cables. Having a 48v system is an advantage over a 24v system The MKS 5K is only available at 48v

I have a pre-loved Microcare LCD 150Voc 20A. How about 50% of retail? They normally cost an arm and a leg, so at 50% it is an arm or leg only

The MKS Plus version is indeed 145Voc as per the attached brochure, but I would still stay away from 3 panels in series as you have a real possibility of exceeding the max 145Voc under certain conditions. I believe that the best option would be to obtain a 4th panel of the same or VERY similar spec, and have 2 strings of 2 panels. You could use the 3 panels in parallel, but may run into problems with another spec on the brochure... MPPT Operating Range - [30v to 115v] or [60v to 115v] From the above I assume that the equipment comes in 2 versions, if you get the [30v to 115v] version then you can run single panel strings, if you get the [60 to 115v] version then it may not work with single panel strings as the panel voltage will be below the 60v minimum. If I was you I would forget about the Axpert 3k and go for the Axpert MKS 5K for very little extra money (and also get the 4th panel) - it is far more versatile and will allow much better options for expanding the system later, which you will definitely need to do if your goal is to kick Eksdom as you mentioned in an earlier post. Axpert MKS Plus.pdf

I don't believe that you will gain anything by "exercising" the batteries - every now and again you will have a grid failure and the batteries will come into use, that is exercise enough.

You originally mentioned fusing of strings - this would typically be in the 10amp to 15amp range where the HRC (High Rupture Capacity) fuses would not be required, the fuses on the page that I attached in my previous reply is the correct item (order if necessary). You could use HRC fuses for your Battery Bank Main and for your PV Array Main (after the string fuses in your combiner box) but I would recommend rather using DC circuit breaker in this instance. The problem with fuses is that they blow, and when they do people typically replace the blown fuse with a nice fat blou-draad because a replacement is not close to hand - then if the fault has not been cleared your equipment is going to turn into a puff of smoke.

My wife used a product to seal an outdoor mosaic table called Pratley-Glow, it is self levelling and looks like clear glass once set. If the panel is laid absolutely level for application then this product will self level to a very thin and waterproof layer. I dont know about UV properties - you would need to look that up.

ACDC Express has 1000v DC fuse and holders (DIN Mount), also DC surge arrestors which is hard to come by (and VERY expensive but much cheaper than surge damage). ACDC - PV accessories.pdf

Yes it can but I misunderstood your requirement - initially you said on/off now you are talking about changeover from grid to inverter. This can be done using two separate 4 pol contactors if the load is 3 phase (one normally open and the other normally closed) or a single 4 pole contactor that has 2x N/O contacts and 2x N/C contacts if your load is single phase. The switching would still be initiated by the BMV-702. Your local electrician should be able to assist you with this.

This would be easy to do using the Victron BMV-702 which has a relay that will switch based on various settable parameters - SOC being one of them. The relay would control a contactor (rather than ATS which may not be the right piece of kit in this instance) with the equipment to be controlled all connected to the correctly rated contactor.

No idea, don't think anyone keeps records, Good quality earth to all components, all linked back to main earth (and most important at surge arrestors), Earth PV panels, Surge protection at main grid connection, Surge protection at Inverter Output, PV Surge protection, Hold thumbs that when the lightning comes it hits the neighbor and leaves you alone.

Not necessarily - you can have a Generator DB that only powers critical circuits if so desired. When grid fails then the Auto-start gen should start up and supply power to the load that is supplied via the ATS - this could be the entire load or a selected load depending on how wired.

I would use a normal auto-start generator. When grid fails and grid-tie inverter shuts off, then auto-start generator starts and runs loads as desired. When grid returns then generator will auto-stop after settlement period.

Something like this...

Yes it is advisable to do so, every installation is different but this is my suggestion for an average home; Keep oven, hob, geysers, aircons, underfloor heating etc directly on grid or use gas/solar as energy source where possible - put lights (all LED or CFL) and selected plugs on the inverter. The more panel power, inverter capacity and battery capacity you have the more you can shift off grid section of the DB and onto the Inverter section. With 1 Axpert I would stick to lights, TV, computers, fridges, and maybe the pool pump if you have sufficient panel power.

Oops - 2500W