SB3600TL readings sound right?

[provr6]

System:

1 roof SE 8 x 195 panels (1.56kw)
1 roof SW 6 x195 panels (1.17)kw

tot sys 2.73 kw

Here are my inverter readings at 1pm today full sun on all panels no shading

Input A
1478 Watts being produced
276 V
4.7 A

Input B

1478 Watts being produced
229 V
1.0 A

the grid on both inputs reads 6.0A

Am I right in saying that the watts being produced is the total wattage of inputs A & B at all times? I was expecting the inverter to show the watts seperately as it flicked between the two inputs and for one roof to be less because of less panels.

Does the watts amount seem right given the size of the system?

Is the low reading of 1.0A on input B anything to worry about and why is so much different to the other input?

I estimate at the end of the day to have generated about 8kwh, which seems ok?, Yes/No?

 

[Somecamel]

Why did they use a SMA 3600 when you only have a 2.73kW System? Inverter is Oversized for your array or am I reading this wrong

 

[provr6]

You have read it correctly and I don't know why. I assumed it was the smallest dual inverter you could get (think the installer said something along those lines).


What sort of watts should I expect to see on the inverter at full sun on all panels?


I'm also wondering if the current reading of 1.0A is bringing the total watts down. Should it be similar to the Input A which is 4.7A ? Could this be related to an oversized inverter?

 

[yorkshiremike]

The power (upper right on display) is always total power out to the grid.
It's the sum of the DC power on each input times by the inverter efficiency (say about 97%).

So on your system, you have:

DC Power:

Input A = VxI = 1297W, Input B = VI = 229W. Sum (total) = 1526W

AC Output Power:

1526x0.97 = 1480W (should also get this if multiply the grid/AC voltage and current shown on the display)

So, input B very much less than input A (eg 6 panels but different orientation?). Also as said earlier, below 'ideal' minimum installed kWp range for the inverter (copes with 3kW - 4.2kW)

 

[provr6]

The power (upper right on display) is always total power out to the grid.
It's the sum of the DC power on each input times by the inverter efficiency (say about 97%).

So on your system, you have:

DC Power:

Input A = VxI = 1297W, Input B = VI = 229W. Sum (total) = 1526W

AC Output Power:

1526x0.97 = 1480W (should also get this if multiply the grid/AC voltage and current shown on the display)

So, input B very much less than input A (eg 6 panels but different orientation?). Also as said earlier, below 'ideal' minimum installed kWp range for the inverter (copes with 3kW - 4.2kW)

Thanks Yorkshiremike and I think I understand your calculations.

It seems to me the low current on input B is pulling it down. Should i expect 4.7A (as on input A) x 229v = 1076W. Would the different orientation effect the current that much? (its still SW)

 

[yorkshiremike]

If (big if) the illumination of the 2 arrays is similar (same relative angle to the Sun), and with each of the two arrays a single string (series connected panels), you'd expect roughly the same current in each string and the voltages in the ratio of the number of panels in each string. So that would be about 4.7A in each and if string A is 276V, then this is 276/8 V per panel (=34.5V), so you'd expect the string with 6 panels to be about the same per panel voltage (ie 207V for the string), but instead it's 229V giving a per panel voltage of about 38V.
The output of array A (about 1.3kW) is what you'd expect with full sun, whereas the output of array B 0.229kW is more what you might expect from panels in diffuse (not direct sun light). If the SW array really is in direct sunlight at 1pm, then I'd be looking for a hard shadow onto 1 or more of the panels. Without the Global Peak Optitrac switched on, you can get this effect where the MPPT trys to maintain a (too high) voltage (preventing the affected panel from bypassing) and draws too little current and power from the string.
Otherwise, if the two arrays really are orientated at 90 degrees to each other - SE and SW (and at the same pitch), then with clear skys you'd expect to get the peak from the larger 8 panel array sometime in the morning and about 3 hours later in the afternoon you should see the peak in the second array and the peak in the smaller array should be something like 6/8 (six eighths) of the larger.

 

[yellowvanman]

What panels have you got?

 

[provr6]

What panels have you got?

ET Solar M572, 195 W panels

 

[provr6]

Is there a way of checking the peak power genereated at some point in the day?

 

[yorkshiremike]

The inverter saves a lot of data, but unfortunately, it doesn't save the separate DC values, so after the event you can't recall the individual A and B values (unless you spend more money on a SMA web box). What you can recall is the AC power output produced at every 5 second interval. On the inverter display, the bar graph shows the hour by hour values, but with a PC + bluetooth and 'sunny explorer' you can view the daily graphs in more detail or even export the data to the PC to view/analyse in excel.