Hi

For a grid tie inverter, my understanding is that you need to size the inverter based on the number of panels and not the load.

With the inverter being able to push power back it doesn't matter what is under the inverter. So does it make sense to have nothing under the inverter so all the power generated by the panels is pushed back to the other loads

correct, size the panels according to the inverter, as there are no essential ( ups ) loads

As an example, an installer told me that if I go with a 3kW grid tied and have my pool pump (1,1kW), Ketterl (2kW) and Geyser (1kW) it will trip the system, I guess that isn't true?

think of a true grid tied system as a water stream emptying into a river, so the size of the stream does not matter, it just adds water to the river ( in a sense )

52 minutes ago, MNK1234 said:

As an example, an installer told me that if I go with a 3kW grid tied and have my pool pump (1,1kW), Ketterl (2kW) and Geyser (1kW) it will trip the system, I guess that isn't true?

That is not true. A true grid-tied system will only trip if you exceed the capacity of the main circuit breaker of the house. If your power demand merely exceeds what is available from the grid-tie inverter, then you simply draw the balance from the grid.

Your installer must have had his terminology confused, something like calling a battery inverter with grid back-up a grid-tied inverter.

1 hour ago, GreenFields said:

That is not true. A true grid-tied system will only trip if you exceed the capacity of the main circuit breaker of the house. If your power demand merely exceeds what is available from the grid-tie inverter, then you simply draw the balance from the grid.

Your installer must have had his terminology confused, something like calling a battery inverter with grid back-up a grid-tied inverter.

This still confuses me, A Sunsynk is a grid tied inverter. Are you saying you can power an 8kw load from a 5kw sunsynk by blending grid and solar?😁

Just now, hoohloc said:

This still confuses me, A Sunsynk is a grid tied inverter. Are you saying you can power an 8kw load from a 5kw sunsynk by blending grid and solar?😁

If takes a battery it is not a grid-tied. I suspect the sunsynk you are referring to is a hybrid.

1 minute ago, P1000 said:

If takes a battery it is not a grid-tied. I suspect the sunsynk you are referring to is a hybrid.

Yes! Hybrid meaning it can work as either grid-tied or off-grid. 

2 hours ago, MNK1234 said:

As an example, an installer told me that if I go with a 3kW grid tied and have my pool pump (1,1kW), Ketterl (2kW) and Geyser (1kW) it will trip the system, I guess that isn't true?

Your installer is correct, if you exceed the capacity of your inverter, it will trip 😀

15 minutes ago, hoohloc said:

Your installer is correct, if you exceed the capacity of your inverter, it will trip 😀

If it is purely grid-tied, I cannot see how you can install it wrong enough that it will trip under those circumstances.

2 minutes ago, P1000 said:

If it is purely grid-tied, I cannot see how you can install it wrong enough that it will trip under those circumstances.

I think there is a reason why we have different capacity inverters. I don't see how you could power up a 5kw load with a 3kw inverter. Grid-tie or not, I have never heard of anyone who has managed to do that. I stand to be corrected and open to learn, please share, which inverter does this? I would like to read up more about that specific inverter 

4 minutes ago, hoohloc said:

I think there is a reason why we have different capacity inverters. I don't see how you could power up a 5kw load with a 3kw inverter. Grid-tie or not, I have never heard of anyone who has managed to do that. I stand to be corrected and open to learn, please share, which inverter does this? I would like to read up more about that specific inverter 

Grid-tie is popular in countries where they have reliable power and don't need batteries. It essentially makes as much power as it can, and pushes it all back into the grid. You then have a 4-quadrant meter that determines how much power you bought and how much you sold (usually at different rates).

So no power feeds through it, it is more like an appliance that just connects to the grid. It does not have an input/grid and output/backup. It only has an output that goes to the grid.

2 minutes ago, P1000 said:

Grid-tie is popular in countries where they have reliable power and don't need batteries. It essentially makes as much power as it can, and pushes it all back into the grid. You then have a 4-quadrant meter that determines how much power you bought and how much you sold (usually at different rates).

So no power feeds through it, it is more like an appliance that just connects to the grid. It does not have an input/grid and output/backup. It only has an output that goes to the grid.

Grid-tie means you do not need a battery to power the inverter, the grid falls, your power gets cut. You inverter works without the need to use a battery. Where off-grid inverters rely on battery use, so when the grid falls, you still have power because you have batteries. Now, I'm still waiting for an example of an inverter that can power the load which is more than its rated capacity 😀

 

4 minutes ago, hoohloc said:

Grid-tie means you do not need a battery to power the inverter, the grid falls, your power gets cut. You inverter works without the need to use a battery. Where off-grid inverters rely on battery use, so when the grid falls, you still have power because you have batteries. Now, I'm still waiting for an example of an inverter that can power the load which is more than its rated capacity 😀

 

You seem to struggle with comprehension. If the load is more than the inverter rating, the inverter is blissfully unaware of it and all excess is sourced from the grid. How is that difficult to understand? No loads are connected to the inverter, the inverter is connected to the grid.

1 minute ago, P1000 said:

You seem to struggle with comprehension. If the load is more than the inverter rating, the inverter is blissfully unaware of it and all excess is sourced from the grid. How is that difficult to understand? No loads are connected to the inverter, the inverter is connected to the grid.

buddy! no need to be rude, and for you to be going around and avoiding to give one example of such an inverter tells me that your responses are based on assumptions. All inverters I have came across have ratings, I have never seen an unlimited or unrated blissful inverter. Again, educate me, I want to learn. After all we are all here to learn, right? 

13 minutes ago, hoohloc said:

buddy! no need to be rude, and for you to be going around and avoiding to give one example of such an inverter tells me that your responses are based on assumptions. All inverters I have came across have ratings, I have never seen an unlimited or unrated blissful inverter. Again, educate me, I want to learn. After all we are all here to learn, right? 

With respect, you're making this far more complicated than it needs to be, and it's not clear if you're really here to learn or start an argument. Anyway, see below.

A grid-tie inverter turns your home into a power station embedded into a larger power grid, like the municipal or national power grid. Similar to Koeberg and Medupi and Kusile, it is fully synchronised in frequency and phase to the national grid, but obviously on a much smaller scale. Nobody is saying that a grid-tie inverter can power a load that is greater than its own rated capacity, just like you wouldn't say that one power station like Koeberg can power the whole country by itself. The grid-tie inverter will inject as much power as it can into the grid, and if that is not enough to power your  home, any shortfall must be supplemented from the other power stations on the grid. If your own home's consumption is lower than what it generates, you basically end up exporting power for your neighbours and others on the grid to use. If the grid in your area goes down like with loadshedding, your grid-tie inverter also shuts down. It does not try to keep your loads up and running.

Examples of pure grid-tie invertes are the SMA Sunny-Boy, or the Enphase Micro-inverter, the Fronius Primo or the Solis 4G. Or the old MicroCare GTI that I've got, that they don't make anymore, but I assure you that if you're looking for an example, mine still works well. You don't need a battery to run these, but they do need to be tied to an active power grid. Because they are grid-tied.

Of course you get true hybrid inverters also such as the Sunsynk 8kW or 5kW. Other examples are the Goodwe EM or ES-series, or even the Infinisolar range or the Imeon. These can operate in a pure grid-tied mode just like the previous examples. As long as the grid is up and running, they can help -  HELP - to power any load you would normally run in your house, and reduce what you draw from Eskom. But you can also add a battery, so that when the grid goes down, you can continue to run your essential loads up to the limits of the available solar and battery power, within the limit of the rated capacity of the inverter. Again, nobody is saying that an inverter can create energy out of thin air to power loads greater than what it's rated for.

Beyond that you'll get off-grid inverters or battery backup inverters like the Axpert MKS or the Growatt, they might have a solar input, and an output to a load, but they don't synchronise to the grid, where some people might call that grid-tied or hybrid anyway, even if it's just not the same thing.

This will be my last comment on this topic. If anything is still not clear, please do some additional research via Google or YouTube.

 

A friend of mine has a 8 KW inverter with solar panels and 3 Hubble batteries, he had the same soc problems, he was told to bring the batteries in to Hubble, so instead of shutting the system down, we ran it as a pure grid tied inverter ( ticking “no battery“ in the Battery screen, all worked fine.

As @P1000said, you could be running 60 amps through the main breaker, the inverter will provide as much solar as available as it can and the rest comes from the grid

@hoohloc

A grid-tie inverter converts direct current (DC) into an alternating current (AC) suitable for injecting into an electrical power grid, to inject electrical power efficiently and safely into the grid, grid-tie inverters must accurately match the voltage and phase of the grid sine wave AC waveform and maintain the output voltage slightly higher than the grid voltage at any instant.

so basically it tracks and matches the grid, and injects slightly higher than the grid voltage causing a small voltage potential that allows any local load to draw off the grid tie first, then the grid.

As a rule grid tie inverters inject the max it can at any given moment, based on its rating and panels connected, time of day etc.

Let's say you are injecting 5kw from solar grid tie and the load draws 8kw, the grid will supply the balance of power needed, in my example 3kw.

You can never exceed a grid tie inverters output through injection as it will self limit to its maximum rating. Possibly think of it as power mixing on the grid itself.

I hope it helps you understand grid tie a bit more. Another topic closely linked to grid tie is the effect of (mass) solar grid tie injection on the traditional duck curve of a power utility.

Here's what (mass) solar grid tie is doing in New England, apparently its being called a Turducken, It's supposedly a chicken stuffed inside a duck that's stuffed inside a turkey along with layers of stuffing (tongue in cheek) 

another decent illustration of the effect, without the actual duck image

 

Edited February 2, 20223 yr by Nitrious

17 minutes ago, Nitrious said:

@hoohloc

A grid-tie inverter converts direct current (DC) into an alternating current (AC) suitable for injecting into an electrical power grid, to inject electrical power efficiently and safely into the grid, grid-tie inverters must accurately match the voltage and phase of the grid sine wave AC waveform and maintain the output voltage slightly higher than the grid voltage at any instant.

so basically it tracks and matches the grid, and injects slightly higher than the grid voltage causing a small voltage potential that allows any local load to draw off the grid tie first, then the grid.

As a rule grid tie inverters inject the max it can at any given moment, based on its rating and panels connected.

Let's say you are injecting 5kw from solar grid tie and the load draws 8kw, the grid will supply the balance of power needed, in my example 3kw.

You can never exceed a grid tie inverters output through injection as it will self limit to its maximum rating.

I hope it helps you understand grid tie a bit more. Another topic closely linked to grid tie is the effect of (mass) solar grid tie injection on the traditional duck curve of a power utility.

 

100% correct however,  one cannot draw more power from the inverter than the rated power output, he is talking about a 3 KW inverter supplying more then the rated wattage, not possible. the inverter will trip.

Just now, Antonio de Sa said:

100% correct however,  one cannot draw more power from the inverter than the rated power output, he is talking about a 3 KW inverter supplying more then the rated wattage, not possible. the inverter will trip.

I think it was the 3kw grid tie supplying a say 5kw (or whatever) load that got things tangled up a bit, so tried to make the description fairly easy and comprehensive. 

1 minute ago, Nitrious said:

I think it was the 3kw grid tie supplying a say 5kw (or whatever) load that got things tangled up a bit, so tried to make the description fairly easy and comprehensive. 

I quote him----- As an example, an installer told me that if I go with a 3kW grid tied and have my pool pump (1,1kW), Ketterl (2kW) and Geyser (1kW) it will trip the system, I guess that isn't true?

close quote--- so he thinks that he can supply more than the rated inverter capacity, so the installer was 100% correct.

 

15 minutes ago, Antonio de Sa said:

I quote him----- As an example, an installer told me that if I go with a 3kW grid tied and have my pool pump (1,1kW), Ketterl (2kW) and Geyser (1kW) it will trip the system, I guess that isn't true?

close quote--- so he thinks that he can supply more than the rated inverter capacity, so the installer was 100% correct.

 

I'm glad someone gets this, and this is where my argument was. All those inverters that he mentioned, will trip if you go over their rated out put power

I ran grid tie years back (when 3kw inverters were big and 240w panels were the order of the day), didn't do as much for my bill as a decent sized inverter with storage.

grid tie can cover your day load to an extent, size depending, but does nothing for the night load at all.

we apparently had load shedding today, didn't notice at all, came up in conversation while buying smokes as having happened.

48 minutes ago, Tariq said:

A friend of mine has a 8 KW inverter with solar panels and 3 Hubble batteries, he had the same soc problems, he was told to bring the batteries in to Hubble, so instead of shutting the system down, we ran it as a pure grid tied inverter ( ticking “no battery“ in the Battery screen, all worked fine.

As @P1000said, you could be running 60 amps through the main breaker, the inverter will provide as much solar as available as it can and the rest comes from the grid

Ask your friend if he can draw 16kw out of his 8kw inverter

4 minutes ago, Nitrious said:

I ran grid tie years back (when 3kw inverters were big and 240w panels were the order of the day), didn't do as much for my bill as a decent sized inverter with storage.

grid tie can cover your day load to an extent, size depending, but does nothing for the night load at all.

we apparently had load shedding today, didn't notice at all, came up in conversation while buying smokes as having happened.

Sure, but I'm pretty sure you could not pull more that 3 Kw from that inverter, yes we had load shedding today I think we all went trough without even feeling it.