Is it looking ok ?

[BackTOschool]

Hello,
I am about to mount a further 2 panels to my small emergency system, and I would very much appreciate if an experienced person here ( not a newbie like me- thanks) would take a quick look and comment if it's wrong! ( or right ? )
Please take a look at my numbers / panel configuration: are they right?
I'm simply trying to optimise my panels output for my controller on my new build ( quite chuffed, it works, but like my teachers says... could do better )
Thank you
kind regards
Steve.

 

[sunshine_eggo]

2S4P array into a combiner box.

330w * 8 = 2640w

2640W / 14.5V = 182A

You are substantially over-paneled, but you are not exceeding the published limits, so you should be good. You will never get more than 14.5V * 70A = 1015W out of your arary.

30A fuses listed should be no higher than the max fuse size listed on the back of the panel - likely 15A.

Confirm 16mm can handle 70A, and you will need a fuse/breaker 1.25X the wire rating (round up) between the MPPT and battery.

 

[BackTOschool]

Hello Sunshine_eggo,

Thank you for taking the time to read and comment, it is appreciated, your comments are well received.

I have a E/W array, half on east side, other on west side. This is why I am over panelling, thanks for your observations.
Concerning fuse size, here is the data on the back of the panels:

Pmax = 330w
Output Tolerance: +- = 3%
Current at Pmax(Imp) = 10.2A
Voltage at Pmax (Vmp) = 32.6V
Short-Circuit Voltage (Isc) = 10.9A
Open-Circuit Voltage(Voc) = 39.12V

I'm not quite sure, so from the above data, which would be the max fuse size please?

kind regards,
Steve.

 

[sunshine_eggo]

Is that data from the label or a data sheet? Often the label itself lists the max fuse size to use.

Regardless, with an Isc of 10.9A, a 15A fuse is fine.

 

[BackTOschool]

I do not have a data sheet, the numbers are direct from the label on each panel, thanks you have been very helpful.

Can I please one final question: (just ask for my own education):

The fact that the power is coming from 2 panels, (not 1) on each positive cable, does not require a larger fuse, ie 2 x 10.9A ?
Thanks for your time,
Regards
Steve.

 

[sunshine_eggo]

if the panels are in series, voltage doubles, current same.

If the panes are in parallel, current doubles, voltage same.

so each of the 4 strings of 2S panels should only push 10.9a max.

 

[BackTOschool]

Thank you very much.
steve.

 

[BackTOschool]

2S4P array into a combiner box.

330w * 8 = 2640w

2640W / 14.5V = 182A

You are substantially over-paneled, but you are not exceeding the published limits, so you should be good. You will never get more than 14.5V * 70A = 1015W out of your arary.

30A fuses listed should be no higher than the max fuse size listed on the back of the panel - likely 15A.

Confirm 16mm can handle 70A, and you will need a fuse/breaker 1.25X the wire rating (round up) between the MPPT and battery.

Hello Sunshine_eggo,
could I just check something else with you please?

This is my thinking for cabling purposes:
With my 2 string 4 parallel array, each string will create 2 x 38.12v ( 76 v ) and 1 x 10.2a.
I am intending to use the: ECO-WORTHY 6 String PV Combiner Box & 63A Circuit Breakers ( Amazon UK)
which contains diodes to prevent backflow*

Each of the 4 strings will connect directly to the combiner box, with no backflow*
Q 1: I think 6mm (10AWG) for the cabling to the combiner box from each of the separate 4 strings will be suitable, Is that correct?

Q 2: The combiner box will then feed to the SCC a (max) combined total of 98v and 43A, I therefore need a minimum of 10mm (7AWG) between the combiner box and the SCC. I've based this cable size to include some headroom: 120v/50A/5m. Is this correct ?

Thank you for your time and knowledge.

kind regards
Steve

 

[sunshine_eggo]

I assume 98V is a typo, and it should be 78V.

Sounds like you've got it.

Not that blocking diodes are RARELY necessary with equivalent strings unless actual blackout shading is an issue, i.e., something is completely covering the panel that prevents any light from reaching the panel.

 

[BackTOschool]

Thanks very much, I will proceed........
kind regards
Steve.

 

[BackTOschool]

If I could ask.....
In the parameter data for the 6 string Eco-Worthy combiner box that I intend to use, it states the following:
"Max input solar system wattage (12v) = 1080W"
"Max input solar system wattage (24v) = 2160W"
"Max input solar system wattage (48v) = 4320W"

My battery is a single 12v 300Amp. my SSC is Victron MPPT 150/70
The panels are each 39.12v (Voc) 32.6 (Vmp), in 2 string 4 parallel array,
I have contacted Eco-Worthy to clarify, and they have confirmed the 1080W limit for 12v systems is for the whole array.

Question 1:
As I will be producing ( a theoretical maximum ) 2,640w, I am thinking this beyond the parameters of the box?
Or, am I misunderstanding this (highly likely):
I'm not sure how the 12v are calculated for the parameters of the combiner box?

Question 2:
Is This combiner box suitable for my array?

Question 3:
If the box is not suitable, how would you approach this, as I am struggling to find a larger capacity one, or is it even possible to fit more than one, in which case I would need 3!

kind regards
Steve.

 

[sunshine_eggo]

1: Your array may be able to produce that, but your MPPT will not permit it. 70A * 14.5V= 1015W. The limitations are likely the fuse holders/breakers, connectors, and wiring used in the box.

2: I'm not sure. In terms of the intended use, it should work. If code compliance or inspections are required, I can't say. If you never intend to draw more than the rated power (1080W @ 12V), and code compliance isn't an option, then I don't see a problem.

3: Midnite makes a range of combiner boxes that are more expensive but their ratings are based on the breakers and wires you select. I have a Midnite MNPV6. I have to select their 150VDC breakers at $15 each, and I have to supply my own wiring. It's more of a DIY combiner box skeleton.

 

[LakeHouse]

I'm not sure how the 12v are calculated for the parameters of the combiner box?

To clarify on this... The combiner box doesn't really care how much power is passing through it, but it does care how much current is passing. So those differing power ratings for different nominal voltages will all be based on the same current limitation of 90A. 90A*12V = 1080, 90A*24V = 2160W, etc.
The 12V they quote will be nominal voltage in this case, i.e., a '12V system' which operates in the 11-14.5V range.

 

[BackTOschool]

1: Your array may be able to produce that, but your MPPT will not permit it. 70A * 14.5V= 1015W. The limitations are likely the fuse holders/breakers, connectors, and wiring used in the box.

2: I'm not sure. In terms of the intended use, it should work. If code compliance or inspections are required, I can't say. If you never intend to draw more than the rated power (1080W @ 12V), and code compliance isn't an option, then I don't see a problem.

3: Midnite makes a range of combiner boxes that are more expensive but their ratings are based on the breakers and wires you select. I have a Midnite MNPV6. I have to select their 150VDC breakers at $15 each, and I have to supply my own wiring. It's more of a DIY combiner box skeleton.

Thanks for your answer,

If I've understood what you have said, in summary:

1:
Although the array can generate a theoretical 2,640w, the MPPT will throttle that to a max of 1015w, which is within the 1080W limit of the combiner box ( so it's what is flowing through the combiner box, not what is available to the combiner box that is specified to 1080w limit)

2:
Provided my array and MPPT capacity are not increased further, ( and I am not seeking any code compliance) I can likely proceed with the eco-worthy box I have selected ?

Thank you so much for your time and patience, it really is appreciated and extremely helpful.
Steve.

 

[sunshine_eggo]

1: I believe so. They are attempting to limit current through the box by specifying a maximum array power. You will likely find that something in the box is limited to 90A continuous, and any wires coming out of the combiner to your MPPT need to be able to handle 90A.

2: You could technically size your array even larger provided it doesn't exceed the input limits of your MPPT. The critical part is not increasing the output of the MPPT.

Again, not considering code compliance.

 

[BackTOschool]

To clarify on this... The combiner box doesn't really care how much power is passing through it, but it does care how much current is passing. So those differing power ratings for different nominal voltages will all be based on the same current limitation of 90A. 90A*12V = 1080, 90A*24V = 2160W, etc.
The 12V they quote will be nominal voltage in this case, i.e., a '12V system' which operates in the 11-14.5V range.

Thank you LakeHouse,
your explanation is helpful.
Steve

 

[BackTOschool]

1: I believe so. They are attempting to limit current through the box by specifying a maximum array power. You will likely find that something in the box is limited to 90A continuous, and any wires coming out of the combiner to your MPPT need to be able to handle 90A.

2: You could technically size your array even larger provided it doesn't exceed the input limits of your MPPT. The critical part is not increasing the output of the MPPT.

Again, not considering code compliance.

Thank you, you have been an enormous help, steve.

 

[sunshine_eggo]

Thank you, you have been an enormous help, steve.

We Steve's gotta stick together.