Small Commercial HVAC Replacement: Title 24 Requirements
A small commercial replacement still triggers a demand responsive thermostat where the old one is not, shut-off controls, and duct sealing for qualifying single-zone systems. The economizer relief is narrow: it covers systems under 54,000 Btu/h that are not single-package air-cooled commercial units, so a split system is the clearer fit.
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Reading the 54,000 Btu/h exception
Section 140.4(e) asks for an economizer above 33,000 Btu/hr of design cooling capacity. On a replacement, Exception 6 to Section 141.0(b)2C removes that duty only when both tests are met: the system is not a single package air-cooled commercial unitary air conditioner or heat pump, and its cooling capacity is below 54,000 Btu/h. A packaged unit between 33,000 and 54,000 is the case to check, since the exception names single package air-cooled commercial units. The Standards do not define "commercial" in that exception, so confirm the equipment class with the building department. Other routes are on the economizer exceptions guide.
What a small replacement still has to do
- Thermostat. Replace one that does not meet Section 110.12 with a demand responsive thermostat.
- Shut-off control. Section 120.2(e) asks for an automatic time switch, occupancy sensor or 4-hour timer. Retail stores, restaurants, grocery stores, churches and theaters may use 7-day programmable timers.
- Duct sealing. For a constant volume single-zone system serving under 5,000 square feet with over 25 percent of its duct surface outdoors or unconditioned, leakage may not exceed 15 percent of nominal air handler airflow, confirmed by acceptance test.
When the duct test is skipped
Exceptions to Section 141.0(b)2Eii cover duct systems documented as sealed before, confirmed under Appendix NA2, and buildings altered so the criteria no longer apply. A system that cannot reach 15 percent has every accessible leak sealed, verified by visual inspection and smoke test from a certified mechanical acceptance test technician. A complete new duct system, at least 75 percent new material, is tested under Section 120.4(g) instead, with a 6 percent limit where the same criteria apply.
Paperwork for a small job
The forms are the same as on a larger job: NRCC-MCH-E at permit, NRCI-MCH-E at installation, NRCA-MCH-03-A for the unit controls test. Compare a rooftop unit replacement, read the general commercial HVAC replacement page, or request a quote for a commercial project.
Common Title 24 Questions
- When does a commercial project need Title 24?
- Does an office tenant improvement need Title 24?
- Does a restaurant remodel need Title 24?
- Does a retail tenant improvement need Title 24?
- What plans are needed for a commercial Title 24 report?
- What is an NRCC certificate of compliance?
Frequently Asked Questions
Unit controls for a constant volume single-zone system are tested on NRCA-MCH-03-A under Section 120.5(a)2, and duct leakage is tested under NA7.5.3 when the ducts meet the criteria. An economizer test applies only if an economizer was required.
It falls outside the 15 percent duct test criteria. New duct added in an alteration then follows the leakage testing in CMC Section 603.9.2, as Section 141.0(b)2Diii states.
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