GUARDIAN Residential Air Cooled 8 KW air cooled 10 KW air cooled 14 KW air cooled 16/17 KW air cooled Model 5504/5505 16/17 KW air cooled Model 5523/5524 18/20 KW air cooled Liquid Cooled 22 KW QuietSource 24/25 KW liquid cooled 24/25 KW QuietSource 29/30 KW liquid cooled 35 KW QuietSource 45 KW liquid cooled 45 KW QuietSource Kohler Residential Air Cooled 8.5 KW air cooled 12 KW air cooled 17 KW air cooled Kohler Liquid Cooled 15 KW liquid cooled 30 KW liquid cooled Briggs and Stratton Residential Air Cooled 6 to 10 KW air cooled 11 to 20 KW air cooled Briggs & Stratton Liquid Cooled 30 to 10 KW liquid cooled