Load Center Question.

[clayswen]

I am installing a sol-ark 12k with a 9.2k solar array. I have a 200 amp load center. This is grid tie and I will be selling back to the local utility. Do I need a subpanel to line side feed back through the load center? The sol ark has a max continous of 9000 watts. I am in Texas with no shading. I wasn't sure what kw of backfeeding through the load center requires a seperate subpanel> Just seeing what you professionals think before I consider a subpanel.

Here is the one I have.

https://www.lowes.com/pd/Square-D-Homeline-200-Amp-40-Spaces-80-Circuit-Indoor-Main-Breaker-Plug-on-Neutral-Load-Center-Value-Pack/50311165?store_code=75&cm_mmc=shp-_-b-_-prd-_-pro-_-ggl-_-LIA_ELC_000_PRO-_-50311165-_-local-_-0-_-0&gad_source=1&gclid=CjwKCAjw7-SvBhB6EiwAwYdCAclD_Thlae7J9pAhvuMDyLN5Fm4IU9meiKdBCu5eGtvowJGc8hEWdhoCN9IQAvD_BwE&gclsrc=aw.ds

 

[Texican]

this panel has a 200 amp bus bar, and a 200 amp main breaker. this makes the max PV breaker you can use 40A
that is to comply with the 120 rule

your solark 12kw puts out a max of 37.5 amps, multiplied by the 1.25 rule means it needs a 50 amp breaker.
that is too much for a 200 amp panel with a 200 amp main breaker

2 choices
1. get a different panel with a 225amp bus bar with a 200 amp main breaker. this would allow for using up to a 70 amp breaker for PV if you ever add more solar and change your inverter

2. use the panel you listed, but change the main breaker from 200 to 150amps

option1 is the better way to go I would think
the 225a panel costs more, but the other option has you not using the 200a breaker that came with it, and buying a 150a breaker to install

 

[Texican]

jus re read your post, so you already have the 200a panel....
so change out the main breaker to a 150a breaker, and use a 50a pv breaker
no subpanel needed as long as your main panel has room for the pv breaker to be added

 

[clayswen]

Thank you for helping me. I love learning about all this and hopefully after owning a solar system for a couple of years I will be a lot more knowledgeable. Thanks again.

 

[scoharri]

this panel has a 200 amp bus bar, and a 200 amp main breaker. this makes the max PV breaker you can use 40A
that is to comply with the 120 rule

your solark 12kw puts out a max of 37.5 amps, multiplied by the 1.25 rule means it needs a 50 amp breaker.
that is too much for a 200 amp panel with a 200 amp main breaker

2 choices
1. get a different panel with a 225amp bus bar with a 200 amp main breaker. this would allow for using up to a 70 amp breaker for PV if you ever add more solar and change your inverter

2. use the panel you listed, but change the main breaker from 200 to 150amps

option1 is the better way to go I would think
the 225a panel costs more, but the other option has you not using the 200a breaker that came with it, and buying a 150a breaker to install

Not meaning to hijack this thread, but I will be running 4 LV6548's to my down graded off grid 200amp to 150amp service panel. Will the 1.25 rule apply in my case?

 

[Hedges]

Draw a schematic?

But if inverter feeds an off-grid panel (no grid-tied inverter backfeeding a panel that is simultaneously supplied from another source like grid or battery inverter), then 120% rule regarding busbars isn't applicable.

Breaker sizing should still be 1.25x continuous current.

 

[clayswen]

Draw a schematic?

But if inverter feeds an off-grid panel (no grid-tied inverter backfeeding a panel that is simultaneously supplied from another source like grid or battery inverter), then 120% rule regarding busbars isn't applicable.

Breaker sizing should still be 1.25x continuous current.

So if I later on add more solar or another inverter I can just keep derating my main panel? Like change the 150 main breaker to a 100 main breaker? Thats if I have room in the panel right. Maybe I'm ovethinking this.

 

[scoharri]

Draw a schematic?

But if inverter feeds an off-grid panel (no grid-tied inverter backfeeding a panel that is simultaneously supplied from another source like grid or battery inverter), then 120% rule regarding busbars isn't applicable.

Breaker sizing should still be 1.25x continuous current.

 

[kscessnadriver]

jus re read your post, so you already have the 200a panel....
so change out the main breaker to a 150a breaker, and use a 50a pv breaker
no subpanel needed as long as your main panel has room for the pv breaker to be added

He wouldn't have to go to a 150A breaker, he could do a 175A main breaker and be ok.

 

[CRenner]

Check the details on the sticker of the panel. Mine has a 225 bus bar.

 

[clayswen]

He wouldn't have to go to a 150A breaker, he could do a 175A main breaker and be ok.

Could you explain to me how you come to this figure? How do you come to 175A breaker over 150A? Thanks in advance.

 

[Texican]

Could you explain to me how you come to this figure? How do you come to 175A breaker over 150A? Thanks in advance.

he is correct .I did not research to see if a 175 is avbl for his model panel. if avbl thats great. all models have a 150a but maybe not a 175a
the calculation is the bus amps (200 in this case) x 1.2 = 240 amps max. now subtract the PV breaker size (50a in this case) and you have 190a max main breaker allowed, which no one makes, so use next lower size avbl

 

[clayswen]

he is correct .I did not research to see if a 175 is avbl for his model panel. if avbl thats great. all models have a 150a but maybe not a 175a
the calculation is the bus amps (200 in this case) x 1.2 = 240 amps max. now subtract the PV breaker size (50a in this case) and you have 190a max main breaker allowed, which no one makes, so use next lower size avbl

So if later on I bring in another 3-6kw worth of panels to put me aroung 12k total I wont need to drop below the 150a breaker unless I use another 50a pv breaker. Math wise then if I was using a 40a and a 50a pv breaker I would be right at 150 correct?

 

[Hedges]

So if I later on add more solar or another inverter I can just keep derating my main panel? Like change the 150 main breaker to a 100 main breaker? Thats if I have room in the panel right. Maybe I'm ovethinking this.

As Texican said, 120% rule ...

You have a 200A panel. 200A x 120% = 240A total main + backfeed breakers allowed.
240A - 150A = 90A PV breakers allowed other end.
240A - 125A = 115A allowed. This would allow the most backfeed.
240A - 100A = 140A allowed (but backfeed to grid is limited by 100A breaker; 100A x 80% = 80A continuous. 80A x 240V = 19.2kW

 

[clayswen]

As Texican said, 120% rule ...

You have a 200A panel. 200A x 120% = 240A total main + backfeed breakers allowed.
240A - 150A = 90A PV breakers allowed other end.
240A - 125A = 115A allowed. This would allow the most backfeed.
240A - 100A = 140A allowed (but backfeed to grid is limited by 100A breaker; 100A x 80% = 80A continuous. 80A x 240V = 19.2kW

Yes that is what I was thinking. Explained very well. Thank you.

 

[Texican]

So if later on I bring in another 3-6kw worth of panels to put me aroung 12k total I wont need to drop below the 150a breaker unless I use another 50a pv breaker. Math wise then if I was using a 40a and a 50a pv breaker I would be right at 150 correct?

yes, thats right.
also as CRenner mentioned above, look for any stickers or info on the panel that indicates what amp the bus bar is, just to be sure it is 200 vs 225. for example, I just ordered a square D QO panel with a copper 225a bus bar with a 200a main breaker. the square d QO is a more expensive panel than the Homeline, but I have seen some Homeline avbl with a 225 bus bar

 

[Hedges]

View attachment 203107

That could work. No way to isolate any inverter. You could use two, 2-pole or four, 1-pole branch breakers and backfeed them from the inverters.

But I have had problems with breaker resistance affecting balancing (of feed-through from grid). Some inverters need matched wire resistance to balance their outputs when off-grid, others are more forgiving.

With just lugs no breakers between two paralleled inverters on one phase, as you show, should be well matched (use exactly identical wire lengths for both line and neutral.)

 

[scoharri]

Wouldnt

That could work. No way to isolate any inverter. You could use two, 2-pole or four, 1-pole branch breakers and backfeed them from the inverters.

But I have had problems with breaker resistance affecting balancing (of feed-through from grid). Some inverters need matched wire resistance to balance their outputs when off-grid, others are more forgiving.

With just lugs no breakers between two paralleled inverters on one phase, as you show, should be well matched (use exactly identical wire lengths for both line and neutral.)

Wouldn’t the main breaker be the isolation circuit from the inverters?

 

[Hedges]

By "isolate" I meant electrically separate from each other to work on one, or operate without it.
You could shut all down and disconnect wires from one before removing or working on it.

Main breaker isolated breaker panel from inverters so you can work on it.