Title 24 · California Energy Code
What are the economizer control requirements and how are economizers functionally tested?
Before occupancy, economizers (and DOAS/HRV/ERV systems) must be acceptance tested per California rules: verify the lockout temperature and sensor placement, confirm outdoor damper goes fully open when economizing and closes to minimum when disabled, and document results on the required MECH‑5A form. Manufacturer factory certification can waive the in‑field functional test but not the construction inspection.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
The California rules require that installed air economizers, DOAS, HRV and ERV systems be acceptance‑tested before an occupancy permit is issued. The acceptance requirement is set out in § 120.5 and the Reference Nonresidential Appendix § NA7.5.4; the detailed functional test procedures, construction inspection items, and acceptance criteria for air‑side economizers are in the California Mechanical Code Appendix E at § E805.5. Factory‑installed economizers that are certified to the Commission are exempt from the in‑field functional testing, but still require the construction inspection (including lockout setpoint verification) to be completed.
The single most important rule: an air economizer must be shown in the field to operate the dampers and controls correctly (open fully for free cooling when allowed, stay closed when locked out) unless the manufacturer provides a valid factory certification — and the construction inspection (including lockout setpoint) must always be completed.
Requirements in detail
Controlling provisions (first mention)
- § 120.5 — Required nonresidential mechanical system acceptance (states air economizers/DOAS/HRV/ERV must be tested per the NA7 acceptance procedures).
- § NA7.5.4 — Reference Nonresidential Appendix acceptance procedure for air economizers (functional testing requirement and factory‑certified exception).
- § E805.5 — CMC Appendix E — detailed Air Economizer Controls Acceptance test procedures, construction inspection checklist, functional test steps, and acceptance criteria.
Key defined terms (first mention bolded)
- economizer (air‑side): a control and damper arrangement that brings in outdoor air to satisfy cooling loads when outdoor conditions are acceptable.
- lockout setpoint: the outdoor air condition (temperature/limit device) above which the economizer must be disabled (locked out) per Appendix E requirements.
What the construction inspection must verify (short list)
- Economizer lockout setpoint is set per the appendix and the high‑limit sensor is located to avoid false readings.
- System is capable of providing up to 100% outside air without over‑pressurizing the building.
- For DDC systems, lockout sensors are factory‑calibrated or field‑calibrated; for non‑DDC systems, manufacturer startup/test procedures are applied.
Functional test objectives (plain)
- Verify that the outdoor air damper and return air damper move to the required positions during economizer mode and when economizer is disabled.
- Verify fans and other dampers preserve building pressure during mode transitions.
- Verify heating is disabled during economizer cooling tests (to prevent simultaneous heating/cooling).
Stepwise functional test (summary of § E805.5 procedure)
- Disable demand‑control ventilation (if applicable).
- Enable economizer and simulate a cooling demand large enough to drive the economizer fully open: verify outdoor air damper 100% open and return air damper 100% closed; fans/dampers maintain pressure; heating disabled.
- Disable economizer and simulate cooling: verify outdoor air damper closes to minimum position, return damper modulates to maintain return (100% open where applicable), fans/dampers maintain pressure; heating disabled.
- Simulate heating demand while economizer is capable of operating (outdoor temp below lockout) and verify economizer is at minimum position.
- Restore any DCV/economizer overrides used in testing.
Acceptance criteria (short table)
| Decision dimension / value | What the inspector looks for | Code Reference |
|---|---|---|
| Functional testing required? | Yes — for field‑installed economizers. Factory‑certified economizers may omit field functional test if manufacturer certificate is attached, but construction inspection (including lockout setpoint) is still required. | § 120.5 / § NA7.5.4; § E805.5 file |
| Outdoor air damper in economizer mode | 100% open (outdoor damper), return air damper 100% closed; for units ≥ 75,000 Btu/h (22 kW), outdoor damper remains 100% open while mechanical cooling is enabled. | § E805.5.1.2 / § E805.5.2 file |
| Outdoor air damper when economizer disabled | Closes to minimum position; return damper modulates 100% open and mechanical cooling remains enabled. | § E805.5.1.2 Step 3 / § E805.5.2 file |
| Lockout setpoint & sensor | Set per Appendix E; sensor located to prevent false readings; DDC sensors factory/field calibrated. | § E805.5.1.1 |
| Damper leakage & reliability (manufactured economizers) | Damper leakage ≤ 10 cfm/sf at 250 Pa; manufacturer certifies 60,000 cycles capability and provides 5‑yr warranty for economizer assembly (requirements for economizer assemblies). | § 140.4 prescriptive features referencing damper leakage and testing (Energy Code). |
(Each table entry above is grounded in the CMC Appendix E procedures and Energy Code prescriptive requirements cited.) file
Exceptions & special cases
- Factory‑certified economizer units: If the HVAC manufacturer installs and certifies the economizer to the Commission as factory‑calibrated and tested, the in‑field functional test may be omitted; the certificate must be attached to the acceptance form, but construction inspection, including verifying the high‑temperature lockout setpoint, is still required. § 120.5 / § NA7.5.4; § E805.5. file
- DOAS/HRV/ERV units that do not meet energy‑recovery requirements: Some DOAS/HRV/ERV units that don’t meet the heat recovery ratio or that do not provide bypass/control to disable recovery may be treated differently under the Energy Code’s exceptions — check § 120.5 exceptions and Section 140.4 cross‑references.
- Small units and climate exceptions: Economizer requirements (and the size threshold for requiring an economizer) are governed elsewhere in Appendix E (see Table E503.5(1)); verify whether the specific equipment is exempt.
Common mistakes
- Assuming a factory certificate removes the need for any inspection — incorrect. The field functional test may be omitted only if a valid factory certificate is provided, but construction inspection (lockout setpoint, sensor location) still must be completed. § 120.5 / § E805.5. file
- Not verifying sensor location — sensors placed near exhausts or heat sources can produce false readings; Appendix E requires sensor placement to avoid false readings. § E805.5.1.1.
- Failing to test damper travel and positions under a simulated full cooling demand — the standard requires outdoor damper 100% open and return damper 100% closed during the full‑open economizer test. § E805.5.1.2 Step 2.
- Overlooking building pressurization effects — the system must be designed to provide up to 100% outside air without over‑pressurizing the building; this is part of construction inspection. § E805.5.1.1.
Worked example — rooftop unit with a 30 ton (360,000 Btu/h) cooling capacity
Project: Single rooftop unit serving a small office. The unit has a field‑installed economizer (no factory certificate provided).
Steps to comply:
- Construction inspection: Verify lockout setpoint is set per the Appendix and the outside air temperature sensor is not influenced by exhaust air or warm surfaces; confirm the system can supply 100% outside air without over‑pressurizing the building; for a DDC system, confirm lockout sensor calibration. (Reference: § E805.5.1.1.)
- Functional test:
- Disable DCV. Enable economizer and force a cooling demand large enough to drive damper fully open (simulate high indoor temperature or command). Verify outdoor damper = 100% open, return damper = 100% closed, fans maintain pressure, and heating is disabled. (Reference: § E805.5.1.2 Step 2.)
- Disable economizer, simulate cooling: verify outdoor damper closes to minimum position and return damper modulates to maintain return (and mechanical cooling remains enabled). (Reference: § E805.5.1.2 Step 3.)
- Acceptance: Record results on Form MECH‑5A; if any item fails (e.g., damper does not go to 100% open), correct and re‑test per § E805.5.
Because the unit is >75,000 Btu/h, an additional check is required to confirm that when mechanical cooling is enabled the outdoor damper stays 100% open while economizer capability is being used, per the acceptance criteria. § E805.5.2 (item 5).
Related provisions
- § 120.2(i) — Economizer Fault Detection and Diagnostics (FDD) requirements for air handlers >33,000 Btu/hr (sensors, reporting, fault detection).
- § 140.4 — Prescriptive requirements for economizers and damper leakage / warranty / durability features referenced for economizer assemblies.
- § E503.5 / Table E503.5(1) — When an economizer is required (minimum unit sizes by climate zone).
- § E503.5.4 / E503.5.5 — Limitations to prevent economizer operation from increasing heating energy or causing simultaneous heating/cooling.
Code references
Grounded in the retrieved California Energy Code — click a citation to read the verbatim passage:
§ 805.4.2 High relevance — show source text
E 805.4.2 Acceptance Criteria. Flexible ducts are not compressed or constricted. Duct connections shall comply with the requirements of this appendix and this code (new ducts only). Joints and seams are properly sealed in accordance with the requirements of this appendix and this code (new ducts only). Duct R-values shall comply with the minimum requirements of this appendix (new ducts only). Insulation is protected from damage and suitable for outdoor usage where applicable (new ducts only). The leakage shall not exceed the rate in accordance with Section E 503.4.7.2.1.
E 805.5 Air Economizer Controls Acceptance (Form MECH-5A). The purpose of functionally testing an air economizer cycle is to verify that an HVAC system uses outdoor air to satisfy space cooling loads where outdoor air conditions are acceptable. There are two types of economizer controls; stand-alone packages and DDC controls. The stand-alone packages are commonly associated with small unitary rooftop HVAC equipment, and DDC controls are typically associated with built-up or large packaged air handling systems. Test procedures for both economizer control types are provided.
For units with economizers that are factory installed and certified operational by the manufacturer to economizer quality control requirements, the in-field economizer functional tests do not have to be conducted. A copy of the manufacturer’s certificate shall be attached to the Form MECH-5A. However, the construction inspection, including compliance with high-temperature lockout temperature setpoint, shall be completed regardless of whether the economizer is field or factory installed.
E 805.5.1 Test Procedure. The procedure for performing a functional test for air economizer controls shall comply with Section E 805.5.1.1 and Section E 805.5.1.2.
E 805.5.1.1 Construction Inspection. Prior to functional testing, verify and document the following:
(1) Economizer lockout setpoint is in accordance with this appendix.
(2) Economizer lockout control sensor is located to prevent false readings.
(3) System is designed to provide up to 100 percent outside air without over-pressurizing the building.
(4) For systems with DDC controls lockout sensor(s) are either factory calibrated or field calibrated.
(5) For systems with non-DDC controls, manufacturer’s startup and testing procedures are applied.
E 805.5.1.2 Functional Testing. The functional testing shall be in accordance with the following steps:
Step 1: Disable demand control ventilation systems (where applicable).
Step 2: Enable the economizer, and simulate a cooling demand large enough to drive the economizer fully open. Verify and document the following:
(1) Economizer damper is 100 percent opened and return air damper is 100 percent closed.
(2) Where applicable, verify that the economizer remains 100 percent open where the cooling demand can no longer be met by the economizer alone.
(3) Applicable fans and dampers operate as intended to maintain building pressure.
(4) The unit heating is disabled.
Step 3: Disable the economizer and simulate a cooling demand. Verify and document the following:
(1) Economizer damper shall close to its minimum position.
(2) Applicable fans and dampers shall operate as intended to maintain building pressure.
(3) The unit heating is disabled.
§ 5.1. High relevance — show source text
(a) Before an occupancy permit is granted, the following equipment and systems shall be certified as meeting the Acceptance Requirements for Code Compliance, as specified by the Reference Nonresidential Appendix NA7. A Certificate of Acceptance shall be submitted to the enforcement agency that certifies that the equipment and systems meet the acceptance requirements:
Outdoor air ventilation systems shall be tested in accordance with NA7.5.1.
Constant volume, single zone unitary air conditioning and heat pump unit controls shall be tested in accordance with NA7.5.2.
Duct systems that are subject to testing under Section 120.4(g)1, Section 141.0(b)2Di or Section 141.0(b)2Dii shall be tested in accordance with NA7.5.3.
Air economizers, DOAS, HRV or ERV systems shall be tested in accordance with NA7.5.4. Exception 1 to Section 120.5(a)4: Air economizers installed by the HVAC system manufacturer and certified to the Commission as being factory calibrated and tested are not required to comply with the Functional Testing section of the air economizer controls acceptance test as described in NA7.5.4.2. Exception 2 to Section 120.5(a)4: The DOAS, HRV, or ERV unit that does not meet the exhaust air heat recovery ratio as specified in Section 140.4(q)1 or does not include bypass or control to disable energy recovery as specified in Section 140.4(q)2.
Demand control ventilation systems required by Section 120.1(c)3 shall be tested in accordance with NA7.5.5.
Supply fan variable flow controls shall be tested in accordance with NA7.5.6.
Hydronic system variable flow controls shall be tested in accordance with NA7.5.7 and NA7.5.9.
Boiler or chillers that require isolation controls as specified by Section 140.4(k)2 or 140.4(k)3 shall be tested in accordance with NA7.5.7.
Hydronic systems with supply water temperature reset controls shall be tested in accordance with NA7.5.8.
Automatic demand shed controls shall be tested in accordance with NA7.5.10.
Fault Detection and Diagnostics (FDD) for Packaged Direct-Expansion Units shall be tested in accordance with NA7.5.11.
Automatic fault detection and diagnostics (FDD) for air handling units and zone terminal units shall be tested in accordance with NA7.5.12.
Distributed Energy Storage DX AC Systems shall be tested in accordance with NA7.5.13.
Thermal Energy Storage (TES) Systems shall be tested in accordance with NA7.5.14.
Supply air temperature reset controls shall be tested in accordance with NA7.5.15.
Water-cooled chillers served by cooling towers with condenser water reset controls shall be tested in accordance with NA7.5.16.
When an energy management control system is installed, it shall functionally meet all of the applicable requirements of Part 6.
Occupant sensing zone controls shall be tested in accordance with NA7.5.17.
Conductivity controls and overflow alarms for open and closed-circuit cooling towers shall be tested according to NA7.5.18.
§ 805.4.1 High relevance — show source text
(1) Outdoors.
(2) In a space directly under a roof where the U-factor of the roof is greater than the U-factor of the ceiling.
(3) In a space directly under a roof with fixed vents or openings to the outside or unconditioned spaces.
(4) In an unconditioned crawl space.
2025 CALIFORNIA MECHANICAL CODE 483
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
APPENDIX E
(5) In other unconditioned spaces.
This test applies to both new duct systems and to existing duct systems being extended or the space conditioning system is altered by the installation or replacement of space conditioning equipment, including: replacement of the air handler; outdoor condensing unit of a split system air conditioner or heat pump; cooling or heating coil; or the furnace heat exchanger. Existing duct systems do not have to be tested where they are insulated or sealed with asbestos. E 805.4.1 Test Procedure. The procedure for performing a functional test for air distribution systems shall be in accordance with Section E 805.4.1.1 and Section E
805.4.1.2.
E 805.4.1.1 Construction Inspection. Prior to functional testing, verify and document the following:
(1) Duct connections shall comply with the requirements of this appendix and this code.
(2) Flexible ducts are not compressed.
(3) Ducts are fully accessible for testing.
(4) Joints and seams are properly sealed in accordance with the requirements of this appendix.
(5) Insulation R-Values shall comply with the minimum requirements of this appendix. E 805.4.1.2 Functional Testing. Perform duct leakage test in accordance with Section E 503.4.7.2.1.
E 805.4.2 Acceptance Criteria. Flexible ducts are not compressed or constricted. Duct connections shall comply with the requirements of this appendix and this code (new ducts only). Joints and seams are properly sealed in accordance with the requirements of this appendix and this code (new ducts only). Duct R-values shall comply with the minimum requirements of this appendix (new ducts only). Insulation is protected from damage and suitable for outdoor usage where applicable (new ducts only). The leakage shall not exceed the rate in accordance with Section E 503.4.7.2.1.
E 805.5 Air Economizer Controls Acceptance (Form MECH-5A). The purpose of functionally testing an air economizer cycle is to verify that an HVAC system uses outdoor air to satisfy space cooling loads where outdoor air conditions are acceptable. There are two types of economizer controls; stand-alone packages and DDC controls. The stand-alone packages are commonly associated with small unitary rooftop HVAC equipment, and DDC controls are typically associated with built-up or large packaged air handling systems. Test procedures for both economizer control types are provided.
For units with economizers that are factory installed and certified operational by the manufacturer to economizer quality control requirements, the in-field economizer functional tests do not have to be conducted. A copy of the manufacturer’s certificate shall be attached to the Form MECH-5A. However, the construction inspection, including compliance with high-temperature lockout temperature setpoint, shall be completed regardless of whether the economizer is field or factory installed.
§ 805.5.1.1 High relevance — show source text
E 805.5.1.1 Construction Inspection. Prior to functional testing, verify and document the following:
(1) Economizer lockout setpoint is in accordance with this appendix.
(2) Economizer lockout control sensor is located to prevent false readings.
(3) System is designed to provide up to 100 percent outside air without over-pressurizing the building.
(4) For systems with DDC controls lockout sensor(s) are either factory calibrated or field calibrated.
(5) For systems with non-DDC controls, manufacturer’s startup and testing procedures are applied.
E 805.5.1.2 Functional Testing. The functional testing shall be in accordance with the following steps:
Step 1: Disable demand control ventilation systems (where applicable).
Step 2: Enable the economizer, and simulate a cooling demand large enough to drive the economizer fully open. Verify and document the following:
(1) Economizer damper is 100 percent opened and return air damper is 100 percent closed.
(2) Where applicable, verify that the economizer remains 100 percent open where the cooling demand can no longer be met by the economizer alone.
(3) Applicable fans and dampers operate as intended to maintain building pressure.
(4) The unit heating is disabled.
Step 3: Disable the economizer and simulate a cooling demand. Verify and document the following:
(1) Economizer damper shall close to its minimum position.
(2) Applicable fans and dampers shall operate as intended to maintain building pressure.
(3) The unit heating is disabled.
Step 4: Simulate a heating demand, and set the economizer so that it is capable of operating (e.g., actual outdoor air conditions are below lockout setpoint). Verify the economizer is at minimum position.
Step 5: Restore demand control ventilation systems (where applicable) and remove system overrides initiated during the test.
E 805.5.2 Acceptance Criteria. Air economizer controls acceptance criteria shall be as follows:
484 2025 CALIFORNIA MECHANICAL CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
APPENDIX E
(1) Where the economizer is factory installed and certified, a valid factory certificate is required for acceptance. No additional equipment tests are necessary.
(2) Air economizer lockout setpoint is in accordance with this appendix. Outside sensor location accurately reads true outdoor air temperature and is not affected by exhaust air or other heat sources.
(3) Sensors are located to achieve the desired control.
(4) During economizer mode, the outdoor air damper shall modulate open to a maximum position and return air damper to 100 percent closed.
(5) The outdoor air damper is 100 percent open before mechanical cooling is enabled and for units 75 000 Btu/h (22 kw) and larger remains at 100 percent open while mechanical cooling is enabled (economizer integration where used for compliance).
§ 140.4 High relevance — show source text
Only the high limit control devices listed are allowed to be used and at the setpoints listed. Others such as Dew Point, Fixed Enthalpy, Electronic Enthalpy, and Differential Enthalpy
Controls may not be used in any climate zone for compliance with Section 140.4(e)1 unless approval for use is provided by the Energy Commission Executive Director.
b. Devices with selectable (rather than adjustable) setpoints shall be capable of being set to within 2°F and 2 Btu/lb of the setpoint listed.
c. At altitudes substantially different than sea level, the Fixed Enthalpy limit value shall be set to the enthalpy value at 75°F and 50% relative humidity. As an example, at approx-
imately 6,000 foot elevation, the fixed enthalpy limit is approximately 30.7 Btu/lb.|a. Only the high limit control devices listed are allowed to be used and at the setpoints listed. Others such as Dew Point, Fixed Enthalpy, Electronic Enthalpy, and Differential Enthalpy
Controls may not be used in any climate zone for compliance with Section 140.4(e)1 unless approval for use is provided by the Energy Commission Executive Director.
b. Devices with selectable (rather than adjustable) setpoints shall be capable of being set to within 2°F and 2 Btu/lb of the setpoint listed.
c. At altitudes substantially different than sea level, the Fixed Enthalpy limit value shall be set to the enthalpy value at 75°F and 50% relative humidity. As an example, at approx-
imately 6,000 foot elevation, the fixed enthalpy limit is approximately 30.7 Btu/lb.|122 2025 CALIFORNIA ENERGY CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—PERFORMANCE AND PRESCRIPTIVE
COMPLIANCE APPROACHES FOR ACHIEVING ENERGY EFFICIENCY
D. If controlled by a DDC system, configured with control sequences of operation in accordance with ASHRAE Guideline 36.
E. The air economizer and all air dampers shall have the following features: i. Warranty. 5-year manufacturer warranty of economizer assembly. ii. Damper reliability testing. Suppliers of economizers shall certify that the economizer assembly, including but not limited to outdoor air damper, return air damper, drive linkage and actuator, have been tested and are able to open and close against the rated airflow and pressure of the system for 60,000 damper opening and closing cycles. iii. Damper leakage. Economizer outdoor air and return air dampers shall have a maximum leakage rate of 10 cfm/sf at 250 Pascals (1.0 in. of water) when tested in accordance with AMCA Standard 500-D. The economizer outside air and return air damper leakage rates shall be certified to the Energy Commission in accordance with Section 110.0.
§ 160.3 High relevance — show source text
(d) Mechanical acceptance testing.
- Common areas. Before an occupancy permit is granted, the following systems and equipment serving multifamily common areas shall be certified as meeting the Acceptance Requirements for Code Compliance, as specified by Reference Nonresidential Appendix NA7. These systems and equipment shall also comply with the applicable requirements of Section
220 2025 CALIFORNIA ENERGY CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS
160.3(d)3. A Certificate of Acceptance shall be submitted to the enforcement agency that certifies that the equipment and systems meet the acceptance requirements: A. Outdoor air ventilation systems shall be tested in accordance with NA7.5.1. B. Constant volume, single zone air conditioning and heat pump unit controls shall be tested in accordance with NA7.5.2. C. Duct systems shall be tested in accordance with NA7.5.3 where either: a. They are new duct systems; or b. They are part of an altered system. D. Air economizers, DOAS, HRV or ERV systems shall be tested in accordance with NA7.5.4. Exception to Section 160.3(d)1D: Air economizers installed by the HVAC system manufacturer and certified to the Commission as being factory calibrated and tested are not required to comply with the Functional Testing section of the Air Economizer Controls acceptance test as described in NA7.5.4.2. E. Demand control ventilation systems required by Section 160.2(c)3 shall be tested in accordance with NA7.5.5. F. Supply fan variable flow controls shall be tested in accordance with NA7.5.6. G. Hydronic system variable flow controls shall be tested in accordance with NA7.5.7 and NA7.5.9. H. Boilers or chillers that require isolation controls as specified by Section 170.2(c)4Iii or 170.2(c)4Iiii shall be tested in accordance with NA7.5.7.
I. Hydronic systems with supply water temperature reset controls shall be tested in accordance with NA7.5.8.
J. Automatic demand shed controls shall be tested in accordance with NA7.5.10.
K. Fault detection and diagnostics (FDD) for packaged direct expansion units shall be tested in accordance with NA7.5.11. L. Automatic fault detection and diagnostics (FDD) for air handling units and zone terminal units shall be tested in accordance with NA7.5.12.
M. Distributed energy storage DX AC systems shall be tested in accordance with NA7.5.13. N. Thermal energy storage (TES) systems shall be tested in accordance with NA7.5.14. O. Supply air temperature reset controls shall be tested in accordance with NA7.5.15. P. Water-cooled chillers served by cooling towers with condenser water reset controls shall be tested in accordance with NA7.5.16.
Q. When an energy management control system is installed, it shall functionally meet all of the applicable requirements of Part 6.
§ 120.2 High relevance — show source text
Exception to Section 120.2(g): Zones designed to be conditioned continuously.
(h) Automatic demand shed controls. See Section 110.12 for requirements for automatic demand shed controls.
(i) Economizer fault detection and diagnostics (FDD). All newly installed air handlers with a mechanical cooling capacity over 33,000 Btu/hr and an installed air economizer shall include a stand-alone or integrated Fault Detection and Diagnostics (FDD) system in accordance with Subsections 120.2(i)1 through 120.2(i)8.
- The following temperature sensors shall be permanently installed to monitor system operation: outside air, supply air, and when required for differential economizer operation a return air sensor, and
- Temperature sensors shall have an accuracy of ±2°F over the range of 40°F to 80°F; and
- The controller shall have the capability of displaying the value of each sensor; and
- The controller shall provide system status by indicating the following conditions: A. Free cooling available; B. Economizer enabled;
C. Compressor enabled; D. Heating enabled, if the system is capable of heating; and E. Mixed-air low limit cycle active. 5. The unit controller shall allow manual initiation of each operating mode so that the operation of cooling systems, economizers, fans and heating system can be independently tested and verified; and 6. Faults shall be reported in one of the following ways: A. Reported to an Energy Management Control System regularly monitored by facility personnel. B. Annunciated locally on one or more zone thermostats, or a device within five (5) feet of zone thermostat(s), clearly visible, at eye level, and meeting the following requirements: i. On the thermostat, device, or an adjacent written sign, display instructions to contact appropriate building personnel or an HVAC technician; and ii. In buildings with multiple tenants, the annunciation shall either be within property management offices or in a common space accessible by the property or building manager. C. Reported to a fault management application which automatically provides notification of the fault to a remote HVAC service provider. 7. The FDD system shall detect the following faults: A. Air temperature sensor failure/fault; B. Not economizing when it should; C. Economizing when it should not; D. Damper not modulating; and
E. Excess outdoor air.
- The FDD System shall be certified to the Energy Commission as meeting requirements of Subsections 120.2(i)1 through 120.2(i)7 in accordance with Section 110.0 and JA6.3. Exception to Section 120.2(i)8: FDD algorithms based in direct digital control systems are not required to be certified to the Energy Commission.
74 2025 CALIFORNIA ENERGY CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
NONRESIDENTIAL, HOTEL/MOTEL OCCUPANCIES, AND COVERED PROCESSES—MANDATORY REQUIREMENTS
(j) Direct Digital Controls (DDC) . Direct Digital Controls to the zone shall be provided as specified by Table 120.2-A. The provided DDC system shall meet the control logic requirements of Sections 120.1(d), 110.12(a) and 110.12(b), and be capable of the following:
The provided DDC system shall meet the control logic requirements of Sections 110.12(a), 110.12(b) and 120.1(d) and be capable of the following:
- Monitoring zone and system demand for fan pressure, pump pressure, heating and cooling;
§ 170.2 High relevance — show source text
Others, such as Dew Point, Fixed Enthalpy, Electronic Enthalpy and Differential Enthalpy
Controls, may not be used in any climate zone for compliance with Section 170.2(c)4Ci unless approval for use is provided by the Energy Commission Executive Director.
b. Devices with selectable (rather than adjustable) setpoints shall be capable of being set to within 2°F and 2 Btu/lb of the setpoint listed.
c. At altitudes substantially different than sea level, the Fixed Enthalpy limit value shall be set to the enthalpy value at 75°F and 50% relative humidity. As an example, at approx-
imately 6,000 foot elevation, the fixed enthalpy limit is approximately 30.7 Btu/lb.|a. Only the high limit control devices listed are allowed to be used and at the setpoints listed. Others, such as Dew Point, Fixed Enthalpy, Electronic Enthalpy and Differential Enthalpy
Controls, may not be used in any climate zone for compliance with Section 170.2(c)4Ci unless approval for use is provided by the Energy Commission Executive Director.
b. Devices with selectable (rather than adjustable) setpoints shall be capable of being set to within 2°F and 2 Btu/lb of the setpoint listed.
c. At altitudes substantially different than sea level, the Fixed Enthalpy limit value shall be set to the enthalpy value at 75°F and 50% relative humidity. As an example, at approx-
imately 6,000 foot elevation, the fixed enthalpy limit is approximately 30.7 Btu/lb.|2025 CALIFORNIA ENERGY CODE 251
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES
iii. The air economizer and all air dampers shall have the following features: a. Warranty. 5-year manufacturer warranty of economizer assembly. b. Damper reliability testing. Suppliers of economizers shall certify that the economizer assembly, including but not limited to outdoor air damper, return air damper, drive linkage and actuator, has been tested and is able to open and close against the rated airflow and pressure of the system for 60,000 damper opening and closing cycles. c. Damper leakage. Economizer outdoor air and return air dampers shall have a maximum leakage rate of 10 cfm/sf at 250 Pascals (1.0 in. of water) when tested in accordance with AMCA Standard 500-D. The economizer outside air and return air damper leakage rates shall be certified to the Energy Commission in accordance with Section 110.0.
§ 805.5.2 High relevance — show source text
Step 3: Disable the economizer and simulate a cooling demand. Verify and document the following:
(1) Economizer damper shall close to its minimum position.
(2) Applicable fans and dampers shall operate as intended to maintain building pressure.
(3) The unit heating is disabled.
Step 4: Simulate a heating demand, and set the economizer so that it is capable of operating (e.g., actual outdoor air conditions are below lockout setpoint). Verify the economizer is at minimum position.
Step 5: Restore demand control ventilation systems (where applicable) and remove system overrides initiated during the test.
E 805.5.2 Acceptance Criteria. Air economizer controls acceptance criteria shall be as follows:
484 2025 CALIFORNIA MECHANICAL CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
APPENDIX E
(1) Where the economizer is factory installed and certified, a valid factory certificate is required for acceptance. No additional equipment tests are necessary.
(2) Air economizer lockout setpoint is in accordance with this appendix. Outside sensor location accurately reads true outdoor air temperature and is not affected by exhaust air or other heat sources.
(3) Sensors are located to achieve the desired control.
(4) During economizer mode, the outdoor air damper shall modulate open to a maximum position and return air damper to 100 percent closed.
(5) The outdoor air damper is 100 percent open before mechanical cooling is enabled and for units 75 000 Btu/h (22 kw) and larger remains at 100 percent open while mechanical cooling is enabled (economizer integration where used for compliance).
(6) Where the economizer is disabled, the outdoor air damper closes to a minimum position; the return damper modulates 100 percent open, and mechanical cooling remains enabled. E 805.6 Demand-Controlled Ventilation Systems Acceptance (Form MECH-6A). The purpose of this test is to verify that systems required to employ demand-controlled ventilation shall be permitted to vary outside ventilation flow rates based on maintaining interior carbon dioxide (CO 2 ) concentration setpoints. Demand-controlled ventilation refers to an HVAC system’s ability to reduce outdoor air ventilation flow below design values where the space served is at less than design occupancy. Carbon dioxide is a good indicator of occupancy load and is the basis used for modulating ventilation flow rates.
E 805.6.1 Test Procedure. The procedure for performing a functional test for demand-control ventilation (DVC) systems shall be in accordance with Section E 805.6.1.1 and Section E 805.6.1.2.
E 805.6.1.1 Construction Inspection. Prior to functional testing, verify and document the following:
(1) Carbon dioxide control sensor is factory calibrated or field-calibrated in accordance with this appendix.
(2) The sensor is located in the high-density space between 3 feet (914 mm) and 6 feet (1829 mm) above the floor or at the anticipated level of the occupants’ heads.
(3) DCV control setpoint is at or below the carbon dioxide concentration permitted by this appendix.
E 805.6.1.2 Functional Testing. The functional testing shall be in accordance with the following steps:
Step 1: Disable economizer controls.
§ 0.293 High relevance — show source text
For SI units: 1000 British thermal units = 0.293 kW
- For mechanical cooling stage control that does not use variable compressor displacement the percent displacement shall be equivalent to the mechanical cooling capacity reduction evaluated at the full load rating conditions for the compressor.
E 503.5.4 Economizer Heating System Impact. HVAC system design and economizer controls shall be such that economizer operation does not increase the building heating energy use during normal operation.
Exception: Economizers on variable air valve (VAV) systems that cause zone level heating to increase due to a reduction in supply air temperature. [ASHRAE 90.1:6.5.1.4] E 503.5.4.1 Economizer Humidification Sys- tem Impact. Systems with hydronic cooling and humidification systems designed to maintain inside humidity at a dew-point temperature more than 35°F (2°C) shall use a fluid economizer where an economizer is required in accordance with Section E 503.5 through Section E 503.5.4.1. [ASHRAE 90.1:6.5.1.5] E 503.5.5 Simultaneous Heating and Cooling Limitation, Zone Controls. Zone thermostatic controls shall prevent the following:
(1) Reheating.
(2) Recooling.
(3) Mixing or simultaneously supplying air that has been previously mechanically heated and air that has
2025 CALIFORNIA MECHANICAL CODE 433
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
APPENDIX E
point up to a maximum setpoint while the airflow is maintained at the dead band flow
rate.
(d) The second stage of heating consists of modulating the airflow rate from the dead band flow rate up to the heating maximum flow rate.
(3) Laboratory exhaust systems that comply with Section E 503.5.11.3.
(4) Zones where at least 75 percent of the energy for reheating or for providing warm air in mixing systems is provided from site-recovered energy (including condenser heat) or on-site renewable energy. [ASHRAE 90.1:6.5.2.1]
E 503.5.5.1 Supply Air Temperature Reheat Limit. Where reheating is permitted in accordance with this appendix, zones that have both supply and return or exhaust air openings more than 6 feet (1829 mm) above the floor shall not supply heating air more than 20°F (11°C) above the space temperature setpoint.
Exceptions:
(1) Laboratory exhaust systems in accordance with Section E 503.5.11.3.
(2) During preoccupancy building warm-up and setback. [ASHRAE 90.1:6.5.2.1.1]
E 503.5.5.2 Hydronic System Controls. The heating of fluids in hydronic systems that have been previously mechanically cooled and the cooling of fluids that have been previously mechanically heated shall be limited in accordance with Section
E 503.5.5.2.1 through Section E 503.5.5.2.3.
[ASHRAE 90.1:6.5.2.2]
§ 805.6 High relevance — show source text
(6) Where the economizer is disabled, the outdoor air damper closes to a minimum position; the return damper modulates 100 percent open, and mechanical cooling remains enabled. E 805.6 Demand-Controlled Ventilation Systems Acceptance (Form MECH-6A). The purpose of this test is to verify that systems required to employ demand-controlled ventilation shall be permitted to vary outside ventilation flow rates based on maintaining interior carbon dioxide (CO 2 ) concentration setpoints. Demand-controlled ventilation refers to an HVAC system’s ability to reduce outdoor air ventilation flow below design values where the space served is at less than design occupancy. Carbon dioxide is a good indicator of occupancy load and is the basis used for modulating ventilation flow rates.
E 805.6.1 Test Procedure. The procedure for performing a functional test for demand-control ventilation (DVC) systems shall be in accordance with Section E 805.6.1.1 and Section E 805.6.1.2.
E 805.6.1.1 Construction Inspection. Prior to functional testing, verify and document the following:
(1) Carbon dioxide control sensor is factory calibrated or field-calibrated in accordance with this appendix.
(2) The sensor is located in the high-density space between 3 feet (914 mm) and 6 feet (1829 mm) above the floor or at the anticipated level of the occupants’ heads.
(3) DCV control setpoint is at or below the carbon dioxide concentration permitted by this appendix.
E 805.6.1.2 Functional Testing. The functional testing shall be in accordance with the following steps:
Step 1: Disable economizer controls.
Step 2: Simulate a signal at or slightly above the carbon dioxide concentration setpoint required by this appendix. Verify and document the following:
(1) For single zone units, outdoor air damper modulates open to satisfy the total ventilation air called for in the certificate of compliance.
(2) For multiple zone units, either outdoor air damper or zone damper modulate open to satisfy the zone ventilation requirements.
Step 3: Simulate signal well below the carbon dioxide setpoint. Verify and document the following:
(1) For single zone units, outdoor air damper modulates to the design minimum value.
(2) For multiple zone units, either outdoor air damper or zone damper modulate to satisfy the reduced zone ventilation requirements.
Step 4: Restore economizer controls and remove system overrides initiated during the test.
Step 5: With controls restored, apply carbon dioxide calibration gas at a concentration slightly above the setpoint to the sensor. Verify that the outdoor air damper modulates open to satisfy the total ventilation air called for in the certificate of compliance.
E 805.6.2 Acceptance Criteria. Demand-controlled ventilation systems acceptance criteria shall be as follows:
(1) Each carbon dioxide sensor is factory calibrated (with calibration certificate) or field calibrated.
(2) Each carbon dioxide sensor is wired correctly to the controls to ensure proper control of the outdoor air damper.
(3) Each carbon dioxide sensor is located correctly within the space 1 foot (305 mm) to 6 feet (1829 mm) above the floor.
(4) Interior carbon dioxide concentration setpoint is not more than 600 parts per million (ppm) plus outdoor air carbon dioxide value where dynamically measured or not more than 1000 ppm where no OSA sensor is provided.
§ 805.2.1.2 High relevance — show source text
E 805.2.1.2 Functional Testing. Where the system has an outdoor air economizer, force the economizer to the minimum position and stop outside air damper modulation (e.g., for a fixed dry-bulb high limit, lower the setpoint below the current outdoor air temperature).
E 805.2.2 Acceptance Criteria. The system has a means of maintaining the minimum outdoor air damper position. The minimum damper position is marked on the outdoor air damper. The measured outside airflow reading shall be within 10 percent of the total ventilation air called for in the certificate of compliance.
482 2025 CALIFORNIA MECHANICAL CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
APPENDIX E
E 805.3 Constant Volume, Single-Zone, Unitary Air Conditioner and Heat Pumps Systems Acceptance (Form MECH-3A). The purpose of this test is to verify the individual components of a constant volume, single-zone, unitary air conditioner and heat pump system function correctly; including: thermostat installation and programming, supply fan, heating, cooling, and damper operation.
E 805.3.1 Test Procedure. The procedure for performing a functional test for constant volume, singlezone, unitary air conditioner and heat pump systems shall be in accordance with Section E 805.3.1.1 and Section E
805.3.1.2.
E 805.3.1.1 Construction Inspection. Prior to functional testing, verify and document the following:
(1) Thermostat is located within the space-conditioning zone that is served by the HVAC sys tem.
(2) Thermostat shall be in accordance with temperature adjustment and dead band requirements.
(3) Occupied, unoccupied, and holiday schedules shall be programmed per the facility’s schedule.
(4) Preoccupancy purge is programmed.
E 805.3.1.2 Functional Testing. The functional testing shall be in accordance with the following steps:
Step 1: Disable economizer and demand control ventilation systems (where applicable).
Step 2: Simulate a heating demand during the occupied condition. Verify and document the following:
(1) Supply fan operates continually.
(2) The unit provides heating.
(3) No cooling is provided by the unit.
(4) Outside air damper is at minimum position.
Step 3: Simulate operation in the dead band during occupied condition. Verify and document the following:
(1) Supply fan operates continually.
(2) Neither heating nor cooling is provided by the unit.
(3) Outside air damper is at minimum position.
Step 4: Simulate cooling demand during occupied condition. Lock out economizer (where applicable). Verify and document the following:
(1) Supply fan operates continually.
(2) The unit provides cooling.
(3) No heating is provided by the unit.
(4) Outside air damper is at minimum position.
Step 5: Simulate operation in the dead band during unoccupied mode. Verify and document the following:
(1) Supply fan is off.
(2) Outside air damper is fully closed.
(3) Neither heating nor cooling is provided by the unit.
Step 6: Simulate heating demand during unoccupied conditions. Verify and document the following:
(1) Supply fan is on (either continuously or cycling).
(2) Heating is provided by the unit.
Frequently asked questions
Who may skip the in‑field economizer functional test?
If the economizer was installed by the HVAC manufacturer and the manufacturer provides a certificate to the Commission certifying the economizer is factory calibrated and tested, the field functional test can be omitted — but the construction inspection (including lockout setpoint verification) still must be completed. § 120.5 / § NA7.5.4; § E805.5. file
What is the required outdoor damper position during economizer mode?
During economizer mode the outdoor air damper shall modulate to 100% open and the return air damper to 100% closed; for units 75,000 Btu/h (22 kW) and larger the outdoor damper remains 100% open while mechanical cooling is enabled. § E805.5.1.2 / § E805.5.2. file
Where must the lockout sensor be located?
The lockout control sensor must be located to prevent false readings (not adjacent to exhausts or heat sources) and must be set to the appendix‑required setpoint. For DDC systems sensors must be factory‑ or field‑calibrated. § E805.5.1.1.
What paperwork is required for acceptance?
Complete the Air Economizer Controls Acceptance form (Form MECH‑5A) and attach any manufacturer factory‑certification if claiming the factory‑certified exception. § 120.5 / § NA7.5.4; § E805.5. file
Do I need to check building pressurization during testing?
Yes — the system design must allow up to 100% outside air without over‑pressurizing the building; the inspector must verify this as part of the construction inspection before functional testing. § E805.5.1.1.
More in California Energy Code
- Compliance paths, energy budgets, performance modeling and forms/software requirements
- Controls, commissioning, demand-response, sensors, and field verification/diagnostic testing
- Domestic hot water systems, efficiency, controls and installation requirements
- Electrical infrastructure, EV charging readiness, load management and demand controls
- Envelope construction, insulation, fenestration and thermal performance
- HVAC systems, ventilation rates, ducting, controls and testing
- Interior and exterior lighting power, controls and daylighting requirements
- Mandatory measures, appliance efficiency and certification requirements
- Photovoltaic requirements, BESS (battery energy storage) sizing and SARA procedures
- Reference appendices, test procedures, product certification and labeling requirements
- Scope, applicability, definitions and administrative requirements
Ask about the California Energy Code
Get cited, plain-English answers on the California Energy Code for your project — any code section, any scenario.
Start Free Trial