Detailed Solar to Inverter

These are the wiring options for my 40kw ground mount solar system and 2 x Flexboss21 inverters. There is 220ft distance between the two. The 40Kw solar system is split between 3 separate 70ft arrays. Each array has 44 solar panels on it for a total of 132 panels.

Each set of 44 panels is divided into 4 series sets of 11. These sets of 11 series panels are then connected in parallel into 2 sets of 22 panels.

There are two Main Solar Wiring Options

DC Wire Option 1: PV Wire Direct Bury

Details: Under the right circumstances it may make sense to direct bury your PV wire. You will still need conduit on each end where it comes out of the ground but for long runs it can save some money. If you have very rocky ground or if you have lots of gophers it might be a good idea to use option 2.

Use 1” Schedule 80 conduit from from the top of the solar array

  • Use 1” Schedule 80

Option 2: THHN Wire Buried in Conduit

Power Drop from the Solar Panels

Quantity is for each power drop. We need 2 full drops and one partial for our 3 array system.

Notes 1:

  • How to Video: How to Glue PVC Pipe

  • There are 4x 10awg solar PV wires coming from the solar arrays. The 3/4” conduit that fits on the disconnect is typically slightly too small according to the NEC unless the 3/4” conduit is shorter than 2ft. This is why we increase the size of the conduit to 1” as soon as possible. Why don’t we just use the 1” conduit? Because the DC disconnect only accepts 3/4” fittings.

  • Procedure for connecting PVC

DC Wire Option 2: THHN Wire in Conduit

Details: THHN Wire is not rated for direct bury. As a result each wire takes less area and you can use smaller conduits.

Selecting Your Wire

  • Use pure copper or tin coated copper

  • Select the minimum gauge based on NEC guidelines (14 awg = 15A, 12awg = 20awg, 10awg = 30awg, Open Air Direct Burial non bundled

  • Derate if in conduit or has a high temperature.

  • Double check minimum gauge with 3% max voltage drop. (175ft long x 2 = 350ft)

  • Make sure the wire is UL rated for UV exposure and direct burial

10AWG PV Wire, OD 0.23”: https://amzn.to/4nCISyB

12AWG PV Wire OD 0.21”: https://amzn.to/464N5VZ

My Solar Array is 175ft from the inverter. You should ensure that the voltage drop stays less than 3%. Multiply the wire length by 2 because there are two wires per circuit. Each set of 11 panels outputs approximately 550V when connected in series and 2 sets of 11 can be connected in parallel resulting in a total current of 17A. With a 10AWG wire the design calculator says we would have a voltage drop of 2.22%, well below the 3% required.

Solar Connectors

There are a lot of cheap junky solar connectors out there. The best balance between quality and price that I have been able to find are the BougeRV connectors.

Video How to Crimp: https://www.youtube.com/watch?v=VrKYlQPHfno

Solar Cable Management

It is important to keep the solar wires from dangling and getting tangled. Solar clips provide an easy way to make your solar panel wiring look nice and sharp.

Grounding The Solar Panels

Disconnects

Sizing Your Conduit

PDF with Tables and example calculations for sizing your conduit

https://pdhonline.com/courses/e276/e276content.pdf

Flexible Non-Metallic Electrical Conduit: https://amzn.to/4mdvq3b

Electric Non-Metallic Conduit (ENT): https://www.homedepot.com/p/Cantex-3-4-in-x-10-ft-Gray-Non-Metallic-PVC-Schedule-40-Conduit-A52AG12H/202352534

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