Really noob dumb question about hybrid inverter wiring

[Tarquinbob]

I have a question that's been bothering me for a while and I haven't seen it answered in any of the hundreds of videos that I've watched, forum posts that I've read or instruction manuals from manufacturers.

When wiring a hybrid inverter, they all have AC input and AC Load Output. My understanding is that the AC load output would be connected to critical loads and the inverter acts as a UPS for those loads. Does that mean that the AC input is actually bi directional and when when there's excess solar it feeds back to the rest of the house and acts as a grid tied inverter?

I'm coming from plug and play systems where the inverter simply plugs in to an AC outlet and backfeeds the grid, but not sure if a hybrid is capable of doing something similar and if I don't need it to operate critical loads in grid down scenarios I can just connect the AC in and a battery?? I would like to have a setup where the priority is for solar to charge the battery and if there's excess solar it feeds to the grid and when there's no solar I want the batteries to output a constant 600-800W even if it means giving some back to the grid for free. I never want to use grid to charge bateries.

Because of the design of my house (fuseboard coming into my living room), the fact that I have 3 phase and the way power is distributed around my house, I've been racking my brain for weeks on a cheap way to add batteries to my basic system. If hybrid inverters work how I hope they work then it's a really easy decision for me to buy one, but every single review video I've seen always show's people connecting up the AC Output Load.

I only use between 10-15kWh/ day on average and my current system is exporting between 2-5kWh/day for free and I'd really prefer to put that into a battery to use at night as most of my loads are in the evening when everyone gets back from work and school.

 

[BentleyJ]

When wiring a hybrid inverter, they all have AC input and AC Load Output. My understanding is that the AC load output would be connected to critical loads and the inverter acts as a UPS for those loads. Does that mean that the AC input is actually bi directional and when when there's excess solar it feeds back to the rest of the house and acts as a grid tied inverter?

Inverters can be divided up into 2 main categories:
Grid-Interactive can sync with the grid and operate in parallel. This means excess solar can be injected back into the grid or can be set up for zero export so only the load is supported, depending on your local utility rules and available net metering agreements. These are the more expensive, sophisticated, full featured inverters and are ideal for self consumption applications where Time-of-Use billing is in place.

Off-Grid Inverters: Do not sync with the grid and do not have sell back functions. While most do have an AC input, this is used for powering loads and charging batteries in Pass-Through mode only. There is no power blending between the utility and the inverter. These are less expensive and can be used for self consumption and TOU billing or simply power the load while Solar and Battery is available then they switch back to Pass-Through. There is a brief interruption in power flow (few mS) due the mechanical relay transition which may not be suitable for some critical loads.

The terminology gets a bit confusing: All-in-One vs. Hybrid vs. Inverter/charger Etc.

I'm coming from plug and play systems where the inverter simply plugs in to an AC outlet and backfeeds the grid, but not sure if a hybrid is capable of doing something similar and if I don't need it to operate critical loads in grid down scenarios I can just connect the AC in and a battery?? I would like to have a setup where the priority is for solar to charge the battery and if there's excess solar it feeds to the grid and when there's no solar I want the batteries to output a constant 600-800W even if it means giving some back to the grid for free. I never want to use grid to charge bateries.

In most cases there is an approval process for installation of a Grid-Interactive, Sell-Back system. Check with your local utility provider. As mentioned above, CT's can be placed on the mains and the inverter can be programmed for near 0 export. Near 0 because in some cases there can be some leakage back into the grid.

Because of the design of my house (fuseboard coming into my living room), the fact that I have 3 phase and the way power is distributed around my house, I've been racking my brain for weeks on a cheap way to add batteries to my basic system. If hybrid inverters work how I hope they work then it's a really easy decision for me to buy one, but every single review video I've seen always show's people connecting up the AC Output Load.

How do you hope it works? A simple diagram would be helpful so we could address your specific case and proposed installation method.

I only use between 10-15kWh/ day on average and my current system is exporting between 2-5kWh/day for free and I'd really prefer to put that into a battery to use at night as most of my loads are in the evening when everyone gets back from work and school.

So you already have a grid-tie system and an interconnect agreement? Then you will need a Hybrid inverter that supports AC coupling.

 

[jpwhit]

I have a question that's been bothering me for a while and I haven't seen it answered in any of the hundreds of videos that I've watched, forum posts that I've read or instruction manuals from manufacturers.

When wiring a hybrid inverter, they all have AC input and AC Load Output. My understanding is that the AC load output would be connected to critical loads and the inverter acts as a UPS for those loads. Does that mean that the AC input is actually bi directional and when when there's excess solar it feeds back to the rest of the house and acts as a grid tied inverter?

I'm coming from plug and play systems where the inverter simply plugs in to an AC outlet and backfeeds the grid, but not sure if a hybrid is capable of doing something similar and if I don't need it to operate critical loads in grid down scenarios I can just connect the AC in and a battery?? I would like to have a setup where the priority is for solar to charge the battery and if there's excess solar it feeds to the grid and when there's no solar I want the batteries to output a constant 600-800W even if it means giving some back to the grid for free. I never want to use grid to charge bateries.

Because of the design of my house (fuseboard coming into my living room), the fact that I have 3 phase and the way power is distributed around my house, I've been racking my brain for weeks on a cheap way to add batteries to my basic system. If hybrid inverters work how I hope they work then it's a really easy decision for me to buy one, but every single review video I've seen always show's people connecting up the AC Output Load.

I only use between 10-15kWh/ day on average and my current system is exporting between 2-5kWh/day for free and I'd really prefer to put that into a battery to use at night as most of my loads are in the evening when everyone gets back from work and school.

Yes, that is the way most hybrid inverters with an AC In and Out connection work if the inverter supports grid export. But there are also hybrid inverters that only have 1 AC connection as well. They are for installations where there is no desire to have a separate backup critical load panel and/or the intention is to backup the whole house, or for when backup isn't desired. Tesla Powerwall, most SMA inverters, and GoodWe offers models for either setup. For that type of inverter setup, if backup is required, you have to have an automatic grid disconnect contactor installed to break the connection with the grid for the backup mode to turn on.

 

[Tarquinbob]

Inverters can be divided up into 2 main categories:
Grid-Interactive can sync with the grid and operate in parallel. This means excess solar can be injected back into the grid or can be set up for zero export so only the load is supported, depending on your local utility rules and available net metering agreements. These are the more expensive, sophisticated, full featured inverters and are ideal for self consumption applications where Time-of-Use billing is in place.

Off-Grid Inverters: Do not sync with the grid and do not have sell back functions. While most do have an AC input, this is used for powering loads and charging batteries in Pass-Through mode only. There is no power blending between the utility and the inverter. These are less expensive and can be used for self consumption and TOU billing or simply power the load while Solar and Battery is available then they switch back to Pass-Through. There is a brief interruption in power flow (few mS) due the mechanical relay transition which may not be suitable for some critical loads.

The terminology gets a bit confusing: All-in-One vs. Hybrid vs. Inverter/charger Etc.

In most cases there is an approval process for installation of a Grid-Interactive, Sell-Back system. Check with your local utility provider. As mentioned above, CT's can be placed on the mains and the inverter can be programmed for near 0 export. Near 0 because in some cases there can be some leakage back into the grid.

How do you hope it works? A simple diagram would be helpful so we could address your specific case and proposed installation method.

So you already have a grid-tie system and an interconnect agreement? Then you will need a Hybrid inverter that supports AC coupling.

I would Hope that I connect as below. In France you can inject up to 3kW back into the grid with no issues and my solar array is under 3kW, so I am never going to exceed that. As my meter sums the usage on all 3 phases, I can inject 1.5kW on a single phase and if my usage on phase 1 is 500W, phase 2 250W and phase 3 250W then my net usage is 0 and I inject 500W to the grid for free.

I want to add a battery to my basic system which is currently connected on a single phase that firstly charges my battery, then dumps the excess into the grid, therefore cancelling my base load during the day and then at night I want to use the battery to supply a constant 600-900W for as long as it lasts to cancel my evening usage which is where most of my electricty is used.

 

[Tarquinbob]

Yes, that is the way most hybrid inverters with an AC In and Out connection work if the inverter supports grid export. But there are also hybrid inverters that only have 1 AC connection as well. They are for installations where there is no desire to have a separate backup critical load panel and/or the intention is to backup the whole house, or for when backup isn't desired. Tesla Powerwall, most SMA inverters, and GoodWe offers models for either setup. For that type of inverter setup, if backup is required, you have to have an automatic grid disconnect contactor installed to break the connection with the grid for the backup mode to turn on.

How do you tell in advance what type you're looking at? I haven't seen any that don't have an in and an out. Certainly the ones on the French market don't appear to make it obvious if they can be grid tied.

 

[jpwhit]

How do you tell in advance what type you're looking at? I haven't seen any that don't have an in and an out. Certainly the ones on the French market don't appear to make it obvious if they can be grid tied.

Assuming adequate technical documentation is available for the inverter you should be able to figure it out. But I'll be the first to say that a lot of technical documentation for inverters leaves a lot to be desired. Most inverter makers offer paid training for installers. So sometimes I think they leave vagueness in the documentation on purpose.

 

[BentleyJ]

There are others on the forum with more experience in European equipment. SRNE seems to be a popular brand.
A 3 phase grid-interactive, hybrid will work per the attached drawing. A critical loads panel could be connected to the AC Output but is not necessary. Excess solar will just get pushed back to the grid as there will be 0 load on the output.

 

[ramandi]

There are others on the forum with more experience in European equipment. SRNE seems to be a popular brand.
A 3 phase grid-interactive, hybrid will work per the attached drawing. A critical loads panel could be connected to the AC Output but is not necessary. Excess solar will just get pushed back to the grid as there will be 0 load on the output.

The new SRNE model also makes it possible to do “battery to grid” and my older SRNE does not have this capability. I am now looking into any solution or way to use that as an option. Is that possible at all? For example can we modify the firmware or use some debug mode or access some deeper level registers via RS485?

 

[ramandi]

I forgot to mention that my existing SRNE has “PV to grid” option already. But not “battery to grid” which i really loce to have