Scope of Proposed Code Change

Justification for Proposed Change

A recent PG&E code readiness report[1] and other similar studies have shown that AWHP equipment frequently realizes much lower efficiencies than advertised. Opportunities exist to establish requirements in the code (and potentially during acceptance and commissioning) to prevent poor design and installation practices from being scaled in the industry as the hydronic heat pump product category continues to grow.

There are also some code-related obstacles to the widespread adoption of AWHPs. While there is a compliance option for AWHPs implemented in the compliance software, the requirements to meet this credit are unclear, hindering adoption. It has been difficult to get projects approved, as designers, plans examiners, and inspectors struggle to discern which requirements and forms to apply.

This measure will improve the communication of “best practice guidelines” for installation, control, management and operation of AWHPs to help ensure that the advertised performance is achieved in practice. In addition, code language related to isolation of inactive units in multi-unit systems, which is already in place for chillers and boilers, will be adapted and applied to AWHPs. Finally, limits to glycol concentration will help improve heat exchanger and pump performance while protecting systems from freezing in colder climates. Additional verification tests will be required to demonstrate compliance.

The preliminary statewide energy savings for the first year from this measure are projected to be 4.24 GWh, which is likely underestimated since the savings were calculated for 4.5 million ft² (new construction only) assuming 10% savings of HVAC and DHW end uses. The final savings will be recalculated based on a more thorough assessment of common installation mistakes and the resulting energy impacts. Final savings analysis will include all non-residential building types along with additions and alterations.

[1] Weitze, H., Stober, W., and Gantley, M., Nonresidential Hydronic Heat Pumps: System Operation Field Study and Analysis, PGNE Code Readiness Final Project Report ET21PGE7201-2, October 2024. https://etcc-ca.com/reports/code-readiness-final-project-report-nonresidential-hydronic-heat-pumps-system-operation

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• Enhanced Air-To-Water Heat Pumps – Proposal Summary

The post Enhanced Air-To-Water Heat Pumps (AWHPs) first appeared on Title 24 Stakeholders.

The post Enhanced Air-To-Water Heat Pumps (AWHPs) appeared first on Title 24 Stakeholders.

Scope of Proposed Code Change

Justification for Proposed Change

HVAC fault detection and diagnostics (FDD) provides building operators with a proactive way to maintain and optimize their systems by bringing operational data together and providing actionable insights for inefficient operation.  FDD can sustain other HVAC efficiency measures by monitoring their performance and identifying repairs.  FDD enables a resilient energy efficiency strategy for buildings.  

HVAC systems are designed, built, and operated to meet conditioning and ventilation needs of the building, ideally using as little energy as possible to do it.  Modern HVAC direct digital control (DDC) systems provide the access to understanding HVAC system operation and automatically controlling the system, while also providing ability to monitor, trend, and analyze the system. However, over time HVAC systems lose their efficiency due to installation error, wear-and-tear on system components, lack of maintenance, and changes in control strategies. 

Already-established processes such as start-up commissioning and existing building commissioning attempts to verify proper operation and/or optimize these systems. FDD is an automated version commissioning, using rule- or model-based approaches to identify faults that raise energy usage and limit the functionality of the system. The FDD system will also identify possible repairs to bring the system back to its original efficient operations or optimize it to save more energy than before. 

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• HVAC Fault Detection and Diagnostics – Proposal Summary

The post HVAC Fault Detection and Diagnostics first appeared on Title 24 Stakeholders.

The post HVAC Fault Detection and Diagnostics appeared first on Title 24 Stakeholders.

Scope of Proposed Code Change

Justification for Proposed Change

In California approximately 22 trillion BTUs are used for water heating in commercial buildings (CBECS microdata 2018).  The majority of the SHW energy use (79%) is from natural gas with just 19% from electricity (CBECS microdata 2018). Utility incentive programs for HP/ER HPWHs have attempted to capture a portion of this opportunity, but configuration and operation issues are demonstrating lower than expected performance (in terms of coefficient of performance, COP) when HP/ER HPWH are installed as the heat source for central DHW systems. 

One key component contributing to reduced COP is the activation of the ER heating elements. ER heating can be triggered for several reasons including but not limited to: 

• HPWH supply air temperature is too low for compressor operation as a result of 
  • Insufficient ventilation in installation location 
  • Cool winter temperatures 
  • HPWH operating mode: some models have 10°F lower compressor cut out temperature in efficiency (HP only) mode versus Hybrid mode setting 
• HPWH control algorithm is attempting to avoid a perceived potential hot water runout event1 from: 
  • The use of master mixing valves or pump controls that improve tank stratification with more cold water in the lower part of the tank but trigger more heating activations 
  • Elevated HPWH temperature setpoints that may trigger more heating activations from the algorithm identifying a larger temperature difference from the top to bottom of the tank which can be related to draws or return temperatures from a recirculation loop 
• HPWH set point temperature is higher than the HPWH can achieve using HP only 

Ensuring that installed Hybrid HPWHs comply with the manufacturer’s installation guidelines will minimize the chance that HPWHs will overcool the space in which they are installed and reduce excessive ER heating. Enforcing a specific HPWH compressor cutoff temperature will improve efficiency and help designers understand the HPWH operation characteristics to ensure that it can deliver hot water in all conditions. 

By accomplishing the above goals, installations of central systems with unitary hybrid HPWHs will be more successful and demonstrate the capability for electrification without the high energy costs associated with ER heating. 

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• Unitary HP/ER Heaters in Systems with Recirculation  – Proposal Summary

The post Unitary HP/ER Heaters in Systems with Recirculation first appeared on Title 24 Stakeholders.

The post Unitary HP/ER Heaters in Systems with Recirculation appeared first on Title 24 Stakeholders.

Scope of Proposed Code Change

Justification for Proposed Change

The current NR prescriptive requirements for water heating do not include requirements specific to HPWH performance despite the increasing use of HPWH in NR applications. Due to air quality rules by the South Coast Air Quality Management District (SCAQMD) and the Bay Area Air Quality Management District (BAAQMD), future HPWH installations in California are expected to apply to about 61% of the NR building stock. This measure, which is focused on NR applications, draws on lessons learned from the development of multifamily (MF) requirements including recent research that indicates that return-to-primary is advantageous over swing tank configuration in many cases. The proposed change is needed to establish a baseline configuration that ensures adequate hot water delivery and reduces energy use and energy costs associated with split-system HPWH in NR applications.

During the 2022 code cycle, in response to reliability concerns when split HPWHs were emerging, the Statewide CASE Team introduced the swing tank configuration as the baseline for new MF construction. However, recent lab tests performed by PG&E Applied Technology Services (PG&E, SCE 2024) to characterize the central HPWHs with recirculation show that return-to-primary with R-134a can maintain reliability while reducing equipment requirements and increase Coefficient of Performance (COP) compared to swing tank configuration. The Association for Energy Affordability (AEA) performed field testing with large CO2 systems (Brooks, Neal and Young 2024) and found that return-to-primary configuration operates at a higher COP and higher reliability compared to swing tank configuration. Additionally, AEA is currently conducting a series of demonstration studies for low global warming potential (GWP) HPWHs with recirculation for a Code Readiness project funded by SCE. If these tests show that the return-to-primary configuration can maintain sufficient hot water delivery performance with high return temperatures for a broader range of refrigerants, they can further support this measure.

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• Return-to-Primary Configuration – Proposal Summary

The post Return-to-Primary Configuration first appeared on Title 24 Stakeholders.

The post Return-to-Primary Configuration appeared first on Title 24 Stakeholders.

Scope of Proposed Code Change

Justification for Proposed Change

Currently, there is a mandatory requirement that circulating pumps are capable of automatically turning off. There are no prescriptive requirements for advanced digital pump controls in Title 24, Part 6 for nonresidential buildings with central water heating systems. Although the experience of the Statewide CASE Team suggests that aquastat and analog timer controls are commonly installed in nonresidential buildings, these control types have longevity challenges. 

Several studies have evaluated the benefits of ECM pumps and controls including the High-Performance Circulator Pump Demonstration Study by National Renewable Energy Laboratory (NREL) (Dean, Honnekeri, & Barker, 2018) and Extended Motor Products Savings Validation Research on Clean Water Pumps and Circulators by Northwest Energy Efficiency Alliance (NEEA) (Group, 2019). The NREL study suggests that the domestic hot water pumps electricity savings range from 90 percent to 96 percent with a simple payback period of 3 to 4 years. Based on the NEEA study results; ECM pumps provide approximately 50 percent savings while added controls can provide up to 84 percent electricity savings at the circulator pump. These studies do not evaluate the potential energy savings at the water heater. Based on these two studies, this measure is highly cost-effective. 

In addition to the above studies, TRC and 2050 Partners are working on a field demonstration study for circulator pump controls. The Statewide CASE Team will leverage data from this study to inform the energy savings for the proposed measure. 

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• Circulator Pump Controls – Proposal Summary

The post Circulator Pump Controls first appeared on Title 24 Stakeholders.

The post Circulator Pump Controls appeared first on Title 24 Stakeholders.

Scope of Proposed Code Change

Justification for Proposed Change

In process steam systems, condensate is formed when steam releases its heat of condensation in a heat exchanger and condenses into liquid. Facilities that recover condensate reduce the need for makeup water, pre-heating fuel, and chemicals for water treatment. Some sites may also benefit from a reduction in wastewater costs. Because condensate is effectively distilled water, its recovery also reduces the need for boiler blowdown, which results in additional energy savings.

Department of Energy (DOE) literature has recommended increasing the percentage of returned condensate as a steam system best practice in since at least the early 2000s, and the DOE provides a steam tip sheet specifically on improving condensate return. This proposed code change originated from discussions with California-based consulting engineers from strategic energy management programs and the DOE Industrial Assessment Center program.

Depending on site conditions, this measure is expected to yield energy savings of approximately 5% to 8% of baseline boiler system fuel use. There are two main sources of savings: (1) the energy difference between returned condensate and cold makeup water and (2) reduced blowdown losses resulting from increased condensate return.

To the knowledge of the Statewide CASE Team, condensate return requirements have not been proposed in previous code cycles. In 2013, Title 24 Part 6 first adopted requirements for process boilers. In 2022, Title 24 Part 6 adopted requirements for strainers and fault detection and diagnostics in steam trap assemblies.

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• Process Steam #2 Condensate Return in Process Systems – Proposal Summary

The post Process Steam #2 Condensate Return in Process Systems first appeared on Title 24 Stakeholders.

The post Process Steam #2 Condensate Return in Process Systems appeared first on Title 24 Stakeholders.

Scope of Proposed Code Change

Justification for Proposed Change

When steam condensate is dropped to a pressure lower than its saturation (boiling-point) pressure, a fraction of it vaporizes, or flashes, into what is known as “flash steam.” Most sites vent flash steam to the atmosphere, resulting in significant fuel, water, and chemical losses. Many steam system design options are available to recover and repurpose flash steam for useful heating to serve low-pressure loads instead of using high-pressure live boiler steam for the same purpose. Flash vessels capture flash steam and allow it to be piped to various applications, and TVR and MVR can boost the flash steam pressure if needed. Alternatively, a pressurized condensate return system can minimize flashing of condensate as it is returned to the deaerator.

Flash steam recovery has been listed in Department of Energy (DOE) literature as a best practice since at least the early 2000s, and the DOE has five steam tip-sheets for different flash steam recovery methods. This proposed code change originated from discussions with California-based consulting engineers from strategic energy management programs and the DOE Industrial Assessment Center program.

To the Statewide CASE Team’s knowledge, flash steam recovery requirements have not been proposed in previous code cycles. In 2013, Title 24 first adopted requirements for process boilers. In 2022, Title 24 adopted requirements for strainers and fault detection and diagnostics in steam trap assemblies.

Requiring flash steam recovery would save fuel, water, and chemicals. When applied throughout typical steam systems, this measure is expected to save approximately 1% to 5% of baseline boiler system fuel use. In addition, the requirement would reduce water and sewer use and the associated chemicals used for water treatment, as the flash steam is no longer vented to the atmosphere and its condensate can be returned to the boiler plant. Ancillary benefits include improved plant safety and improved public perception through reduction of steam plumes.

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• Process Steam #1 Flash Steam Recovery or Reduction – Proposal Summary

The post Process Steam #1 Flash Steam Recovery or Reduction first appeared on Title 24 Stakeholders.

The post Process Steam #1 Flash Steam Recovery or Reduction appeared first on Title 24 Stakeholders.

Scope of Proposed Code Change

Justification for Proposed Change

A DOAS is an energy-efficient HVAC system that maintains indoor air quality by bringing fresh air into interior spaces and handling ventilation independently from heating or cooling. Unlike typical rooftop units that mix large portions of return air with outdoor air, it brings in a dedicated supply of fresh outdoor air, dehumidifies it, conditions it, and then delivers at the right temperature and humidity to occupied spaces, decoupling the latent loads from sensible loads. 

Smart DOAS incorporates into existing acceptance testing and automatically complies with both the demand control ventilation (DCV) and energy recovery requirements. It uses Variable Frequency Drive (VFD) fans to precisely match ventilation demand, and leverages energy recovery ventilators to precondition the incoming air – reducing cooling and heating loads. 

This proposal seeks mandatory requirements to include air valves for all DOAS systems. Some DOAS designs do not have outlets for each thermal zone, just one outlet for several thermal zones. This does not meet the T24 ventilation requirements. Adding air valve not only complies with Occupied Standby but also saves energy and improves IAQ by dynamically ventilating the zones as needed.   

The proposal also seeks to clarify the code language in section 120.1(d). This will expand the occupied standby control requirements to non-mandated zones when they are scheduled to be occupied but unoccupied. 

Space decoupled ventilation systems (e.g., DOAS) serving spaces required to have occupant sensing ventilation controls shall include modulating pressure independent air valves or other means of modulating outside air at all space conditioning zones. This shall be done to disable ventilation to unoccupied zones while maintaining measured outside air ventilation rates to occupied zones within 10% of the design minimum outside air ventilation rate per 120.1(f)2 and shall include demand ventilation controls for high-density spaces per 120.1.(d)3.    

Both these sub measures offer the potential for significant energy savings. 

The sub-measure 3 of “Expand Variable Speed DOAS” is a prescriptive measure that proposes to replace the current 3-speed fan requirement with a Variable Frequency Drive (VFD) to provide more precise ventilation and airflow management. This will reduce energy consumption and fine-tune the total airflow based on the individual zone requirement, which may consequently result in cooling and heating savings.   

Requiring the DOAS system to be a variable air volume (VAV) could reduce energy consumption, in addition to providing system balancing and reducing stress on motors and other components during startup and operation.  

The sub-measure 4 proposes to reduce the DOAS supply air temperature (SAT) from current 60⁰F under heating or heat recovery mode to 55°F when most zones require cooling. This will result in energy savings as allowing warmer air to enter the space will increase the energy for the space cooling equipment. The current 60°F was based on ASHRAE 90.1 Section 6.5.2.6, which was arbitrarily chosen. ASHRAE TC1.4 has completed a research project (DOAS RP-1865: Optimizing Supply Air Temperature Control for Dedicated Outdoor Air Systems) on revising the SAT. Tentatively, the CASE team proposes 55°F to estimate the preliminary analysis. The final proposal will be revised based on the outcome of the RP-1985 voting.   

The proposed recommendations will reduce the fan energy at part load, improve indoor air quality, eliminate or reduce recooling energy of warm ventilation air when the majority of the zones call for cooling, and reduce ventilation system cooling and heating energy for all zones.

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• Enhanced Dedicated Outdoor Air Systems (DOAS) – Proposal Summary

The post Enhanced Dedicated Outdoor Air Systems (DOAS) first appeared on Title 24 Stakeholders.

The post Enhanced Dedicated Outdoor Air Systems (DOAS) appeared first on Title 24 Stakeholders.

Scope of Proposed Code Change

Justification for Proposed Change

This measure is inspired by Addendum u to ASHRAE 90.1-2022, which ASHRAE and ANSI approved on December 31, 2024 (ASHRAE 90.1-2022, Addendum u). This new ASHRAE measure was brought as a candidate to Title 24 because of its energy savings and relative simplicity.  

Section 140.4(d)(2)(ii) requires that the terminal units in the individual zones turn down airflow to no greater than the design outdoor airflow during deadband operation when there is no demand for heating or cooling. In many applications, this would be equivalent to 15 percent or less of the air handler’s design airflow. However, there is no requirement that the central air handler be able to turn down flow to any level.  

The preliminary energy savings analysis offers significant potential in the proposed measure resulting in annual Electricity Savings of approximately 0.08 kWh/ft2 for medium offices, large schools, and laboratories. The modeling assumptions will be updated and could yield different savings estimates. 

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• Reducing Maximum Airflow During Deadband Operation for Variable Air Volume HVAC Systems – Proposal Summary

The post Reducing Maximum Airflow During Deadband Operation for Variable Air Volume HVAC Systems first appeared on Title 24 Stakeholders.

The post Reducing Maximum Airflow During Deadband Operation for Variable Air Volume HVAC Systems appeared first on Title 24 Stakeholders.

Scope of Proposed Code Change

Justification for Proposed Change

The state-of-the-art for data center design has advanced significantly since the 2022 requirements were developed in 2020 and will further evolve by 2029, when the 2028 standards take effect. One major change is the rapid growth of liquid-cooled servers, which are often cooled by 80-120oF supply water. It is also now common to cool air-cooled servers with 75-85oF supply air. This measure offers a tremendous opportunity to capture various advancements as described above via sub-measures that will improve the energy efficiency of data centers and computer rooms significantly.    

It may also be noted that data center floor area is growing at an alarming rate year over year, and data centers are quite energy intensive.  

Relevant Documents

Round One Utility-Sponsored Stakeholder Meeting Materials

• Data Centers Efficiency Improvements – Proposal Summary

The post Data Centers Efficiency Improvements first appeared on Title 24 Stakeholders.

The post Data Centers Efficiency Improvements appeared first on Title 24 Stakeholders.