400a main panel needed?

[Subestile]

first of likely many questions with this project of adding to my existing system.

I currently have 20 rec370 panels on iq7+ inverters (30.25a) and a 200a solar ready main panel with a 70a breaker on the solar.

I am going to add 31 455w panels on iq7A inverters (44.95a) all will go to the same combiner box (still assuming that this will work with the single existing combiner with reworking the bridges)

am I going to have to go to a 400a main panel to support this level of amps going to the main panel due to the backfeed 120% rule? currently working on the diagrams to submit to SRP for the expansion permits.

Edit: derating the main breaker to 150a seems to be my most viable option as long as I am understanding it correctly would give me a backfeed max of 90A

 

[zanydroid]

How much does the panel specs say can you backfeed into the solar breaker? The point of solar ready is to have an pre-engineered solar backfeed location so you don’t need to use a generic rule like 120%

120% rule is not the only game in town. It becomes a question of learning yourself how to design and draft m the plans correctly using the more complicated rules in 705.12 or hiring someone who is willing to do it for you; vs just ponying up the $$ for a 400A panel.

You can also use conductors + taps to build your own busbar. This however would probably still require adding a subpanel and moving circuits from the main to the subpanel.

 

[zanydroid]

Of course you should still look up what your solar ready panel allows for max backfeed.

Another option is 225A busbar panel, that might be cheaper than 400A or 320A

225*1.2=270

 

[Hedges]

Here's my approach, a 200A main breaker only. No busbar for 120% rule, use Polaris to split for multiple panels.

Square D QO 200 Amp 2-Pole Outdoor Circuit Breaker Enclosure with QOM2200VH Breaker QOM2E2200NRB - The Home Depot

The Square D by Schneider Electric QO 200 Amp Outdoor Circuit Breaker Enclosure includes a two-pole QOM2 frame sizes circuit breakers 100-225 amp capacity for use as an exterior disconnect. This breaker

www.homedepot.com

It will feed 100A disconnect for PV, 200A panel for house, 125A panel for backup loads (generator interlock switch to select battery inverter vs. grid feed.)

 

[zanydroid]

200a solar ready main panel

Highly recommend posting a picture of the panel (EDIT: as installed), the FULL & LEGIBLE wiring diagram sticker etc (saves us time googling leaving time to help), and panel model number.

EDIT2: also with that many panels that’s a lot of money on microinverters, you might consider APsystems or Hoymiles HM1500 multiport microinverters (save money vs new IQ7A). Or even a SolArk (slightly more). EDIT3: or NEP. I’m only personally familiar with the HM.

 

[Subestile]

Highly recommend posting a picture of the panel (EDIT: as installed), the FULL & LEGIBLE wiring diagram sticker etc (saves us time googling leaving time to help), and panel model number.

EDIT2: also with that many panels that’s a lot of money on microinverters, you might consider APsystems or Hoymiles HM1500 multiport microinverters (save money vs new IQ7A). Or even a SolArk (slightly more).

I believe its a 100a solar bus. Its less cost effective to change the existing enphase system and go to a different inverter setup I did the breakdown. Less than 3k for the iq7a inverters I needed vs ~16k for two 12k solarks that would be needed for the 21.5kw of panels

 

[zanydroid]

Dont your new microinverters fit in 100A, along with your old? 31+45, works even if you gave the AC nameplate (125%) and not breaker size. Change the feeder from the combiner panel to larger conductors. Combiners most likely are 100A or 125A busbar, and also small and easy to change.

No reason to go to two 12k/switch out existing microinverters except for consistency.

It’s not clear that a residential setup has enough complexity/scale that single pane monitoring via having everything one brand will buy you much from an operational efficiency angle. And you might be able to merge two systems with Home Assistant or other third party software into a single view. Plus how often would you even be looking at the monitoring on grid tie after commissioning, except for fun (which I do every other day but that’s a irrational personal failing)

 

[zanydroid]

Hmm I wonder if the solar breaker (which is effectively almost like line side tap) can be combined with 120% rule to yield 140A max solar breakers on a 200A main breaker

 

[Hedges]

I think so. Nothing gets overloaded doing that.

It appears they do NOT allow you to draw any current on M1, because together with 200A main breaker, more than 200A would go through meter socket. So you can't feed a hybrid from M1.

 

[zanydroid]

I think so. Nothing gets overloaded doing that.

It seems OK to me. It might be extra annoying to get through code review though because it's somewhat out of the ordinary. I'm having issues with only a slightly weird thing on my current code review (2 different kinds of solar panels instead of 1 like normal people, how exotic ) causing two extra resubmission (so far), and solar breaker +120% rule is much more exotic than that.

It appears they do NOT allow you to draw any current on M1, because together with 200A main breaker, more than 200A would go through meter socket. So you can't feed a hybrid from M1.

Yeah, that is a good catch.

 

[Shimmy]

Really should look at an AIO rather than microinverters at that level of capacity. Batteries make everything work much better and give you an easy way to fit within existing equipment.

 

[Subestile]

Really should look at an AIO rather than microinverters at that level of capacity. Batteries make everything work much better and give you an easy way to fit within existing equipment.

system already has a tesla battery.

 

[zanydroid]

With SolArk adding incremental battery capacity is MUCH cheaper than with PowerWall.

With PowerWall each increment requires paying for the embedded inverter, plus other markup.

With SolArk you can do UL9540 installation with server rack batteries, at ~$1.5k/5kWh (plus shipping and racking), and you can choose to scale the inverter independently of battery capacity.

 

[Subestile]

With SolArk adding incremental battery capacity is MUCH cheaper than with PowerWall.

With PowerWall each increment requires paying for the embedded inverter, plus other markup.

With SolArk you can do UL9540 installation with server rack batteries, at ~$1.5k/5kWh (plus shipping and racking), and you can choose to scale the inverter independently of battery capacity.

the tesla battery is already in with the original system, unless someone wants to buy it not really worth the time/effort to remove it and change it at this point unfortunately. also its a tesla powerwall 2 not a powerwall plus. no inverter in mine

 

[zanydroid]

I thought all PowerWalls are AC coupled. IE have an AC STORAGE (EDIT added clarification) inverter, specifically a grid forming one. They have to be AC Coupled (EDIT clarified), to work with your IQ7+'s, right?

Powerwall+ has an integrated SOLAR inverter.

Does it need to be removed? Depends on how they can interop when grid tying, it's a little dicy. Check out EG https://diysolarforum.com/threads/e...f-installer-hurdles.56267/page-12#post-803443 for some theorycrafting in the latest message.

 

[Subestile]

I thought all PowerWalls are AC coupled. IE have an AC STORAGE (EDIT added clarification) inverter, specifically a grid forming one. They have to be AC Coupled (EDIT clarified), to work with your IQ7+'s, right?

Powerwall+ has an integrated SOLAR inverter.

Does it need to be removed? Depends on how they can interop when grid tying, it's a little dicy. Check out EG https://diysolarforum.com/threads/e...f-installer-hurdles.56267/page-12#post-803443 for some theorycrafting in the latest message.

great question, that I do not have an answer for but I know the person that physically sourced every single part for the Powerwall while working for tesla I can ask him.

 

[zanydroid]

great question, that I do not have an answer for but I know the person that physically sourced every single part for the Powerwall while working for tesla I can ask him.

You can probably ask here too.

It's more of a firmware programming question than a component question. If you parallel two PowerWalls together, that is certainly a supported combination, and they probably have a parallel stacking cable to ensure that they share the load equally, among other things. If you couple a PowerWall with another grid forming inverter, probably the lowest common denominator is that one discharges completely, followed by the other. There are some inverters that would theoretically be capable of doing battery inverter output in parallel with another AC source (these are used for peak shaving or generator assist), but probably not that many people out there using this combination. Actually most vendors allow paralleling two of their AC batteries together. Because that makes them more money, if they can sell you more than one

Thinking about this some more, having two grid forming batteries from two different vendors seems like too much of a science experiment, involving complex product behavior. Unless one of the vendors explicitly has tested & documented making the combination work together.

Are you aware of the limits that Tesla officially places on the amount of AC solar that you can put on a single PowerWall (this limit is present in the vast majority of AC coupled batteries)? You are adding a lot of solar in your plan.

You will have to figure out a way to avoid violating those, I think it probably involves tying in the inverters in excess of the limit outside whatever disconnect relay the PowerWall uses to drop from grid. I'm not sure if this is officially supported.

 

[Shimmy]

the tesla battery is already in with the original system, unless someone wants to buy it not really worth the time/effort to remove it and change it at this point unfortunately. also its a tesla powerwall 2 not a powerwall plus. no inverter in mine

The question is ultimately why are you adding the additional solar. Do you have some new daytime load that you want to power?

You can make your new system independent of the Enphase/Tesla system if you so desire, or you can expand the existing. You would likely need to go to 400A if you kept going down the existing path, which will require additional investment on the Tesla side.

Or you could install a SolArk 15k or EG4-18kPV with a server rack or two of batteries to support a critical loads panel (or base loads panel) downstream. It really comes down to why are you adding the PV.

Either way is a it messy--you end up with stranded backup capacity. The problem is smaller with the AIO inverter though.

 

[Subestile]

The question is ultimately why are you adding the additional solar. Do you have some new daytime load that you want to power?

You can make your new system independent of the Enphase/Tesla system if you so desire, or you can expand the existing. You would likely need to go to 400A if you kept going down the existing path, which will require additional investment on the Tesla side.

Or you could install a SolArk 15k or EG4-18kPV with a server rack or two of batteries to support a critical loads panel (or base loads panel) downstream. It really comes down to why are you adding the PV.

Either way is a it messy--you end up with stranded backup capacity. The problem is smaller with the AIO inverter though.

the system was never done correctly to begin with, I am in az and it was improperly sized for my house to meet the summer demands, honestly if they would have been honest when selling the system I never would have done solar initially. Ill have to look into the battery issue this was not something I was aware would have been an issue. I have considered a second battery anyways just really was not wanting to spend the money on a second one at this point.

 

[Shimmy]

the system was never done correctly to begin with, I am in az and it was improperly sized for my house to meet the summer demands, honestly if they would have been honest when selling the system I never would have done solar initially. Ill have to look into the battery issue this was not something I was aware would have been an issue. I have considered a second battery anyways just really was not wanting to spend the money on a second one at this point.

If you want to stick with Tesla/Enphase then there are other options, like a generation panel with a 200A main and 200A subfeed (back to all your existing loads) that all your solar and battery tie into. That panel can have a 400A bus and not require major re-work. At 21.5kW of PV though the utility might have some issues; most states limit you to <~16kW grid tied.