"Similar" Panels...

[LDVV]

I realise this isn't ideal, but, at least in this situation, it doesn't seem catastrophic (from what I've read so far)...

I have two different types of panels - 13 of one type, and four of the other.

Ideally I'm wanting five strings of three, so 15 panels altogether.

Can I mix them to achieve the arrangement that I want;

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AND

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[MisterSandals]

Can I mix them to achieve the arrangement that I want;

Sorry, working on tiny screen…can you post watts, Voc and Imp for these panels.
And if you know how many of each, we can get best configuration.

Your SCC max input voltage too.

 

[LDVV]

REC Model NumberREC315TP2M
STC Rating315.0
PTC Rating289.9
Open Circuit Voltage (V)39.9 V
Short Circuit Current10.05 A

Vs

Model NumberREC315NP
STC Rating315.0
PTC Rating294.4
Open Circuit Voltage (V)40.5
Short Circuit Current (A)9.98

MPPT/Inverter Voltage range:
64-130VDC
Max. Solar Voltage:
145VDC
Max. Charge Current:
140A

 

[MisterSandals]

Those are close enough to call identical! The differences between like panels are probably that much.

 

[MisterSandals]

Ideally I'm wanting five strings of three, so 15 panels altogether.

That looks like the best you can do.
You will need to fuse each string before combining in parallel 15A fuse (look for MC4 inline fuses). There might be a handy 5:1 MC4 connector to make wiring easy.

 

[LDVV]

That looks like the best you can do.
You will need to fuse each string before combining in parallel 15A fuse (look for MC4 inline fuses). There might be a handy 5:1 MC4 connector to make wiring easy.

Thanks for the fuse warning, will look for inline type.

I was given a 5Kva MPPT Inverter.

However, it's 48v 80A, so I don't think it's going to handle the ~4.7Kw that the panels will supply.

I realise it's not exactly "prestigious", but would this be suitable to make the most of 15 of my panels?

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[A.Justice]

I have a set of used panels (in service) that have substantially more deviation than those. I'm sure there's a few lost watts in there, but they work just fine.

I would use them together if it were my setup, they're so close that I wonder if they aren't the same panels, from different manufacturing runs.

 

[MisterSandals]

However, it's 48v 80A, so I don't think it's going to handle the ~4.7Kw that the panels will supply.

The charging volts and amps (56V charging volts x 80A = 4480W) pretty much uses all the watts your panels can/will supply. Maybe an hour or 2 midday it will clip a couple hundred watts under ideal conditions but that's chump change.

Prestigious or not, is that the only reason you are looking to replace it? Not sure if it was working as advertised i would not be looking to buy a new unit.

 

[LDVV]

Attached is an image, from the box, of the Inverter that I have.

Are you saying that it would handle my 15 x 315w panels safely?

I'd rather not have to go and buy a new inverter if this one will efficiently use my existing panels.

 

[12VoltInstalls]

was given a 5Kva MPPT Inverter

You were given that Epever?!

That’s a decent unit. For the money too bad there’s not 120V available too. Way cheaper in US$ apparently. As bad as our taxes are here Britain must be really impressed with itself.

 

[LDVV]

You were given that Epever?!

That’s a decent unit. For the money too bad there’s not 120V available too. Way cheaper in US$ apparently. As bad as our taxes are here Britain must be really impressed with itself.

No, I was given the one in the image.

The Epever was the one that I considered buying.

 

[MisterSandals]

Are you saying that it would handle my 15 x 315w panels safely?

I'd rather not have to go and buy a new inverter if this one will efficiently use my existing panels.

You really only need to keep the array voltage, adjusted for temperature, below 145V.

Your panels are 40Voc so 3 in series make 120Voc which is perfect for your SCC.
So you take 3 panels, connect them in series (+ of panel 1 to - of panel 2, + of panel 2 to - of panel 3). Do this 5 times to make 5 strings. The strings are "3S", 3 in series.

You connect these 5 strings in parallel (connect the 5 + ends of the strings, connect the 5 - ends of the strings) to make a 3S5P array. This will have 3x the panel Voc (3 x 40) and the amperage of 5x the panel Imp (10A).

You will need to put a fuse on the 5 + wires from your strings. 15A fuses or breakers should be fine.
You will need to combine your 5 strings in a combiner box that will house the fuses/breakers.

I don't know much about combiner boxes, @12VoltInstalls (or anybody), can you recommend a combiner box (and suitable fuses/breakers)?

Maybe something like this:

https://www.amazon.com/PowGrow-Combiner-Current-Protective-Pre-Wired/dp/B09BTX2YQ5/

 

[12VoltInstalls]

@12VoltInstalls, can you recommend a combiner box (and suitable fuses/breakers)?

Unfortunately no hands-on there.

My strings have 8A MC4 fuseholders. The cables run inside where I have a dbl 10A CHTAIXI DC circuit breaker for each string as shutoffs/disconnects.
From the string circuit breakers I have 10ga solar wire that I crimped to 8ga welding cable for “Y” branch connectors to the SCC. The SCC to busbar a is 6ga

several folks have mentioned a couple of brands. Signature Solar has a nice one with metal case. I thought about this one in a shopping cart.

 

[MisterSandals]

several folks have mentioned a couple of brands. Signature Solar has a nice one with metal case. I thought about this one in a shopping cart.

Yea there are a bunch of 4 string boxes for ~$100. OP needs 5 which means a 6 string box. Those look line ~$175 (bigger main breakers and main lugs make it significantly more). But it looks like it has all the safety features in one convenient enclosure.

 

[12VoltInstalls]

OP needs 5 which means a 6 string box. Those look line ~$175 (bigger main breakers and main lugs make it significantly more). But it looks like it has all the safety features in one convenient enclosure.

I would do that.
My setup is smaller/simpler. And I am aware of the ‘risks’ and was comfortable with what I did. If I had more strings it’s hard to not just buy a metal enclosure preloaded with the goodies like that ecoworthy.
What bothers me is that it is configured assuming MC4s- I run cables inside for these connections to keep the ‘combining’ and breakers close to the SCC or AIO/hybrid because it makes sense, plus it will avert weather intrusion.
Iirc watts247 has a decent multi-string combiner as well.

 

[LDVV]

Thanks for the Junction Box links.

I'd read about Blocker Diodes, and I see 'anti-reverse' mentioned in the adverts (didn't see anything Diode specific). Is this the same thing? If not, I don't think there's anything else in my proposed set up, so far, to prevent the panels consuming the power back at night.

 

[LDVV]

Apologies, for this apparently boring question, BUT...any input, Anyone?

 

[MisterSandals]

I'd read about Blocker Diodes, and I see 'anti-reverse' mentioned in the adverts (didn't see anything Diode specific). Is this the same thing?

Yes, most/all of the nicer ones have the blocking diodes. The fusing is the main thing for sure. I do not own any combiner boxes but would opt for one with them if not significantly more expensive.
Get the box capacity right first. Then fuse sizing (they can all be replaced within the spec of the holders and combiner box).

Helpful to what you were asking?

 

[LDVV]

Yes, thanks.

However, two options (for a Combiner Box) were linked in here. I particularly liked the one that you posted, but it doesn't seem to have these diodes. At least not from what the description reads.

...and to clarify, you mentioned further back int his thread: '15A fuses or breakers should be fine.'

Each of my Strings should be ~30A(?).

The total, just before the Inverter, should be ~50(?).

Did you make a typo, or am I calculating something incorrectly?

 

[MisterSandals]

but it doesn't seem to have these diodes. At least not from what the description reads.

Agreed. Perhaps why lower price than others that have them.

Each of my Strings should be ~30A(?)

No, your 5 strings will each be 3S. Sum the volts for each string. Amps are limited to lowest amp panel 9.98A.

So fusing each of the 5 strings with 15A is correct.

The total, just before the Inverter, should be ~50(?).

combiner box combines in parallel so amps are added: (5x 9.98A) = 50.
Your combiner box will need to be 60A bare minimum. Output breaker should be 60-80A too (lower amp handling than wire the breaker protects to the SCC. You want breaker to trip before wire following it burns up).