An auxiliary drain pan used in secondary drain systems for an A/C system shall have a minimum depth of ______ inch.

• A. 1/2 inch
• B. 1 inch
• C. 1 1/2 inches
• D. 2 inches

Answer: (C)

Auxiliary drain pans serve as a safety feature when a secondary drainage path exists under the evaporator coil. They must be deep enough to hold condensate if the primary drain backs up or becomes clogged, giving time for the safety controls to react and preventing immediate overflow into the area or equipment. A minimum depth of 1 1/2 inches provides enough storage volume to accommodate typical condensate loads and to delay overflow long enough for a corrective action to occur. Shallower depths would overflow more quickly, while the 1 1/2 inch depth is a practical, code-approved balance between safety and cost.