Planning the solar array configuration will help you ensure the right voltage/current output for your PV system. In this section, we explain what these items are and their importance.
The maximum DC voltage has to be limited for safety reasons, NEC regulations, and to match the technical specifications for a string inverter. The limit for residential PV systems is 600V for NEC regulations, but this can vary depending on the centralized inverter.
Minimum DC Input Voltage
There is a required minimum DC input voltage to start up a string inverter, which is why this is an important planning configuration for PV systems. This number drastically varies according to the selected model and brand.
The maximum DC input current is limited by the technical specifications of the inverter. This value is designed after the current-voltage curve (IV-Curve) for a solar cell. This is an important factor to be considered when wiring solar panels as the system DC output should not exceed the maximum input current for the inverter.
MPPT trackers optimize power output for PV systems considering the IV-Curve. Centralized inverters with several MPPT trackers can optimize power output for solar panel strings featuring different specifications from one another, allowing you to wire a more complex solar array to the inverter. If your inverter has two or more MPPT inputs, make sure to take advantage of them properly, especially in scenarios with multiple orientations or shading impact.
Up to this point, you learned about the key concepts and planning aspects to consider before wiring solar panels. Now, in this section, we provide you with a step-by-step guide on how to wire solar panels.
Most solar panels come with pre-installed MC4 connectors, which will allow you to interlock solar panels between them. For the ending points of the system, you may be able to use an MC4 extension cable that generally comes in multiple sizes to interconnect the PV system and the inverter.
However, it is still important to learn how to properly install a PV connector, since in some cases or sections, the system may require you to make the connection yourself. This will probably occur if you do not find an MC4 extension cable with the right length.
Strip the wire.
Place the connecting plate on it and use the crimping tool.
Insert the lower components of the connector (terminal cover, strain reliever, and compression sleeve).
Insert the upper components (safety foil, male/female MC4 connector housing, O-ring).
Attach all the components together and slightly tighten them by hand.
Give the final torque to the MC4 connector by using the solar connector assembly tool.
PV modules operate at high temperatures and are exposed to a variety of environmental conditions. The NEC limits various PV array applications to USE-2 or PV wire. These cables need to meet the required sunlight resistance and temperature ratings for the environment.
PV wires are manufactured for use in photovoltaic applications, while USE-2 cable types are typically manufactured for underground service entrance applications. Both cable types commonly contain XLPE insulation and can be sunlight resistant and/or rated for direct burial.
PV wire is set apart from USE-2 wire in terms of insulation thickness, voltage ratings and operating temperatures. PV wire contains thicker insulations suitable for protection against various harsh environments. USE-2 is rated up to 600 V, while PV wire is available in three voltage ratings: 600 V, 1 kV, and 2 kV. USE-2 cable types’ maximum cable operating temperature is 90ºC, while PV wire can be rated to higher temperatures.
PV wire is one of the few single-conductor wire types that can be rated over 600 V and be direct buried per the NEC without needing to be shielded.
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Size |
Diameter of conductor |
Min. Number of Strands |
Insulation Thickness |
Nominal O.D. |
Net Weight |
Maximum conductor resistance at 20ºC |
AWG or kcmil |
mm |
n |
mm |
mm |
kg/km |
Ω/km |
12 |
2.16 |
7 |
1.90 |
6.0 |
46 |
8.880 |
10 |
2.72 |
7 |
1.90 |
6.5 |
56 |
5.590 |
8 |
3.40 |
7 |
2.15 |
7.7 |
80 |
3.520 |
6 |
4.29 |
7 |
2.15 |
8.6 |
102 |
2.210 |
4 |
5.41 |
7 |
2.15 |
9.7 |
135 |
1.390 |
3 |
6.02 |
7 |
2.15 |
10.3 |
156 |
1.100 |
2 |
6.81 |
7 |
2.15 |
11.1 |
183 |
0.875 |
1 |
7.59 |
18 |
2.66 |
12.9 |
244 |
0.693 |
1/0 |
8.53 |
18 |
2.66 |
13.9 |
286 |
0.550 |
2/0 |
9.55 |
18 |
2.66 |
14.9 |
337 |
0.436 |
3/0 |
10.74 |
18 |
2.66 |
16.1 |
400 |
0.346 |
4/0 |
12.07 |
18 |
2.66 |
17.4 |
477 |
0.274 |
250 |
13.21 |
35 |
3.04 |
19.3 |
579 |
0.232 |
300 |
14.48 |
35 |
3.04 |
20.6 |
665 |
0.194 |
350 |
15.65 |
35 |
3.04 |
21.7 |
750 |
0.166 |
400 |
16.74 |
35 |
3.04 |
22.8 |
836 |
0.145 |
450 |
17.78 |
35 |
3.04 |
23.9 |
914 |
0.129 |
500 |
18.69 |
35 |
3.04 |
24.8 |
1028 |
0.116 |
550 |
19.69 |
58 |
3.43 |
26.6 |
1133 |
0.1060 |
600 |
20.65 |
58 |
3.43 |
27.5 |
1217 |
0.0967 |
650 |
21.46 |
58 |
3.43 |
28.3 |
1298 |
0.0893 |
700 |
22.28 |
58 |
3.43 |
29.1 |
1382 |
0.0829 |
750 |
23.06 |