RabidBunny

I have recently been looking at this topic lately and have come to find there is no fix standard for vendors to adhere to which leads to wildly different specs. If you need to meet a standard/regulation for your install, use that as the guide line as Justin suggested. If not, let your budget decide the best mm2/meter per rand product.

Yes, that's what I'm trying to confirm, thanks!
 
You clearly outlined it nicely in this quoted section:
What baffles me though, is that if you phone (almost any supplier), asking for the amperage rating for 35mm² Battery Cables, I can guarantee you almost every single one of them will tell you something different and at the end of the day, no-one is any wiser as to how can some say 147A, some say 162A some say 240A (high current rating - expensive as hell from the UK), then they all start "googling" because even they aren't even sure anymore - and before you know it - you can run half of Eskom on a 35mm² Battery Cable ... 😆
 
Why on the AC side of things is this more common and straight forward, ie. ask them for 2.5mm GP Wire and almost all of them will tell you the exact same.
 
I understand with Battery / Welding Cable comes complexities like number of strands, insulation type, etc. but if I search for 35mm² Battery Cable, almost every supplier (some even selling the same cables are way out of bounds from any kind of "normality").
 
I'm trying to get to the bottom, not just of what is right (according to SANS), but also what is safe, ie. not trying to skimp on cable or such ~ but even a 25% over-spec leaving room for "additional" safety.

AC house wiring is old just sold as per the SANS-10142 ratings. Because, ultimately, some sparky has to sign off the CoC, and if it is not SANS-10142 spec, he will want to see full manufacturer data sheets and SANS certificates before he signs it.
The same applies to DC house wiring, so if you vary from the SANS-10142 current ratings, your sparky is going to want proper evidence that the wires are up to spec.
For general industrial wiring, the specs vary wildly.  I have browsed a few, and they all have different specs based on intended application. Some allow for higher conductor temperatures. Some have time limits at max load, some use lower ambient temperature.  You need to read the datasheets very carefully to make sure that it will actually apply to your installation (and be prepared to prove this to your sparky).

The voltages does not have to be 100% the same for the MPPT's (I think there is a margin of tolerance).
I won't say 50V difference between them would be OK (you'll most likely get a unbalanced error/warning); but between 5 and 15 volts I'm pretty sure it would be OK?
Today was very bad weather and they ran around the 249V / 250V peak (each of the 4 x MPPT's, taking into account that they are "paralleled" - voltages roughly stay the same for the 2 x strings, but the amps double) ... on a good sunny day they push up to around the 300V mark.
I've added a few more panels since my original post, I started out with 24 x 410W panels and added another 12 x 410W panels (during summer), and then recently last week added another 12 x 415W panels.
I'm currently running 8 x Strings of 6 each (36 @ 410W 6S2P, 12 @ 415W 6S2P), I can still add 2 x panels per string and still be within the safe zone with regards to the 500V limits as I still have enough roof space 😀
Panels are facing 18 degrees North-East at a 8 to 10 degree tilt (I don't really have shading problems, even though I do have a lot of big trees, they are mostly far away not to cast shadows) ... (optimal tilt in summer is about 23 degrees and in winter around 53 degrees), but when I had 14.76kWp during summer I generated 15.5kWp on most of the sunny days.

Yes, i have also noticed this on my instance

The voltage ratings won't be exceeded (6x Panels per String and 2x Strings per MPPT), since the PV Array is paralleled, the amp ratings doubled when I connected the second PV String (per MPPT).
 
Voltage ratings stayed within the MPPT min and max range ~ taking the lower of the two into account, which is correct.
 
On sunny days I tend to average around 79.86% of the PV Array capacity.
 
PS: be aware with 9 x Panels per String, exceeding the optimal MPPT range - 125V ~ 425V ~ may negatively affect performance.

Hi Guys,
 
I've been reading up on many posts before and have studied the manuals from top-to-bottom ... but to-date I cannot find a "reasonable" answer as to the correct information I am seeking in terms of "PV Array / String Calculations" per MPPT Tracker [using multiple strings], etc.
 
I have the following setup:
 
2x Deye 8KW Hybrid Inverters ~ connected in parallel
24x 400W Mono Panels ~ strings are connected in series
 
Specifications for the Deye 8KW Hybrid Inverters:
Max. DC Input Power                     - 10400W
PV Input Voltage                            - 370V (100V~500V)
MPPT Range                                  - 125V ~ 425V
Start-up Voltage                            - 150V
PV Input Current                            - 22A + 22A
No. of MPPT Trackers                   - 2
No. of Strings Per MPPT Tracker - 2 + 2
 
Specifications for the 400W Mono Panels:
Maximum Power - Pmax (W)               - 400W
Positve Power Tolerance                     - 0 ~ +5W
Open Circuit Voltage - Voc (V)            - 49.76V
Short Circuit Current - Isc (A)              - 10.3A
Maximum Power Voltage - Vmpp (V)  - 41.19V
Maximum Power Current - Impp (A)    - 9.74A
 
Here is how I calculated the maximum PV Array Input Strings:
 
1. Deye 8KW Hybrid Inverter [PV Array Max - 10400W] / 400W Mono [PV Panel Max - 400W] = Max. 26 Panels ~ per Inverter
2. Max. 26 Panels / 2 (MPPT Trackers) = Max. 13 Panels [per MPPT]
3. [each MPPT Supports 2x Strings], therefore each string can theoretically be Max. 13 Panels [per MPPT] / 2 = 6.5 ~ Max. 6 Panels per String (rounded-down) [2x Strings per MPPT, 4x Strings per Inverter]
4. In order to balance the Strings - [i.e. 6x Panels per String] = Max. 12 Panels per MPPT ~ Max. 24 Panels per Inverter
 
Now let's verify the MPPT Range:
49.76V * 6 [volt increases in series connection] = 298.56V [theoretical V limit per String]
10.3A * 1 [amp does not increase in series connection] = 10.3A [theoretical A limit per String]
 
HERE is where I am stuck:
*each MPPT = 22A (max) or 500V (max) - if you will*
 
I *assume* that each string will be "combined" inside the internals of the Inverter itself, i.e. the Voltage will stay roughly the same [usually the lower of the two Strings], but the Amperage will double [since they will be connected in "Parallel"]?
 
Please can someone confirm for me whether the above logic is correct, are the Strings indeed "Paralleled" when each string is connected to A MPPT Tracker, or are they kept in "Series"?
 
The manual, online resources, searching countless hours, etc. ... nothing had produced any favorable results in terms of getting to the end-result of my *assumption*.
 

One consideration if you install a Sunsynk, it comes with a CT coil that clips over your main incoming grid supply cable this then connects to the inverter. It comes with wires about 5 meters long. The manual say you can extend them another 10 meters with same type of wiring. This could be a potential problem for installers who honor the manual if the distance is further than the 10 meter. I was worried about that distance as mine is about 25meters, I extended my own wires with 1.5mm flat twin and it works, but just be aware of this fact.

You can run great distances with cabling, no need to have the inverter connected close to the DB, mine is running > 50 meters.

It is important to know what time of day (or night) your usage spikes are and if you possibly have such graphs that definitely would be beneficial in calculating your inverter size, battery size, (and later solar size), etc.
 
Solar will only take you so far during the day, for both summer and less so much in winter (taking an average of 7.5 hours of solar sun in winter and maybe 8.5 or 9 hours during summer), and this is where your battery decisions comes into play, which also drive the factor of lithium vs gel vs lead acid, should they be able to communicate with one-another and even the inverter, etc ...
 
If you do plan on up-scaling later on, like adding panels, more batteries, blending Eskom, etc. rather look at getting a proper Hybrid Inverter now (possibly one that can run parallel for larger scaling later), than being stuck with something you will most likely end up selling again 3 months or 4 months down the line.
 
By the looks of it with 2 x 200L geysers your usage is surprisingly low, unless they are already converted to solar / gas?
 
I average on 50kW ~ 60kW daily ... (used to be lower), but once you realize that "free-powa" is a nice thing, you'll soon be turning every device on in your house almost daily ~ well that was in my case ... 😂
 
Basics first ...
 
Replace all light-bulbs with LED If possible look at geyser conversions (I found that the best option is the EV Tubes, where your existing geysers are converted to "solar" - with 30 tubes you should be able to easily share the load between 2x 200 L geysers with a smile + your maintenance on them is very low compared to other options) If possible look at gas - stove / hob replacements  
Just with the above 3 items alone you will already cut probably about 50% on your electricity bill (and solar / battery / inverter size alone).
 
This most definitely will bring down your usage, so you can "scale" for much smaller systems and calculate accordingly.
 
Some might argue rather scale bigger so you can cater for the electric stove, etc ... but just the above items #2 and #3 will ensure hot water even during load-shedding, hot food and coffee during those dark nights, and will teach you to change your lifestyle accordingly, and may even reduce your usage habits further.
 
* That's just my opinion of where I started from
 
PS: I had wasted thousands on useless installers, etc... etc ... and ended up doing everything myself - I do have some background though, but got a lot of help on this forum ~ watch out for replies form others who will tell you who to look for (installers) and who to duck and dodge!
 
Best of luck to you on this journey!

It is important to know what time of day (or night) your usage spikes are and if you possibly have such graphs that definitely would be beneficial in calculating your inverter size, battery size, (and later solar size), etc.
 
Solar will only take you so far during the day, for both summer and less so much in winter (taking an average of 7.5 hours of solar sun in winter and maybe 8.5 or 9 hours during summer), and this is where your battery decisions comes into play, which also drive the factor of lithium vs gel vs lead acid, should they be able to communicate with one-another and even the inverter, etc ...
 
If you do plan on up-scaling later on, like adding panels, more batteries, blending Eskom, etc. rather look at getting a proper Hybrid Inverter now (possibly one that can run parallel for larger scaling later), than being stuck with something you will most likely end up selling again 3 months or 4 months down the line.
 
By the looks of it with 2 x 200L geysers your usage is surprisingly low, unless they are already converted to solar / gas?
 
I average on 50kW ~ 60kW daily ... (used to be lower), but once you realize that "free-powa" is a nice thing, you'll soon be turning every device on in your house almost daily ~ well that was in my case ... 😂
 
Basics first ...
 
Replace all light-bulbs with LED If possible look at geyser conversions (I found that the best option is the EV Tubes, where your existing geysers are converted to "solar" - with 30 tubes you should be able to easily share the load between 2x 200 L geysers with a smile + your maintenance on them is very low compared to other options) If possible look at gas - stove / hob replacements  
Just with the above 3 items alone you will already cut probably about 50% on your electricity bill (and solar / battery / inverter size alone).
 
This most definitely will bring down your usage, so you can "scale" for much smaller systems and calculate accordingly.
 
Some might argue rather scale bigger so you can cater for the electric stove, etc ... but just the above items #2 and #3 will ensure hot water even during load-shedding, hot food and coffee during those dark nights, and will teach you to change your lifestyle accordingly, and may even reduce your usage habits further.
 
* That's just my opinion of where I started from
 
PS: I had wasted thousands on useless installers, etc... etc ... and ended up doing everything myself - I do have some background though, but got a lot of help on this forum ~ watch out for replies form others who will tell you who to look for (installers) and who to duck and dodge!
 
Best of luck to you on this journey!

Firstly, a deal with the block next door is going to fall foul of the law. OK, maybe you want to take the position that it's only a problem if you get caught. But also what happens when the occupants of one block decide that it's the guys next door who are using more than their fair share of the juice?

Many years ago I lived in a rent controlled flat. The owner of the block used to get a bill for the whole building and split that across all the flats (each flat had their own submeter, but these weren't read). 

There was unhappiness because it was known that in one flat a lot of baking was going on. In another the occupant left all his lights burning all the time. I was in one of two bachelor flats in the building, why was I paying the same as a person with a 2 bedroom flat with 3 people living it? Etc etc. The landlady soon had a fight on her hands. Muggins here volunteered to read the sub meters. After all, it's not rocket science. I soon had neighbours pounding on my door demanding that their be re-read NOW! They can't possibly be using that much etc etc

So I think even doing it for one building, the body corporate is making a stick for their own back.

How do they track who got the biggest bonus from the system, because it's a dead cert that not everybody has the same loads.

Tenant jharber might be careful with his usage, keeps his geyser under control, and is generally thrifty.

Meanwhile tenant bobster keeps tropical fish for a hobby, which means a heated tank. Oh and he has a couple of spotlights trained on that tank so the fish can be seen at their best. And he likes his electric blanket, and his wife is baking all day long because she sells at the tuisnywerheid to make some extra. And boy does that microwave oven ping all day!

And then you get loadshedding, and the one or two bobsters in the building soon deplete the battery and then nobody has anything. 

Sorry to be a bucket of cold water, but I think there are lots of problems looming on the body corporate's horizon. You could put meters on the feed to each flat, but even then what are you going to do? Tenant bobster really likes his tropical fish. Without those fish, life has no meaning. He's not draining the batteries deliberately, but what would you have him do? Poor piranhas... they have a right to a comfortable life, don't they?

Heaven forbid that somebody gets an EV and charges it every night.

They are paralleled inside the mppt 

mmm ...
 
Low and behold, can you believe ... ?
 
So I've monitored my logs and it seems that I'm easily pushing between 7kW and 8kW now (in winter on a flat IRB roof)!
 
Enough to carry the home load and charge the batteries, so Eskom has been permanently shutdown 2 days ago!
 
Let me explain in brief:
 
Originally the installers order decent panels (Grade A panels), however the installation was done with fong-kong ^&*%# panels (Grade C panels) as the suppliers sent the wrong panels - according to some knowledge people in the industry. I was invoiced for the Grade A panels, so I wrote a few threatening e-mails and all 28x panels were removed and replace with 28x 400W mono panels (Grade A) - less than the 420W fong-kong %$#%^ panels ... and what do you know my PV production increased by almost 90%

Further to this, the supplier refused to rectify the mistake as "the panels were already installed".
 
I was at work and didn't have oversight of the process, the wife didn't know and I didn't think to ask for pictures of the installation, only once I saw the boxes did I realize something is off, and have since been fighting with them to rectify the mistake - realizing the utter crap output I got ... (joined here to ask assistance on this post), and that's when I started sending emails that their next communications would be from a laywer ...
 
2 days later, they delivered the correct panels and removed the fong-kong crap ...
 
Correct panels installed and I saw a close to 90% increase in PV Production - even the software for PV Forecasting supplied earlier match the generation so close you can't even get a needle through it (at times exceeding it a little)...

The problem here is that the installer was outsourced and did not know which panels should have been supplied or installed.
 
The shop where I purchased the panels has sent me the invoice / order placed for the panels from their supplier and it matched my invoice exactly - in this case the supplier stuffed up and really did send the wrong panels (probably thinking no one would have noticed).