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How many panels per mppt


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My solar setup is 2 x 8kw Sunsynk Hybrid inverters in parralel with 36 Canadian 550w panels. So basically it will be 9 panels per string/mppt. My concern is that the on set of panels (18) is quite a distance from the inverters. I have not keasured yet but think in the region of 30to35mts. Can confirm exact distance tomorrow after measuring cable routing distances. The other set of panels is much closer to the inverters. Both roofs are north facing although one get a lot of shade winter time. I will try up load pic. Pic was taken today at 16h30. Most of the panels will be on the shade from 15h00 winter time.

What is the max distance panels can be from the inverters and in my case would it be a proble.?

Any advise/suggestions/recommendations more than welcome.

IMG-20240528-WA0013.jpg

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My solar setup is 2 x 8kw Sunsynk Hybrid inverters in parralel with 36 Canadian 550w panels. So basically it will be 9 panels per string/mppt. My concern is that the on set of panels (18) is quite a distance from the inverters. I have not keasured yet but think in the region of 30to35mts. Can confirm exact distance tomorrow after measuring cable routing distances. The other set of panels is much closer to the inverters. Both roofs are north facing although one get a lot of shade winter time. I will try up load pic. Pic was taken today at 16h30. Most of the panels will be on the shade from 15h00 winter time.

What is the max distance panels can be from the inverters and in my case would it be a proble.?

Any advise/suggestions/recommendations more than welcome.

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15 hours ago, Intaka said:

What is the max distance panels can be from the inverters and in my case would it be a proble.?

There is a few technical aspects involved to determine the voltdrop over distance. The first point to consider is the voltage distributed over distance. In your case the vmp for 9 panels in series will be ~350v. The second point to consider is the wire gauge or thickness. At your dc voltage if 4mm² pv cable was used the voltdrop will be 1%. So no will not be a problem. Below calculation done on Vmp of 350v and Imp at 8 amps( average).

Screenshot_20240529_152800_Chrome.jpg.36a84bebeec5b8a601243f84fa03a4eb.jpg

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4 hours ago, TaliaB said:

There is a few technical aspects involved to determine the voltdrop over distance. The first point to consider is the voltage distributed over distance. In your case the vmp for 9 panels in series will be ~350v. The second point to consider is the wire gauge or thickness. At your dc voltage if 4mm² pv cable was used the voltdrop will be 1%. So no will not be a problem. Below calculation done on Vmp of 350v and Imp at 8 amps( average).

Screenshot_20240529_152800_Chrome.jpg.36a84bebeec5b8a601243f84fa03a4eb.jpg

It might be interesting to see what the actual voltage drop would be in the above calculation. 

Also if the 13A is used instead of 8A as I think 550W panels would not only provide 8A.

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22 hours ago, Intaka said:

My solar setup is 2 x 8kw Sunsynk Hybrid inverters in parralel with 36 Canadian 550w panels. So basically it will be 9 panels per string/mppt. My concern is that the on set of panels (18) is quite a distance from the inverters. I have not keasured yet but think in the region of 30to35mts. Can confirm exact distance tomorrow after measuring cable routing distances. The other set of panels is much closer to the inverters. Both roofs are north facing although one get a lot of shade winter time. I will try up load pic. Pic was taken today at 16h30. Most of the panels will be on the shade from 15h00 winter time.

What is the max distance panels can be from the inverters and in my case would it be a proble.?

Any advise/suggestions/recommendations more than welcome.

Replies are on the similar topic. 

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1 hour ago, Scorp007 said:

Also if the 13A is used instead of 8A as I think 550W panels would not only provide 8A.

I agree 550w panel could provide 13A at STC(1000wm²) for a very short period out of a 8 hour day during summer. At NOCT the average 550w panel could produce ~10A. The average produced current during the 8 hour day would be much closer to 8~9 amps than the Imp at STC. You might see 13A during cloud edge for a very short time.

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10 hours ago, TaliaB said:

I agree 550w panel could provide 13A at STC(1000wm²) for a very short period out of a 8 hour day during summer. At NOCT the average 550w panel could produce ~10A. The average produced current during the 8 hour day would be much closer to 8~9 amps than the Imp at STC. You might see 13A during cloud edge for a very short time.

Agree as pointed out but the losses are at a high during those peak hours and I feel one would do the calculations for those few hours when current will be at the highest and not the average during the day. 

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5 hours ago, Intaka said:

Thank you everyone for your input on this.

Would it be safe to rather use 6mm cable instead of 4mm.

As was indicated earlier there is nothing wrong with 4mm² cable. I merely asked if one could indicate the figures related to the voltage drop. 

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Thank you but will also discuss this with the installer next week. I also understand the pv positive and negative cables have to be in separate condute and the earth cable also have to run in the positive condute. Now since this roof will be having 2 sets of 9 panels mppt1 and mppt2 can I run the cables in 2 x 40mm pvc pipes which will be underground en-route? So both mppt,s positive and earth cables will run together in 1pvc pipe. Is this allowed?

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  • 2 weeks later...
On 2024/06/02 at 9:04 PM, Intaka said:

Thank you but will also discuss this with the installer next week. I also understand the pv positive and negative cables have to be in separate condute and the earth cable also have to run in the positive condute. Now since this roof will be having 2 sets of 9 panels mppt1 and mppt2 can I run the cables in 2 x 40mm pvc pipes which will be underground en-route? So both mppt,s positive and earth cables will run together in 1pvc pipe. Is this allowed?

Maybe this above was a stupid question. Let me rather ask it this way: Is there any official regulation in South Africa stating no DC cables, (positive, negative and earth) not allowed in a single condute from the array to combiner box? And if so can you please reference the applicable regulation?

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