Elbow Posted February 15, 2019 Share Posted February 15, 2019 HI, I'm trying to design the split of my house circuits and maximise load on the inverter / solar system whilst avoiding overloading and tripping the inverter. Its hard to figure out since load is almost always well under 3Kw, but the heavy load items cause short periods of heavy load. I have some "essential loads" so I'd like to avoid that putting the kettle and dishwasher on together trips off those loads. The easiest would be to operate in grid-tie mode but it doesn't seem cost effective to do that in CoCT land. I've got a question about that that I'll post separately. But how much power can my inverter supply? Headline rating says 3kVA, and specification says nominal output current 13A which comes to about 3kVA But my Replus inverter says the following in the manual about off-grid mode (with no grid side feed-in allowed): Quote PV energy supply priority setting: 1 Load, 2 Battery PV power will provide power to the load first and then charge battery. Feed-in to the grid is not allowed under this mode. At the same time, the grid relay is connected in Inverter mode. That means the transfer time from inverter mode to battery mode will be less than 15ms. Besides, it will avoid overload fault because grid can supply load when connected load is over 3KW. If I read it right, the last sentence says that the inverter can supply more than its rated 3kVA on the output if the grid is present. But how much more? I'm also not clear whether the inverter will augment the PV power with some extra from the grid, or if they are just saying that the inverter will "trip" the load back to the grid in the case of an overload of the inverter (and hopefully switch back when the load goes away). Thoughts? Elbow Quote Link to comment Share on other sites More sharing options...
Jaco De Jongh Posted February 15, 2019 Share Posted February 15, 2019 32 minutes ago, Elbow said: But how much more? Would be interesting to see what the non Blue inverters can do. This is for interest sake and I am not trying to answer your question with this. I have recently installed a 4kw Victron for a client. We decided to take the supply to the house through the inverter. The 4 kw has a Passthrough rating of 100 amp. Yesterday for example, we decided to charge the battery from Grid due to rain and wanting to keep the battery's full for load shedding. Somewhere during the morning I saw the inverter charge the Bats at 3.5kwh while 6.5kwh load was drawn. In total just over 10kwh was taken from the grid and send in different directions by a 4kw Multiplus. I was surprised, I have limited experience and only dealt with a couple of inverter makes and models, but I never saw something like this. Does anyone know of other 4 to 6 kw inverters that can allow for the complete house loads to be passed through? My own Quattro is rated for 100A passthrough plus its own 22 amps it can contribute from solar, so total rating on combined output is 122amps from a 8000va unit. I did limit AC input on both at 50 Amps though so effectively it will only allow the 50Amps plus its own contribution to its outputs. Quote Link to comment Share on other sites More sharing options...
Elbow Posted February 15, 2019 Author Share Posted February 15, 2019 2 minutes ago, Jaco de Jongh said: In total just over 10kwh was taken from the grid and send in different directions by a 4kw Multiplus. Yeah - that would make it so easy - put it all on the inverter and it will figure it out. On mine I don't see any "pass through" rating - I guess in other markets it will usually be setup for grid-tie where it isn't necessary for it to "pass through" a lot of load. Quote Link to comment Share on other sites More sharing options...
Mark Posted February 15, 2019 Share Posted February 15, 2019 (edited) My Infinisolar 3+ can pass through 8000W plus for periods (by mistake I might add) ... I'm to scared to push harder Edited February 15, 2019 by Mark Quote Link to comment Share on other sites More sharing options...
Elbow Posted February 15, 2019 Author Share Posted February 15, 2019 Just now, Mark said: My Infinisolar 3+ can pass through 8000W plus for periods... I'm to scared to push harder It complains and threatens to trip or just sucks it up? Quote Link to comment Share on other sites More sharing options...
Mark Posted February 15, 2019 Share Posted February 15, 2019 Sucks it up with a warning flashing... but just goes... Elbow 1 Quote Link to comment Share on other sites More sharing options...
Elbow Posted February 23, 2019 Author Share Posted February 23, 2019 (edited) On 2019/02/15 at 11:38 AM, Mark said: My Infinisolar 3+ can pass through 8000W plus for periods (by mistake I might add) ... I'm to scared to push harder Hi Mark, I wanted to ask you how you setup your loads on the output side of the inverter? Since surely if your grid supply goes off when the inverter is pushing through much more than 3kW then something bad will happen? At best the inverter shuts down, worse - the fuses blow - worst of all the mosfets let their smoke out. I'm trying to figure out how to do the breakers on the output side of the inverter. The inverter manual doesn't say what breaker to use - it says that the nominal output current is 13A, "maximum output fault current" 51A - that's a big range. So I can size the breaker based on the capacity of the inverter when the grid is present - say a 32A breaker so about 6000w - and then we'll ride out the burst of heavy load (hairdryer and kettle and ... ) Or I can size for the 3000W - so a 15A breaker I suppose. But there will be lots of accidental trips. Can't figure out how to square this circle and protect my inverter. Edited February 23, 2019 by Elbow cleanup Quote Link to comment Share on other sites More sharing options...
Mark Posted February 23, 2019 Share Posted February 23, 2019 (edited) I would go with the 15A (or 20A) breaker... I have my high loads on a transfer switch (Hager in pic) which allows them to be direct on Eskom. When power fails I have a choice (use inverter but be carefull) or just leave them off ... See the Red Label (Stove and Geyser on RED phase) I have tenants on one phase (Blue) and they stay on Eskom no matter what. Thats the reason for the second Infini on their phase...;) I DM'd you about the frequency change on the Infini. Did it work...... Cheers M Edited February 23, 2019 by Mark Quote Link to comment Share on other sites More sharing options...
Elbow Posted March 5, 2019 Author Share Posted March 5, 2019 On 2019/02/23 at 10:47 AM, Mark said: I would go with the 15A (or 20A) breaker... I have my high loads on a transfer switch (Hager in pic) which allows them to be direct on Eskom. When power fails I have a choice (use inverter but be carefull) or just leave them off ... Yes, I was able to tweak my Infinisola settings, thanks. I made up this board to get going: Top row: 32A 2P trip from grid, indicator for grid, 2P 32A trip from inverter, indicator for inverter, change-over switch, RCD Bottom row on the left are fed from before the RCD and are my red plugs for the computers and 3 lights Ccts. all 10A. On the right side at the bottom these are the plugs circuits. I put one 15A trip for them all, and then 3 10A for three plugs circuits. The idea is that hopefully an overload on the plugs will trip that 15A trip and leave the computers and lights on. Quote Link to comment Share on other sites More sharing options...
Analytical Posted March 5, 2019 Share Posted March 5, 2019 Hi Here is a previous response I provided on the load on my 3KW Infini: https://powerforum.co.za/topic/2858-reverse-power-flow-blocking-protection/?tab=comments#comment-44961 I currently have my whole house connected except for geyser. The largest load on it is the oven, which is 4 KW, which it can sustain whilst the oven heats up, which is around 15 min. The total loan regularly peaks at 5KW with the oven, with the highest recorded being 7KW for a short period of time. I dont think there is much of a benefit keeping this on the inverter, so will split it out with the geyser, but the live wire is too short at the moment to reach the top rail at the moment. Dishwasher, washing machine and aircon will remain on the inverter, but I will put these on a contactor as the load capability is much lower without the grid present (trips when the lawnmower tries to start when no grid present). I havent seen smoke yet, but have seen it trip with overload, so seems safe. The manual says to connect the AC Input to a 30A circuit breaker. I have a 32A one, both on in and out. @Mark I'm keen to hear about the frequency change being mentioned below please. Hope it helps. Quote Link to comment Share on other sites More sharing options...
Elbow Posted March 5, 2019 Author Share Posted March 5, 2019 25 minutes ago, Analytical said: The manual says to connect the AC Input to a 30A circuit breaker. I have a 32A one, both on in and out. Yep - I remember your post. As you see I used 32A coming from the inverter, though I’ve put the plug circuits behind a 15A breaker to start with. This is because I don’t have PV yes, so it is being used as a UPS and without grid it will be limited to 3000va. When o do my PV panels I’ll experiment with a high breaker rating; though I’m hoping that CoCT will agree that I can grid-tie it and I’ll rather support the heavy loads on the grid-tied side. Your figures are impressive - 7kw total on a 3000va rated inverter! Quote Link to comment Share on other sites More sharing options...
Youda Posted March 5, 2019 Share Posted March 5, 2019 (edited) This is the reason, why you can pass much more power thru InfiniSolar then what internal inverter circuit can deliver: In the majority of the InfiniSolar's operating modes, the internal "grid relay" physically connects AC-in with AC-out. Then, the power from the inverter circuit is mixed with the power from the grid. Since the voltage produced by internal inverter circuit is slightly higher then the voltage of the grid, it gets consumed first. If there's a huge load, the missing electricity is "sucked" from the grid: Yes, there is a current measurement inline, so the Infini knows, how much current is passing thru and can warn you if it's too much. Edited March 5, 2019 by Youda Mark, Nicholas and ___ 1 2 Quote Link to comment Share on other sites More sharing options...
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