Duct systems, HVAC equipment, efficiency and controls

Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:

• CRC § 503.5.6.2. High relevance — show source text

  (1) The system serves a single HVAC zone.

  (2) The equipment shall comply with the variable flow requirements of Section E 503.5.6.2.

  (3) Cooling (where any) shall be provided by a unitary packaged or split-system air conditioner that is either air-cooled or evaporatively cooled, with efficiency that is in accordance with the requirements shown in Table E 503.7.1(1) for air conditioners, Table E 503.7.1(2) for heat pumps, or Table E 503.7.1(4) for packaged terminal and room air conditioners and heat pumps for the applicable equipment category.

  (4) The system shall have an air economizer in accordance with Section E 503.5 and Section E 503.4.6.13.

  (5) Heating (where any) shall be provided by a unitary packaged or split-system heat pump that is in accordance with the applicable efficiency requirements shown in Table E 503.7.1(2) for heat pumps or Table E 503.7.1(4) for packaged terminal and room air conditioners and heat pumps, a fuel-fired furnace that is in accordance with the applicable efficiency requirements shown in Table E 503.7.1(5) for furnaces, duct furnaces, and unit heaters, an electric resistance heater, or a baseboard system connected to a boiler that is in accordance with the applicable efficiency requirements shown in Table E 503.7.1(6) for boilers.

  (6) The system shall comply with the exhaust air energy recovery requirements in accordance with Section E 503.5.10.1.2.

  (7) The system shall be controlled by a manual changeover or dual setpoint thermostat.

  (8) Where a heat pump equipped with auxiliary internal electric resistance heaters is installed, controls shall be provided that prevent supplemental heater operation where the heating load is capable of being met by the heat pump alone during both steady-state operation and setback recovery. Supplemental heater operation shall be permitted during outdoor coil defrost cycles. The heat pump shall be controlled in accordance with one of the following:

  (a) A digital or electronic thermostat designed for heat pump use that energizes auxiliary heat where the heat pump has insufficient capacity

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  APPENDIX E

  to maintain setpoint or to warm up the space at a sufficient rate.

  (b) A multistage space thermostat and an outdoor air thermostat wired to energize auxiliary heat on the last stage of the space thermostat and where outdoor air temperature is less than 40°F (4°C).

  Exceptions: Heat pumps that comply with the following:

  (1) Have a minimum efficiency regulated by NAECA.

  (2) In accordance with the requirements shown in Table E 503.7.1(2).

  (3) Include all usage of internal electric resistance heating.

  (9) The system controls shall not permit reheat or other form of simultaneous heating and cooling for humidity control.

  (10)Systems serving spaces other than residential spaces, that do not require continuous operation with a cooling or heating capacity more than 7000 Btu/h (2.1 kW) shall comply with Section E 503.4.6.3.1 and Section E 503.4.6.3.2.

• CRC § 90.1 High relevance — show source text

  (1) Monitor zone damper positions or other indicator of need for static pressure.

  (2) Automatically detect those zones that are capable of excessively driving the reset logic and generate an alarm to the system operator.

  (3) Readily allow operator removal of zones from the reset algorithm. [ASHRAE 90.1:6.5.3.2.3]

  E 503.5.6.2.3 Return and Relief Fan Con-

  trol. Return and relief fans used to meet Section E 503.5.1.4 shall comply with all of the following:

  (1) Relief air rate shall be controlled to maintain building pressure either directly, or indirectly through differential supplyreturn airflow tracking. Systems with constant speed or multispeed supply fans shall also be allowed to control the relief system based on outdoor air damper position.

  (2) Fans shall have variable-speed control or other devices that will result in total return/relief fan system demand of no more than 30 percent of total design power at 50 percent of total design fan flow.

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  APPENDIX E

  Exceptions:

  (1) Return or relief fans with total motor size less than or equal to 0.5 hp (0.37 kW).

  (2) Staged relief fans with a minimum of four stages. [ASHRAE 90.1:6.5.3.2.4]

  E 503.5.6.3 Multiple-Zone VAV System Venti- lation Optimization Control. Multiple-zone VAV systems with DDC of individual zone boxes reporting to a central control panel shall include means to automatically reduce outdoor air intake flow below design rates in response to changes in system ventilation efficiency in accordance with Section 404.0 or ASHRAE 62.1.

  Exceptions:

  (1) VAV systems with zonal transfer fans that recirculate air from other zones without directly mixing it with outdoor air, dual-duct dual-fan VAV systems, and VAV systems with fanpowered terminal units.

  (2) Systems where total design exhaust airflow is more than 70 percent of total design outdoor air intake flow requirements. [ASHRAE 90.1:6.5.3.3]

  E 503.5.6.4 Supply Air Temperature Reset Controls. Multiple zone HVAC systems shall include controls that are capable of and configured to automatically reset the supply air temperature in response to representative building loads, or to outdoor air temperature. The controls shall reset the supply air temperature to at least 25 percent of the difference between the design supply air temperature and the design room air temperature. Controls that adjust the reset based on zone humidity shall be permitted in Climate Zones 0B, 1B, 2B, 3B, 3C, and 4 through 8. HVAC zone that are expected to experience relatively constant loads shall have maximum airflow designed to accommodate the fully reset supply air temperature.

  HVAC zones that are expected to experience relatively constant loads typically include electronic equipment rooms and interior zones.

  Exceptions:

  (1) Systems in Climate Zones 0A, 1A, and 3A with less than 3000 cubic feet per minute (1.4 m [3] /s) of design outdoor air.

• CRC § 90.1 High relevance — show source text

  Exceptions:

  (1) VAV systems with zonal transfer fans that recirculate air from other zones without directly mixing it with outdoor air, dual-duct dual-fan VAV systems, and VAV systems with fanpowered terminal units.

  (2) Systems where total design exhaust airflow is more than 70 percent of total design outdoor air intake flow requirements. [ASHRAE 90.1:6.5.3.3]

  E 503.5.6.4 Supply Air Temperature Reset Controls. Multiple zone HVAC systems shall include controls that are capable of and configured to automatically reset the supply air temperature in response to representative building loads, or to outdoor air temperature. The controls shall reset the supply air temperature to at least 25 percent of the difference between the design supply air temperature and the design room air temperature. Controls that adjust the reset based on zone humidity shall be permitted in Climate Zones 0B, 1B, 2B, 3B, 3C, and 4 through 8. HVAC zone that are expected to experience relatively constant loads shall have maximum airflow designed to accommodate the fully reset supply air temperature.

  HVAC zones that are expected to experience relatively constant loads typically include electronic equipment rooms and interior zones.

  Exceptions:

  (1) Systems in Climate Zones 0A, 1A, and 3A with less than 3000 cubic feet per minute (1.4 m [3] /s) of design outdoor air.

  (2) Systems in Climate Zone 2A with less than 10 000 cubic feet per minute (4.7 m [3] /s) of design outdoor air.

  (3) Systems in Climate Zones 0A, 1A, 2A, and 3A with at least 80 percent outdoor air and employing exhaust air energy recovery complying with Section E 503.5.10.1.

  (4) Systems that prevent reheating, recooling, or mixing of heated and cooled supply air.

  (5) Systems in which at least 75 percent of the energy for reheating (on an annual basis) is from site recovered energy or on-site renewable energy. [ASHRAE 90.1:6.5.3.5]

  E 503.5.6.5 Fractional Horsepower Fan Motors. Motors for fans that are [1] ⁄ 12 hp (62.1 W) or more and less than 1 hp (0.7 kW) shall be electronically-commutated motors or shall have a motor efficiency of not less than 70 percent where rated in accordance with DOE 10 CFR 431. These motors

  shall also have the means to adjust motor speed for either balancing or remote control. Belt-driven fans shall be permitted to use sheave adjustments for airflow balancing in lieu of a varying motor speed.

  Exceptions:

  (1) Motors in the airstream within fan coils and terminal units that operate when providing heating to the space served.

  (2) Motors installed in space conditioning equipment certified in accordance with Section E

  503.4 through Section E 503.4.4.1.

  (3) Motors shown in Table E 503.5.6.5(1) or Table E 503.5.6.5(2). [ASHRAE 90.1:6.5.3.6]

  E 503.5.6.6 Low Power Fans. Fans that are not

• CRC § 503.7 Medium relevance — show source text

  (4) Section E 503.7, “Minimum Equipment Efficiency Tables.” [ASHRAE 90.1:6.2.1]

  E 503.2.2 Additional Requirements. Mechanical equipment and systems shall comply with one of the following:

  (1) Section E 503.3, “Simplified Approach Building Compliance Path for HVAC Systems”

  Exception: When compliance is shown using Section E 503.2.2(1), compliance with Section E 503.4 is not required.

  (2) Section E 503.5, “Prescriptive Compliance Path”

  Exception: HVAC systems only serving the heating, cooling, or ventilating needs of a computer room with IT equipment load greater than 10 kW (34 000 Btu/h) shall be permitted to comply with Section E 503.4, “Equipment Efficiencies, Verification, and Labeling Requirements” and Section E

  503.8, “Alternative Compliance Path, Computer Room Systems.” [ASHRAE 90.1:6.2.2] E 503.3 Simplified Approach Building Compliance Path for HVAC Systems. The simplified approach shall be an optional path for compliance where the following conditions are met:

  (1) The building is not more than two stories in height. (2) Gross floor area is less than 25 000 square feet (2322.6 m [2] ).

  (3) The HVAC system in the building is in accordance with the requirements listed in Section E 503.3.1. [ASHRAE 90.1:6.3.1] E 503.3.1 Criteria. The HVAC system shall comply with all of the following criteria:

  (1) The system serves a single HVAC zone.

  (2) The equipment shall comply with the variable flow requirements of Section E 503.5.6.2.

  (3) Cooling (where any) shall be provided by a unitary packaged or split-system air conditioner that is either air-cooled or evaporatively cooled, with efficiency that is in accordance with the requirements shown in Table E 503.7.1(1) for air conditioners, Table E 503.7.1(2) for heat pumps, or Table E 503.7.1(4) for packaged terminal and room air conditioners and heat pumps for the applicable equipment category.

  (4) The system shall have an air economizer in accordance with Section E 503.5 and Section E 503.4.6.13.

  (5) Heating (where any) shall be provided by a unitary packaged or split-system heat pump that is in accordance with the applicable efficiency requirements shown in Table E 503.7.1(2) for heat pumps or Table E 503.7.1(4) for packaged terminal and room air conditioners and heat pumps, a fuel-fired furnace that is in accordance with the applicable efficiency requirements shown in Table E 503.7.1(5) for furnaces, duct furnaces, and unit heaters, an electric resistance heater, or a baseboard system connected to a boiler that is in accordance with the applicable efficiency requirements shown in Table E 503.7.1(6) for boilers.

  (6) The system shall comply with the exhaust air energy recovery requirements in accordance with Section E 503.5.10.1.2.

  (7) The system shall be controlled by a manual changeover or dual setpoint thermostat.

• CRC § 90.1 Medium relevance — show source text

  (5) A complete narrative of how each system is intended to operate, including suggested setpoints. [ASHRAE 90.1:6.7.3.2] E 503.6.5.3 System Balancing. Construction documents shall require that HVAC systems be balanced in accordance with generally accepted engineering standards. Construction documents shall require that a written balance report be provided to the building owner or the designated representative of the building owner for HVAC systems serving a total conditioned space or zone exceeding 5000 square feet (464.52 m [2] ). {ASHRAE 90.1:6.7.3.3.1}

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  APPENDIX E

  »

  E 503.6.5.3.1 Air System Balancing. Air systems shall be balanced in a manner to first minimize throttling losses. Then, for fans with fan system power greater than 1 hp (0.7 kW), fan speed shall be adjusted to meet design flow conditions. [ASHRAE 90.1:6.7.3.3.2]

  E 503.6.5.3.2 Hydronic System Balanc- ing. Hydronic systems shall be proportionately balanced in a manner to first minimize throt tling losses; then the pump impeller shall be trimmed or pump speed shall be adjusted to meet design flow conditions.

  Exceptions: Impellers need not be trimmed nor pump speed adjusted.

  (1) For pumps with pump motors of 10 hp (7.5 kW) or less.

  (2) Where throttling results is not greater than 5 percent of the nameplate horsepower draw, or 3 hp (2.2 kW), whichever is greater, above that required where the impeller was trimmed. [ASHRAE 90.1:6.7.3.3]

  E 503.6.5.4 Minimum Level of Commission.

  Commissioning shall be performed for HVAC systems in accordance with Level 1, Basic Commissioning of the SMACNA HVAC Systems Commissioning Manual. (See Section E 801.0 for additional information on HVAC system commissioning)

  E 503.7 Minimum Equipment Efficiency Tables. The minimum efficiency requirements for equipment shall comply with Section E 503.7.1; duct insulation shall comply with Section E 503.7.2, and pipe insulation shall comply with Section E 503.7.3.

  E 503.7.1 Minimum Efficiency Requirement Listed Equipment – Standard Rating and Oper- ating Conditions. The minimum efficiency requirements for equipment shall comply with Table E 503.7.1(1) through Table E 503.7.1(20).

  E 503.7.2 Duct Insulation Tables. Duct insulation

  shall comply with Table E 503.7.2.

  E 503.7.3 Pipe Insulation Tables. Pipe insulation shall comply with Table E 503.7.3(1) and Table E 503.7.3(2).

• CRC § 805.4.1 Medium 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.

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  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.

• CRC § 110.3 Medium relevance — show source text

  SECTION 110.3—MANDATORY REQUIREMENTS FOR SERVICE WATER-HEATING SYSTEMS AND EQUIPMENT

  (a) Certification by manufacturers. Any service water- heating system or equipment may be installed only if the manufacturer has certified that the system or equipment complies with all of the requirements of this subsection for that system or equipment.

  1. Temperature controls for service water-heating systems. Service water-heating systems shall be equipped with automatic temperature controls capable of adjustment from the lowest to the highest acceptable temperature settings for the intended use as listed in Table 3, Chapter 50 of the ASHRAE Handbook, HVAC Applications Volume or Table 613.1 of the Cali- fornia Plumbing Code for healthcare facilities. Exception to Section 110.3(a)1: Residential occupancies.

  (b) Efficiency. Equipment shall meet the applicable requirements of the Appliance Efficiency Regulations as required by Section 110.1, subject to the following:

  1. If more than one standard is listed in the Appliance Efficiency Regulations, the equipment shall meet all the standards listed; and

  2. If more than one test method is listed in the Appliance Efficiency Regulations, the equipment shall comply with the applicable standard when tested with each test method; and

  3. Where equipment can serve more than one function, such as both heating and cooling, or both space heating and water heating, it shall comply with all the requirements applicable to each function; and

  4. Where a requirement is for equipment rated at its “maximum rated capacity” or “minimum rated capacity,” the capacity shall be as provided for and allowed by the controls, during steady-state operation.

  (c) Installation. Any service water-heating system or equipment may be installed only if the system or equipment complies with all of the applicable requirements of this subsection for the system or equipment.

  1. Outlet temperature controls. On systems that have a total capacity greater than 167,000 Btu/hr, outlets that require higher than service water temperatures as listed in the ASHRAE Handbook, Applications Volume, shall have separate remote heaters, heat exchangers or boosters to supply the outlet with the higher temperature. Exception to Section 110.3(c)1: Systems covered by California Plumbing Code Section 613.0 shall instead follow the requirements of that section.
  2. Controls for hot water distribution systems. Service hot water systems with circulating pumps or with electrical heat trace systems shall be capable of automatically turning off the system. Exception to Section 110.3(c)2: Systems serving healthcare facilities.
  3. Insulation. Unfired service water heater storage tanks and backup tanks for solar water-heating systems shall have: A. External insulation with an installed R -value of at least R-3.5; or

  B. Internal and external insulation with a combined R -value of at least R-16; or

  C. The heat loss of the tank surface based on an 80°F water-air temperature difference shall be less than 6.5 Btu per hour per square foot. 4. Water heating recirculation loops serving multiple dwelling units, high-rise residential, hotel/motel, and nonresiden- tial occupancies. A water heating recirculation loop is a type of hot water distribution system that reduces the time needed to deliver hot water to fixtures that are distant from the water heater, boiler or other water heating equipment. The recirculation loop is comprised of a supply portion, connected to branches that serve multiple dwelling units, guest rooms, or fixtures and a return portion that completes the loop back to the water heating equipment.

• CRC § 5.3 Medium relevance — show source text

  (g) Duct sealing. Duct systems shall comply with Subsection 1 or 2 below:

  1. New duct systems that meet the criteria in Subsections A, B, C and D below shall be sealed to a leakage rate not to exceed 6 percent of the nominal air handler airflow rate as confirmed through acceptance testing, in accordance with Reference Nonresidential Appendix NA7.5.3; A. The duct system does not serve a healthcare facility; and B. The duct system provides conditioned air to an occupiable space for a constant volume, single zone, space-conditioning system; and C. The space-conditioning system serves less than 5,000 square feet of conditioned floor area; and D. The combined surface area of the ducts located outdoors or in unconditioned space is more than 25 percent of the total surface area of the entire duct system.
  2. New duct systems that are not subject to testing under Section 120.4(g)1 shall instead meet the duct leakage testing requirements of CMC Section 603.9.2.

  Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code. Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.8, and 25943, Public Resources Code.

  SECTION 120.5—REQUIRED NONRESIDENTIAL MECHANICAL SYSTEM ACCEPTANCE

  Nonresidential and hotel/motel buildings shall comply with the applicable requirements of Sections 120.5(a) through 120.5(b).

  Exception to Section 120.5: Systems serving healthcare facilities.

  (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:

  1. Outdoor air ventilation systems shall be tested in accordance with NA7.5.1.

  2. Constant volume, single zone unitary air conditioning and heat pump unit controls shall be tested in accordance with NA7.5.2.

  3. 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.

  4. 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.

  5. Demand control ventilation systems required by Section 120.1(c)3 shall be tested in accordance with NA7.5.5.

  6. Supply fan variable flow controls shall be tested in accordance with NA7.5.6.
• CRC § 106.11. Medium relevance — show source text

  **Locate orient and shade the building as
  required in Section A6.106.11.||||| |SECTION A6.205 Building Envelope||||| |A6.205.1 Fenestration products and exterior doors.
  A6.205.1.1 Certification of fenestration products and exterior door other than field-
  fabricated.||||| |A6.205.1.2 Installation of field-fabricated fenestration and exterior doors.||||| |A6.205.2 Joints and other openings.||||| |A6.205.3 Installation and roofing products.|||||

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  APPENDIX A6.1 — VOLUNTARY STANDARDS FOR HEALTH FACILITIES [OSHPD 1, 2 & 4]

  NONRESIDENTIAL OCCUPANCIES APPLICATION CHECKLIST [OSHPD 1, 2 and 4] — continued

  FEATURE OR MEASURE	COMPLIANCE LEVELS	Col3	Col4	NOTES
  FEATURE OR MEASURE	Mandatory CALGreen	VOLUNTARY CALGreen	VOLUNTARY CALGreen	VOLUNTARY CALGreen
  FEATURE OR MEASURE	Mandatory CALGreen	Tier 1	Tier 2	Tier 2
  SECTION A6.207 HVAC Design, Equipment and Installation
  A6.207.1 Space-conditioning equipment certification by manufacturers. A6.207.1.1 Efficiency. A6.207.1.2 Controls for heat pumps with supplementary electric resistance heaters. A6.207.1.3 Thermostats. A6.207.1.4 Gas-and oil-fired furnace standby loss controls.		    	    
  A6.207.2 Space conditioning systems. A6.207.2.1 Supply air temperature reset controls. A6.207.2.2 Electric resistance heating. A6.207.2.3 Heat rejection systems. A6.207.2.4 Hydronic system measures. A6.207.2.5 Air distribution system duct leakage sealing. **A6.207.2.6 Variable air volume control for single zone systems.

• CRC § 150.0 Medium relevance — show source text

  Entirely new or complete replacement duct systems installed as part of an alteration is constructed of at least 75 percent new duct material, and up to 25 percent may consist of reused parts from the dwelling unit’s existing duct system, including but not limited to registers, grilles, boots, air handler, coil, plenums, duct material; if the reused parts are accessible and can be sealed to prevent leakage. Entirely new or complete replacement duct systems shall also conform to the requirements of Sections 150.0(m)12 and 150.0(m)13. If the air handler and ducts are located within a vented attic, the requirements of Section 150.2(b)1J shall also be met.

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  SINGLE-FAMILY RESIDENTIAL BUILDINGS—ADDITIONS AND ALTERATIONS TO EXISTING RESIDENTIAL BUILDINGS

  b. Extension of an existing duct system. If the new ducts are an extension of an existing duct system serving single-family dwellings, the combined new and existing duct system shall meet one of the following requirements: I. The measured duct leakage shall be equal to or less than 10 percent of system air handler airflow as confirmed by field verification and diagnostic testing utilizing the procedures in Reference Residential Appendix Section RA3.1.4.3.1; or II. The measured duct leakage to outside shall be equal to or less than 7 percent of system air handler airflow as confirmed by field verification and diagnostic testing utilizing the procedures in Reference Residential Appendix Section RA3.1.4.3.4; or III. If it is not possible to meet the duct sealing requirements of either Section 150.2(b)1DiibI or 150.2(b)1DiibII, then all accessible leaks shall be sealed and verified through a visual inspection and a smoke test by a certified ECC-Rater utilizing the methods specified in Reference Residential Appendix RA3.1.4.3.5. Exception to Section 150.2(b)1Diib: Duct sealing. Existing duct systems that are extended, which are constructed, insulated or sealed with asbestos.

  c. Altered ducts and duct system components in garage spaces. When new or replacement space-conditioning ducts, air-handling units, cooling or heating coils, or plenums are located in a garage space, compliance with either I or II below is required. I. The measured system duct leakage shall be less than or equal to 6 percent of system air handler airflow as determined utilizing the procedures in Reference Residential Appendix Section RA3.1.4.3.1; or II. All accessible leaks located in the garage space shall be sealed and verified through a visual inspection and a smoke test by a certified ECC-Rater utilizing the methods specified in Reference Residential Appendix RA3.1.4.3.5. E. Altered space-conditioning system—duct sealing. In all climate zones, when a space-conditioning system serving a single-family dwelling is altered by the installation or replacement of space-conditioning system equipment, including replacement of the air handler, outdoor condensing unit of a split system air conditioner or heat pump, or cooling or heating coil, the duct system that is connected to the altered space-conditioning system equipment shall be sealed, as confirmed through field verification and diagnostic testing in accordance with the applicable procedures for duct sealing of altered existing duct systems as specified in Reference Residential Appendix RA3.1, and the leakage compliance criteria specified in Subsection i, ii, or iii below.

• CRC § 603.9.2.1 Medium relevance — show source text

  603.9.2.1 Duct Leakage Tests for Buildings that Meet Air Distribution System Duct Leak- age Sealing Criteria in Title 24, Part 6. For duct leakage testing, see California Energy Code Sec- tions 150.0(m)(11) for single family buildings, Sec- tion 160.3(b) for multifamily buildings, and Section 120.4(g) for nonresidential and Hotel Motel build- ings. 603.10 Cross Contamination. Exhaust ducts that convey Class 4 air shall be negatively pressurized relative to ducts, plenums, or occupiable spaces through which the ducts pass. Exhaust ducts under positive pressure that convey Class 2 or Class 3 air shall not extend into or pass through ducts, plenums, or occupiable spaces other than the space from which the exhaust air is drawn.

  603.11 Underground Installation. Ducts installed underground shall be approved for the installation and shall have a slope of not less than [1] ⁄ 8 inch per foot (10.4 mm/m) back to the main riser. Ducts, plenums, and fittings shall be permitted to be constructed of concrete, clay, or ceramics where installed in the ground or in a concrete slab, provided the joints are sealed and duct is secured in accordance with SMACNA

  HVAC Duct Construction Standards – Metal and Flexible.

  Metal ducts where installed in or under a concrete slab shall be encased in not less than 2 inches (51 mm) of concrete, secured in accordance with SMACNA HVAC Duct Con struction Standards – Metal and Flexible.

  603.12 Air Dispersion Systems. Where installed, air dispersion systems shall be completely in exposed locations in duct systems under positive pressure, and not pass through or penetrate fire-resistant-rated construction. Air dispersion systems shall be listed and labeled in accordance with UL 2518.

  603.13 Clearances. Duct clearances shall be in accordance with Section 603.13.1 through Section 603.13.6.

  603.13.1 General. Duct clearances to combustible construction shall be in accordance with the listing and the manufacturer’s installation instructions.

  603.13.2 Supply Air Ducts to Listed Furnaces. Supply air ducts connecting to listed central heating furnaces shall have the same minimum clearance to combustibles as required for the furnace supply plenum for a distance of not less than 3 feet (914 mm) from the supply plenum. Clearance shall not be required beyond the 3 feet (914 mm) distance. [NFPA 54:10.3.3.7] 603.13.3 Supply Air Ducts to Unlisted Furnaces. Supply air ducts connecting to unlisted central heating furnaces equipped with temperature limit controls with a maximum setting of 250°F (121°C) shall have a minimum clearance to combustibles of 6 inches (152 mm) for a distance of not less than 6 feet (1829 mm) from the furnace supply plenum. Clearance shall not be required beyond the 6 feet (1829 mm) distance. [NFPA 54:10.3.3.8]

  140 2025 CALIFORNIA MECHANICAL CODE

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  DUCT SYSTEMS

• CRC § 805.4.2 Medium 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.