Solar Sizing | I thing I done goofed.

[Solar Guppy]

Okay. Previously I had all (9) panels in series and ran them through an inline fuse before going into a single MPPT. Was that the right thing to do?

Use the calculator to have the correct answer. In my array's I run 10 in series, but I'm in Florida an the lowest temperature is about 30F as I'm only 3 miles from the gulf. In general it is always the most efficient to run as high a voltage as possible for the mppt as that is the most efficient for AIO's

Fuses do nothing for single string solar inputs on AIO's, no need. Most hybrids already have the disconnect switch built in ( my Solis S6 does )

 

[Over9000]

There's no need for a fuse or breaker for a single string or two strings in parallel. They serve no purpose. Once you parallel three strings or more thats when you need ocp.

Okay, let me provide (3) different setups that I have:

Setup #1 (Small System):

• (4) 100W panels in Series ==> ANL Fuse ==> MPPT ==> LFP Battery ==> Inverter [All Separates]

Setup #2a (Big System):

• (9) 460W panels in Series ==> Inline Fuse #2 ==> AIO unit ==> CNN Fuse ==> Battery

Setup #2b (Big System):

• (9) 460W panels configured as (3) strings of (3) ==> AIO unit ==> CNN Fuse ==> Battery

If I'm understanding @Brucey and @MisterSandals correct, I don't need Inline Fuse #1 or Inline Fuse 2, correct?

Also @42OhmsPA - I I won't be adding any more panels. No place to put them.

Lastly, is it completely safe to run out of balanced strings into an AIO with separate MPPTs?

• Let's say I had (4) 460W + (5) 460W + (4) 100W going into MPPT #1 / #2 / #3 (respectively). Is there any issues with doing that?

 

[MisterSandals]

I don't need Inline Fuse #1 or Inline Fuse 2, correct?

The opposite. You need to fuse when you combine 3 or more panels or 3 or more strings in parallel (3P).

 

[Over9000]

The opposite. You need to fuse when you combine 3 or more panels or 3 or more strings in parallel (3P).

What? Each setup combines (3) or more panels. and Setup 2b has (3) strings in parallel. Where does the fuse go?

 

[MisterSandals]

Each setup combines (3) or more panels.

Only 2b combines 3 or more in parallel.

Setup 2b has (3) strings in parallel. Where does the fuse go?

Between each series string and the point where they are combined in parallel. So 3 fuses. Look for the max fuse rating on your panel (likely 15A).

 

[Over9000]

Only 2b combines 3 or more in parallel.

Between each series string and the point where they are combined in parallel. So 3 fuses. Look for the max fuse rating on your panel (likely 15A).

What? I'm running the (3) parallel strings directly into the (3) MPPTs that are built into the AIO. The (3) parallel strings aren't "combined".

 

[MisterSandals]

What? I'm running the (3) parallel strings directly into the (3) MPPTs that are built into the AIO. The (3) parallel strings aren't "combined".

I reread the last few pages and see that you cleaned up your usage of "3 parallel strings" and "3p". I see it tripped up a couple others too.

Sorry for not keeping up with that. Your 3 strings running to 3 MPPTs are fine without fuses.

 

[Over9000]

I reread the last few pages and see that you cleaned up your usage of "3 parallel strings" and "3p". I see it tripped up a couple others too.

Sorry for not keeping up with that. Your 3 strings running to 3 MPPTs are fine without fuses.

Thank you for confirming. And in Setup #1, I don't need any fuse in the system? Anywhere?

 

[MisterSandals]

Setup #1 (Small System):

• (4) 100W panels in Series ==> Inline Fuse #1 ==> MPPT ===> Inverter [All Separates]

...
Thank you for confirming. And in Setup #1, I don't need any fuse in the system? Anywhere?

I didn't catch this before but how does an MPPT SCC output get sent to an inverter? A battery should be powering the SCC and SCC should be providing charge current to the battery... at least all the ones i've seen.

 

[Over9000]

@MisterSandals - Sorry, I made a mistake in that post. I've corrected it but here it is:

• (4) 100W panels in Series ==> ANL Fuse ==> MPPT ==> LFP Battery ==> Inverter [All Separates]

Is a fuse needed somewhere?

 

[MisterSandals]

@MisterSandals - Sorry, I made a mistake in that post. I've corrected it but here it is:

• (4) 100W panels in Series ==> ANL Fuse ==> MPPT ==> LFP Battery ==> Inverter [All Separates]

Is a fuse needed somewhere?

You need a fuse to protect the wire from the battery to the inverter. An MRBF at a minimum, Class T fuse the top ($$ too) solution.
How many watts is your inverter?

No fuse needed between array and SCC. A solar cutoff switch is pretty much a necessity. Some use a breaker because high voltage cutoff switches get spendy.

 

[Over9000]

You need a fuse to protect the wire from the battery to the inverter. An MRBF at a minimum, Class T fuse the top ($$ too) solution.
How many watts is your inverter?

No fuse needed between array and SCC. A solar cutoff switch is pretty much a necessity. Some use a breaker because high voltage cutoff switches get spendy.

@MisterSandals here is the current setup that is about to be replaced:

• (4) 100W Panels ==> Renogy 40A MPPT ==> ANL Fuse ==> 12V 280Ah LFP ==> 1000W Renogy Inverter

Here is the replacement setup:

• (5) 100W Panels ==> Victron 150/35 MPPT (SCC115035210) ==> ANL Fuse ==> (2) 12V 280Ah LFPs in parallel ==> Victron 2kVA Inverter/Charger (PMP122200102) <== SGP 7.6kW Unit

It sounds like you want me to move the ANL fuse to the ==> connection above, therefore running the MPPT into the Batteries directly.

Is that correct?

 

[MisterSandals]

Is that correct?

That’s what I do. I think you need better fuses than ANL between battery and inverter, those may be ineffective for large DC loads.
Some sticklers for details fuse from SCC to battery. I keep those runs very short and do not.

<== SGP 7.6kW Unit

You lost me here. Providing AC to the multiplus which is the transfer switch to/from battery power?
What powers the SGP (Sungoldpower I assume?)?
You will need a fuse to protect the wire from SGP to the Multiplus.

 

[Over9000]

That’s what I do. I think you need better fuses than ANL between battery and inverter, those may be ineffective for large DC loads.
Some sticklers for details fuse from SCC to battery. I keep those runs very short and do not.


You lost me here. Providing AC to the multiplus which is the transfer switch to/from battery power?
What powers the SGP (Sungoldpower I assume?)?
You will need a fuse to protect the wire from SGP to the Multiplus.

It's all in this thread, but I have a 4140W array powering the SGP (separate system). It's split phase and running my heavy 240V items and the 120 is the "backup" going into my multiplus via a single pole breaker in my main panel.