Hi I have a 7KVA (5.8 KW) diesel generator to back up my solar system. The generator is brand new but when I run it the lights in the house flicker rapidly. Also as soon as I pull more than 4.4 kw load, the output from the generator drops from 230V to 205V and the generator runs erratically. I have replaced the air filter with no improvement. Please can someone advise me on the cause. Thanks in advance.

Since the genset is new, best to have it checked by a factory approved technician for warranty repair.

Most gensets use electronic voltage regulators, difficult to troubleshoot and repair without proper knowledge and equipment. Assuming all is wired properly, this is most likely the problem.