Trying to understand Combiner Box sizing / restrictions

[HelmutB]

Hi whoever is out there,

I have decided to put my toes in the water re DIY Solar systems down here in Melbourne Australia.

For better or worse I have ordered the components for an Eco-Worthy 2400W system, consisting of :

8*300W panels to be set up as 4 strings of 2 panels in series giving me 10a, 24V each
4*130AH batteries to be set up as 2 strings of 2 batteries in series giving me 24V system
1*60A controller

However this system does not come with a combiner Box!!!!!
I thought this would be a simple issue to fix, but am coming across many boxes that seem to have a 1440W limit.
They have 4 PV string inputs rated at 15A and a 63A circuit breaker, but still have 1400W limit??

eg the following

VEVOR PV Combiner Box, 4 String with 15A Rated Current Fuse, 63A Circuit Breaker, Lightning Arreste Connector for On/Off Grid Solar Panel System, IP65​

• This is in the specs:
• Extensive Application: The combiner box is a perfect device for outdoor installation and use. Suitable for photovoltaic on-grid/off-grid solar power generation systems, solar panel systems, PV array, RV solar power, home solar panel systems. It can support solar panel systems up to 720W in 12V system, 1440W in 24V system, 2880W in 48V system.

Can anyone explain this to me, as I cannot get any real answer from the suppliers??

 

[DIYrich]

1440w at 24v is 60 amps.
Main circuit breaker is 63amps.
Each incoming string can be up to 15a.
Combine 4 strings, and you get 60 amps.

You have 300 watt panels at 24v. that is 12.5 amps per panel.
Using the combiner box, you can connect 4 panels into one string.
If you put two panels on one string, you either get 25 amps (parallel), or 48v (series). 25 amps exceeds the rating of the combiner box for an incoming line.

 

[HelmutB]

Thanks DIYRich,
That makes sense now.
I will go with the 2 strings of 4 panels as this allows me to use 2 fuses in the combiner box as compared to only one if I follow the suppliers configuration of only one string.
Thanks again from down under

 

[Brucey]

If you only have two strings you don't need to use a combiner, and could go straight to an IMO type PV disconnect, using MC Y adaptor cables for example.

 

[Brucey]

Please provide the specifics of the 60A charge controller you've ordered and also the Voc of the solar panels. There will be a voltage limit that is never exceed and string voltage increases as temps decrease.

 

[HelmutB]

Hi, Brucey, Thanks for your reply.

I have attached 3 photos giving some detail of the Eco-Worthy 2400W kit I ordered.
I assume I can install it as per the suppliers diagram, but wanted to add a combiner box to more easily include fuses and breakers etc, and
in doing so I thought that I could change the layout to use 4 PV strings of two panels each in series, as I stated to DIYRich.

 

[DIYrich]

The 60 amp charger controller is at 48v. The picture of the wiring for the panels is 2s4p, for 48v. What is the DC voltage of the inverter? If 48v, then you need to wire the batteries for 48v (4s1p).

BTW, at 48v the combiner box can pass 2880 watts.

 

[HelmutB]

Hi Gents, Thanks for your patience, the saga continues.

I have now received a few things, no batteries yet.
The pictures are what has arrived i.e. 8 panels as per the spec on the back of the panel, a controller for a 12V or 24V system and an inverter for a 24v system (and a few cables etc)

so I am back to how to use these panels with the other equipment that was all supplied as a KIT!!??

I have sent messages to the supplier but have not had a reply yet (probably too soon).

Any further ideas I can try? I thought my only problem was what combiner box I was going to use!!

?

 

[robot_zombie]

the charge controller looks similar to this one, https://www.eco-worthy.com/products...harge-controller-regulator-12v-24v-autoswitch
max PV OCV=<55V (confirm this value for your controller before plugging anything in!)
so you can use 2x panels in series x 4 strings in P, each string having a max voltage of around 48V and 15(6?).57A, cant quite see on the pic. You could use the suggested PV combiner box as your solar voltage is around 48. its all pretty much max tho. I would use at least 2x4mm2 PV wire from the combiner to charge controller, as you could have too much current for 1x4 and marginal for 1x6mm2 depending on the length. That charge controller looks pretty light to handle 60A, see how it goes....

 

[HelmutB]

hi guys, I am having to start from the beginning.

It is now clear that at least the solar panels have been incorrectly labelled as 300w but seem to be 120w.

I am returning the 2400w complete KIT to the supplier.

This is one example of many reviews found since I purchased the system:
"WARNING -WARNING -WARNING - Fraudulent seller. DONT PURCHASE - DO NOT PURCHAS -WARNING - WARNING. I Purchased 4 x 300w Panels. They sent me 120W Small Panels with Fake 300W Stickers on them. This is no mistake, it is fraud. When I asked for a return label they ran me around for a week before sending me a CORRUPT LINK saying it was a link to Labels. DONT CLICK ON THE LINK THEY SEND. I contacted Ebay and Ebay agreed it is a scam. I ended up getting a refund through EBAY not the seller."

My starting point is that I now have access to 4 x 12.8V 120Ah lithium batteries. configured to 24v or 48v system??
Can you suggest a panel configuration of about 8*300w or 4*600w panels, using an MPPT 150v/70 A controller or similar??
Probably still use a Combiner Box just for simplicity of cabling and fusing/breakers etc??
The inverter I expect to be about 3000w (peak to 6000w), to 240V ac,
Any assistance would be appreciated.

Thanking you in advance, and thanks for your patience, it's a great learning process, but I am enjoying it!!

 

[Brucey]

I have a 150/35 and Hyundai 300W panels with a Voc of 39V, currently running at 24V.

So can series three of them, for around 120V. Leaves room for V to increase as temps drop and stay below the 150V critical point.

Two strings will get you to the ~1000W max output of 35A at 24V.

With the 150/70 you could do four parallel strings of three panels.

If you only series two panels then you leave a bunch of available voltage on the table and need more parallel strings.

Need a combiner/fusing once you go beyond two parallel strings for protection.