Max Solar Panels

[UDC]

Hi, based on the Inverter specs in the pic, how many solar panels can the unit handle, numbers of strings etc to get the best out of it

[Buyeye]

Hi if you have 40voc, 10 amp panels you could have 2 in series at 80 volts. 10 amp x 12 is 120 amps.

So 2s5p? Max 2s6p.

Series connection increases voltage and parallel increases amperage. 

[Scorp007]

7 minutes ago, Buyeye said:

Hi if you have 40voc, 10 amp panels you could have 2 in series at 80 volts. 10 amp x 12 is 120 amps.

So 2s5p? Max 2s6p.

Series connection increases voltage and parallel increases amperage. 

If Voc is 40V even at low temps 3 in series will still be providing some gravy below the 145V all time max. 

Vmp for 40Voc panels will also be close to the sweet spot for the MPPT for most areas if one uses the NOCT Watts from the panels. 

Once Voc for the panels exceed 40V then I would stick to 2S.

Less parallel strings mean thinner cable. 

[UDC]

I want to install 10 x 550watt panels, so not sure if system will handle it or would it be better if I use 2 strings of 5 panels each.

[Scorp007]

5 minutes ago, UDC said:

I want to install 10 x 550watt panels, so not sure if system will handle it or would it be better if I use 2 strings of 5 panels each.

Then you use as suggested 2S5P and have a suitable combiner box for those 5P strings. That is the only way. 

Edited November 14, 2023 by Scorp007

[UDC]

27 minutes ago, Scorp007 said:

Then you use as suggested 2S5P and have a suitable combiner box for those 5P strings. That is the only way. 

cool thanks, will 6 panels in series on a single string work.....then can maybe add a 2nd string of 6panels at a later stage

[GreenFields]

1 hour ago, UDC said:

cool thanks, will 6 panels in series on a single string work.....then can maybe add a 2nd string of 6panels at a later stage

I don't think you're understanding the issue, so forgive me if it sounds a bit preachy, but I'm going to spell it out.

You cannot use either 5 or 6 of those panels in series. The Voltage would be far too high.

This is a low-Voltage MPPT-input inverter. The safest way to put that type of panel on it is to put at most 2 panels on a string in series - and then to connect 5 such strings of 2 in parallel.

You are confusing 2S5P with 5S2P.  The difference is small on paper when you read it, but the implications on the installation are more far-reaching.

Edited November 14, 2023 by GreenFields

[UDC]

5 minutes ago, GreenFields said:

I don't think you're understanding the issue, so forgive me if it sounds a bit preachy, but I'm going to spell it out.

You cannot use either 5 or 6 or those panels in series. The Voltage would be far too high.

This is a low-Voltage MPPT-input inverter. The safest way to put that type of panel on it is to put at most 2 panels on a string in series - and then to connect 5 such strings of 2 in parallel.

You are confusing 2S5P with 5S2P.  The difference is small on paper when you read it, but the implications on the installation are more far-reaching.

thank you for that, this is exactly what I need to hear, much appreciated.....was definitely confused about 2S5P with 5S2P.

[UDC]

6 hours ago, Buyeye said:

Hi if you have 40voc, 10 amp panels you could have 2 in series at 80 volts. 10 amp x 12 is 120 amps.

So 2s5p? Max 2s6p.

Series connection increases voltage and parallel increases amperage. 

forgive my silly question please...but where did the figure 12 come from in this equation...would that be the number of panels

"10 amp x 12 is 120 amps."

as in 120 / 10 amp of each panel = 12 panels

Edited November 14, 2023 by UDC

[Scorp007]

2 minutes ago, UDC said:

forgive my silly question please...but where did the figure 12 come from in this equation...would that be the number of panels

"10 amp x 12 is 120 amps."

as in 120 / 10 amp of each panel = 12 panels

That was without know what size panels you wanted to use. 

It was indicated if the panels were Voc=40 and they were good for 10A as a Imp then you could fit up to 12 as per the maximum your inverter can use. 

[UDC]

1 hour ago, Scorp007 said:

That was without know what size panels you wanted to use. 

It was indicated if the panels were Voc=40 and they were good for 10A as a Imp then you could fit up to 12 as per the maximum your inverter can use. 

cool...will be using 550w Alaska panels...VOC 49.65 at 14.13A...or am I reading it wrong, so max panels would be 8

[Buyeye]

1 hour ago, UDC said:

cool...will be using 550w Alaska panels...VOC 49.65 at 14.13A...or am I reading it wrong, so max panels would be 8

Yes 8 panels at 14 amps gets you to 112amps which is within spec but you might feel underpannelled at 4400 watt peak only. If you are happy with that than you are good to go.

Lower amperage panels might get you closer to the 6000 watt which might come in handy on partly cloudy days. Dark rain clouds completely destroy pv production. 

[Scorp007]

2 hours ago, Buyeye said:

Yes 8 panels at 14 amps gets you to 112amps which is within spec but you might feel underpannelled at 4400 watt peak only. If you are happy with that than you are good to go.

Lower amperage panels might get you closer to the 6000 watt which might come in handy on partly cloudy days. Dark rain clouds completely destroy pv production. 

The 120A is not related to the current from the panels but the current you can charge to the battery. 

You can use 10 panels as indicated as 2S in 5P strings. This implies the current from PV will be 14.13*5=70.65A.

There won't be 8 strings but 5.

You MPPT is rated for 5700W.

Edited November 14, 2023 by Scorp007

[TaliaB]

12 hours ago, GreenFields said:

This is a low-Voltage MPPT-input inverter. The safest way to put that type of panel on it is to put at most 2 panels on a string in series - and then to connect 5 such strings of 2 in parallel.

@Buyeye

Above description from @GreenFields depicted in a drawing of how your solar array should be wired. 

[Buyeye]

1 hour ago, TaliaB said:

@Buyeye

Above description from @GreenFields depicted in a drawing of how your solar array should be wired. 

How do we get to 70A? Sorry I see it. It's 14 x 5.

Edited November 14, 2023 by Buyeye

[TaliaB]

10 minutes ago, Buyeye said:

How do we get to 70A? Sorry I see it. It's 14 x 5.

Yes it is 14.13 ISC x 5 = 70.65A but it will be only in the solar array short curcuit state, should we calculate when the array is connected to the Mppt you will use Vmp and Imp. So Imp = 13.42 x 5 = 67.1A and Vmp = 40.99V x 2 = 81.98V, array power then Vmp 81.98V × Imp 67.1A = 5501 watts and your Mppt is rated for 5760 watts so you good to go.

[Scorp007]

Just some junk info. The string with a 11.2A Isc I mentioned the other day produced a 12.5A peak current yesterday during cloud edge. This as recorded by my multi function power meter that records the peak value during any day of power, amps and the lowest voltage. 

[UDC]

On 2023/11/14 at 9:39 PM, TaliaB said:

@Buyeye

Above description from @GreenFields depicted in a drawing of how your solar array should be wired. 

How does one install 6 of these panel on the apex of a roof, 3 on East wing and 3 of West wing without running a cable over the apex.

I can connect 2 in Series on each wing and run that string to the combiner box or branch connector...but how do I connect the remaining single panels on each wing of the roof in series. Do I go over the apex or the long way around or is there a better solution to this problem.....cannot add another 2 panels due to space

[TaliaB]

35 minutes ago, UDC said:

3 on East wing and 3 of West wing without running a cable over the apex.

Use Dektite Lead Multicable Solar Flashing (Tiled or Slate) then run the wires on the inside of the roof

38 minutes ago, UDC said:

Do I go over the apex

Or you can use pvc conduit then you need to go over the apex.

 

The pvc is quite visible but you can disguise it next time you paint the roof.

Please just don't do this (below)

 

[Scorp007]

1 hour ago, UDC said:

 

I can connect 2 in Series on each wing and run that string to the combiner box or branch connector...but how do I connect the remaining single panels on each wing of the roof in series. Do I go over the apex or the long way around or is there a better solution to this problem.....cannot add another 2 panels due to space

I think we need to explore your 3rd string where you want to run a east and west panel in series. In winter time this string could have a very low contribution. 

[UDC]

thanks for the info....on the pvc conduit, is there a bracket available that can be used to secure the conduit to the roof tiles

[TaliaB]

10 hours ago, Scorp007 said:

I think we need to explore your 3rd string where you want to run a east and west panel in series. In winter time this string could have a very low contribution. 

@UDC What @Scorp007mentioned above is very important i missed that bit maybe post a pictures of your east and west roof as it is best to group east panels and west panel in string then run the 2 strings to the mppt. About the conduit mounting i have never used them but below video of how it is done. Maybe you can make these brackets yourself as i am not sure if they are available in SA, maybe someone on the forum has used a similar design before.

 

[Buyeye]

18 hours ago, Scorp007 said:

I think we need to explore your 3rd string where you want to run a east and west panel in series. In winter time this string could have a very low contribution. 

@UDC Please reconsider putting parallel strings on different sides of the roof. It would probably cause more frustration. 

Edited November 21, 2023 by Buyeye

[UDC]

On 2023/11/21 at 5:10 PM, Buyeye said:

@UDC Please reconsider putting parallel strings on different sides of the roof. It would probably cause more frustration. 

Thanks....planning on fitting 8 panels, so 4 either side on a larger section of the roof so that it will fit...thanks for all the valuable input and advise guys.

[HelgaR]

Another approach would be to do the maths on the cable costs and see if it is not better to have a separate high voltage mppt to charge your batteries. I found this solution worked to help my friends with solar addition problems.