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diy solar

Please help me with panel placement

ArthurEld

Solar Wizard
Joined
Aug 3, 2020
Messages
2,271
Location
Palm Harbor, Florida
I've been working on my solar panel layout and I need to know if there is anything wrong with my ideas.
It seems doable to me but I don't have any experience.
Please tell me what you think. I really want to be comfortable with my ideas before I apply for permits and order everything.
I will start a thread about my complete system next but it is clumsy for me to draw this stuff up so it will be a while.
There are 8 panels on the east side, 20 panels on the west. 3 south and 5 southwest. There are 8 panels with micro inverters.
The rest will have optimizers. I don't have much shade and when I got quotes they said I get a lot of sun and I don't need to worry about shade.
But it's only $14 extra per panel for optimizers because I already have Tico rapid shut down modules.

36 Qcell 330 watt panels.
panel layout.pngsunroof.png
 
Panels go wherever you put them. Knowing their performance is the key.

Use link #6 in my signature to evaluate every individual group of panels. Add them up, and and you can assess the performance of the total system.
 
Do you know the maximum watts/amps you'll be able to feed into your breaker panel?
Many 200A panels have a limit of 40A breaker, 32A current backfeed, and you may be approaching that with your panels.
Some will accommodate 70A. Line-side tap can let you hook up more.

Various orientations or tilt could reduce the peak and spread it over the day or seasons to fit under any limits.
Time of use rates may make different orientations preferable.

Fireman access rules may require 3' from panels to roof ridge and side, 3' between panels at valleys.
 
If you want a visual overhead view, check this out - just put in your address:

Also, once you have your address in there - use the center marker to position where you would like your panels to be, you can rotate also.

You can also view sun angle degrees with a specific spot..etc.

You can also pick any date and see what that might be, like for official solar winter..etc.
 
In my area, if rooftop panels are low (less than about 12" or maybe 18" above) and weight per attachment point is less than 40 pounds, then we don't need a structural permit. And we can get an expedited PV permit on-line. No one looks at the drawings until the inspector comes to see finished installation. You just need enough feet or standoffs to meet that. (and then if you can measure to lag screw into rafters and not just shakes/tar paper or whatever you've got, it will be really strong.)
 
Panels go wherever you put them. Knowing their performance is the key.

Use link #6 in my signature to evaluate every individual group of panels. Add them up, and and you can assess the performance of the total system.

Thanks snoobler. I used the calculator and came up with 16128kWh per year. Which is 1344kWh / month
I guess that is about as accurate as I can get. That also seems like more than I will ever use. Our current usage is about 900kWh / month.
My wife and I plan to get electric cars but we don't drive much. I probably should remove some panels.
 
Do you know the maximum watts/amps you'll be able to feed into your breaker panel?
Many 200A panels have a limit of 40A breaker, 32A current backfeed, and you may be approaching that with your panels.
Some will accommodate 70A. Line-side tap can let you hook up more.

Various orientations or tilt could reduce the peak and spread it over the day or seasons to fit under any limits.
Time of use rates may make different orientations preferable.

Fireman access rules may require 3' from panels to roof ridge and side, 3' between panels at valleys.
Thanks for the reply Hedges, I am not sure about the max breaker size my panel can handle. I plan to use the Sol-Ark 12k and the manual wants me to connect to two 50a breakers in the main panel. I will research this further.
I adjusted my picture to try and show 3' of clearance. The horizontal panels might be a problem. I think it might be ok as long as there is 3' on the other side of the ridge or hip. I will find out.
I was trying to use multiple angles. I'd like to get as many as possible facing south but I have limited roof facing south.panel layout.png
 
Also, once you have your address in there - use the center marker to position where you would like your panels to be, you can rotate also.

You can also view sun angle degrees with a specific spot..etc.

You can also pick any date and see what that might be, like for official solar winter..etc.
Thanks NCblueridge. That is pretty cool. I can use this tool and the one snoobler suggested to figure out if it is worth while to use special racking to tilt my panels.
 
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In my area, if rooftop panels are low (less than about 12" or maybe 18" above) and weight per attachment point is less than 40 pounds, then we don't need a structural permit. And we can get an expedited PV permit on-line. No one looks at the drawings until the inspector comes to see finished installation. You just need enough feet or standoffs to meet that. (and then if you can measure to lag screw into rafters and not just shakes/tar paper or whatever you've got, it will be really strong.)
Thanks again Hedges. I am fairly sure they have expedited permits here too. A friend of mine who installs panels told me they deviate from the plan all the time. I guess they realize it is difficult to get it planned out perfect ahead of time. I hope to make last minute adjustments if I can.
I plan to be sure to hit the rafters. My area has hurricanes so my racking has to meet a high wind requirement.
 
Thanks snoobler. I used the calculator and came up with 16128kWh per year. Which is 1344kWh / month
I guess that is about as accurate as I can get. That also seems like more than I will ever use. Our current usage is about 900kWh / month.
My wife and I plan to get electric cars but we don't drive much. I probably should remove some panels.

At 30kWh/day present usage, the addition of electric vehicles could bump that up significantly. You could estimate your usage based on kWh of battery pack and vehicle range, e.g., if a 100mi range vehicle has a 30kWh pack, 10 mi/day driving would be 3kWh - a 10% increase over your existing usage.

Also, PVWatts reports monthly harvest. You may find that there are times of the year where you don't meet your average.
 
Thanks for the reply Hedges, I am not sure about the max breaker size my panel can handle. I plan to use the Sol-Ark 12k and the manual wants me to connect to two 50a breakers in the main panel. I will research this further.
I adjusted my picture to try and show 3' of clearance. The horizontal panels might be a problem. I think it might be ok as long as there is 3' on the other side of the ridge or hip. I will find out.
I was trying to use multiple angles. I'd like to get as many as possible facing south but I have limited roof facing south.

The panel will take as large a breaker as is available in the model line. For instance, 125A breakers in the case of my Square-D panels.
The panels are rated (have busbars for) 225A, 125A, 100A, 70A.

Problem is NEC, what regulators decided to permit.

With a 225A panel, typically there is a 200A main breaker although sometimes 150A.
If two, 100A PV breakers were installed at the far end, panel would be fed with up to 200A from one end and up to 200A from the other end, but regardless of what breakers were installed for loads, no point in the busbar would ever carry more than 200A. Current supplied by PV breakers subtract from current supplied by main breakers, don't add to it. (If PV breakers were installed adjacent to main breaker, then current would add and busbar could carry 400A, would burn out.)

So even though there is nothing wrong from a physics or electrical engineering perspective with installing large PV breakers at far end of the panel, code placed a smaller limit on it (as well as requiring they be placed at far end.) The limit is main breaker plus PV breakers can't exceed 120% of busbar rating. That way, if someone rearranges the breakers, busbar will only be overloaded 20% and will still be safe.

If your panel has main breaker centered in busbar, with branch circuit breakers on both sides of main, then main + PV breaker is limited to 100% of busbar rating (neither end of busbar accomplishes the goal of subtract, don't add current.) What you can do is a "supply side tap", connect PV to wires between meter and main breaker. Utility may offer an adapter which fits under the meter for that purpose. PG&E does, with 40A limit.

If you have a Zinser panel, replace it before your house burns down.

If your panel has main breaker at one end, read the labels to determine rating of busbar. In some cases, 200A breaker and 200A busbar, so you're allowed 40A of PV breaker. Limit PV system to 32A so breaker is 25% larger, avoiding nuisance trips. If 200A breaker and 225A busbar, you're allowed 70A of PV breaker. Limit PV to 56A. For more than this, either reduce size of main breaker or do a supply-side tap.

"Sol-Ark 12k and the manual wants me to connect to two 50a breakers in the main panel"

Sure that isn't one two-pole 50A breaker? At 80% (40A) make PV delivered to grid 9600W max.

Continuous AC power to Grid (On-Grid)9000W 37.5A L-L (240V)

Looks to me like one, two pole 50A breaker. So you need the 225A busbar, 200A breaker situation for this. Otherwise, 40A breaker if you can program a lower limit or if not too many panels (as I mentioned earlier, multiple angles reduces peak current.)

As I indicated earlier, this limit is NEC's rule, a concession to allow PV which appears to exceed busbar rating but doesn't really unless an idiot installs/rearranges breakers. In which case it keeps the system idiot-proof.


Our rules do allow the 3' clearance to be either side of a valley or split between them (e.g. panels on each side of the valley, 18" away from it.)
The rules do NOT allow panels < 3' from ridge, even though other side is clear. Reason is fireman decides which side of ridge to hack a hole based on wind direction, wants to let heat out without wind blowing heat & smoke back in.
Hip may be OK to split clearance (provide walking path either side) because heat inside will rise along the hip to the ridge.

East may be more valuable than South. Power per panel is reduced, but more power is consumed by A/C later in the day and time of use rates are higher. South will do more in winter.
 
I am not sure about the max breaker size my panel can handle.
For starters you could find out what the main disconnect Amperage is on your panel. @Hedges walked through the rule that calculates how much backfeed the buss bar can sustain. I don't recall if you are powering your whole house or separating some loads into a critical loads panel? In any event you will need to have a separate sub panel that will be powered by the SolArk. When the grid is up the power flows through the SolArk to this panel. When the grid is down the SolArk isolates itself and powers this panel. That way the grid is not backfed.
 
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Or a line-side tap (e.g. fused disconnect) feeding SolArk.
Then by using an interlocked breaker on the main panel, he could manually switch to either feed house directly from grid, or feed it from SolArk as a UPS.
But a separate "important loads" panel could be a better way to power some things from battery without including an electric range and furnace.

So I would suggest all of those. Line side tap feeding SolArk feeding important loads panel, and manual interlocked switch for main panel, so anything there could be powered off PV if desired.
Also put such an interlock on the important loads panel, so if SolArk is down for the count, those loads could be fed from main panel.

Panels cost $50 to $200. Interlocks cost $50. All pretty cheap if DIY and not electrician rates.
 
Also put such an interlock on the important loads panel, so if SolArk is down for the count, those loads could be fed from main panel.
That is good advice. As an example, my Outback Skybox froze during a firmware upgrade and Outback sent me a new inverter. In the meantime I had to use that interlock to power my important loads panel. It is also useful the few times i have had to reboot the Skybox.
Incidentally, I like your use of the term "important loads" to describe what are sometimes called critical or essential loads.
 
"important loads"

I just coined the phrase, thinking that critical or essential would be communications and alarm. Important would be lights and refrigerator (although I want to shed refrigerator at night, "let it eat ice".) Less important would be A/C and laundry. Those could be shed at some point closer to fully charged, but I'd rather operate them only with surplus power when battery already fully charged. Electric furnace I'll only run on-grid; I have gas as well.

Here's the interlock which fits my outdoor main load center:

 
My main breaker is 150a and I have one breaker for an electric stove that is 50a.
I do plan to use a important loads panel and I plan to start with just 2 refrigerators, lights and fans and TV, cable and internet.
Maybe someday I will try to run everything but I am not in a rush. My house is 100% electric. There's no gas here
It is going to take me a while to understand everything you guys are saying. I'm sure I will have questions soon. I also plan to make a layout of my complete system. And I will start another thread. I would like to understand as much as possible about the whole system even though I will have help from an electrician and a solar installer.
 
Main breaker is 150A. What is the busbar rating? (should be on a sticker visible inside box if you remove bezel over breakers.)
If busbar is 150A, you will be limited to 30A breaker, 24A continuous current. (assuming main breaker at end not middle.)
Supply-side tap is best way to go. Probably, this requires utility shutting off your power while you install it.
But if main breaker is not at panel, rather at separate meter, you can do everything downstream just by shutting it off. In that case you would probably need an additional overload device before main panel, so utility + PV can't put excessive current into it.

Can you post a photo of everything?
(and check labels inside panel when convenient.)

You should be able to most of the physical work as well. Many things like snapping MC connectors together can be visually inspected. Torquing of electrical screw connections is important and not as obvious. Ideally do everything short of final connection to grid (if that needs to get done after utility shuts off power) and have the experienced one inspect your work.
 
Hedges, I think you were saying above that I probably won't be able to do the horizontal panels and I should put them facing east.

Here's my panel and label

.Electrical panel.jpgElectrical panel label.jpg
 
That's a Square-D QO panel. 150A main, you said? Under the cover, labels on the box will say if it has 225A or whatever bus.
Even if 200A bus, would be allowed 240A main + PV, so up to 90A PV.
It is an indoor panel. Meter is outdoors. I don't suppose there is another disconnect at the meter? If so that would make line-side tap easy if desired.

Simplest way to go is put a 50A breaker in this panel in the available #18 & #20 slots for your inverter. Add another panel downstream of the inverter for important loads, give it a main breaker and an interlocked backfeed breaker. The main panel has two single breakers left, also some 15A 2-pole breakers. Using more tandem breakers you can free up an additional pair of slots, for one more 2-pole breaker for bypass to the important loads panel. (tandem breakers can be ganged to make 2-pole. There are also 20/30A and 30/20A tandem available.)

Anything left on the main panel will be off during a grid failure. Anything on the important load panel will be run with battery and PV when necessary, and can be switched to run off grid if the inverter is down.

If you free up additional space in the main panel and interlock a breaker with the 150A main, then you can manually feed it from inverter output (use a breaker in the important loads panel.) Then you can run your electric range off PV/battery too, in case you want scrambled eggs after sun comes up during grid failures. You would manually turn off the breaker feeding inverter so it doesn't confuse itself driving its input from its output. (That's my temporary setup until I complete a line-side tap.)
 
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