Condensate Disposal for Ductless Mini-splits
It has come to our attention that Section M1411.3.1 of the International Residential Code (IRC), related to auxiliary drain pans and secondary drain requirements for condensate disposal, has been interpreted and applied in different ways across municipalities. To support consistency and provide clarity, this advisory outlines the intent and requirements of this section. The purpose is to assist all jurisdictions in applying the code uniformly, ensuring alignment with statewide standards and promoting clear understanding for both officials and the regulated community.
Ductless mini-split systems can experience drainage issues due to several common causes such as clogged drain lines, where dirt, debris, or algae can accumulate, blocking water flow and causing overflow; dirty air filters that can restrict airflow, leading to evaporator coil freezing and subsequent water leakage; and low refrigerant levels that can cause coils to freeze and melt, resulting in heat leaks and potential water damage.
Since ductless mini splits have cooling coils and evaporators, they are required to comply with Section M1411.3 of the 2021 IRC portion of the CSBC. In addition, Sections 314.2.3 of the 2021 IPC and 307.2.3 of the 2021 IMC portions of the CSBC, have similar criteria as those found in the IRC. According to these sections, “a secondary drain or auxiliary drain pan shall be required for each cooling or evaporator coil where damage to any building components will occur as a result of overflow.”
Building components are essential materials for building construction and include, but are not limited to, electrical, mechanical equipment, plumbing, structural, floors, walls, beams, etc. A review of the proposed installation location by the local building official is necessary to determine if an overflow of the drain pan will cause damage to building components and if determined that the location of one of these units can cause such damage, then compliance with Section M1411.3.1 is required.
The IRC provides four methods for auxiliary drain pan and secondary drain compliance, one of which includes the installation of a water level detection device that is required to conform to UL 508.
Sincerely,
Omarys Vasquez, AIA, NOMA
State Building Inspector
