diy solar

diy solar

To over Watt, or not

Since this is where all the cool kids hang out I would love some sign off on this setup. Getting ready to start spending money and want to make sure my permits are setup correctly.

Sol-Ark 12k
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Solarever 445 Watt.
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East - West panel configuration.
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Sol-Ark has 2 MPPT's that allow 2 inputs per MPPT to combine.

East Roof - 8 Panels Series
West Roof - 8 Panels Series

Combined at MPPT1 to make 8s2p

West Roof - 6 Panels Series

MPPT2 6s
~~~~~~~~~~~
MPPT1
21.62 Amps Max
399 VOC
My thought on this setup is Amps is cutting it close and VOC is kinda close. I am in Northern CA so I dont see super cold temps. Also with each string being on different roof planes they will never see max at the same time. Is this a good idea? Bad idea? Will one side drag the other down?

MPPT2
10.81 Amps Max
300 VOC
My plan is to add panels to this MPPT down the road but if MPPT1 can't handle what is on it I can always move some panels over to this MPPT.

Thanks for all your responses!
 
Since this is where all the cool kids hang out I would love some sign off on this setup. Getting ready to start spending money and want to make sure my permits are setup correctly.
...
399 VOC
My thought on this setup is Amps is cutting it close and VOC is kinda close. I am in Northern CA so I dont see super cold temps. Also with each string being on different roof planes they will never see max at the same time. Is this a good idea? Bad idea? Will one side drag the other down?
...

Thanks for all your responses!
NorCal is a big place with many different climates. Your local National Weather Service office has records which are worth viewing. Many folks are surprised just how cold it has been in their location. The climate is doing strange things and who knows what it will be like in 15 years.

It just takes 1 brief episode of "too cold" to fry a controller. Approaching max voltage is never a good idea. Many controllers will accept overpaneling to a limit.
 
NorCal is a big place with many different climates. Your local National Weather Service office has records which are worth viewing. Many folks are surprised just how cold it has been in their location. The climate is doing strange things and who knows what it will be like in 15 years.

It just takes 1 brief episode of "too cold" to fry a controller. Approaching max voltage is never a good idea. Many controllers will accept overpaneling to a limit.
I redid some of my calculations and the world would have to freeze over before I hit 550v to damage the MPPT.
18 amp clipping starts at 500v and 20 amp clipping at 450v.

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I guess the main thing then is the East-West setup for the 2 parallel strings. Will that help with being over amp'd? Anyone have any experience with 8s2p?
 

It is possible those walkway setbacks are out of date or will go away with the next update.
The more recent one I saw was 36" on the ridge and a single 36" walkway on the street side up to the ridge, which could eliminate it on 3 out of four edges.

Some states appear to allow eaves as part of the 3' edge walkway, while others require 3' within the outer walls (not all eaves were created equal and able to safely hold a fireman's weight.)


Voc - never violate that. use record historical cold for your location and temperature coefficient from panel data sheet.
Amperage I would like to over-panel, but don't exceed maximum Isc.

The multiple panels angles won't do anything for Voc especially if into separate MPPT.
You may get 2% higher production if the two angles are on separate MPPT. Then again, two angles on each of two MPPT, if it means not clipping, might produce more.
 
Look for maximum panel Isc in your inverter specs. Stay under it. My 7.6k are 18a+18a mppt, Max panel isc is 25a. The inverter will clip the amps from there. I will be at 22a +- panel Isc. Do a panel calculator, and get your historical low temps. With info from hedges. I am calculating at -65c way up here to be safe not sorry. We have experienced -50c +-
 
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Too many volts = smoke. Where there is smoke,,,, well you know. Try to stay under 400v during the coldest calculated temp. The highly expensive, Sol-Ark will thank you long term. California is not Costa Rica temp. Higher altitude is not lower altitude temp.
 
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I can't speak to the internal electronic architecture of all products. That said, each MPPT input most likely does go to a separate charge controller, its just that if both are being use together there is 2x heat and they both tie together at the battery + and - terminal so the total system current may be limited to a value less than the sum of each individual MPPT controller if one or the other were being used alone.
 
I can't speak to the internal electronic architecture of all products. That said, each MPPT input most likely does go to a separate charge controller, its just that if both are being use together there is 2x heat and they both tie together at the battery + and - terminal so the total system current may be limited to a value less than the sum of each individual MPPT controller if one or the other were being used alone.

Splitting same PV array so it goes through two MPPT rather than same total current through one MPPT and other MPPT carrying zero, could mean 1/2 the heat.

Heat is produced by I^2R.

I^2R is twice as much as 2 x (I/2)^2R

That is assuming the two MPPT are completely independent SCC. It is possible their current combine and go through a common circuit.
In the case of a SolArk, I would expect two MPPT feeding a high-voltage rail, and one buck converter charging battery from that rail.
 
The SCC pulls the power from panel as needed up to the maximum power the SCC can provide to charge the batteries, the panels do not push power into the SCC.
I.E. you US AC outlet can supply up to 1800W of power (120V x 15A), so if you plug in 100W lamp, the lamp will only draw 100W from the outlet.
Max PV input Voltage is the one you need to watch out for.
This makes perfect sense. I was doing some research on this and some folks in this forum were advising to monitor the amperage which from what I know about electronics, isn't the case, but I still had my self-doubts just in case these MPPTs worked differently than standard electronics. Theoretically once I keep my voltages in check, my panels could have the potential to output a million amps. The MPPT will only draw the amps it needs but it can't control the voltage it gets and that's why it cant clip the voltage but can only clip the amps. Amps are pulled by the load (in this case the MPPT/inverter/SCC), and voltage is pushed to the load. I'm looking to over panel for my own project so when I have those cloudy days, I can still generate a reasonable amount of power.
 
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