Signature Solar has a nice video " Growatt 5kw ES + Mid-point Transformer explained"; however, the video is for a setup with solar/battery. Can anybody explain how to connect the utility to the AC input of the inverter? Is it L1 and L2 to L and N of the inverter AC input(240 volts)? What about when there's an unbalanced load(120volt) that the utility has to supply power to? Normally there's current in the utility neutral in that case. Any help would be appreciated.
Growatt 5kW ES + Mid-Point Transformer explained but not AC input from grid
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timselectric
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You can't implement that setup with a grid connection, safely. Only for a completely off grid setup. Or isolated from grid with a transfer switch.
timselectric
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Growatt is made in China, like almost all electronics.
But the 5000 ES has a built in transfer switch, no? Of course, that only switches L1 and L2 but according the thread I found after starting this thread you don't need the neutral from the utility(it can remain isolated). See issue #2: https://diysolarforum.com/threads/safe-grid-use-of-the-5000es-and-transformer.34121/. So when I don't have enough solar/battery to supply my loads and I have L1 and L2 from the utility connected to the inverter's AC input then the utility can provide the power to the unbalanced loads through the mid-point transformer. The thread linked above says the mid-point transformer's neutral should be bonded to ground with a rod to earth. But are you saying this is unsafe?
timselectric
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You can't isolate the grid neutral, and still be connected to the grid L1 and L2. The neutral is bonded to ground at the main panel. Without a neutral wire. The loads will use the ground wire for a return path.
I explain the issues here.
diysolarforum.com
I explain the issues here.
Growatt SPF-5000-ES AT and N/G solutions
First, let's point out the issues with this inverter for use in a split-phase system. 1) this inverter was designed for use in a 230v grounded installation. (European standards) It's input and output are L1 and "N". This input "neutral" is expected to be grounded by the grid, and at the...
diysolarforum.com
Thanks. This is going to require some study on my part...You can't isolate the grid neutral, and still be connected to the grid L1 and L2. The neutral is bonded to ground at the main panel. Without a neutral wire. The loads will use the ground wire for a return path.
I explain the issues here.
Growatt SPF-5000-ES AT and N/G solutions
First, let's point out the issues with this inverter for use in a split-phase system. 1) this inverter was designed for use in a 230v grounded installation. (European standards) It's input and output are L1 and "N". This input "neutral" is expected to be grounded by the grid, and at the...
I read through the link that you provided. Do you know if the Growatt low frequency split-phase inverters do what you've done? I mean can I put the split-phase inverter between my main panel(N-G bonded) and my load panel(N-G bonded through main panel) using L1 and L2 from the main panel as input? Is this setup safe?You can't isolate the grid neutral, and still be connected to the grid L1 and L2. The neutral is bonded to ground at the main panel. Without a neutral wire. The loads will use the ground wire for a return path.
I explain the issues here.
Growatt SPF-5000-ES AT and N/G solutions
First, let's point out the issues with this inverter for use in a split-phase system. 1) this inverter was designed for use in a 230v grounded installation. (European standards) It's input and output are L1 and "N". This input "neutral" is expected to be grounded by the grid, and at the...
timselectric
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If you are referring to the 6k, 8k, and 12k units.
The bonding issue can be resolved by connecting the main panel neutral to the sub panel. And not having a N/G bond in the sub panel. But, the built-in transformer is used as an autotransformer in bypass mode. So, the transformer is still in parallel with the grids transformer in bypass mode. Not sure if there's an automatic way to resolve that.
So what's the problem with having the transformer connected in parallel with grids in bypass mode? How is it different than any 240 volt appliance in standby mode that's plugged in?
timselectric
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It's not an appliance.
If the grid is out of balance, your autotransformer can try to help balance the neighborhood.
If the grid is out of balance, your autotransformer can try to help balance the neighborhood.
BartHenry
Solar Enthusiast
I only mentioned a 240 volt appliance because many have transformers inside. Forget I mentioned that. Now I'm thinking that as long as the neutral from the output of say the Growatt 6kw split phase inverter SPF 6000T DVN-MPV is open in bypass mode it should be safe, right? Assuming, of course, that the inverter is between the main panel with N-G bond and the load panel with N-G bonded through the main panel.
RCinFLA
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Whenever you put an autotransformer in parallel with grid, along with grid neutral connection the autotransformer will attempt to balance any imbalance in grid L1-N and L2-N voltage difference. This will consume some of autotransformer power handling capability.
99% of time it is usually not a significant problem, but when it is it can overheat autotransformer.
99% of time it is usually not a significant problem, but when it is it can overheat autotransformer.
But if the autotransformer(I'm assuming this a transformer with a center tap) has its center tap(neutral) not connected to anything then it's just like any other transformer connect to 240 volts in your house. I'm guessing this is how the Growatt split phase inverter accomplishes bypass mode - by disconnecting the neutral output from the neutral of the load panel while connecting L1 and L2 from the mains to the load panel. Let me know if I'm wrong.
timselectric
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The problem is that in those models, the autotransformer is always connected to the load. (In all modes)
But if the autotransformer's center tap is not connected to anything than it's just like any other 240 volts transformer connected to L1 and L2. Tell me what I'm missing.
timselectric
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Yes, if "you" disconnect the neutral.
The inverter doesn't do that.
My setup actually disconnects both L1 and L2, in bypass mode.
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