RhysMcW Posted February 5, 2019 Share Posted February 5, 2019 I currently have an Infinisolar 3kw+ hybrid inverter with solar panels, batteries and connected to the Eskom supply. Currently the inverter is set in off-grid mode so that it does not feed back to the house and grid. This is quite a waste as the solar energy produced is way over what we're using on the load circuit of the inverter. I would love to feed the excess solar back to the house/grid but the City of Cape Town makes it extremely uninviting to do so, with their incredibly ridiculous AMI meter "service charge". I would end up paying almost twice as much to the council monthly just to have their special meter so I could feed to the grid, but yet I would be providing power, at a low credit value to me, that they would then sell on to another consumer, would typically be my closest neighbor, at the normal consumption rate and they didn't even have to do any work to get the power. Why is it that government "systems" in this country discourage consumers from producing power, especially when our only main line energy provider is so useless... Anyway, enough ranting for now.. I can't remember whether I read it or heard someone mention that you can get/install/fit something I think was referred to as "reverse power flow blocking" or something like that. Is this something I could install with my system and then be able to set my inverter to grid-tie mode and get to use the excess solar energy in the rest of the house, without actually feeding back to the grid? Quote Link to comment Share on other sites More sharing options...
___ Posted February 5, 2019 Share Posted February 5, 2019 2 hours ago, RhysMcW said: Why is it that government "systems" in this country discourage consumers from producing power, especially when our only main line energy provider is so useless... In a word, inequality, and the way that we presently deal with it. We deal with it by giving away free and cheap power to the poorest of the poor (a practice I agree with for the most part). To fund that, you have to charge the other guys more. The last thing you can afford is to make it attractive for people to leave that funding pool. That, in very dry terms, is the main reason. Quote Link to comment Share on other sites More sharing options...
Guest Posted February 5, 2019 Share Posted February 5, 2019 34 minutes ago, plonkster said: That, in very dry terms, is the main reason. The second one following this is that it is a national grid, not a regional or even suburban grid, which makes it very complex to manage and control ito not breaking it. National grids need large power stations that cannot simply start / stop at a drop of a hat like sunset, when people go home to cook. Also, very high level notes. 2 hours ago, RhysMcW said: Is this something I could install with my system and then be able to set my inverter to grid-tie mode and get to use the excess solar energy in the rest of the house, without actually feeding back to the grid? Your other question, the others would need to jump in, as what Plonk and I use has got the built in, or you get a Ziehl, which is quite expensive. Quote Link to comment Share on other sites More sharing options...
Elbow Posted February 5, 2019 Share Posted February 5, 2019 1 hour ago, The Terrible Triplett said: Your other question, the others would need to jump in, as what Plonk and I use has got the built in, or you get a Ziehl, which is quite expensive. I presume that to do this your setup must have an external current probe that is fitted at the entry from the grid - so that your inverter can adjust its output on the grid side based on the flow at the entrance from Eskom rather than what it sees on its own input into the inverter? I have CT probes so I wonder if I could retrofit my inverter like that, hijacking the existing internal measuring point. Quote Link to comment Share on other sites More sharing options...
Guest Posted February 5, 2019 Share Posted February 5, 2019 2 hours ago, Elbow said: I presume that to do this your setup must have an external current probe that is fitted at the entry from the grid Nope, ours is all built in. I added the Carlo Gavazzi for data purposes, but it is not needed. Multigrid and Multiplus II does all that automatically, with the Venus GX and software. Solis for example needs a current sensor extra as do some other inverters, to throttle. So it depends on how the inverter is designed to operate. Quote Link to comment Share on other sites More sharing options...
Analytical Posted February 5, 2019 Share Posted February 5, 2019 Hi I have the same inverter, and also running it in off-grid plus backup. I have recently connected the AC out of the inverter into my main DB and it is working very well. As long as there is grid power the inverter can sustain much higher loads than 3KW for short periods of time. I removed the geyser from the inverter circuits, but the oven is still on the inverter since the wire in the DB is too short to reach the top rail next to the geyser circuit breaker. When the oven is on the inverter supplies between 4 and 5KW, and continues to do so until the oven reaches temperature. The screen shows overload but the alarm does not sound yet, as it takes the oven about 10-15 minutes to reach temp. The intention is to remove the oven soon, as there is no benefit keeping it on the inverter. i think/know that the gardener also plugs the lawnmower into the inverter supplied sockets, and the inverter can supply the high initial load, but only when grid is available. I will also put the Aircon, washing machine and dishwasher on a contractor soon so that these are disconnected in case of power failure and running on batteries. I had the same questions as you and eventually figured it out by trial, and must say I am very impressed with this inverter considering the price paid, especially with the added functionality of ICC. Also to note, I’m on prepaid and can’t risk feeding back into the grid, but using it in off grid mode is working really well. Hope this helps a bit. Elbow 1 Quote Link to comment Share on other sites More sharing options...
RhysMcW Posted February 6, 2019 Author Share Posted February 6, 2019 14 hours ago, The Terrible Triplett said: or you get a Ziehl, which is quite expensive. I had a look around for Ziehl and came across what I think would be the model(s) and wow, they are expensive. I found an online price for an ERF3000 for R6k on special plus shipping of R850. The ERF3000 (and the new ERF4000IP) seems a little overkill for what I need, maybe there is a different model I should be looking at... @Analytical your reply pretty much answers my other post (Infinisolar 3KW Plus Hybrid inverter) regarding using a contactor to let the inverter feed the load to other devices and supply over its rate 3kw, as long as grid power exists, hence the use of the contactor. I think I'm going to continue with my contactor plans for now but I'll still look for something to stop the feed to the grid, hopefully I'll find something simpler than the Ziehl ERF3000 and therefore hopefully less expensive. Quote Link to comment Share on other sites More sharing options...
Guest Posted February 6, 2019 Share Posted February 6, 2019 38 minutes ago, RhysMcW said: think I'm going to continue with my contactor plans for now but I'll still look for something to stop the feed to the grid, hopefully I'll find something simpler than the Ziehl ERF3000 and therefore hopefully less expensive. My suggestion, get a qualified electrician to weigh in, even ask a Engineer his opinion, as at the end of the day both have to sign off your system seeing as you are in Cape Town, assuming the Munic supplies your power. And if it is supplied by Eskom, whole new ballgame. Their will be no ducking and diving I suspect as they can see the panels on areal photo's, making it easier than pie and in their "interest" to check that in due course, as making a quick R6700 in fines is easy cash. Quote Link to comment Share on other sites More sharing options...
Elbow Posted February 6, 2019 Share Posted February 6, 2019 19 hours ago, The Terrible Triplett said: Nope, ours is all built in. I added the Carlo Gavazzi for data purposes, but it is not needed. Multigrid and Multiplus II does all that automatically, with the Venus GX and software. So now I'm curious. How does the inverter know how much it can push out the grid side so that local consumption is covered but there is no excess to push back through the meter? Quote Link to comment Share on other sites More sharing options...
Elbow Posted February 6, 2019 Share Posted February 6, 2019 7 hours ago, RhysMcW said: I think I'm going to continue with my contactor plans for now but I'll still look for something to stop the feed to the grid, hopefully I'll find something simpler than the Ziehl ERF3000 and therefore hopefully less expensive. It's got to meet the CTCC requirements - i.e. be on their big list - so don't be too creative. Quote Link to comment Share on other sites More sharing options...
Guest Posted February 6, 2019 Share Posted February 6, 2019 (edited) 54 minutes ago, Elbow said: So now I'm curious. How does the inverter know how much it can push out the grid side so that local consumption is covered but there is no excess to push back through the meter? @plonkster can give you the technical side. All I know is that Multi's when grid tied, with a VenusGX and ESS software, checks the watts pulled from the grid, what is available from the panels and / or batteries, and balances that as close as it can. There obviously are overruns, few seconds of feedback, perfectly normal and cannot be helped or ever stopped, like when big appliances go off. At that point in time I'm paying cents for that feedback via the PAYG meter, as it registers it. Set mine to have a min of 20w drawn from the grid. See the panels, powers the house (AC Loads) plus the Critical loads (always on) and busy charging the batts, with min draw from the grid. Near perfection if you ask me ... no, it averages about +-20-30w truth be told. Edited February 6, 2019 by Guest Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted February 6, 2019 Share Posted February 6, 2019 https://www.acdc.co.za/products/440vac-1-phase-reverse-power-detector?variant=30483756940 Maybe you could use this to turn on more loads? Quote Link to comment Share on other sites More sharing options...
___ Posted February 6, 2019 Share Posted February 6, 2019 5 hours ago, Elbow said: So now I'm curious. How does the inverter know how much it can push out the grid side so that local consumption is covered but there is no excess to push back through the meter? Alright, there are two ways you can wire this thing up, either with an external energy meter, or without it. The Multi has a current sensor on its input (and another one on the output side, but that one is not relevant now). You can choose either THIS sensor inside the Multi, or attach an external meter, but whichever way you do it, it is going to attempt to zero the power at the point you select. What this means is if all your loads are on the output(s) of the Multi, you don't need the Carlo Gavazzi meter. Remember also that the Multi has two outputs and the second one is disconnected if the grid goes down, so you can put your larger loads on this second output. So when would you rather use the Carlo Gavazzi meter? Well... it saves you a whole bunch of rewiring... and even though there is a second output on the Multi, the overall capacity of the transfer switch is still limited (eg 50A on the 3KVA model). Enter the Multiplus-II model, and you have a third option. On this inverter, you can buy an optional current transformer that sits around the cable at the point where you want the power to be zero. It plugs into the Multi and replaces the signal from the internal current sensor (it happens in hardware, from the software side it is indistinguishable). So those are the ways that the inverter knows how much to feed back. TTT and I use a Carlo Gavazzi meter as reference. The reason why I did it that way, is because I had a 1600VA inverter installed for a long time, and it only had a 16A transfer switch. I couldn't put all my loads on the output. anotherbrownbear 1 Quote Link to comment Share on other sites More sharing options...
Elbow Posted February 7, 2019 Share Posted February 7, 2019 17 hours ago, plonkster said: Enter the Multiplus-II model, and you have a third option. On this inverter, you can buy an optional current transformer that sits around the cable at the point where you want the power to be zero. It plugs into the Multi and replaces the signal from the internal current sensor (it happens in hardware, from the software side it is indistinguishable). Thanks - that makes sense to me - you can move the measurement point where the inverter zeroes the current flow. Steve ___ 1 Quote Link to comment Share on other sites More sharing options...
___ Posted February 8, 2019 Share Posted February 8, 2019 15 hours ago, Elbow said: Thanks - that makes sense to me - you can move the measurement point where the inverter zeroes the current flow. Indeed. Now wrap your head around this: If you connect a PV inverter so that extra power is being fed into the grid BEFORE this sensing point, then instead of attempting to zero this point by taking power from the battery, the Multi will not attempt to zero it by putting the power INTO the battery. It works in both directions. Quote Link to comment Share on other sites More sharing options...
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