I am trying to plan out my "shopping cart" as well as design of my new solar/inverter setup.

I am missing a few crucial components that I am not 100% sure on, and some questions

• Combiner box (ac/dc), should this be diy'd? Or should I buy a premade one? Any suggestions?
• What other breakers am I forgetting, or safety protocols
• Is my solar array specd correctly? There is no shading
• Is 6mm cable the correct sizing for the PV?

What other things am I not taking into consideration? I am not planning to go off grid now, and will later add another 5kw inverter.

I will also add another 8 panels in a couple of months, my question on this, should both strings be of equal length? and what is the max length a string can be? As my property (roofs) are split, and the first array will be the closest to the inverter. 

The inverter is also not set in stone yet, as I am still deciding on Lux, Solis S6 Pro (1Kw extra for the price is attractive) or SunSynk

 

Any advice, recommendations are highly appreciated!

 

Here is the rought draft

I have found a very interesting software to instantly calculate solar panels, and production possibility, for those interested.  For my use case I was only interested in my roofs facing north. 

 

Free for first 5 projects: https://www.pvsketch.com/

 

Hi you didn't give any reasons to prefer one inverter over the other, if you are worried about overloading then the 8kw deye/sunsynk are well priced at the moment. The usual questions about why you need a true hybrid apply.

The panel is not the best choice for this inverter, ie. 17A Imp, when the DC input is 13A on the 5kW Luxpower and Sunsynk, a bit higher at 16A on the Solis, but that's still below the panel's Imp. A better option could be a 500W or 550W panel, of which there are some good prices around. In that case I'd opt for two strings of 5 panels, one on each MPPT, ie. not combined into a single input, but using the two inputs that the inverter provides for it.

Otherwise, if you like the thought of the 600W panel, and if you're thinking of another 8 panels later, then a better option could be to go for a bigger inverter from the outset, ie. an 8kW, with a 20-22A DC input. A better match, also because the inverter can handle the power of two such strings of 8 x 605W.

Benefit of a hybrid inverter over the Luxpower also that you can use the GEN input port of the inverter, rather than an ATS on the DB board, and manage the autostart of the generator based on the battery level, etc. It's just a cleaner install, a more integrated system. For me at least in theory, maybe someone else can give a first-hand opinion on this.

Edited October 27, 20232 yr by GreenFields

21 minutes ago, GreenFields said:

The panel is not the best choice for this inverter, ie. 17A Imp, when the DC input is 13A on the 5A Luxpower and Sunsynk, a bit higher at 16A on the Solis, but still below the panel's Imp. A better option could be a 500W or 550W panel, of which there are some good prices around. In that case I'd opt for two strings of 5 panels, one on each MPPT, ie. not combined into a single input, but using the two inputs that the inverter provides for it.

Otherwise, if you like the thought of the 600W panel, and if you're thinking of another 8 panels, then a better option could be to go for a bigger inverter from the outset, ie. an 8kW, with a 20-22A DC input. A better match, also because the inverter can handle the power of two such strings of 8 x 605W.

Benefit of a hybrid inverter over the Luxpower also that you can use the GEN input port of the inverter, rather than an ATS on the DB board, and manage the autostart of the generator based on the battery level, etc. It's just a cleaner install, a more integrated system. For me at least in theory, maybe someone else can give a first-hand opinion on this.

Since originally posting this, I have read more into the Solis S6, they seem a like a much better bang for much, so will be going with this. 

Regarding the panels, I have found Longis 555w, although my annual predicted generation is lower, the ROI is 5% higher. 

The longi's I haven't found a proper spec sheet for yet, but seems they are rated at the following:
Input Voltage: 42.10V
Output Current: 13.19A

So these should be fine.  Thank you for spotting this.

22 minutes ago, Pho3niX90 said:

Since originally posting this, I have read more into the Solis S6, they seem a like a much better bang for much, so will be going with this. 

Regarding the panels, I have found Longis 555w, although my annual predicted generation is lower, the ROI is 5% higher. 

The longi's I haven't found a proper spec sheet for yet, but seems they are rated at the following:
Input Voltage: 42.10V
Output Current: 13.19A

So these should be fine.  Thank you for spotting this.

 Data sheet for Longi 555w below.

https://static.longi.com

 

Edited October 27, 20232 yr by TaliaB

Good afternoon @Pho3niX90 and welcome to the forum.

8 hours ago, Pho3niX90 said:

The inverter is also not set in stone yet, as I am still deciding on Lux, Solis S6 Pro (1Kw extra for the price is attractive) or SunSynk

A] First decide on an inverter then you do your design around the inverter.

 

7 hours ago, Pho3niX90 said:

Combiner box (ac/dc), should this be diy'd? Or should I buy a premade one? Any suggestions?

B] I found that it is cheaper to build your own DC combiner box than to buy an assembled box, then you can decide how the box is laid out and leave space for future expansion if you add another inverter.

 

7 hours ago, Pho3niX90 said:

What other breakers am I forgetting, or safety protocols

C] That depends on the design of the system. 

C1] In the event that the batteries are flat and utility power is not available and the sun did not shine for a couple of days are you going to use a generator to power the system through the inverter and let the inverter charge the battery or batteries or are you only going to power the essential items from the generator and not charge the battery or batteries through the inverter?

The bare minimum on the AC side for protection that I would recommend is an Isolator and circuit breaker on both the input and output of the inverter and a change over.

 

8 hours ago, Pho3niX90 said:

Is my solar array specd correctly? There is no shading

D] I do not know the brand of solar panel that you are referring to (CP) so I cannot verify if the solar array is specced correctly, please advise on the following specs as per the datasheet of the solar panel Pmp, Voc and Isc - all values must be the STC values and not the NOCT values. Another factor that I take into account is the physical size and weight of the solar panel usually I opt to go for smaller panels e.g. 460 watt panels.

 

8 hours ago, Pho3niX90 said:

Is 6mm cable the correct sizing for the PV?

E] Yes the 6mm2 cable is sufficient and a lot better than the 4mm2 in terms of voltage drop over the cable.

 

8 hours ago, Pho3niX90 said:

Should both strings be of equal length? and what is the max length a string can be? As my property (roofs) are split, and the first array will be the closest to the inverter.

F] I do not think that a few volt difference would have a huge impact on the inverter as long as the difference is not Voc of one or two solar panels, the max string length depends on the cable thickness and would only play a big role if the solar panels are a couple of 100m away from the inverter.

 

I had a quick look at the Solis S6 Pro 5kW, 6kW and the 8kW at The Power Forum Store and the Solis S6 Pro 5kW is R 20347.85 the 6kW is R 22793.52 and the 8kW is R 32743.49

The solar panel array size of the Solis S6 Pro 5kW can go upto 8 kW, the 6kW can go upto 9.6kW and the 8kW can go upto 12.8kW. The maximum solar input current for the 5kW and the 6kW are 16A and the maximum short circuit current is 24A per MPPT for the 8Kw the maximum solar input current is 32A and 20A and the maximum short circuit current is 36A and 30A across the 3 inputs.

If you are going to use the 555W Longi solar panels then you can go upto 7 panels in series per MPPT for the 5kW inverter, 8 panels in series per MPPT for the 6kW inverter and upto 11 panels in series per input for the 8kW inverter.

If I were you I would go for the 6kW inverter to pay almost R 10k more for 2kW is absurd and later on add another 6kW unit in parallel.

Here is the link to the datasheet of the 555W Longi solar panel https://static.longi.com/L_Gi_LE_T_TMD_059_107_LR_5_72_HPH_535_555_M_35_35_and_15_V14_895e6db05e.pdf have a look at the datasheet and make a note of the physical size of the solar panel, once you know the physical size of the solar panel then measure the size of your roof or roofs and calculate how many solar panels you will be able to fit on the roof or roofs, just to check that the figures that you got from the pvsketch website is correct. The orientation of the solar panels are also roof type specific because the solar panel have specific mounting points also pointed out in the datasheet of the solar panel so ask if you are not sure which type of mounting your roof requires.

You did not mention what battery or batteries you are going to use with the inverter, just remember that Solis has a preferred battery list on their website which lists all the LiFePO4 batteries that is compatible with the inverter.

3 hours ago, GerhardK83 said:

Good afternoon @Pho3niX90 and welcome to the forum.

A] First decide on an inverter then you do your design around the inverter.

 

B] I found that it is cheaper to build your own DC combiner box than to buy an assembled box, then you can decide how the box is laid out and leave space for future expansion if you add another inverter.

 

C] That depends on the design of the system. 

C1] In the event that the batteries are flat and utility power is not available and the sun did not shine for a couple of days are you going to use a generator to power the system through the inverter and let the inverter charge the battery or batteries or are you only going to power the essential items from the generator and not charge the battery or batteries through the inverter?

The bare minimum on the AC side for protection that I would recommend is an Isolator and circuit breaker on both the input and output of the inverter and a change over.

 

D] I do not know the brand of solar panel that you are referring to (CP) so I cannot verify if the solar array is specced correctly, please advise on the following specs as per the datasheet of the solar panel Pmp, Voc and Isc - all values must be the STC values and not the NOCT values. Another factor that I take into account is the physical size and weight of the solar panel usually I opt to go for smaller panels e.g. 460 watt panels.

 

E] Yes the 6mm2 cable is sufficient and a lot better than the 4mm2 in terms of voltage drop over the cable.

 

F] I do not think that a few volt difference would have a huge impact on the inverter as long as the difference is not Voc of one or two solar panels, the max string length depends on the cable thickness and would only play a big role if the solar panels are a couple of 100m away from the inverter.

 

Thank you for the welcome. And the detailed response. 

A. I have my mind set now on the Solis S6 6kW, since Tuesday the mains have been running on a 25A breaker (5500w), so 6kw is more than enough. Geyser is solar, stove and oven is gas.

B. I have been doing the BOM on solar inverter warehouse after reading some threads on here. I have decided this route mainly due to the fact that I would know exactly whats going in, and knowing in the future what the limitations are, and where to expand, just as you suggested. 

C. The idea is to run the genny in the severe cases, it's a 7kw generator so should be able to pull loads and charge the batteries at the same time. Unfortunately, it doesn't have autostart, but will venture into doing a arduino project to auto actuate the choke, and start. But at the start, it would be manual. 

D. I was abbreviating the Canadian Solar, but since the reply I have been looking into the Jinko, or Longi, (555w) since I need to stay in the amperage limitations of the Inverter.

E/F. Thanks, I did some calculations on 14amps, it's extreme estimate since non of the 6mm PV cables have proper specs (that I could find), but drop of worked out to around 3.5v over 50meters, calc

Voltage Drop (V) = 14 A x 0.0005 ohms/m x 50 m = 3.5 V

44 minutes ago, GerhardK83 said:

I had a quick look at the Solis S6 Pro 5kW, 6kW and the 8kW at The Power Forum Store and the Solis S6 Pro 5kW is R 20347.85 the 6kW is R 22793.52 and the 8kW is R 32743.49

The solar panel array size of the Solis S6 Pro 5kW can go upto 8 kW, the 6kW can go upto 9.6kW and the 8kW can go upto 12.8kW. The maximum solar input current for the 5kW and the 6kW are 16A and the maximum short circuit current is 24A per MPPT for the 8Kw the maximum solar input current is 32A and 20A and the maximum short circuit current is 36A and 30A across the 3 inputs.

If you are going to use the 555W Longi solar panels then you can go upto 7 panels in series per MPPT for the 5kW inverter, 8 panels in series per MPPT for the 6kW inverter and upto 11 panels in series per input for the 8kW inverter.

If I were you I would go for the 6kW inverter to pay almost R 10k more for 2kW is absurd and later on add another 6kW unit in parallel.

Here is the link to the datasheet of the 555W Longi solar panel https://static.longi.com/L_Gi_LE_T_TMD_059_107_LR_5_72_HPH_535_555_M_35_35_and_15_V14_895e6db05e.pdf have a look at the datasheet and make a note of the physical size of the solar panel, once you know the physical size of the solar panel then measure the size of your roof or roofs and calculate how many solar panels you will be able to fit on the roof or roofs, just to check that the figures that you got from the pvsketch website is correct. The orientation of the solar panels are also roof type specific because the solar panel have specific mounting points also pointed out in the datasheet of the solar panel so ask if you are not sure which type of mounting your roof requires.

You did not mention what battery or batteries you are going to use with the inverter, just remember that Solis has a preferred battery list on their website which lists all the LiFePO4 batteries that is compatible with the inverter.

My idea is exactly this, get the S6 6Kw, and later add another for the extra capacity as well as extra mppts. 

I assume the 7 panels per string is due to the bottleneck being the 600v limit? 

 

The batteries for now are 4 x 200ah gels, I replaced 2 of them around 2 months ago. The idea is to replace them all with lithiums around Feb/March, when I am able to match the capacity replacement. 

1 hour ago, Pho3niX90 said:

Voltage Drop (V) = 14 A x 0.0005 ohms/m x 50 m = 3.5 V

Small typo in your calculation voltdrop over 50 meters 0.35v.

22 minutes ago, Pho3niX90 said:

A. I have my mind set now on the Solis S6 6kW, since Tuesday the mains have been running on a 25A breaker (5500w), so 6kw is more than enough. Geyser is solar, stove and oven is gas.

Good choice, once you start saving money then you will realize that you want to live a little bit more comfortable and then you realize that you do not have enough power to do so.

 

30 minutes ago, Pho3niX90 said:

B. I have been doing the BOM on solar inverter warehouse after reading some threads on here. I have decided this route mainly due to the fact that I would know exactly whats going in, and knowing in the future what the limitations are, and where to expand, just as you suggested. 

Good, I found this shop https://e-glow.co.za/ that is extremely well priced for DC Miniature Circuit Breakers (MCB), DC Molded Case Circuit Breakers (MCCB), DC Isolators and DC Surge Arresters.

 

37 minutes ago, Pho3niX90 said:

C. The idea is to run the genny in the severe cases, it's a 7kw generator so should be able to pull loads and charge the batteries at the same time. Unfortunately, it doesn't have autostart, but will venture into doing a arduino project to auto actuate the choke, and start. But at the start, it would be manual. 

If you want to charge the batteries while the generator is running then the change over must be before the inverter so that you can choose between the utility as one power source and the generator as another power source, I am not sure if the generator input into the inverter must be used if a generator is connected to the inverter or is that input only for the inverter reporting functions of the software to distinguish between utility energy usage and generator energy usage. I would not worry about an autostart for now because I am sure that you would not be very happy at 2 am, 3 am or 4 am in the morning when the generator starts up.

 

56 minutes ago, Pho3niX90 said:

D. I was abbreviating the Canadian Solar, but since the reply I have been looking into the Jinko, or Longi, (555w) since I need to stay in the amperage limitations of the Inverter.

Ok, when I started to do research regarding the system that we run at home I created an Excel spreadsheet where I compared most of the popular solar panels and these solar panels are below the 16A solar input current limit of the Solis inverter 550W JA Solar, 550W Jinko, 550W Seraphim, 550W TW, 555W Jinko, 555W Longi, 560W Seraphim, 575W Jinko, 575W Longi. The physical size of these solar panels are all the same and the open circuit voltage differ by 2 to 3 volts and output current differ between 12.9A and 13.62A.

 

1 hour ago, Pho3niX90 said:

I assume the 7 panels per string is due to the bottleneck being the 600v limit? 

No the 7 panel limit is because of the recommended maximum PV power which is 9600W over two mppt's that gives you 9600 / 2 = 4800W per mppt. FYI the 7 panel limit is for the 5kW inverter, the 6kW inverter is 8 panels per MPPT. If the 600v was the limiting factor then you would be able to use 11 panels in series per MPPT but the recommended maximum PV power is the limiting factor.

 

1 hour ago, Pho3niX90 said:

The batteries for now are 4 x 200ah gels, I replaced 2 of them around 2 months ago. The idea is to replace them all with lithiums around Feb/March, when I am able to match the capacity replacement. 

Ok, the 4 x 200Ah gels are better than nothing but LiFePO4 batteries are king. Let me explain the 4 x 200Ah batteries would have 9.6kWh available if they can be 100% discharged but if they are discharged to 100% DOD the life expectancy would be severely shortened so in order to lengthen the life expectancy of the batteries they are only discharged to 30% DOD or maybe 50% DOD so if you discharge only 30% then the usable energy is only 2.88kWh if you discharge to 40% DOD then you have 3.84kWh available and if you discharge to 50% DOD then you have 4.8kWh available so from an energy point of view those 4 200Ah gel batteries can be replaced by 2 Greenrich UP3686 or 1 Greenrich UP5000 or WM5000 battery or 1 Freedom Won Lite or eTower battery. I prefer batteries where the lugs on the power cables can be bolted to the battery rather than the clip in power connector like the power connector on the Pylontech type batteries. I would purchase the LiFePO4 battery and the inverter from the same seller just in case there is any issues with the communications between the battery and the inverter so that you can ask for support from the seller before contacting the inverter manufacturer.

5 hours ago, GerhardK83 said:

5 hours ago, GerhardK83 said:

Ok, when I started to do research regarding the system that we run at home I created an Excel spreadsheet where I compared most of the popular solar panels and these solar panels are below the 16A solar input current limit of the Solis inverter 550W JA Solar, 550W Jinko, 550W Seraphim, 550W TW, 555W Jinko, 555W Longi, 560W Seraphim, 575W Jinko, 575W Longi. The physical size of these solar panels are all the same and the open circuit voltage differ by 2 to 3 volts and output current differ between 12.9A and 13.62A.

I think the 9.6kw on the solis is the overall limit combined on both pv inputs. The limit per mppt is the current and/or the voc. I don't think it's limited to 4800w per mppt? I have 10 X jinko 550w panels on my solis 6kw and haven't had any issues. Interesting these hit 5500 - 6000w peak often. Haven't had any issues yet

50 minutes ago, cp69 said:

I think the 9.6kw on the solis is the overall limit combined on both pv inputs. The limit per mppt is the current and/or the voc. I don't think it's limited to 4800w per mppt? I have 10 X jinko 550w panels on my solis 6kw and haven't had any issues. Interesting these hit 5500 - 6000w peak often. Haven't had any issues yet

I think you are right. For many years Solis has been very clear on the maximum full time current their inverters can use. Over the short term they could also exceeded the inverter rating and would then go into clipping. Slight over panelling is fine. 

What I also found if you exceeded the Isc by a big margin the older models would immediately switch off. 

Should one use say  200V parallel strings you will not even be able to connect 50% of the Watt power of the inverter based on the 16A limit per MPPT for the 6kW.

The above based on older models but could still be valid on the latest. 

Edited October 28, 20232 yr by Scorp007

7 hours ago, GerhardK83 said:

Good choice, once you start saving money then you will realize that you want to live a little bit more comfortable and then you realize that you do not have enough power to do so.

 

Good, I found this shop https://e-glow.co.za/ that is extremely well priced for DC Miniature Circuit Breakers (MCB), DC Molded Case Circuit Breakers (MCCB), DC Isolators and DC Surge Arresters.

 

If you want to charge the batteries while the generator is running then the change over must be before the inverter so that you can choose between the utility as one power source and the generator as another power source, I am not sure if the generator input into the inverter must be used if a generator is connected to the inverter or is that input only for the inverter reporting functions of the software to distinguish between utility energy usage and generator energy usage. I would not worry about an autostart for now because I am sure that you would not be very happy at 2 am, 3 am or 4 am in the morning when the generator starts up.

 

Ok, when I started to do research regarding the system that we run at home I created an Excel spreadsheet where I compared most of the popular solar panels and these solar panels are below the 16A solar input current limit of the Solis inverter 550W JA Solar, 550W Jinko, 550W Seraphim, 550W TW, 555W Jinko, 555W Longi, 560W Seraphim, 575W Jinko, 575W Longi. The physical size of these solar panels are all the same and the open circuit voltage differ by 2 to 3 volts and output current differ between 12.9A and 13.62A.

 

No the 7 panel limit is because of the recommended maximum PV power which is 9600W over two mppt's that gives you 9600 / 2 = 4800W per mppt. FYI the 7 panel limit is for the 5kW inverter, the 6kW inverter is 8 panels per MPPT. If the 600v was the limiting factor then you would be able to use 11 panels in series per MPPT but the recommended maximum PV power is the limiting factor.

 

Ok, the 4 x 200Ah gels are better than nothing but LiFePO4 batteries are king. Let me explain the 4 x 200Ah batteries would have 9.6kWh available if they can be 100% discharged but if they are discharged to 100% DOD the life expectancy would be severely shortened so in order to lengthen the life expectancy of the batteries they are only discharged to 30% DOD or maybe 50% DOD so if you discharge only 30% then the usable energy is only 2.88kWh if you discharge to 40% DOD then you have 3.84kWh available and if you discharge to 50% DOD then you have 4.8kWh available so from an energy point of view those 4 200Ah gel batteries can be replaced by 2 Greenrich UP3686 or 1 Greenrich UP5000 or WM5000 battery or 1 Freedom Won Lite or eTower battery. I prefer batteries where the lugs on the power cables can be bolted to the battery rather than the clip in power connector like the power connector on the Pylontech type batteries. I would purchase the LiFePO4 battery and the inverter from the same seller just in case there is any issues with the communications between the battery and the inverter so that you can ask for support from the seller before contacting the inverter manufacturer.

I see, my calcs were as follows:

9.6kW / 0.555 = 17

600v / 45.34v = 13

So would have gone 8 to 10 panels, and then another 8 to 10 in a couple months.

The thinking was that I over power a little bit for the overcast days, and reaching the max a little bit earlier the day, to later. That being said, I am not sure if this would have any implications on warranty or the longevity of the inverter

The battery makes ssense.when I did the batteries initially it made sense to replace them every 2years due to the pricing, however, gel has gone up in prices, whilst lith has come down, so now lith just seems much better.

Edited October 28, 20232 yr by Pho3niX90

On 2023/10/28 at 8:13 AM, Pho3niX90 said:

I see, my calcs were as follows:

9.6kW / 0.555 = 17

600v / 45.34v = 13

So would have gone 8 to 10 panels, and then another 8 to 10 in a couple months.

The thinking was that I over power a little bit for the overcast days, and reaching the max a little bit earlier the day, to later. That being said, I am not sure if this would have any implications on warranty or the longevity of the inverter

To be safe I would stick to 8 panels in series per MPPT, some of the distributors are full of nonsense if they find out that the unit has been subjected to either an over voltage or an over current or an overpower of the unit and might refuse to honor the warranty. You could also contact the manufacturer and ask them if there is a power limit per MPPT or does the one input's power deduct from the Max Recommended PV Input Power e.g. 11 550W panels in series = 6050W Max Recommended PV Input  9600W 9600 - 6050 = 3550W.