Built in with 4pcs individual 15A rated fuse (10x38mm). Max current of single PV input array is 10A. Their function is over load protection. The Combiner Box protects PV solar panel and inverter. Besides it will reduce the length of cable connect from panel to inverter, optimize system instruction makes the system more useful and maintenance. All in all. It will make the PV power system increase output power.
50A air circuit breaker. It can provide short circuit fault protection and controls the combiner box output. Here is a Surge Protective Device/Lighting Arrester provides lightning protection. The Green indicates Normal, once it changes into Red. Remember to replace the SPD with a new one.