East/West PV Array with 1 mppt?

mantusk

New Member
Joined
Jan 8, 2022
Messages
6
Hello Everyone.

I have a dilemma with setting up my pv arrays to inverter.
Place: East/west roof (quite steep)

Inventory Specs
8x 400w mono half-cell solar modules
STC* 49.8 VOC
10.14 Isc
MPP voltage: 41.5
MPP current: 9.64

Inverter: Growatt SPF 5000ES
max PV array open circuit voltage: 450Vdc
MPPT voltage range: 120Vdc-430Vdc
Max solar charge current: 100A
Strings per MPPT: 1/1

I'm thinking of 2 strings of 4Modules for each roof side and all connected parallel to inverter. Because it's west/east roof not sure how to get around the possible bottleneck as only one side at the time will be producing at its optimum. Growatt inverter as well has only 1 PV input.

Is there a possible solution how I could connect these 2 strings to my one inverter mppt input without losing too much power?

Thank you in advance
 

mantusk

New Member
Joined
Jan 8, 2022
Messages
6
You need at least 3s to get into your MPP voltage range.

I think that's a poor choice of inverter for your application.
Is my math off? 4x module of 40V in 1 series = that's about 160V. You think its not enough?
4s2p
 

Supervstech

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Messages
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Hello Everyone.

I have a dilemma with setting up my pv arrays to inverter.
Place: East/west roof (quite steep)

Inventory Specs
8x 400w mono half-cell solar modules
STC* 49.8 VOC
10.14 Isc
MPP voltage: 41.5
MPP current: 9.64

Inverter: Growatt SPF 5000ES
max PV array open circuit voltage: 450Vdc
MPPT voltage range: 120Vdc-430Vdc
Max solar charge current: 100A
Strings per MPPT: 1/1

I'm thinking of 2 strings of 4Modules for each roof side and all connected parallel to inverter. Because it's west/east roof not sure how to get around the possible bottleneck as only one side at the time will be producing at its optimum. Growatt inverter as well has only 1 PV input.

Is there a possible solution how I could connect these 2 strings to my one inverter mppt input without losing too much power?

Thank you in advance
I think I know what you are asking… to be clear, you have a roof that has an east facing side, and a west facing side, correct?
You want to have 1 string on the east side, and one string on the west side. And you want to parallel both strings to the single mppt input?
I would not do this.
I would pick a side to input to the growatt, and purchase an additional mppt for the other string.
 

Supervstech

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Is my math off? 4x module of 40V in 1 series = that's about 160V. You think its not enough?
4s2p
40.1 is the max power voltage… in average solar conditions, it will be less… and your mppt will not produce output until it reaches 120V, so you will be missing out on morning or evening photons…
 

mantusk

New Member
Joined
Jan 8, 2022
Messages
6
That is correct
I think I know what you are asking… to be clear, you have a roof that has an east facing side, and a west facing side, correct?
You want to have 1 string on the east side, and one string on the west side. And you want to parallel both strings to the single mppt input?
I would not do this.
I would pick a side to input to the growatt, and purchase an additional mppt for the other string.
Yes you described it perfectly. In your scenario, buying additional mppt, would I need to hook it up directly to my 48v battery? Won't there be any conflict between growatt charging the battery and this second mppt? Thank you
 

Supervstech

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That is correct

Yes you described it perfectly. In your scenario, buying additional mppt, would I need to hook it up directly to my 48v battery? Won't there be any conflict between growatt charging the battery and this second mppt? Thank you
Correct.
Multiple charge controllers function all the time, there should be no conflict.
 

mantusk

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Joined
Jan 8, 2022
Messages
6
40.1 is the max power voltage… in average solar conditions, it will be less… and your mppt will not produce output until it reaches 120V, so you will be missing out on morning or evening photons…
Maybe a stupid question but is there an optimal way to bump this up? I guess putting an extra inverter in between would do the job?
 

wiseacre

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Aug 8, 2021
Messages
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Location
North of the Adirondacks
Although I've learned a lot on the forum I still am uncertain about many things.

I see the logic of a second charge controller
I also think a combiner box would be an acceptable solution with 4s2p panel configuration.
(I'm biased in favor of combiner boxes, I like the built in fuses for each string input and the breaker for the output and the ease of adding more strings in the future.)
40.1 is the max power voltage… in average solar conditions, it will be less… and your mppt will not produce output until it reaches 120V, so you will be missing out on morning or evening photons…
How much less?
potential 160v to 120v seems like there's a bit of leeway and the loss acceptable in a "compromised" array strings configuration.

adding another panel to both series strings possible? Do you have space available?
 

mantusk

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Joined
Jan 8, 2022
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Although I've learned a lot on the forum I still am uncertain about many things.

I see the logic of a second charge controller
I also think a combiner box would be an acceptable solution with 4s2p panel configuration.
(I'm biased in favor of combiner boxes, I like the built in fuses for each string input and the breaker for the output and the ease of adding more strings in the future.)

How much less?
potential 160v to 120v seems like there's a bit of leeway and the loss acceptable in a "compromised" array strings configuration.

adding another panel to both series strings possible? Do you have space available?
1.I was looking into combiner box as well, as a solution to this, however, I still can't get a clear picture of whether combination of East and West strings would bottleneck each other as only one can get optimal sunlight at the time.
2. Unfortunately both roof sides are maxed out. There is an extra 1.5 meters of terrace roof facing south where could attach an extra panel, but not sure it is worth the hassle trying to connect it as a boost
 

efficientPV

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Sep 24, 2019
Messages
720
East facing arrays are the best idea ever. It is an old tired idea of waiting till mid day to recharge the batteries. This is left over from when batteries were cheap and panels were expensive. My batteries are recharged and water heater up to temperature by 10:30 in the morning. I don't use a combiner box and yes the east panels still contribute later in the day.
 

wiseacre

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Location
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1.I was looking into combiner box as well, as a solution to this, however, I still can't get a clear picture of whether combination of East and West strings would bottleneck each other as only one can get optimal sunlight at the time.
2. Unfortunately both roof sides are maxed out. There is an extra 1.5 meters of terrace roof facing south where could attach an extra panel, but not sure it is worth the hassle trying to connect it as a boost
Not sure how to answer the bottleneck question, I don't understand what you mean by bottleneck

I have a 2s4p array with shading, not as extreme as your east /west orientation but nevertheless a problem in winter as the house progressively shades my array. There is no "bottleneck" as shade progresses over one string after another the overall production reduces but those still in sun continue to deliver power to the SCC. Basically, when a string has enough sun to produce power it will go to the SCC regardless of what the other string(s) are doing.

Too bad you ran out of space. Your Growatt is going to be hungry but I don't think it will starve with a 4s string. That 120v PV input minimum means you'll lose some power until the sun is strong enough on a string to kick up the voltage. Cloudy/overcast day and you may not get there.

Too bad the shade isn't coming from a money tree, then you could get a different inverter or
forget the combiner box and go with another SCC for one string
You'll be able to see the difference between the 2 strings and may want to add a second independent SCC and not use the PV input on the inverter at all.
 

mantusk

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Messages
6
Not sure how to answer the bottleneck question, I don't understand what you mean by bottleneck

I have a 2s4p array with shading, not as extreme as your east /west orientation but nevertheless a problem in winter as the house progressively shades my array. There is no "bottleneck" as shade progresses over one string after another the overall production reduces but those still in sun continue to deliver power to the SCC. Basically, when a string has enough sun to produce power it will go to the SCC regardless of what the other string(s) are doing.

Too bad you ran out of space. Your Growatt is going to be hungry but I don't think it will starve with a 4s string. That 120v PV input minimum means you'll lose some power until the sun is strong enough on a string to kick up the voltage. Cloudy/overcast day and you may not get there.

Too bad the shade isn't coming from a money tree, then you could get a different inverter or
forget the combiner box and go with another SCC for one string
You'll be able to see the difference between the 2 strings and may want to add a second independent SCC and not use the PV input on the inverter at all.
Thank you for your response.
It is much more clearer now. I will consider a second scc if wasting too much sunlight
 

Hedges

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Mar 28, 2020
Messages
11,594
I think I know what you are asking… to be clear, you have a roof that has an east facing side, and a west facing side, correct?
You want to have 1 string on the east side, and one string on the west side. And you want to parallel both strings to the single mppt input?
I would not do this.

I would, and I recommend it highly.
SMA ran a test, and found two strings in parallel, each string of different orientation, produced 2% less than having separate MPPT for each string.
That's a win in my book; loses 2% of possible PV production, but achieves higher utilization of SCC. SCC or GT inverter these days cost about 20% to 40% of PV panels, cheaper to add 2% more PV panels.

Where this won't work great is if one string also gets shading over a percentage of its panels. Then it needs lower Vmp operation so better to have separate SCC. But if only 10% of panels in a string are shaded, it's close enough for DIY work.

8x 400w mono half-cell solar modules
MPP voltage: 41.5


Inverter: Growatt SPF 5000ES
MPPT voltage range: 120Vdc-430Vdc

I'm thinking of 2 strings of 4Modules for each roof side

168 Vmp and 120V MPPT range ought to work fine, seems enough headroom.
Longer string (without risking excessive Voc on cold day) could be better.
 

wattmatters

Photon Sorcerer
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Apr 16, 2021
Messages
1,709
Paralleling PV arrays of different orientations into an MPPT is perfectly fine, provided of course your arrays remain within the overall specifications of the MPPT input (lower and upper voltage limits in particular). Also the arrays in each string should be made up of the same number of panels and panel rating.

All that will happen is the MPPT will sort out how to drag the most power out of the system but it will work just fine. I doubt adding an extra MPPT will result in much of an increase in production, a few % perhaps. Yes, having 2 x MPPT inputs might have been a bit better but frankly the extra expense just isn't worth it at this scale.

8x 400w mono half-cell solar modules
STC* 49.8 VOC
10.14 Isc
MPP voltage: 41.5
MPP current: 9.64

Inverter: Growatt SPF 5000ES
max PV array open circuit voltage: 450Vdc
MPPT voltage range: 120Vdc-430Vdc
Max solar charge current: 100A
Strings per MPPT: 1/1

I'm thinking of 2 strings of 4Modules for each roof side and all connected parallel to inverter.
The main issue with the proposed set up is the 4s string voltages are going to be a touch on the low side for that MPPT. It will work, the MPPT will do its thing but it would be better if you could add one more panel to each string or perhaps use panels with a higher voltage rating.

Unfortunately both roof sides are maxed out. There is an extra 1.5 meters of terrace roof facing south where could attach an extra panel, but not sure it is worth the hassle trying to connect it as a boost
Since that's the space you have, then run with it. I'm pretty confident it will be just fine.

Forget about adding the extra South facing panel.

Basic rules for parallel arrays into one MPPT:
- each string to have the same number of panels (of same panel type/rating), e.g. 4s + 4s is good, 4s + 6s is not good.
- all panels in each string to have the same orientation (azimuth and tilt)
- array within the MPPT operating limits

Other than that, the same rules apply wrt avoiding shade on the sun facing array, or at least recognise the limitations shade introduces.

Another solution to multifaceted set ups is to use microinverters.
 

kanelr

Solar Enthusiast
Joined
Mar 1, 2022
Messages
190
Hello Everyone.

I have a dilemma with setting up my pv arrays to inverter.
Place: East/west roof (quite steep)

Inventory Specs
8x 400w mono half-cell solar modules
STC* 49.8 VOC
10.14 Isc
MPP voltage: 41.5
MPP current: 9.64

Inverter: Growatt SPF 5000ES
max PV array open circuit voltage: 450Vdc
MPPT voltage range: 120Vdc-430Vdc
Max solar charge current: 100A
Strings per MPPT: 1/1

I'm thinking of 2 strings of 4Modules for each roof side and all connected parallel to inverter. Because it's west/east roof not sure how to get around the possible bottleneck as only one side at the time will be producing at its optimum. Growatt inverter as well has only 1 PV input.

Is there a possible solution how I could connect these 2 strings to my one inverter mppt input without losing too much power?

Thank you in advance
Electric dpdt switch with timer.
Relay to flip switch when power drops (ie sun crosses roof ridge) will flip again at sundown which should serve as preset for morning...
Highest row of panels mounted tilted with bottom edge outward but not shading the row beneath.
Any or all?
 
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