13. PV Solar System Wiring and Safety Devices

Selection of Cable and Safety devices will play an important role in the budget of the system

AC Voltage drop based on impedance
DC Voltage drop based in resistance
PV Cable Sizing
Maximum current = No of modules (strings) wired in parallel  x the short circuit current Isc x 1.25

OCPD Sizing
Over Current Protection Device
The Conductors are designed for 80% of capacity for 3Hr continuous rating.

OCPD = 1.25 x 1.25 = 1.56-Multiplication factor'

Nominal Voltage - Baseline of measuring Voltage - PV Modules will be availabel @ 12V & 24V modules

Nominal Voltage   - 12Volt
Operating Voltage - 17 to 18Volt




Solar PV System Devices

• Underground Feeder (UF)—may be used for interconnecting balance-of-systems (BOS) but not recommended for use within battery enclosures; single conductor UF wire may be used to interconnect modules in the array but this type of wire is not widely available.
• Tray Cable (TC)—multi-conductor TC wire may be used for interconnecting BOS; TC has good resistance to sunlight but may not be marked as such.
• Service Entrance (SE)—may be used for interconnecting BOS
• Underground Service Entrance (USE)—may be used for interconnecting modules or BOS; may be used within battery enclosures
• THHN—indicates wire with heat resistant thermoplastic sheathing; it may be used for interconnecting BOS but must be installed in conduit, either buried or above ground. It is resistant to moisture but should not be used in wet locations.
• TW—refers to moisture resistant thermoplastic sheathing; it may be used for interconnecting BOS but must be installed in conduit. May be used in wet locations.