Title 24 · California Energy Code

Are circulating pumps and electrical heat trace required to be capable of automatic shutoff?

If your hot‑water system uses circulating pumps or electric heat trace, the California Energy Code requires the system to be provided with controls that can automatically turn it off (§ 110.3(c)2), except for systems serving healthcare facilities; the California Plumbing Code gives acceptable control methods and timing limits (on‑demand, time clocks + temperature sensors, 5‑minute limits for certain pump uses).

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

Yes. Service hot water systems with circulating pumps and electrical heat trace systems must be capable of automatically turning off under § 110.3(c)2 of the California Energy Code. The rule is a capability requirement (the system must be provided with controls that allow automatic shutoff); an express exception is provided for systems serving healthcare facilities.

The single most important rule: any hot‑water distribution system that uses circulating pumps or electrical heat trace must be furnished with controls so the system can automatically be turned off (except for healthcare facilities).

Requirements in detail

Short plain-English restatement of the rule

  • If your hot‑water distribution uses a circulating pump or electrical heat trace, you must provide controls so the pump or heat‑trace circuit can be turned off automatically (not merely physically removable) — this is the requirement in § 110.3(c)2.

Decision‑relevant dimensions and values

Decision dimension Requirement / value Code reference
Systems covered Service hot water systems with circulating pumps and electrical heat trace systems § 110.3(c)2
Required capability Be capable of automatically turning off (i.e., provided with automatic shutoff controls) § 110.3(c)2
Exception (occupancy type) Healthcare facilities — the automatic turn‑off requirement does not apply § 110.3(c)2 (Exception)
Circulation pump control options (low‑rise residential guidance) Pumps “capable of being turned off (automatically or manually)” — on‑demand, time clocks + temperature sensing recommended L 501.3.1 / L 501.4 (CA Plumbing Code)
Time limit when pump maintains storage temperature Where used to maintain storage tank temperature, pump operation limited to start of heating cycle through a maximum of 5 minutes after end of heating cycle L 501.3.2 / L 503.3.4(2) (CA Plumbing Code)
Time‑clock / on‑demand controls for maintenance systems (heat trace & recirc) Systems (recirculation or heat trace) shall be equipped with automatic time switches or other controls capable of being set to switch off during extended periods; time clocks for pumps shall not let pump operate more than 15 minutes every hour (when used as a control method) L 501.5 / L 501.4 (CA Plumbing Code)

Notes:

  • The Energy Code § 110.3(c)2 supplies the mandatory capability requirement for installation; the Plumbing Code (Appendix L / body L sections) contains more prescriptive guidance on acceptable control strategies and specific time limits for pump/heat‑trace control behavior.

How to interpret “capable of automatically turning off”

  • “Capable” means the installed system must include controls (time switches, on‑demand controls, temperature sensors, DDC, or similar) that can automatically stop the pump or de‑energize the heat trace without relying solely on manual disconnection. This capability is the minimum the Energy Code requires; the Plumbing Code provides examples of acceptable methods (on‑demand, time clocks + temperature sensors, automatic time switches).

Exceptions & special cases

  • Healthcare facilities: the exception in § 110.3(c)2 explicitly excludes systems serving healthcare facilities from the automatic‑turn‑off capability requirement.
  • Low‑rise residential guidance: Appendix/chapters of the California Plumbing Code make clear that for low‑rise residential circulating systems, pumps “shall be arranged so that the circulating pump(s) are capable of being turned off (automatically or manually).” That phrasing recognizes manual turn‑off as acceptable for certain residential contexts, but the Energy Code imposes the automatic‑capability requirement on installed service hot water systems generally. Compare § 110.3(c)2 with L 501.3.1.
  • Systems that maintain storage tank temperature: where a pump is used specifically to maintain tank temperature, the Plumbing Code requires controls to limit that pump operation to the heating cycle plus no more than 5 minutes after the end of the cycle. That is a specific timing control separate from the general automatic shutoff capability.

Common mistakes

  • Treating “capable of automatically turning off” as optional: the Energy Code requires the capability — the system must be provided with controls that can perform automatic shutoff. Don’t assume “manual only” satisfies § 110.3(c)2 unless the applicable plumbing provisions for that specific occupancy explicitly allow manual only (see low‑rise residential guidance).
  • Forgetting the healthcare exception: owners and designers sometimes overlook the explicit exception for healthcare facilities in § 110.3(c)2. That exception matters for hospitals, long‑term care, etc.
  • Confusing “capable” with mandated continuous shutdown: the code requires the capability to automatically turn off, not that the system must always be off. Controls should be provided and set consistent with occupancy needs, on‑demand service, or scheduled operation.
  • Mixing Energy Code text and Plumbing Code numbers incorrectly: the Energy Code gives the mandatory capability; the Plumbing Code gives acceptable control strategies, time limits, and sensor placement — cite and apply both where relevant.

Worked example — concrete scenario

Scenario: A 4‑story apartment building has a central hot‑water system with a recirculation loop serving all units. The recirculation loop uses a circulating pump and electric heat trace on a remote branch.

What the code requires:

  1. Under § 110.3(c)2, both the recirculation pump and the electrical heat trace must be capable of automatically turning off (controls must be provided to automatically stop each system).
  2. For the recirculation pump, provide one of these acceptable control approaches from the Plumbing Code:
    • On‑demand activation (push‑button or app) OR
    • Time clock combined with temperature sensing (temperature sensor located at/near last fixture on loop) OR
    • Automatic time switches that are able to switch off during extended periods when hot water is not required.
  3. If the pump’s purpose included maintaining storage tank temperature, ensure controls limit pump operation to from start of the heating cycle to no more than 5 minutes after the end of that cycle. (Noting this specific 5‑minute limit applies where the pump is used to maintain storage tank temperature.)
  4. For the heat trace, install automatic time switches or other controls that can be set to turn the heat trace off during extended unoccupied periods (per L 501.5). This satisfies the Energy Code requirement that the heat‑trace system be capable of automatic shutoff.

Concrete numbers:

  • Provide a time‑clock that runs the recirculation pump only during morning and evening peaks (for example, 6:00–9:00 and 16:00–20:00). If a time‑clock approach is used, ensure the control and temperature sensor arrangement prevents pump runs longer than allowed by the Plumbing Code (if that limit applies), and that the system can be set or overridden to shut off for extended vacancy periods.
  • If the system maintains tank temperature, configure interlock so the pump stops within 5 minutes after the boiler/heater cycle ends.

Related provisions (referenced code sections)

  • § 110.3(c)2 — Controls for hot water distribution systems (main controlling provision).
  • § 110.3(a)1 — Temperature controls for service water‑heating systems (related certification/controls requirements).
  • § L 501.3.1 (California Plumbing Code) — Circulating hot water systems: pumps capable of being turned off (automatically or manually); on‑demand and time clock/temperature sensing guidance.
  • § L 501.3.2 / L 503.3.4(2) (California Plumbing Code) — Limits for pumps used to maintain storage tank temperature (start of heating cycle to max 5 minutes after end).
  • § L 501.5 (California Plumbing Code) — Temperature maintenance controls; heat trace and recirculation systems must have automatic time switches or other controls capable of being set to switch off during extended periods.

If you want, I can:

  • provide sample control wiring/sequence diagrams for a pump plus heat‑trace circuit that meet § 110.3(c)2 and the plumbing guidance; or
  • draft the specification text you can insert in construction documents to describe the required automatic shutoff controls (including sensor location and timing requirements).

Code references

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

  • § 110.3 High 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.

  • § 110.3 High relevance — show source text
    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. A water heating recirculation loop shall meet the following requirements: A. Air release valve or vertical pump installation. An automatic air release valve shall be installed on the recirculation loop piping on the inlet side of the recirculation pump and no more than 4 feet from the pump. This valve shall be mounted on top of a vertical riser at least 12 inches in length and shall be accessible for replacement and repair. Alternatively, the pump shall be installed on a vertical section of the return line. B. Recirculation loop backflow prevention. A check valve or similar device shall be located between the recirculation pump and the water heating equipment to prevent water from flowing backwards though the recirculation loop. C. Equipment for pump priming. A hose bibb shall be installed between the pump and the water heating equipment. An isolation valve shall be installed between the hose bibb and the water heating equipment. This hose bibb is used for bleeding air out of the pump after pump replacement. D. Pump isolation valves. Isolation valves shall be installed on both sides of the pump. These valves may be part of the flange that attaches the pump to the pipe. One of the isolation valves may be the same isolation valve as in Item C. E. Cold water supply and recirculation loop connection to hot water storage tank. Storage water heaters and boilers shall be plumbed in accordance with the manufacturer’s specifications The cold water piping and the recirculation loop piping shall not be connected to the hot water storage tank drain port. F. Cold water supply backflow prevention. A check valve shall be installed on the cold water supply line between the hot water system and the next closest tee on the cold water supply line.

  • § 501.2.2 High relevance — show source text

    Exception: Vertical supports, and horizontal and vertical anchors shall be installed on the pipe inside the pipe insulation.

    L 501.2.2 Building Cavities. Building cavities used for hot water supply and return piping shall be large enough to accommodate the combined diameter of the pipe plus the insulation, plus any other objects in the cavity that the piping must cross. L 501.3 Recirculation Systems. Recirculation systems shall comply with Section L 501.3.1 and Section L 501.3.2.

    L 501.3.1 For Low-Rise Residential Buildings. Circulating hot water systems shall be arranged so that the circulating pump(s) are capable of being turned off (automatically or manually) where the hot water system is not in operation. [ASHRAE 90.2-2007:7.2] L 501.3.2 For Pumps Between Boilers and Stor- age Tanks. Where used to maintain storage tank water temperature, recirculating pumps shall be equipped with controls limiting operation to a period from the start of the heating cycle to a maximum of 5 minutes after the end of the heating cycle. [ASHRAE 90.1:7.4.4.4] L 501.4 Recirculation Pump Controls. Pump controls shall include on-demand activation or time clocks combined with temperature sensing. Time clock controls for pumps shall not let the pump operate more than 15 minutes every hour. Temperature sensors shall stop circulation where the temperature set point is reached and shall be located on the circulation loop at or near the last fixture. The pump, pump controls, and temperature sensors shall be accessible. Pump operation shall be limited to the building’s hours of operation. L 501.4.1 Hot Water On-Demand Pumping Sys- tems. Hot water on-demand pumping systems manually actuated or automatically activated hot water pumping systems shall comply with IAPMO PS 115. L 501.5 Temperature Maintenance Controls. Systems designed to maintain usage temperatures in hot-water pipes, such as recirculating hot water systems or heat trace, shall be equipped with automatic time switches or other controls that are capable of being set to switch off the usage temperature maintenance system during extended periods where hot water is not required. [ASHRAE 90.1:7.4.4.2] L 501.6 System Balancing. Systems with multiple recirculation zones shall be balanced to distribute hot water uniformly, or they shall be operated with a pump for each zone. The circulation pump controls shall comply with the provisions of Section L 501.4.

    L 501.7 Flow Balancing Valves. Flow balancing valves shall be a factory preset automatic flow control valve, a flow regulating valve, or a balancing valve with memory stop.

    L 501.8 Air Elimination. Provision shall be made for the elimination of air from the return system. L 501.9 Gravity or Thermosyphon Systems. Gravity or thermosyphon systems are prohibited.

    L 502.0 Service Hot Water – Low-Rise Residential Buildings. L 502.1 General. The service water heating system for single-family houses, multi-family structures of three stories or fewer above grade, and modular houses shall comply with Section L 502.2 through Section L 502.7.3. The service water heating system of all other buildings shall comply with Section L 503.0.

  • § 1716.1.2 High relevance — show source text

    1716.1.2 Fifth Generation (5G) System Configu- rations. An advanced Ambient Temperature Loop (ATL) System or fifth generation (5G) ATL system shall also be capable of interacting with the electric utility system as well as other utility systems and systems compo nents.

    The system components shall include, but not limited to, the following:

    (1) Thermally diverse buildings with independent hydronic systems

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    2025 CALIFORNIA MECHANICAL CODE 355

    ), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

    GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE LOOPS

    (2) Circulation loop

    (3) Global control system

    (4) Segment isolation capability

    The system components may include, but not limited to, the following:

    (1) Electric grid-interactive enabled buildings

    (2) Hybrid components

    (3) Other renewable systems

    1716.2 Permitting. Permits required for the installation and application of an ATL distributed energy system shall be obtained as required by the Authority Having Jurisdiction.

    1716.3 Ambient Loop Temperature Range. The operating loop temperature range of an ambient temperature loop (ATL) system shall be not less than the freeze point of the circulating fluid and not more than the maximum temperature as required by the manufacturer’s installation instructions for the attached heat pump equipment in accordance with Section 1716.3.1 and Section 1716.3.2. The ATL system shall use treated water as the heat transfer medium.

    1716.3.1 ATL Operating Temperature. For equipment listed to AHRI/ASHRAE/ISO 13256-1 and AHRI/ASHRAE/ISO 13256-2, the controlled temperature range of the ambient closed loop shall be not less than 7°F (4°C) above the freeze point of the transport fluid and 10°F (6°C) below the (collective) heat pump lowest maximum inlet supply temperature as recommended by the manufacturer’s instructions.

    Exception: Equipment that is not listed to AHRI/ASHRAE/ISO 13256-1 and AHRI/ASHRAE/ISO 13256-2. The controlled temperature range of the ambient closed loop shall be in accordance with Section 1716.3.2 for minimum and maximum temperatures.

    1716.3.2 ATL Operating Temperature Range for Mixed Equipment Certifications. The source inlet temperature range of any attached equipment shall govern the design operating temperature range. Such equipment shall be identified in the design documentation. In any case the most restrictive minimum and maximum inlet supply temperatures, as recommended by the manufacturer’s instructions, shall determine the system operating temperature range.

    1716.4 Shutoff Valve. An automatic shutoff valve shall be provided for each individual building or facility transferring energy to or from an ATL distribution system. The automatic shutoff valve shall automatically shutoff upon operating command.

    1716.4.1 Shutoff Valve Operation. The operation of the automatic shutoff valve shall be in accordance with the system operating procedures. Where the operation of a shutoff valve was due to an emergency response, an auxiliary heating or cooling methodology shall be provided in accordance with Section 1717.1.2.

    1716.5 Bypass. The ATL distributed energy system shall be provided with bypass path(s) to reroute the circulating fluid when necessary.

  • § 12.5. High relevance — show source text

    (1) The tank surface is thermally insulated to R-12.5.

    (2) A standing pilot light is not installed.

    (3) Gas- or oil-fired storage water heaters have a flue damper or fan-assisted combustion. [ASHRAE 90.1:7.4.2]

    L 503.3.3 Service Hot Water Piping Insulation. Insulation of hot water and return piping shall meet the provisions in Section L 501.2.

    L 503.3.4 Hot Water System Design. Hot water systems shall comply with the following:

    (1) Circulating hot water systems shall be arranged so that the circulating pump(s) are capable of being turned off (automatically or manually) where the hot water system is not in operation.

    Exception: For healthcare facilities, long term care facilities, hotels, or motels, devices that automatically turn off the circulation pump(s) shall not be required.

    (2) Where used to maintain storage tank water temperature, circulating pump(s) shall be equipped with controls limiting operation to a period from the start of the heating cycle to a maximum of 5 minutes after the end of the heating cycle.

    (3) The maximum volume of water contained in hot water distribution lines between the water heater and the fixture stop or connection to showers, kitchen faucets, and lavatories shall be determined in accordance with Section L 502.7.

    L 503.3.5 Service Water Heating System Con- trols. Service water heating system controls shall comply with Section L 503.3.5(1) and Section L 503.3.5(2).

    (1) Temperature controls shall be provided that allow for storage temperature adjustment from 120°F (49°C) or lower to a maximum temperature compatible with the intended use.

    Exception: Where the manufacturer’s installation instructions specify a higher minimum thermostat setting to minimize condensation and resulting corrosion. [ASHRAE 90.1:7.4.4.1]

    (2) Temperature controlling means shall be provided to limit the maximum temperature of water delivered from lavatory faucets in public facility restrooms to 110°F (43°C). [ASHRAE 90.1:7.4.4.3]

    L 503.3.6 Pools. Pool heating systems shall comply with Section L 503.3.6(1) through Section L 503.3.6(3).

    2025 CALIFORNIA PLUMBING CODE 511

    ), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

    APPENDIX L

    (1) Pool heaters shall be equipped with a readily accessible ON/OFF switch to allow shutting off the heater without adjusting the thermostat setting. Pool heaters fired by natural gas shall not have continuously burning pilot lights. [ASHRAE 90.1:7.4.5.1] (2) Heated pools shall be equipped with a vapor retardant pool cover on or at the water surface. Pools heated to more than 90°F (32°C) shall have a pool cover with a minimum insulation value of R-12.

  • § 170.2 High relevance — show source text

    Chillers that are piped in series for the purpose of increased temperature differential shall be considered as one chiller.

    iii. Boiler isolation. When a hot water plant includes more than one boiler, provisions shall be made so that flow through any boiler is automatically shut off when that boiler is shut off while still maintaining flow through other operating boiler(s). iv. Chilled and hot water temperature reset controls. Systems with a design capacity exceeding 500,000 Btu/hr supplying chilled or heated water shall include controls that automatically reset supply water temperatures as a function of representative building loads or outside air temperature. Exception to Section 170.2(c)4Iiv: Hydronic systems that use variable flow to reduce pumping energy in accordance with Section 170.2(c)4Ii.

    v. Water-cooled air conditioner and hydronic heat pump systems. Water circulation systems serving watercooled air conditioners, hydronic heat pumps or both, that have total pump system power exceeding 5 hp, shall have flow controls that meet the requirements of Section 170.2(c)4Ivi. Each such air conditioner or heat pump shall have a two-position automatic valve interlocked to shut off water flow when the compressor is off.

    vi. Variable flow controls.

    a. Variable speed drives. Individual pumps serving variable flow systems and having a motor horsepower exceeding 5 hp shall have controls or devices (such as variable speed control) that will result in pump motor demand of no more than 30 percent of design wattage at 50 percent of design water flow. The pumps shall be controlled as a function of required differential pressure. b. Pressure sensor location and setpoint. I. For systems without direct digital control of individual coils reporting to the central control panel, differential pressure shall be measured at the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure. II. For systems with direct digital control of individual coils with a central control panel, the static pressure setpoint shall be reset based on the valve requiring the most pressure, and the setpoint shall be no less than 80 percent open. Pressure sensors may be mounted anywhere. Exception 1 to Section 170.2(c)4Ivi: Heating hot water systems. Exception 2 to Section 170.2(c)4Ivi: Condenser water systems serving only water-cooled chillers. vii. Hydronic heat pump (WLHP) controls. Hydronic heat pumps connected to a common heat pump water loop with central devices for heat rejection and heat addition shall have controls that are capable of providing a heat pump water supply temperature deadband of at least 20°F between initiation of heat rejection and heat addition by the central devices.

    254 2025 CALIFORNIA ENERGY CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES

    Exception to Section 170.2(c)4Ivii: Where a system loop temperature optimization controller is used to determine the most efficient operating temperature based on real-time conditions of demand and capacity, deadbands of less than 20°F shall be allowed .

    J. Reserved.

    K. **Fan control.

  • § 170.2 High relevance — show source text
    • 40 percent of the design chiller cooling capacity. Exception 3 to Section 170.2(c)4G: Chillers used to charge thermal energy storage systems where the charging temperature is < 40°F. Exception 4 to Section 170.2(c)4G: In buildings with more than three chillers, only three chillers are required to meet the Path B efficiencies.

    H. Limitation of air-cooled chillers. Chilled water plants shall not have more than 300 tons provided by air-cooled chillers.

    Exception 1 to Section 170.2(c)4H: Where the water quality at the building site fails to meet manufacturer’s specifications for the use of water-cooled chillers.

    Exception 2 to Section 170.2(c)4H: Chillers that are used to charge a thermal energy storage system with a design temperature of less than 40°F (4°C). I. Hydronic system measures . i. Hydronic variable flow systems. HVAC chilled and hot water pumping shall be designed for variable fluid flow and shall be capable of reducing pump flow rates to no more than the larger of: a) 50 percent or less of the design flow rate; or b) the minimum flow required by the equipment manufacturer for the proper operation of equipment served by the system. Exception 1 to Section 170.2(c)4I: Systems that include no more than three control valves. Exception 2 to Section 170.2(c)4I: Systems having a total pump system power less than or equal to 1.5 hp. ii. Chiller isolation. When a chilled water system includes more than one chiller, provisions shall be made so that flow through any chiller is automatically shut off when that chiller is shut off while still maintaining flow through other operating chiller(s). Chillers that are piped in series for the purpose of increased temperature differential shall be considered as one chiller.

    iii. Boiler isolation. When a hot water plant includes more than one boiler, provisions shall be made so that flow through any boiler is automatically shut off when that boiler is shut off while still maintaining flow through other operating boiler(s). iv. Chilled and hot water temperature reset controls. Systems with a design capacity exceeding 500,000 Btu/hr supplying chilled or heated water shall include controls that automatically reset supply water temperatures as a function of representative building loads or outside air temperature. Exception to Section 170.2(c)4Iiv: Hydronic systems that use variable flow to reduce pumping energy in accordance with Section 170.2(c)4Ii.

    v. Water-cooled air conditioner and hydronic heat pump systems. Water circulation systems serving watercooled air conditioners, hydronic heat pumps or both, that have total pump system power exceeding 5 hp, shall have flow controls that meet the requirements of Section 170.2(c)4Ivi. Each such air conditioner or heat pump shall have a two-position automatic valve interlocked to shut off water flow when the compressor is off.

    vi. Variable flow controls.

    a. Variable speed drives. Individual pumps serving variable flow systems and having a motor horsepower exceeding 5 hp shall have controls or devices (such as variable speed control) that will result in pump motor demand of no more than 30 percent of design wattage at 50 percent of design water flow. The pumps shall be controlled as a function of required differential pressure. b. Pressure sensor location and setpoint.

  • § 503.7.1 High relevance — show source text

    ** Heat pumps equipped with internal electric resistance heaters shall have controls 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. Exception: Heat pumps whose minimum efficiency is regulated by U.S. National Appliance Energy Conservation Act (NAECA) and whose ratings are in accordance with the requirements shown in Table E 503.7.1(2) and includes the use of an internal electric resistance heating. [ASHRAE 90.1:6.4.3.5] E 503.4.6.7 Humidification and Dehumidifica- tion Control. Humidification and dehumidification

    control shall be in accordance with Section E 503.4.6.7.1 through Section E 503.4.6.7.3. E 503.4.6.7.1 Dehumidification. Humidistatic controls shall not use mechanical cooling to reduce the humidity below the lower of a dew point of 55°F (12.8°C) or relative humidity of 60 percent in the coldest zone served by the system. Exceptions: (1) Lower humidity shall be permitted when operating mechanical cooling for temperature control.

    (2) Systems serving zones where specific humidity levels are required, such as museums and hospitals, and approved by the Authority Having Jurisdiction or required by accreditation standards, and where humidistatic controls are capable of and configured to maintain a dead band of at least 10 percent relative humidity where no active humidification or dehumidification takes place.

    (3) Systems serving zones where humidity levels are required to be maintained with precision of not more than ±5 percent relative humidity to comply with applicable codes or accreditation standards or as approved by the Authority Having Jurisdiction.

    [ASHRAE 90.1:6.4.3.6.1]

    E 503.4.6.7.2 Humidification. Humidistatic controls shall not use fossil fuel or electricity to produce relative humidity above 30 percent in the warmest zone served by the system.

    Exceptions:

    (1) Systems serving zones where specific humidity levels are required, such as museums and hospitals, and approved by the Authority Having Jurisdiction or required by accreditation standards, and where humidistatic controls are capable of and configured to maintain a dead band of at least 10 percent relative humidity where no active humidification or dehumidification takes place.

    TABLE E 503.4.6.4.2 MAXIMUM DAMPER LEAKAGE [1, 2]

    (cubic foot per minute per square foot) at 1.0 inch water gauge

    [ASHRAE 90.1: TABLE 6.4.3.4.3]

  • § 90.1 High relevance — show source text

    Humidistatic Controls. Automatic controls used to maintain humidity at a fixed or adjustable set point. [ASHRAE 90.1:3.2]

    Integrated Energy Efficiency Ratio (IEER). A singlenumber figure of merit expressing cooling part-load EER efficiency for commercial unitary air-conditioning and heat pump equipment on the basis of weighted operation at various load capacities for the equipment. [ASHRAE 90.1:3.2] Integrated Part-Load Value (IPLV.I-P). A single-number figure of merit based on part-load EER, COP C, or kW/kW expressing part-load efficiency for air-conditioning and heat pump equipment on the basis of weighted operation at various load capacities for the equipment. [ASHRAE 90.1:3.2]

    Joint, Transverse . Connections of two duct sections oriented perpendicular to airflow. Maintenance. The upkeep of property or equipment by the owner of the property in accordance with the requirements of this appendix. Minimum Efficiency Reporting Value (MERV). Filter minimum efficiency reporting value, in accordance with ASHRAE 52.2.

    Multi-Occupant Spaces. Indoor spaces used for presentations and training, including classrooms and conference

    rooms.

    On-Site Renewable Energy. Energy generated from renewable sources produced at the building site. [ASHRAE 90.1:3.2] Packaged Terminal Air Conditioner (PTAC). A wall sleeve and a separate unencased combination of heating and cooling assemblies specified by the manufacturer and intended for mounting through the wall. It includes refrigeration components, separable outdoor louvres, forced ventilation, and heating availability by purchaser’s choice of hot water, steam, or electrical resistance heat.

    Packaged Terminal Heat Pump (PTHP). A separate unencased refrigeration system installed in a cabinet having a function and configuration similar to that of a packaged terminal air-conditioner. It uses reverse cycle refrigeration as its prime heat source and should have other supplementary heat source(s) available to purchasers with the choice of hot water, steam, or electric resistance heat.

    Parking Garage Section. A part of a parking garage where airflow is restricted from other parts of the garage by solid walls. [ASHRAE 90.1:3.2]

    Process Application. A manufacturing, industrial, or commercial procedure or activity where the primary purpose is other than conditioning spaces and maintaining comfort and amenities for the occupants of a building. [ASHRAE 90.1:3.2] Recirculation System. A system of hot water supply and return piping with shutoff valves, balancing valves, circulating pumps, and a method of controlling the circulating system.

    2025 CALIFORNIA MECHANICAL CODE 413

    ), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

    APPENDIX E

    Renewable Energy Resources. Energy from solar, wind, biomass or hydro, or extracted from hot fluid or steam heated within the earth. [ASHRAE 90.1:3.2] Seam, Longitudinal . Joints oriented in the direction of airflow.

    Seasonal Energy Efficiency Ratio (SEER). The total cooling output of an air conditioner during its normal annual usage period for cooling in Btu (kW•h) divided by the total electric energy input during the same period in Btu (kW•h).

  • § 501.4.1 Medium relevance — show source text

    L 501.4.1 Hot Water On-Demand Pumping Sys- tems. Hot water on-demand pumping systems manually actuated or automatically activated hot water pumping systems shall comply with IAPMO PS 115. L 501.5 Temperature Maintenance Controls. Systems designed to maintain usage temperatures in hot-water pipes, such as recirculating hot water systems or heat trace, shall be equipped with automatic time switches or other controls that are capable of being set to switch off the usage temperature maintenance system during extended periods where hot water is not required. [ASHRAE 90.1:7.4.4.2] L 501.6 System Balancing. Systems with multiple recirculation zones shall be balanced to distribute hot water uniformly, or they shall be operated with a pump for each zone. The circulation pump controls shall comply with the provisions of Section L 501.4.

    L 501.7 Flow Balancing Valves. Flow balancing valves shall be a factory preset automatic flow control valve, a flow regulating valve, or a balancing valve with memory stop.

    L 501.8 Air Elimination. Provision shall be made for the elimination of air from the return system. L 501.9 Gravity or Thermosyphon Systems. Gravity or thermosyphon systems are prohibited.

    L 502.0 Service Hot Water – Low-Rise Residential Buildings. L 502.1 General. The service water heating system for single-family houses, multi-family structures of three stories or fewer above grade, and modular houses shall comply with Section L 502.2 through Section L 502.7.3. The service water heating system of all other buildings shall comply with Section L 503.0.

    L 502.2 Water Heaters and Storage Tanks. Residentialtype water heaters, pool heaters, and unfired water heater storage tanks shall comply with the minimum performance requirements specified by federal law. Unfired storage water heating equipment shall have a heat loss through the tank surface area of less than 6.5 British thermal units per square foot hour [Btu/(ft [2] - h)] (20.5 W/m [2] ).

    [ASHRAE 90.2-2007:7.1] L 502.3 Recirculation Systems. Recirculation systems shall comply with the provisions of Section L 501.3. L 502.4 Central Water Heating Equipment. Service water heating equipment (central systems) that do not fall under the requirements for residential-type service water heating equipment addressed in Section L 502.2 shall comply with the applicable requirements for service water-heating equipment found in Section L 503.0. [ASHRAE 90.2-2007:7.3] L 502.5 Insulation. Insulation for hot water and return piping shall comply with the provisions of Section L 501.2. L 502.6 Hard Water. Where water has hardness equal to or exceeding 9 grains per gallon (gr/gal) (154 mg/L) measured as total calcium carbonate equivalents, the water supply line to water heating equipment in new one- and two-family dwellings shall be roughed-in to allow for the installation of water treatment equipment. L 502.7 Maximum Volume and Length of Hot Water. The maximum volume of water contained in a hot water

    branch shall be in accordance with Section L 502.7.1. The maximum length per volume of piping shall comply with Section L 502.7.2.

  • § 140.4 Medium relevance — show source text

    Exception 1 to Section 140.4(k)4: Hydronic systems that use variable flow to reduce pumping energy in accordance with 140.4(k)1.

    Exception 2 to Section 140.4(k)4: Systems serving healthcare facilities. 5. Water-cooled air conditioner and hydronic heat pump systems. Water circulation systems serving water-cooled air conditioners, hydronic heat pumps, or both that have total pump system power exceeding 5 hp shall have flow controls that meet the requirements of Section 140.4(k)6. Each such air conditioner or heat pump shall have a two-position automatic valve interlocked to shut off water flow when the compressor is off.

    1. Variable flow controls.

    A. Variable speed drives. Individual pumps serving variable flow systems and having a motor horsepower exceeding 5 hp shall have controls or devices (such as variable speed control) that will result in pump motor demand of no more than 30 percent of design wattage at 50 percent of design water flow. The pumps shall be controlled as a function of required differential pressure. B. Pressure sensor location and setpoint. i. For systems without direct digital control of individual coils reporting to the central control panel, differential pressure shall be measured at the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure. ii. For systems with direct digital control of individual coils with a central control panel, the static pressure setpoint shall be reset based on the valve requiring the most pressure, and the setpoint shall be no less than 80 percent open. Pressure sensors may be mounted anywhere.

    Exception 1 to Section 140.4(k)6: Heating hot water systems.

    Exception 2 to Section 140.4(k)6: Condenser water systems serving only water-cooled chillers.

    2025 CALIFORNIA ENERGY CODE 125

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—PERFORMANCE AND PRESCRIPTIVE

    COMPLIANCE APPROACHES FOR ACHIEVING ENERGY EFFICIENCY

    1. Hydronic heat pump (WLHP) controls. Hydronic heat pumps connected to a common heat pump water loop with central devices for heat rejection and heat addition shall have controls that are capable of providing a heat pump water supply temperature dead band of at least 20°F between initiation of heat rejection and heat addition by the central devices.

    Exception to Section 140.4(k)7: Where a system loop temperature optimization controller is used to determine the most efficient operating temperature based on real-time conditions of demand and capacity, dead bands of less than 20°F shall be allowed. 8. High capacity space heating gas boiler systems. In Climate Zones 1 through 6, 9 through 14, and 16, gas hot water boiler systems for space heating with a total system input of at least 1 MMBtu/h but no more than 10 MMBtu/h shall meet all of the following requirements. A. Boiler system efficiency. Gas hot water boilers shall have a minimum thermal efficiency of 90 percent. Systems with multiple boilers can meet this requirement if the space-heating input provided by equipment with thermal efficiencies above and below 90 percent has an input capacity-weighted average thermal efficiency of at least 90 percent. For boilers federally regulated by combustion efficiency, the calculation for the input capacity-weighted average thermal efficiency shall use the combustion efficiency value. B. **Hot water distribution design.

  • § 502.7.3 Medium relevance — show source text

    L 502.7.3 Hot Water System Submeters. Where a hot water pipe from a circulation loop or electric heat trace line is equipped with a submeter, the hot water distribution system downstream of the submeter shall have either an end-of-line hot water circulation pump or shall be electrically heat traced. The maximum volume of water in a branch from the circulation loop or electric heat trace line downstream of the submeter shall not exceed 16 oz (473 mL).

    Where there is no circulation loop or electric heat traced line downstream of the submeter, the submeter shall be located within 2 feet (610 mm) of the central hot water system; or the branch line to the submeter shall be circulated or heat traced to within 2 feet (610 mm) of the submeter. The maximum volume from the submeter to each fixture shall not exceed 32 oz (946 mL).

    The circulation pump controls shall comply with the provisions of Section L 501.4.

    L 503.0 Service Hot Water – Other Than Low-Rise Residential Buildings.

    L 503.1 General. The service hot water, other than singlefamily houses, multifamily structures of three stories or fewer above grade, and modular houses shall comply with this section.

    L 503.1.1 New Buildings. Service water-heating systems and equipment shall comply with the requirements of this section as described in Section L 503.2.

    [ASHRAE 90.1:7.1.1.1]

    L 503.1.2 Additions to Existing Buildings. Service water heating systems and equipment shall comply with the requirements of this section.

    Exception: Where the service water-heating to an addition is provided by existing service water-heating systems and equipment, such systems and equipment shall not be required to be in accordance with this appendix. However, new systems or equipment installed shall be in accordance with specific requirements applicable to those systems and equipment. [ASHRAE 90.1:7.1.1.2]

    L 503.1.3 Alterations to Existing Buildings. Building service water-heating equipment installed as a direct replacement for existing building service water-heating equipment shall be in accordance with the requirements of Section L 503.0 applicable to the equipment being replaced. New and replacement piping shall comply with Section L 503.3.3.

    Exception: Compliance shall not be required where there is insufficient space or access to meet these requirements. [ASHRAE 90.1:7.1.1.3]

    L 503.2 Compliance Paths. Service water heating systems and equipment shall comply with Section L 503.2.1 and Section L 503.2.2.

    L 503.2.1 Requirements for All Compliance Paths. Service water heating systems and equipment shall comply with Section L 503.1, Section L 503.3, and Section L 503.5. [ASHRAE 90.1:7.2.1]

    TABLE L 502.7.1 WATER VOLUME FOR DISTRIBUTION PIPING MATERIALS* Col2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11 Col12 Col13 Col14 Col15
    OUNCES OF WATER PER FOOT LENGTH OF PIPING **OUNCES OF WATER PER FOOT LENGTH OF

Frequently asked questions

Are systems already installed required to be retrofitted to meet § 110.3(c)2?

Not necessarily. § 110.3(c)2 is an installation requirement; applicability to replacements or alterations depends on the specific retrofit/alteration rules and the scope of work. The code text cited addresses installations; consult the Authority Having Jurisdiction for retrofit enforcement.

Does “capable of automatically turning off” mean the pump must be off most of the time?

No — it means the system must include controls that can automatically stop operation when appropriate. How those controls are scheduled or set (on‑demand, time clocks, temperature sensors) depends on occupancy needs and the prescriptive guidance in the Plumbing Code.

Do hotels and motels fall under the healthcare exception?

No. The explicit exception in § 110.3(c)2 applies to healthcare facilities; hotels and motels are not listed in that exception. However, other plumbing code sections provide specific guidance for hotels/motels. Confirm with your AHJ for occupancy‑specific interpretations.

If I use on‑demand controls, do I still comply?

Yes. The Plumbing Code lists on‑demand activation as an acceptable control strategy for hot‑water on‑demand pumping systems; such a system would meet the “capable of automatically turning off” requirement when configured properly.

Where should the temperature sensor for a loop be located?

The Plumbing Code directs that temperature sensors used to stop circulation when set‑point is reached should be located on the circulation loop at or near the last fixture. Use that placement when specifying temperature‑based shutoff.

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