No provision of this code shall be interpreted to require that a registered installer of heating systems, air-conditioning systems, air-cooling systems, or refrigerating systems, or other similar systems, shall be licensed under the provisions of this chapter in order to install, or to secure permits to install, any equipment forming part of such systems when such equipment requires no plumbing work other than a water connection or connections and a waste connection or connections discharging as an indirect waste over an open sink, floor drain or other similar open receptacle, or to install such indirect waste connections is made by or under the direct supervision of the registrant and in conformity with the provisions of this Code and rules and regulations promulgated thereunder, and that all permits, inspections and approvals required by this Code are secured.