Interpretation #9091

Original Request

Code Version: 2023
Code: ENERGY
Code Description
Chapter
Section: R403.7.1
Topic: Residential HVAC Equipment Sizing

Question

Cooling equipment must fall within 100-115% of the calculated heat load, "or the closest available size provided by the manufacturer product lines". For a project, the builder has elected to use multi-speed/two stage equipment, which only comes in whole tons sizes. Our options for the equipment line selected (multi-speed, 16 SEER) are a 2 ton - 88% of load and a 3-ton at 134% of the load. We selected the 3-ton equipment. Per the "closest available size" language, we are within compliance, correct? Are we required to search for alternative equipment from the manufacturer that falls within 100-115% (different product line, capabilities, SEER rating)?

Answer Published 08/13/2025 at 11:36 AM

The described condition does appear to fall within the code guidelines. The 2 ton unit described is only 12% below and the 3 ton is 34% higher. The 2 ton unit should be selected to comply with the governing code.

Commentary

Many units today are oversized creating a "short cycle" situation. When this happens the units do not remove sufficient humidity before reaching the temperature setpoint. In a tropical climate with high humidity, it is very important to remove the humidity for creature comfort. The Energy Conservation volume limits the cooling to a temperature of 75 degrees in sections C302.1 and R302.1 which should be attainable if the construction is code compliant.