Title 24 · California Energy Code

What are the variable‑flow pump control and differential pressure sensor requirements for hydronic systems?

If your building has hydronic pumps larger than 5 hp, Title 24 § 140.4(k)6 requires variable‑speed (or equivalent) controls so the pump draws no more than 30% of its design electrical power at half the design flow, and the system’s differential pressure sensor must be located and/or the pressure setpoint reset so it reflects the most demanding heat exchanger (or is adjusted by valve position when you have DDC to coils).

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

The California Energy Code requires variable‑flow hydronic systems with pumps larger than 5 hp to be equipped with controls (typically variable speed drives (VSDs)) that reduce pump electrical demand to no more than 30 percent of design wattage at 50 percent of design flow, and to be controlled as a function of differential pressure. Differential pressure must be measured at the most remote heat exchanger (or, for systems with DDC to individual coils, the static pressure setpoint must be reset based on the valve requiring the most pressure and the setpoint shall be no less than 80 percent open) — see § 140.4(k)6.

The single most important rule: For pumps > 5 hp, use VSD or equivalent so at 50% design flow the pump motor electrical demand ≤ 30% of design wattage, and locate/operate the differential pressure sensor to reflect the most demanding coil (or reset it where DDC to coils exists). § 140.4(k)6.

Requirements in detail

Key defined terms (first use bolded)

Variable speed drive (VSD) — a control/device that varies pump speed to match system flow demand. § 140.4(k)6.A.
Design flow — system flow rate at design conditions; code requires ability to reduce flow to 50% of design (or to manufacturer minimum) per § 140.4(k)1.
Design wattage — the pump motor electric power at design conditions (used to set the 30% threshold). § 140.4(k)6.A.
Differential pressure sensor — device that measures system pressure used to control pump speed; location and setpoint rules in § 140.4(k)6.B.

Decision‑relevant values (quick reference table)

Decision dimension	Required value / threshold	When it applies	Code Reference
Pump horsepower threshold	> 5 hp	Individual pumps serving variable‑flow systems	§ 140.4(k)6.A
Required motor demand at 50% flow	≤ 30% of design wattage	Pumps > 5 hp; achieved by VSD or equivalent	§ 140.4(k)6.A
Required minimum turndown / flow reduction	50% of design flow (or manufacturer minimum)	All hydronic variable‑flow systems per §140.4(k)1	§ 140.4(k)1
Differential pressure measurement location	Most remote heat exchanger or HX requiring greatest ΔP	Systems without DDC to coils	§ 140.4(k)6.B.i
Differential pressure setpoint/reset rule (DDC)	Reset based on valve needing most pressure; setpoint no less than 80% open; sensor may be mounted anywhere	Systems with DDC to individual coils reporting to central panel	§ 140.4(k)6.B.ii
Acceptance / testing	Pressure sensors factory or field calibrated; functional tests (increase to ~90% flow, reduce to 50% flow) and stability criteria	Appendix/Mechanical test procedures (E805.10)	E805.10 (Cal. Mechanical Code)

How it must be controlled

Pumps required to vary speed must be controlled as a function of the required differential pressure (i.e., the VSD adjusts speed to maintain the differential pressure setpoint) — § 140.4(k)6.A–B.
For systems without DDC to coil level, the pressure sensor must be located at or near the most remote heat exchanger (or the one requiring the greatest differential pressure) so the sensor reflects the worst‑case pressure need — § 140.4(k)6.B.i.
For systems with DDC to individual coils, the static pressure setpoint must be reset so the control responds to valve positions; the setpoint must be sized so at least one valve is essentially wide open — the code phrases this as "no less than 80 percent open" — § 140.4(k)6.B.ii.

Testing, calibration, and acceptance (what inspectors will check)

Pressure sensors must be factory‑calibrated or field‑calibrated and documented. Functional testing steps described in the Mechanical Code Appendix include: increase valves to ~90% of design flow and verify pump speed increases; then reduce valves to 50% design flow and verify pump speed decreases and setpoint behavior — see E805.10 procedures and acceptance criteria.
Appendix E (Mechanical Code) requires the sensor to be located at/near the most remote HX for acceptance and that the system stabilize within prescribed tolerances during testing.

Exceptions & special cases

Heating hot water systems are exempt from § 140.4(k)6 (Exception 1 to § 140.4(k)6).
Condenser water systems serving only water‑cooled chillers are exempt from § 140.4(k)6 (Exception 2 to § 140.4(k)6).
Systems or equipment specifically referenced elsewhere: the general variable‑flow performance requirement (ability to reduce flow to 50%) has its own exceptions (e.g., systems with ≤ three control valves, total pump system power ≤ 1.5 hp) under § 140.4(k)1.
The Mechanical Code / Appendix E contains related language (including an ASHRAE‑derived limit that the differential pressure setpoint should not exceed 110% of that required to achieve design flow) — that is a related acceptance/interpretation in the mechanical appendix and should be reviewed for testing details, but the controlling prescriptive language for Title 24 compliance is § 140.4(k)6.

If you need to apply this to a system not covered above (for example, primary/secondary pump arrangements, coil‑freeze‑protection pumps, or electric‑boiler dominant systems), those situations may be excluded or have separate rules in the Mechanical Code — consult the specific exceptions in the code sections cited above.

Common mistakes

Assuming the 30% target refers to flow rather than motor electrical demand. The code requires motor demand ≤ 30% of design wattage at 50% flow, not 30% flow or 30% of torque. § 140.4(k)6.A.
Placing the pressure sensor near the pump or where it is convenient rather than at/near the most remote heat exchanger for non‑DDC systems — that defeats the intent to protect the worst‑case coil. § 140.4(k)6.B.i.
For DDC systems, failing to implement proper setpoint reset logic tied to valve position so the static pressure setpoint remains higher than necessary (or is never reduced until a valve is nearly open). The code requires reset based on valve requiring the most pressure and a setpoint that results in at least one valve being near 80% open. § 140.4(k)6.B.ii.
Not documenting sensor calibration and the functional test results required by E805.10 (sensor calibration certificates or field calibration records). Inspectors will look for calibration and test records. E805.10 (Cal. Mechanical Code) describes the required documentation.

Worked example — concrete scenario

Scenario: A chilled‑water plant has a single variable‑flow pump with motor nameplate (design) electrical input of 15 kW and a design flow of 2,000 gpm. The pump is > 5 hp, so § 140.4(k)6 applies.

Steps to comply:

Select/install a VSD and control scheme that modulates pump speed by maintaining differential pressure. § 140.4(k)6.A–B.
Confirm VSD control achieves motor demand ≤ 30% of 15 kW = 4.5 kW when flow is 50% of design = 1,000 gpm. During commissioning measure motor input at 1,000 gpm; it must be ≤ 4.5 kW. § 140.4(k)6.A.
Place the differential pressure sensor at or near the most remote heat exchanger (or the coil requiring the greatest ΔP) if the system does not have DDC to coils. During testing follow the E805.10 sequence: open valves to ~90% design flow and verify pump speed increases; then reduce to 50% design flow and verify pump speed decreases and setpoint behavior. E805.10 requires sensors be calibrated and the system stabilize within specified tolerances.
If this plant has DDC reporting for each coil to the central panel, implement setpoint reset logic so the static pressure setpoint is reset based on valve positions and sized so one valve is approximately 80% open (i.e., the setpoint is not reduced beyond the point that would close all valves tighter than 80% open). § 140.4(k)6.B.ii.

If the measured motor input at 50% flow exceeds 4.5 kW during the functional test, adjust control strategy (pump curve, VSD trim, parallel pumping, or impeller modifications) until the requirement is met and document results per E805.10.

Related provisions

§ 140.4(k)1 — Hydronic variable flow systems; ability to reduce flow to 50% of design flow (or manufacturer minimum).
§ 140.4(k)6 — Variable flow controls and differential pressure sensor requirements (primary controlling text for pumps > 5 hp).
Mechanical Code Appendix E, E805.10 — Hydronic system variable flow controls functional test procedure and acceptance (sensor calibration, 90%/50% flow tests).
Mechanical Code Appendix E / ASHRAE‑derived language — additional explanatory/acceptance language about differential pressure setpoint limits (e.g., not exceed 110% of required ΔP) and valve‑position reset behavior.

If you want, I can:

Review your pump curve and controls spec and show the calculations that demonstrate compliance with the ≤ 30% motor demand at 50% flow; or
Draft acceptance‑test checklists and required documentation (calibration certificates, VSD performance readings, E805.10 test sheet) for use at commissioning.

Code references

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

§ 140.4 High 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.
§ 90.1 High relevance — show source text
[ASHRAE 90.1:6.5.4.1]

2025 CALIFORNIA MECHANICAL CODE 439

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

APPENDIX E

TABLE E 503.5.7.2

PUMP FLOW CONTROL REQUIREMENTS

[ASHRAE 90.1: TABLE 6.5.4.2]

BOILER SYSTEM DESIGN INPUT, Btu/h MINIMUM TURNDOWN RATIO

≥1 000 000 and≤5 000 000 3 to 1

>5 000 000 and≤10 000 000 4 to 1

>10 000 000 5 to 1

»

TABLE E 503.5.7

BOILER TURNDOWN

[ASHRAE 90.1: TABLE 6.5.4.1]

For SI units: 1000 British thermal units per hour = 0.293 kW

E 503.5.7.2 Hydronic Variable Flow Systems. Chilled- and hot-water distribution systems that include three or more control valves designed to modulate or step open and close as a function of load shall be designed for variable fluid flow and shall be capable of and configured to reduce pump flow rates to not more than the larger of 25 percent of the design flow rate or the minimum flow required by the heating/cooling equipment manufacturer for the proper operation of equipment. Individual or parallel pumps serving variable-flow heating-water or chilledwater systems, where the nameplate horsepower of the motor or combined parallel motors is not less than the power shown in Table E 503.5.7.2, shall have controls or devices that will result in pump motor demand of not more than 30 percent of design wattage at 50 percent of design water flow. The controls or devices shall be controlled as a function of desired flow or to

maintain a minimum required differential pressure. Differential pressure shall be measured at or near the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure. The differential pressure setpoint shall not exceed 110 percent of that required to achieve design flow through the heat exchanger. Where differential pressure control is used to comply with this section, and DDC systems are used, the setpoint shall be reset downward based on valve positions until one valve is nearly wide open.

Exceptions:

(1) Differential pressure set-point reset is not required where valve position is used to comply with Section E 503.5.7.4.

(2) Variable-pump flow control is not required on heating-water pumps where more than 50 percent of annual heat is generated by an electric boiler.

(3) Variable flow is not required for primary pumps in a primary/secondary system.

(4) Variable flow is not required for a coil pump provided for freeze protection.

(5) Variable flow is not required for heat recovery coil runaround loops. [ASHRAE 90.1:6.5.4.2]
§ 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.

§ 503.5.7.2 High relevance — show source text

Individual or parallel pumps serving variable-flow heating-water or chilledwater systems, where the nameplate horsepower of the motor or combined parallel motors is not less than the power shown in Table E 503.5.7.2, shall have controls or devices that will result in pump motor demand of not more than 30 percent of design wattage at 50 percent of design water flow. The controls or devices shall be controlled as a function of desired flow or to

maintain a minimum required differential pressure. Differential pressure shall be measured at or near the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure. The differential pressure setpoint shall not exceed 110 percent of that required to achieve design flow through the heat exchanger. Where differential pressure control is used to comply with this section, and DDC systems are used, the setpoint shall be reset downward based on valve positions until one valve is nearly wide open.

Exceptions:

(1) Differential pressure set-point reset is not required where valve position is used to comply with Section E 503.5.7.4.

(2) Variable-pump flow control is not required on heating-water pumps where more than 50 percent of annual heat is generated by an electric boiler.

(3) Variable flow is not required for primary pumps in a primary/secondary system.

(4) Variable flow is not required for a coil pump provided for freeze protection.

(5) Variable flow is not required for heat recovery coil runaround loops. [ASHRAE 90.1:6.5.4.2]

CHILLED WATER PUMPS IN THESE CLIMATE ZONES	HEATING WATER PUMPS IN THESE CLIMATE ZONES	MOTOR NAMEPLATE HORSEPOWER
0A, 0B, 1A, 1B, 2B	NR	≥2 hp
2A, 3B	NR	≥3 hp
3A, 3C, 4A, 4B	7, 8	≥5 hp
4C, 5A, 5B, 5C, 6A, 6B	3C, 5A, 5C, 6A, 6B	≥7.5 hp
─	4A, 4C, 5B	≥10 hp
7, 8	4B	≥15 hp
─	2A, 2B, 3A, 3B	≥25 hp
─	1B	≥100 hp
─	0A, 0B, 1A	≥200 hp

For SI units: 1 horsepower = 0.746 kW

§ 140.4 High relevance — show source text
Exception 4 to Section 140.4(i): In buildings with more than three chillers, only three chillers are required to meet the Path B efficiencies.

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

Exception 1 to Section 140.4(j): 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 140.4(j): Chillers that are used to charge a thermal energy storage system with a design temperature of less than 40°F (4°C).

Exception 3 to Section 140.4(j): Systems serving healthcare facilities.

(k) Hydronic system measures.
1. 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 140.4(k)1: Systems that include no more than three control valves.

Exception 2 to Section 140.4(k)1: Systems having a total pump system power less than or equal to 1.5 hp. 2. 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.
1. 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).
2. 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 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.
§ 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.
§ 805.10 High relevance — show source text
E 805.10 Hydronic System Variable Flow Controls (Form MECH-10A). The purpose of this test is to ensure that hydronic variable flow chilled water and water-loop heat pump systems with circulating pumps larger than 5 hp (3.7 kW) vary system flow rate by modulating pump speed using a variable frequency drive (VFD) or equivalent. As the loads within the building fluctuate, control valves modulate the amount of water passing through each coil and add or remove the desired amount of energy from the air stream to satisfy the load. In the case of water-loop heat pumps, each two-way control valve associated with a heat pump will be closed where that unit is not operating. As each control valve modulates, the pump variable frequency drive (VFD) responds accordingly to meet system water flow requirements. This is not required on heating hot water systems with variable flow designs or for condensing water serving water cooled chillers. E 805.10.1 Test Procedure. The procedure for performing a functional test for hydronic system variable flow controls shall be in accordance with Section E

805.10.1.1 and Section E 805.10.1.2.

E 805.10.1.1 Construction Inspection. Prior to functional testing, verify and document the pressure sensors are either factory or field calibrated. E 805.10.1.2 Functional Testing. The functional testing shall comply with the following steps:

Step 1: Open control valves to increase water flow to not less than 90 percent design flow. Verify and document the following:

(1) Pump speed increases.

(2) System pressure is either within plus or minus 5 percent of current operating setpoint, or the pressure is below the setpoint, and the pumps are operating at 100 percent speed.

(3) System operation shall stabilize within 5 minutes after test procedures are initiated.

Step 2: Modulate control valves to reduce water flow to 50 percent of the design flow or less, but not lower than the pump minimum flow. Verify and document the following:

(1) Pump speed decrease.

(2) Current operating setpoint has decreased (for systems with DDC to the zone level).

(3) Current operating setpoint has not increased (for all other systems).

(4) System pressure is within 5 percent of current operating setpoint.

(5) System operation stabilizes within 5 minutes after test procedures are initiated.

2025 CALIFORNIA MECHANICAL CODE 487

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APPENDIX E

E 805.10.2 Acceptance Criteria. The differential pressure sensor is either factory calibrated (with calibration certificates) or field calibrated. The pressure sensor shall be located at or near the most remote HX or control valve. The setpoint system controls shall stabilize.

E 805.11 Automatic Demand Shed Control (Form MECH-11A). The purpose of this test is to ensure that the central demand shed sequences have been properly programmed into the DDC system.

E 805.11.1 Test Procedure. The procedure for performing a functional test for automatic demand shed controls shall be in accordance with Section E 805.11.1.1

and Section E 805.11.1.2.
§ 207.2.4 High relevance — show source text
A6.207.2.4 Hydronic system measures.

A6.207.2.4.1 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.

Exceptions:
1. Systems that include no more than three control valves.
2. Systems having a total pump system power less than or equal to 1 [1] / 2 HP.
A6.207.2.4.2 Chiller isolation. When a chilled water plant 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.

A6.207.2.4.3 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).

A6.207.2.4.4 Chilled and hot water temperature reset controls. Chilled and hot water systems with a design capacity exceeding 500,000 Btu/hr supplying chilled or heated water (or both) shall include controls that automatically reset supply water temperatures as a function of representative building loads or outside air temperature.

Exception: Hydronic systems that use variable flow to reduce pumping energy in accordance with Section A6.207.2.4.1.

A6.207.2.4.5 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 A6.207.2.4.6. Each air conditioner or heat pump shall have a two-position automatic valve interlocked to shut off water flow when the compressor is off.

A6.207.2.4.6 Variable flow controls.

A6.207.2.4.6.1 Variable speed drives. Individual pumps serving variable flow systems and having a motor horsepower exceeding 5 hp shall have controls and/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.

A6.207.2.4.6.2 Pressure sensor location and setpoint.
1. For systems without direct digital control of individual coils reporting to the central control panel, differential pressure shall be measured at or near the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure.
2. For systems with direct digital control of individual coils with central control panel, the static pressure set point shall be reset based on the valve requiring the most pressure and the set- point shall be no less than 80 percent open. The pressure sensor(s) may be mounted anywhere.
Exceptions:
1. Heating hot water systems.
2. Condenser water systems serving only water-cooled chillers.
§ 207.2.4.1. High relevance — show source text
Exception: Hydronic systems that use variable flow to reduce pumping energy in accordance with Section A6.207.2.4.1.

A6.207.2.4.5 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 A6.207.2.4.6. Each air conditioner or heat pump shall have a two-position automatic valve interlocked to shut off water flow when the compressor is off.

A6.207.2.4.6 Variable flow controls.

A6.207.2.4.6.1 Variable speed drives. Individual pumps serving variable flow systems and having a motor horsepower exceeding 5 hp shall have controls and/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.

A6.207.2.4.6.2 Pressure sensor location and setpoint.
1. For systems without direct digital control of individual coils reporting to the central control panel, differential pressure shall be measured at or near the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure.
2. For systems with direct digital control of individual coils with central control panel, the static pressure set point shall be reset based on the valve requiring the most pressure and the set- point shall be no less than 80 percent open. The pressure sensor(s) may be mounted anywhere.
Exceptions:
1. Heating hot water systems.
2. Condenser water systems serving only water-cooled chillers.
A6.207.2.4.7 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: 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.

A6.207.2.5 Air distribution system duct leakage sealing. All duct systems shall be sealed to a leakage rate not to exceed 6 percent of the fan flow if the duct system:

A6.207.2.5.1 Is connected to a constant volume, single zone, air conditioners, heat pumps or furnaces; and

A6.207.2.5.2 Serves less than 5,000 square feet of floor area; and

A6.207.2.5.3 Has more than 25 percent duct surface area located in one or more of the following spaces:
1. Outdoors; or
2. In a space directly under a roof where the U -factor of the roof is greater than the U -factor of the ceiling; or Exception: Where the roof meets the requirements of Section 143(a)1C of Title 24, Part 6.
3. In a space directly under a roof with fixed vents or openings to the outside or unconditioned spaces; or
4. In an unconditioned crawlspace; or
5. In other unconditioned spaces.
§ 170.2 High relevance — show source text
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. Each cooling system listed in Table 170.2-H shall be designed to vary the indoor fan airflow as a function of load and shall comply with the following requirements: i. DX and chilled water cooling systems that control the capacity of the mechanical cooling directly based on occupied space temperature shall (i) have a minimum of two stages of fan control with no more than 66 percent speed when operating on stage 1; and (ii) draw no more than 40 percent of the fan power at full fan speed, when operating at 66 percent speed. ii. All other systems, including but not limited to DX cooling systems and chilled water systems that control the space temperature by modulating the airflow to the space, shall have proportional fan control such that at 50 percent air flow the power draw is no more than 30 percent of the fan power at full fan speed. iii. Systems that include an air side economizer to meet Section 170.2(c)4Ci shall have a minimum of two speeds of fan control during economizer operation. Exception to Section 170.2(c)4K: Modulating fan control is not required for chilled water systems with all fan motors <1 HP, or for evaporative systems with all fan motors < 1 HP, if the systems are not used to provide ventilation air and all indoor fans cycle with the load. L. Mechanical system shut-off. Any directly conditioned common use area space with operable wall or roof openings to the outdoors shall be provided with interlock controls that disable or reset the temperature setpoint to 55°F for mechanical heating and disable or reset the temperature setpoint to 90°F for mechanical cooling to that space when any such opening is open for more than 5 minutes. Exception 1 to Section 170.2(c)4L: Interlocks are not required on doors with automatic closing devices.

§ 140.4 High relevance — show source text

.

TABLE 140.4-H-2—MINIMUM EFFICIENCY FOR PROPELLER OR AXIAL FAN OPEN-CIRCUIT COOLING TOWERS (GPM/HP)	Col2	Col3	Col4	Col5	Col6	Col7	Col8	Col9	Col10	Col11	Col12	Col13	Col14	Col15	Col16
CZ 1	CZ 2	CZ 3	CZ 4	CZ 5	CZ 6	CZ 7	CZ 8	CZ 9	CZ 10	CZ 11	CZ 12	CZ 13	CZ 14	CZ 15	CZ 16
42.1	70	60	70	70	80	80	80	80	80	60	70	80	60	80	42.1

(i) Minimum chiller efficiency. Chillers shall meet or exceed Path B from Table 110.2-D.

Exception 1 to Section 140.4(i): Chillers with electrical service > 600V.

Exception 2 to Section 140.4(i): Chillers attached to a heat recovery system with a design heat recovery capacity > 40 percent of the design chiller cooling capacity.

Exception 3 to Section 140.4(i): Chillers used to charge thermal energy storage systems where the charging temperature is < 40°F.

Exception 4 to Section 140.4(i): In buildings with more than three chillers, only three chillers are required to meet the Path B efficiencies.

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

Exception 1 to Section 140.4(j): 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 140.4(j): Chillers that are used to charge a thermal energy storage system with a design temperature of less than 40°F (4°C).

Exception 3 to Section 140.4(j): Systems serving healthcare facilities.

(k) Hydronic system measures.

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 140.4(k)1: Systems that include no more than three control valves.

Exception 2 to Section 140.4(k)1: Systems having a total pump system power less than or equal to 1.5 hp. 2. 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.

§ 805.9.1 High relevance — show source text
This requirement applies to chilled and hot water systems that are not designed for variable flow, and that have a design capacity greater than or equal to 500 000 Btu/h (147 kW).

E 805.9.1 Test Procedure. The procedure for performing a functional test for supply water temperature reset controls shall be in accordance with Section E

805.9.1.1 and Section E 805.9.1.2.

E 805.9.1.1 Construction Inspection. Prior to functional testing, verify and document the supply water temperature sensors shall be either factory or field calibrated.

E 805.9.1.2 Functional Testing. The functional testing shall be in accordance with the following steps:

Step 1: Change reset control variable to its maximum value. Verify and document the following:

(1) Chilled or hot water temperature setpoint is reset to appropriate value.

(2) Actual supply temperature changes to meet setpoint.

(3) Verify that supply temperature is within 2 percent of the control setpoint.

Step 2: Change reset control variable to its minimum value. Verify and document the following:

(1) Chilled or hot water temperature setpoint is reset to appropriate value.

(2) Actual supply temperature changes to meet setpoint.

(3) Verify that supply temperature is within 2 percent of the control setpoint.

Step 3: Restore reset control variable to automatic control. Verify and document the following:

(1) Chilled or hot water temperature setpoint is reset to appropriate value.

(2) Actual supply temperature changes to meet setpoint.

(3) Verify that supply temperature is within 2 percent of the control setpoint.

E 805.9.2 Acceptance Criteria. The supply water temperature sensors are either factory calibrated (with calibration certificates) or field-calibrated. Sensor performance shall comply with the specifications. The supply water reset is operational.

E 805.10 Hydronic System Variable Flow Controls (Form MECH-10A). The purpose of this test is to ensure that hydronic variable flow chilled water and water-loop heat pump systems with circulating pumps larger than 5 hp (3.7 kW) vary system flow rate by modulating pump speed using a variable frequency drive (VFD) or equivalent. As the loads within the building fluctuate, control valves modulate the amount of water passing through each coil and add or remove the desired amount of energy from the air stream to satisfy the load. In the case of water-loop heat pumps, each two-way control valve associated with a heat pump will be closed where that unit is not operating. As each control valve modulates, the pump variable frequency drive (VFD) responds accordingly to meet system water flow requirements. This is not required on heating hot water systems with variable flow designs or for condensing water serving water cooled chillers. E 805.10.1 Test Procedure. The procedure for performing a functional test for hydronic system variable flow controls shall be in accordance with Section E

805.10.1.1 and Section E 805.10.1.2.

E 805.10.1.1 Construction Inspection. Prior to functional testing, verify and document the pressure sensors are either factory or field calibrated. E 805.10.1.2 Functional Testing. The functional testing shall comply with the following steps:

Step 1: Open control valves to increase water flow to not less than 90 percent design flow. Verify and document the following:

Frequently asked questions

What exactly does the "**30% of design wattage at 50% flow**" measurement mean?

It means the measured electrical power draw of the pump motor under operating conditions that produce 50% of the design water flow must be no greater than 30% of the motor’s design (nameplate/contract) electrical wattage. This requirement is in § 140.4(k)6.A.

Where must the differential pressure sensor be mounted?

For systems without DDC to individual coils, the sensor must be located at or near the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure (§ 140.4(k)6.B.i). For systems with DDC to coils, sensors may be mounted anywhere if static setpoint is reset based on valve positions so one valve is near 80% open (§ 140.4(k)6.B.ii).

Are heating hot water pumps always covered by this rule?

No. Heating hot water systems are explicitly excepted from § 140.4(k)6 (Exception 1). Check the exception language in § 140.4(k)6 to confirm applicability.

What documentation will the inspector expect?

Calibration certificates for pressure sensors (factory or field calibration), and commissioning test records showing the E805.10 functional tests (90% design flow and 50% design flow steps), pump speed and power readings, and stabilization within specified tolerances. See E805.10 (Mechanical Code Appendix E).

If my system has DDC to coils, can I put the sensor anywhere?

Yes — the code allows sensor mounting anywhere when DDC to individual coils exists, but you must implement setpoint reset based on valve positions (setpoint sized so the valve requiring the most pressure is no less than 80% open) per § 140.4(k)6.B.ii.

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