Yingli Solar PV Modules, Installation and User Manual / page 3
E L E C T R I C A L I N S TA L L AT I O N
Electrical Configuration
Under normal conditions, a photovoltaic module is likely to experience
conditions that produce more current and/or voltage than reported
at Standard Test Conditions (STC: 1000 W/m
2
, AM 1.5, and 25ºC cell
temperature). As required by the US National Electric Code (NEC), the
short-circuit current (ISC) should be multiplied by a factor of 1.25 and the
open-circuit voltage (VOC) should be multiplied by a factor of up to 1.25
based on the lowest ambient temperature recorded for the installation
location when determining component voltage ratings, conductor
current ratings, fuse sizes, and size of controls connected to the PV
output. Follow Section 690.7 in the (NEC) to determine the adjusted
system voltage value.
Refer to Section 690.8 of the NEC for an additional multiplying factor of
125 percent (80 percent de-rating) which may be applicable for sizing
fuses and conductors.
Voltages are additive when PV modules are connected directly in series,
and module currents are additive when PV modules are connected
directly in parallel, as illustrated in Figure 4. PV modules with different
electrical characteristics must not be connected directly in series. The use
of suitable third-party electronic devices connected to PV modules may
enable different electrical connections and must be installed according
to the manufacturer’s specified instructions.
Figure 4: Electrical diagrams of series and parallel wiring
The maximum number of PV modules that can be connected in a series
string must be calculated in accordance with applicable regulations in
such a way that the specified maximum system voltage of the PV module
and all other electrical DC components will not be exceeded in open-
circuit operation at the lowest temperature expected at the PV system
location.
An appropriately rated overcurrent protection device must be used when
the reverse current could exceed the value of the maximum fuse rating
of the module. An overcurrent protection device is required for each
series string if more than two series strings are connected in parallel.
Cables and Wiring
Yingli PV modules are provided with two (2) stranded, sunlight resistant
output cables that are terminated with PV connectors ready for
most installations. The positive (+) terminal has a female connector
while the negative (-) terminal has a male connector. The module
wiring is intended for series connections (i.e. female (+) to male (-)
interconnections), but can also be used to connect suitable third-party
electrical devices that may have alternative wiring configurations so long
as the manufacturer’s instructions are followed.
Use field wiring with suitable cross-sectional areas that are approved for
use at the maximum short-circuit current of the PV module. Yingli Solar
recommends installers use only sunlight resistant cables qualified for
direct current (DC) wiring in PV systems. The minimum wire size should
be 12 AWG.
Table 1: Required minimum field wiring specifications
Cables should be fixed to the mounting structure in such a way that
mechanical damage of the cable and/or the module is avoided. Do not
apply stress to the cables. For fixing, use appropriate means, such as
sunlight resistant cable ties and/or wire management clips specifically
designed to attach to the PV module frame. While the cables are
sunlight resistant and waterproof, where possible, avoid direct sunlight
exposure and water immersion of the cables.
Connectors
Keep connectors dry and clean, and ensure that
connector caps are hand tight. Do not attempt
making an electrical connection with wet, soiled, or
otherwise faulty connectors. Avoid sunlight exposure
and water immersion of the connectors. Avoid
connectors resting on the ground or roof surface.
Faulty connections can result in arcs and electrical shock. Check that all
electrical connections are securely fastened. Make sure that all locking
connectors are fully engaged and locked.
Figure 5: Series interconnection of a male (-) and female (+) connector
The junction boxes used with Yingli Solar PV modules contain bypass
diodes wired in parallel with the PV cell strings. In the case of partial
shading, the diodes bypass the current generated by the non-shaded
cells, thereby limiting module heating and performance losses. Bypass
diodes are not overcurrent protection devices.
Bypass diodes divert current from the cell strings in the event of partial
shading. See Figure 6 for a diagram showing how the cell strings are
electrically connected with the diodes.
Figure 6: Electrical circuitry of cells and bypass diodes
In the event of a known or suspected diode failure, installers or
maintenance providers should contact the company the PV modules
were purchased from. Never attempt to open the junction box of a Yingli
Solar PV module yourself.
Series Wiring (Voltage Additive)
Parallel Wiring (Current Additive)
Fully engage and lock
Cap
+
–
Type
Wire Size
Temperature Rating
Required Minimum Field Wiring
USE-2 or PV Wire
12 AWG
-40ºC to +90ºC
