Not understanding grid-tied power priority

[inowhavesolar]

Hello. Newbie here. I'm having a hard time understanding how a grid-tied inverter setup works without completely rewiring my main breaker panel. Here is my rudimentary diagram. My electric company does not do credits for surplus. Still, as I understand it, a grid-tied system can "slow down" the meter spin and use the solar power first. But again, how does "solar power" get priority if everything is in one breaker box?

I have a 200 amp mains panel. Breakers B-H go to various things around the house. From the videos I've watched, I would use breaker A to output A/C to the inverter. I would also connect the solar panels, and batteries to the inverter. The inverter would output A/C from solar/batteries onto line P. If there isn't enough solar, or batteries are low, the inverter will "top up" any demand using mains. Am I correct so far?

So, where does wire 'P' connect? This is the inverter A/C output, coming from solar/batteries/mains. Do I add another breaker 'J' into the main panel and wire in the inverter output there? Doesn't that create a loop? How do breakers B-H know to use the power coming from line P vs coming from mains? It seems like I would have to add a new panel, relocate breakers B-H to it plus J. The main panel would then only have incoming grid and breaker A to the inverter. The subpanel would have incoming A/C breaker J from the inverter, and breakers B-H for everything else in the house. But I haven't really seen anyone do this in their setups.

 

[McKravitts]

Make and model of inverter/charger?

 

[BentleyJ]

Hello. Newbie here. I'm having a hard time understanding how a grid-tied inverter setup works without completely rewiring my main breaker panel. Here is my rudimentary diagram. My electric company does not do credits for surplus. Still, as I understand it, a grid-tied system can "slow down" the meter spin and use the solar power first. But again, how does "solar power" get priority if everything is in one breaker box?
View attachment 159466
I have a 200 amp mains panel. Breakers B-H go to various things around the house. From the videos I've watched, I would use breaker A to output A/C to the inverter. I would also connect the solar panels, and batteries to the inverter. The inverter would output A/C from solar/batteries onto line P. If there isn't enough solar, or batteries are low, the inverter will "top up" any demand using mains. Am I correct so far?

Yes

So, where does wire 'P' connect? This is the inverter A/C output, coming from solar/batteries/mains. Do I add another breaker 'J' into the main panel and wire in the inverter output there? Doesn't that create a loop? How do breakers B-H know to use the power coming from line P vs coming from mains? It seems like I would have to add a new panel, relocate breakers B-H to it plus J. The main panel would then only have incoming grid and breaker A to the inverter. The subpanel would have incoming A/C breaker J from the inverter, and breakers B-H for everything else in the house. But I haven't really seen anyone do this in their setups.

You are missing a KEY component in your diagram. That style of Battery back-up Hybrid Inverter/Charger has an AC input (Breaker A) and a separate AC Output (P) that would have to be connected to a newly installed critical loads subpanel for things like your refrigerator, freezer, router, some lights, couple of receptacles, medical equipment, well pump Etc.

If the Inverter/charger is large enough or 2 or more are stacked you could back-up your whole house via the main panel but you would have to remove the utility input from your main breaker and route it directly to the inverter AC input (would need a new main breaker). Then inverter AC output (P) could be connected to the main breaker in the main panel.

 

[cdherman]

In a conventional grid tie system, your "A" breaker feeds power in both directions. The grid tied inverter sees the grid, matches the frequency etc and starts putting power back into your main panel. If you produce too much, it does not get used up by your other loads, B-H and it goes back into your meter and out to the grid.

Your diagram adds batteries. So you are likely contemplating a hybrid system. If it is practical, you can do exactly what you desicribe: Move B-H to a new subpanel. Your diagram cannot really work -- in a system with batteries (unless you are just wanting to load shift due to a TOU situation) there is an assumption that when the main power is lost, your inverter will still power things. BUT -- in your drawing, such an event, powering your panel via "A" would feed back power into the grid. Big no-no when the grid goes down.

And yes, a "J" breaker back in the main panel would create a similar loop, and be similarly dangerous.

 

[drewb42]

Hello. Newbie here. I'm having a hard time understanding how a grid-tied inverter setup works without completely rewiring my main breaker panel. Here is my rudimentary diagram. My electric company does not do credits for surplus. Still, as I understand it, a grid-tied system can "slow down" the meter spin and use the solar power first. But again, how does "solar power" get priority if everything is in one breaker box?
View attachment 159466
I have a 200 amp mains panel. Breakers B-H go to various things around the house. From the videos I've watched, I would use breaker A to output A/C to the inverter. I would also connect the solar panels, and batteries to the inverter. The inverter would output A/C from solar/batteries onto line P. If there isn't enough solar, or batteries are low, the inverter will "top up" any demand using mains. Am I correct so far?

So, where does wire 'P' connect? This is the inverter A/C output, coming from solar/batteries/mains. Do I add another breaker 'J' into the main panel and wire in the inverter output there? Doesn't that create a loop? How do breakers B-H know to use the power coming from line P vs coming from mains? It seems like I would have to add a new panel, relocate breakers B-H to it plus J. The main panel would then only have incoming grid and breaker A to the inverter. The subpanel would have incoming A/C breaker J from the inverter, and breakers B-H for everything else in the house. But I haven't really seen anyone do this in their setups.

Check this picture out. see the sub panel middle top that is where p goes in my setup

 

[inowhavesolar]

If you produce too much, it does not get used up by your other loads, B-H and it goes back into your meter and out to the grid.

I think I would need to prevent this since my meter can't "spin" backwards and it would end up adding to my bill would it not? I'm still not understanding how breakers B-H use the power from the inverter before power from the grid. If it's a just electrons, how does inverter A/C get priority over grid A/C?

Make and model of inverter/charger?

Any of the many grid-tied ones out there. I have not purchased yet. I'm still trying to learn my options.

If the Inverter/charger is large enough or 2 or more are stacked you could back-up your whole house via the main panel but you would have to remove the utility input from your main breaker and route it directly to the inverter AC input (would need a new main breaker). Then inverter AC output (P) could be connected to the main breaker in the main panel.

Thank you. This is exactly what I thought I would need to do in order to isolate the power. This would be the eventual plan, two grid-tied inverters to do split phase for the entire house. If it's a cloudy day, the inverters would pass-through A/C mains to the new sub-panel, and if it was super sunny, the solar/batteries would be used?

 

[#40Fan]

I think I would need to prevent this since my meter can't "spin" backwards and it would end up adding to my bill would it not? I'm still not understanding how breakers B-H use the power from the inverter before power from the grid. If it's a just electrons, how does inverter A/C get priority over grid A/C?

Think of the power coming into the panel as a water hose.

Your inverter would be another water hose.

If your inverter can create more water pressure than the power coming to the panel, it will push the water back out.

Turning the meter backwards would happen with older style meters, but todays are (mostly) all electric and smart enough to know which way the power is flowing.

 

[inowhavesolar]

If your inverter can create more water pressure than the power coming to the panel, it will push the water back out.

That makes sense. Thanks for the analogy.
I do have an electric meter, but it's not a special kind of net meter, AFAIK. It's my understanding you have to have a special kind to do net metering, right? As I said above, my elec company doesn't do credits/buy-back, but if my elec meter is smart enough to know there's more "pressure" on my side, then it will just slow down and/or stop any incoming from grid? I've read horror stories of people pushing back to the grid excess but still getting charged because their dumb meter just sees power flowing.

 

[#40Fan]

I don't know enough about the meters to answer those questions.

I do know that it can be quite the hassle when going the net-metering route (back feeding to make money) because of the legalities, insurance differences (increases likely), etc.

Stick with an All In One that will take Breaker A, feed the AIO which will feed Breaker B-H through P on a separate box, and you won't have to worry about any of it.

 

[cdherman]

Interestingly, when I first installed my system in 2009, for a couple weeks, I still had the old meter. Utility did not complain, we had asked. It was a spinning disc, but with remote read. Well the disk did indeed spin backwards and the numbers, analog, went backwards.

BUT, the remote read sensor just saw the number of time the hall magnet (I assume) passed the sensor! So I got a massive bill. Billed for every KW I produced and every KW I used. No mater which way the meter was turning, I got billed! It was like $120, even though I actually turned the meter backwards. I just paid it. At that point, KCP&L was on the verge of sending me a $8,100 check (they had a $1 per watt installed rebate going) and I was not thinking of messing with my situation.

All in the past.

To the O.P point. Unless you have a net metering contract, most utilities frown on putting power back into the grid these days, indeed.

 

[BarrieM]

And of course with a modern AIO you set the priority of the feed in the software. SBU (solar, battery, utility ) or SUB ( solar, utility, battery). The inverter then does it for you automatically without any transfer switches etc.

 

[inowhavesolar]

And of course with a modern AIO you set the priority of the feed in the software. SBU (solar, battery, utility ) or SUB ( solar, utility, battery). The inverter then does it for you automatically without any transfer switches etc.

That's awesome! Do you have any specific make/model recommendations? I'm still researching my options.

 

[BarrieM]

I use an Orient Power 7.2kw AIO but it's just a rebadged EG4.

 

[bfaubion]

@desiresolar @cdherman I have a similar question for my setup. I'm looking at buying an EG4 6000xp. It has maximum 50 amp passthrough, I think it could work for me for the whole house (but maybe not). I use gas appliances and heating. The exception is an oven which is 220, and of course my A/C compressor/blower unit.

I have an exterior main panel next to the meter, and inside my house I have the sub-panel, everything is connected there. In my main exterior panel, I have 2 slots for large breakers (whole house I guess) - one is a 200 amp breaker, and one slot is empty.. I'm wondering if that means an electrician would somehow be able to connect the inverter there.

First main breaker takes in utility, THEN goes to the inverter, THEN the inverter load connects the line that goes to the sub-panel. Maybe a second breaker there isn't needed, since the 6000XP has breakers on the input/output. From what I understand, the inverter physically interrupts the line between the main panel and my sub-panel?

OR, is it that I must add a new critical loads sub-panel, which receives the load from the inverter and goes to select circuits? So essentially part of the home still gets powered by grid directly on my existing sub-panel, and will always take up the utility power, and the other part that is connected to the inverter and critical load will fluctuate between grid/solar/batter as the software determines.