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MPP Solar LV2424 Wire Size

Laurentiuss

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Joined
Apr 12, 2022
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Hello,

This is my first post and I'm just recently getting started in researching these things so thanks for your patience.

I'm working on building a system using the MPP Solar LV2424 and a 24v 200Ah Lithium battery. I'm trying to get the wire sizes correct because I don't want to cry over my final copper costs. I was reading through Will's book and I was wondering if I should size my wire based on the 80a charge controller in the device, or on the 2.4kw inverter? I'm sure it should be the inverter but I wanted to check with people smarter than me. The manual says 1*4AWG. Is that 1x4, 1to4...

Secondly, The typical amperage is 100A, should my bolt on fuse be based on this number and size up to 150A?

Lastly, The manual also states that PV cable size should be 6AWG. Almost all the MC4 lines I've seen are 10AWG. I've seen some 8 as well. Am I misinterpreting something or is this not really an issue? If you need this info, I plan on running six 240w panels. The configuration I've chosen currently should produce around 74w and 24A. I don't have the panel info with me right now for exact numbers. the configuration may change later.

Thanks in advance. I look forward to being more active here.
 
wondering if I should size my wire based on the 80a charge controller in the device, or on the 2.4kw inverter?
The wire from the 80A SCC to the battery is based on the 80A, voltage and length of wire. You need to tell us length.

The wire to the inverter is based in the same metrics but we need to figure out the amps:
Assuming your 24V inverter has 20V low voltage disconnect (lowest voltage):

2400W inverter / 20V / .85 efficiency x 1.25 headroom = 176A (will need a 200A breaker)

And we need length from battery to inverter.
 
The wire from the 80A SCC to the battery is based on the 80A, voltage and length of wire. You need to tell us length.

The wire to the inverter is based in the same metrics but we need to figure out the amps:
Assuming your 24V inverter has 20V low voltage disconnect (lowest voltage):

2400W inverter / 20V / .85 efficiency x 1.25 headroom = 176A (will need a 200A breaker)

And we need length from battery to inverter.

Thanks for the reply. The battery is slightly under 5 feet away from the unit.

The LV2424 is an all-in-one unit so it has the SCC and inverter in the same housing. That led to my confusion because I only make one connection from the battery to the unit. I can add AC in/out and PV input also.
 
On my setup:

PV in = 12awg to combiner box, 8awg from combiner to PV input (~2 feet)
AC In = 12awg extension cord
AC out = 12awg extension cord
Battery = 2awg (2 foot)
 
I thought the 2424msd unit has n to gr. Bond in the inverter. So we can't do it in your small breaker panel? It looks like you have 3 home runs coming out of panel bbox?
I am not aware of a N/G bond. The unit has input for Hot, Neutral, and ground, so I don't see why it would bond the two on the output. I guess I could test it next time I am out at the garage.

This unit is in a detached metal building and is completely stand alone. I have everything grounded to an 8' ground rod outside, but the only N/G bond is in the little sub panel pictured. The extension cord feed to the sub panel is temporary as well as the PV input wires. Of course they have been temporary for over a year now. :p
 
The wire from the 80A SCC to the battery is based on the 80A, voltage and length of wire. You need to tell us length.

The wire to the inverter is based in the same metrics but we need to figure out the amps:
Assuming your 24V inverter has 20V low voltage disconnect (lowest voltage):

2400W inverter / 20V / .85 efficiency x 1.25 headroom = 176A (will need a 200A breaker)

And we need length from battery to inverter.
Is a fuse absolutely necessary from battery to the lv2424 unit, battery has bms and inverter has protection built in as well. This part is confusing. Thanks
 
I do not think it’s necessary. It’s a smaller SCC with a good voltage.

A class T fuse from battery to loads is a necessity.

This I believe is the beauty/simplicity of discrete charge and discharge wiring.
 
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