Limited to 100 amp service from utility - options for more PV?

Short_Shot said:

Honestly I've never heard of this limitation of 20a breakers in a 100a panel.

That's certainly not an issue here, as I've got 30a breakers in place for my stove and hvac and the 10 awg wiring to go with it.

So just for my curiosity (you certainly don't need to bother to reply if you're strapped for time):

I've never touched a grid tie system myself so I'd like to learn how the connection is physically made.

Is this only related to "PV"? I've always thought pv means panel voltage, which of course wouldn't be in your utility breaker box.

I assume you are just referring to the solar system as "pv" and this is the inverter tie in breaker?

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Yes, I mean "PV" as photo-voltaic i.e. solar panels. Sorry for the confusion!

jmzorko said:

Yes, I mean "PV" as photo-voltaic i.e. solar panels. Sorry for the confusion!

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Oh yeah duh. That makes sense lmao

So yeah the PV tie in of course would be after the inverter. That's what I get for replying while half asleep.

Great thread. Please keep us posted. I’m in the middle of planning to install a 100 amp underground ($) service with a 200 amp panel to allow for future solar install. I’m going to send this thread to the electrician.

jmzorko said:

I've been told by a few local electricians (including one who is a neighbor and knew the previous owner) that the 100 amp main panel can only have a 20 amp PV breaker, limiting me to a 4-ish kw PV system.

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Short_Shot said:

Honestly I've never heard of this limitation of 20a breakers in a 100a panel.

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The limitation is a 20A PV breaker in a breaker panel with 100A rated busbar and 100A main breaker.
That's 20A + 100A of sources putting current into a 100A busbar.

(You could overstuff a 100A panel with 10x 50A breakers and that would never make busbar exceed the 100A available through main breaker.)
But if you put 20A PV breaker right next to 100A main breaker, there would be 120A available to flow through busbar, causing 1.44 times the temperature rise.

Yet if you put a 100A PV breaker at far end of the busbar, together with 100A main breaker there would be 200A available for loads and the busbar would never carry more than 100A, because current flowing in opposite directions would cancel.

The NEC authors knew a large PV breaker at far end would not be a problem, but were afraid it might later get relocated to near end. Allowing main breaker + PV breaker to total 120% of busbar rating was a compromise to allow PV to be added to existing panels where main breaker rating is equal to busbar rating.


OP's photo doesn't show a breaker panel. It shows what is probably a meter panel, with 100A disconnect, and a second position that has a 20A PV disconnect.

1) I think up to a 100A PV disconnect in place of the 20A would not cause an (technical) problem, so long as it was only a source of power not a consumer. Don't want 100A load from main disconnect and house while drawing additional load on 100A PV disconnect. SolArk is bidirectional, so problem is it could draw current (for protected loads or battery charging.) If strictly grid-tie PV inverter, I don't see a (technical) problem.

Some utilities allow a "line side tap" of up to 40A breaker. That's an additional 40A breaker connected between meter and what is usually a 100A main disconnect on customer's breaker panel. Replacing your 20A PV breaker with 40A would be like that. But for bidirectional SolArk might overheat utility drop wires.

2) We don't have details on breaker panel. With suitable busbar rating it could have up to 100A PV breaker on it. It would either receive up to 100A from grid, or backfeed up to 100A from grid (utility agreement will have a limit on backfeed due to their system planning and grid stability.)

This is where I said, "Just put in a 200A panel and you can have up to 100A PV breaker."

3) Not using that 20A PV breaker, could tap off that 100A breaker to feed two panels. One is the existing breaker panel, another would feed Sol-Ark. Instead of a panel, could just be fused for Sol-Ark. If you do this, 100A from main breaker + ??A from Sol-Ark are available to go to breaker panel and the wire feeding it. This could easily be excessive. I would put a suitable main breaker in (or fuse before) the breaker panel, likely 100A.

Yeah that makes sense.

So simply putting in a larger rated panel solves the issue, while upgrading to 200a service just gives you potentially the same issue if the new panel is only rated for 220a for example.

What worked for me was I have a Square-D QO panel with 225A busbar rating and 200A main breaker, so I'm allowed 70A PV breaker.
That was sufficient for any reasonable PV production.

But if I want a hybrid or similar setup, the 70A limit works both ways. And with 80% loading, 70A breaker should only feed 56A continuous.
I prefer to have 100A or greater feeding my house. My inverters are good for 56A continuous but can be stacked & paralleled for 120/240V 112A.

Because I have a 200A main breaker in the meter panel and 200A breaker in breaker panel, I can tap off in between with a 100A fused disconnect. (The inverters are each fed through 63A DIN rail breakers.)
The house with its 100A panel is now fed from the inverters. Or I can throw some interlocked breakers to bypass inverters (in case of failure) and feed house from the 200A panel. Other interlocked breakers let me feed 200A panel from inverter, for my workshop.

In normal operation, house is on UPS and workshop has manual transfer switch. Only trick is not leaving excessive house loads on if running from batteries; I need to automate disconnecting them.

Hedges said:

What worked for me was I have a Square-D QO panel with 225A busbar rating and 200A main breaker, so I'm allowed 70A PV breaker.
That was sufficient for any reasonable PV production.

But if I want a hybrid or similar setup, the 70A limit works both ways. And with 80% loading, 70A breaker should only feed 56A continuous.
I prefer to have 100A or greater feeding my house. My inverters are good for 56A continuous but can be stacked & paralleled for 120/240V 112A.

Because I have a 200A main breaker in the meter panel and 200A breaker in breaker panel, I can tap off in between with a 100A fused disconnect. (The inverters are each fed through 63A DIN rail breakers.)
The house with its 100A panel is now fed from the inverters. Or I can throw some interlocked breakers to bypass inverters (in case of failure) and feed house from the 200A panel. Other interlocked breakers let me feed 200A panel from inverter, for my workshop.

In normal operation, house is on UPS and workshop has manual transfer switch. Only trick is not leaving excessive house loads on if running from batteries; I need to automate disconnecting them.

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I started looking into the Square-D 200 amp panels, and found this one: https://www.lowes.com/pd/Square-D-2...ug-On-Neutral-Load-Center-Value-Pack/50311165

Question: Right now the 20 amp PV breaker is installed alongside the 100 amp breaker in the main panel outside (the one in the photo I posted earlier in this thread). That panel feeds the panel in the garage with all of the other breakers (lights, appliances, etc) in it. If I were to replace the panel in the garage with the Square-D 200 amp panel above, could I move the PV breaker from the panel outside to the Square-D panel, thereby allowing me to put a 50 amp breaker in it and connect a lot more solar? Is there a reason for the 20 amp PV breaker being installed alongside the 100 amp breaker in the outside panel connecting me to PG&E?

On another note, the Sol-Ark is installed (though it's currently only doing what the previous Delta inverter was doing i.e. connected to the same 3kw array). I've not attached any of the batteries to it yet though, bc that outside PV breaker is only 20 amps.

Can you move the breaker inside? I believe it would be required to go 50 amp.

time2roll said:

Can you move the breaker inside? I believe it would be required to go 50 amp.

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That's exactly what i'm asking (unless I misunderstand). The 20 amp PV breaker is currently installed alongside the 100 amp breaker in the outside panel (the one connecting me to the utility). If I upgrade the panel in the garage to 200 amps, can I move the PV breaker from the outside panel to the garage panel and hence use a 50 amp breaker for PV?

jmzorko said:

I started looking into the Square-D 200 amp panels, and found this one: https://www.lowes.com/pd/Square-D-2...ug-On-Neutral-Load-Center-Value-Pack/50311165

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That one is indoor use only. It is also the "Homeline" series with aluminum bus. Several other brand breakers fit.
I prefer "QO" series with copper bus. More money, but better quality.

jmzorko said:

That's exactly what i'm asking (unless I misunderstand). The 20 amp PV breaker is currently installed alongside the 100 amp breaker in the outside panel (the one connecting me to the utility). If I upgrade the panel in the garage to 200 amps, can I move the PV breaker from the outside panel to the garage panel and hence use a 50 amp breaker for PV?

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If you put a 200A panel in, if that has a 200A busbar and 200A breaker, possibly you would be allowed only 40A PV breaker.
If it had main lugs not breaker, possibly the 100A breaker at meter would allow up to 140A PV.
(Of course, the 100A breaker limits current either way, just not clear on where OCP has to be to be interpreted by inspector.)

You can get a smaller breaker, 150A. Then you could have up to 90A PV on 200A busbar.

If you get QO panel which has 225A busbar, 200A main plus 70A PV is allowed.

Hedges said:

That one is indoor use only. It is also the "Homeline" series with aluminum bus. Several other brand breakers fit.
I prefer "QO" series with copper bus. More money, but better quality.



If you put a 200A panel in, if that has a 200A busbar and 200A breaker, possibly you would be allowed only 40A PV breaker.
If it had main lugs not breaker, possibly the 100A breaker at meter would allow up to 140A PV.
(Of course, the 100A breaker limits current either way, just not clear on where OCP has to be to be interpreted by inspector.)

You can get a smaller breaker, 150A. Then you could have up to 90A PV on 200A busbar.

If you get QO panel which has 225A busbar, 200A main plus 70A PV is allowed.

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I definitely would prefer it passing inspection, and i'm not opposed to getting permits if required. How does indoor use vs. outdoor use inform the decision? Is it against code to put a PV breaker on an indoor panel?

jmzorko said:

I definitely would prefer it passing inspection, and i'm not opposed to getting permits if required. How does indoor use vs. outdoor use inform the decision? Is it against code to put a PV breaker on an indoor panel?

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Not sure on that one. Wouldn't think that is any problem itself.
Utility may want a disconnect they can reach to prevent backfeed. Or maybe these days they rely on yanking meter.
May be required to have a disconnect near inverter; is that to be indoors or out?

And then PV DC disconnect maybe is supposed to be outside, cutting power from reaching house. I'm not sure. Yours probably predates RSD, so only a mechanical switch would disconnect it.

You could see if your city has PV requirements info on line.

I think we're allowed to replace "equipment" without a permit. Of course adding breaker panels goes beyond that.

OK, I had an installer install the Sol-Ark 5k and connect it via MPPT1 to my existing 3kw array. He did a great job, and so far it's working well. I've the batteries in my garage, though not connected to the Sol-Ark bc i'm waiting for a cable to be delivered. I've also 10 300w Hyundai panels that I already verified will work on the other MPPT in the Sol-Ark, which would give me 6kw when installed. I also believe that the 90a main / 30a PV breaker plan on the main electrical plan will work.

I want to learn as much as I can, and - being far from the brightest bulb on the string (please forgive the bad pun) - I learn best by doing. So, I want to do as much as I can myself. Things i'll need professionals for include:

1. high-voltage electrical
2. solar plans and diagrams
3. electrical plans to add the critical loads panel and stuff

I've reached out to someone locally who says they can do #2, and i'll be able to use their plans to get the permits from the city. I'm looking for someone to do #3, as I assume i'll need permits for that as well.

Am I missing anything? My journey of learning (and hopefully not dying) in the pursuit of a better PV system continues.

Did you end up upgrading your panel to a 200amp rated busbar with a 100amp service?

Balake said:

Did you end up upgrading your panel to a 200amp rated busbar with a 100amp service?

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No, but I found out that the panel was actually rated for 125a, even with my 100a service. So, I was able to put a 30a breaker in there to handle the additional 3kw of PV that will be going up there soon. The permit hasn't been approved yet, but the designer tells me that it should be.

jmzorko said:

Hello, all ...

My home has 100 amp service from PG&E and I have a small 3kw PV array that came with the home that I would like to expand to 6-7kw. In a previous home, I just had the main panel upgraded and all was well, but with this home, the electrical service from the utility is underground. From what I've read, this could make a main panel upgrade far more expensive due to the digging involved.

Yet, 3kw is nowhere near enough to cover my needs. What options are there to expand the PV given the limitations of my 100 amp service? The inverter I'm planning to use is the Sol-Ark 5k, and I'm leaning toward the Fortress Power eFlex batteries. I also want the capability to run off-grid for extended periods if required (due to a bad experience in my last home that required us to be disconnected from PG&E for 3 months, where we lived off just solar and battery).

Regards,

John

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Go off grid. No worries. Expand to your hearts content.

jmzorko said:

No, but I found out that the panel was actually rated for 125a, even with my 100a service. So, I was able to put a 30a breaker in there to handle the additional 3kw of PV that will be going up there soon. The permit hasn't been approved yet, but the designer tells me that it should be.

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Hi jmzorko, I am wondering how you found out that the panel is rated for 125A? I also would like to know if my panel is rated for 100A or 125A. Unfortunately I do not have the sticker that provides this information.

Thanks,

The sticker was still visible on my main panel (Challenger SMB12), and it indicated 125 amps max.

vbalik said:

I also would like to know if my panel is rated for 100A or 125A. Unfortunately I do not have the sticker that provides this information.

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Are there any model numbers stamped on the case? The main breaker should have a number. The operative issue is also the bus bar rating. Sometimes a panel will have a 100 Amp breaker and a 125 Amp bus bar.
There are also some workarounds using sub panels if you are trying to add more solar capacity. Those may have been discussed throughout this thread but I did not give it a thorough read.
What are you trying to accomplish? More solar or just more circuits?