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Multifamily Domestic Hot Water

Measure descriptions are subject to change.

Proposal Description

The Multifamily Domestic Hot Water Systems topic covers measures related to hot water distribution, heat pumps systems, and electric readiness, as described below.

Data may be provided anonymously. To participate or provide information, please email Dove Feng ([email protected]) directly and CC [email protected]

California Plumbing Code (CPC) Appendix M Pipe Sizing

This measure would add a prescriptive requirement for pipe sizing according to CPC Appendix M for both central and individual DHW systems in multifamily buildings pending final adoption in CPC. The California Building Standards Commission approved the Department of Housing and Community Development (HCD) proposal to adopt UPC Appendix M in March 2023. HCD has jurisdiction over multifamily buildings and final adoption of UPC Appendix M expected in August 2023 will allow builders to utilize the new pipe sizing procedure as a voluntary option in the California Plumbing Code.

Data Needs/Stakeholder Information Requests

  • What standard or method do you use to size piping in MF buildings?
  • Have you sized piping using Appendix M? If no, why not? If yes, do you have any concerns or feedback on the design, submittal or installation process?
  • Would you size piping using Appendix M if it is adopted by the CPC as an alternative pipe sizing methodology?

Pipe Insulation Enhancement

This measure would add a mandatory requirement for field verification of pipe insulation quality. The measure would also focus on investigating the pipe insulation requirements of sections 160.4 for possible cleanup. These sections would require that all appurtenances (pumps, valves, strainers, etc.) in series in the DHW system heating plant and recirculation loop be insulated. It would add a requirement for insulating pipe supports or hangers. Continuous pipe insulation requirements at the heating plant and recirculation loop including hangers and appurtenances would reduce pipe heat losses by ensuring all exposed elements are insulated. It adds installation quality requirements to seal seems, use extended stem isolation valves and specific insulation installation practices for tees and elbows. The clarifications to section 160.4 should simplify pipe insulation verification.

Data Needs/Stakeholder Information Requests

  • On a percentage basis, how often is pipe insulation not installed according to drawings and instructions?
  • What standard pipe insulation requirements do you provide on drawings as a designer or apply from drawings as an installer?
  • What are the typical field issues encountered with pipe insulation installs? Here is a list of example issues: gaps, insulation thickness doesn’t meet code minimum, damaged insulation, uninsulated fittings or valves, uninsulated pipe supports, and direct contact with metal pipe hangers to pipe.

Require Balancing Valves

This measure would add a compliance option for thermostatic (thermal) balancing valves for each riser or zone (minimum of two) in combination with installation of variable speed pumps with differential pressure control on a centralized DHW system with recirculation. This compliance option would be available to distribution systems with smaller circulation systems as determined by calculating the total developed length of the circulation return piping. This measure is also applicable to additions and alterations of existing buildings, and is most likely to apply when the heating plant is being replaced at end of life.

Data Needs/Stakeholder Information Requests

  • Can the installation of automatic balancing valves reduce installation costs as compared to the installation of manual balancing valves?
  • What is common practice for balancing manual valves serving multi-riser distribution systems, and how does this impact installed performance?
  • Are you aware of any independent field or lab studies that isolate the energy savings due to thermal balancing valves?

Master Mixing Valves

This measure would add a prescriptive measure to install thermostatic master mixing valves (MMV) on the centralized heating plant hot water supply outlet header leading to the recirculation loop. MMVs are traditionally used to mitigate pathogen growth and scalding risk, but new research has shown that they offer energy saving benefits from lower recirculation loop heat losses and improved tank water temperature stratification versus mixing or tempering the hot water at each dwelling unit. MMVs precisely control the distribution supply temperature and redirect the warm return water back to the distribution system and away from the water heating plant. MMVs enhance load shifting capabilities with HP based heating plants and provide the ability to safely increase storage heating capacity of the heating plant without adding additional storage volume.

Data Needs/Stakeholder Information Requests

  • What types of master mixing valves do you specify or install in MF central hot water systems with continuous recirculation? Here is a list of example types: 1) Single Mechanical Thermostatic Valve, 2) High/Low Set of Mechanical Valves, 3) Digital/Electronic Thermostatic Valve
  • Do you install parallel MMVs for sizing purposes, redundancy purposes or to conduct routine maintenance?
  • Do you see maintenance issues with thermostatic or digital MMVs?
  • What performance, cost or reliability factors influences your MMV specification?

Demand Control Clean-up

The CASE team proposes to remove the prescriptive requirement for demand recirculation systems serving multiple dwelling units to align with technical considerations for multifamily applications (Prescriptive).

Data Needs/Stakeholder Information Requests

  • What is current practice in the industry, and are there performance concerns?
  • Is it possible to capture the energy savings potential of demand control with another method of pump/distribution system control?

Individual HPWH Ventilation

This measure would establish ventilation criteria and requirements for consumer individual HPWHs. The CASE Team will evaluate ventilation approaches such as ducting and net free area for louvered doors, and venting sources (indoor vs. outdoor). Savings per dwelling unit are expected to be the same for both multifamily and single family. The measure would include mandatory requirements for minimum ventilation for all occupancies. This includes requirements for ventilation with three installation methods:

  • Large unvented room, with minimum room volume of 100 ft3 / kBtu/h of compressor capacity or manufacturer provided requirements.
  • Small vented room.
    • Minimum room volume of 20 ft3 / kBtu/h of compressor capacity or manufacturer provided requirements.
    • Larger of 125 in2 plus 25 in2 per kBtu of compressor capacity net free area or manufacturer provided requirements.
  • Directly ducted in any size room, with some basic requirements like insulating the exhaust duct and sealing joints.
  • Novel ventilation methods approved by the manufacturer and included in permit application.

Data Needs/Stakeholder Information Requests

  • Technical Feasibility
    • What is the typical DHW room size?
    • How common is ducting in HPWH installs?
    • What is the current practice to determine if a HPWH should be ducted or not?
  • Market Readiness
    • Are there unitary HPWH models available that do not provide a ducted option?
    • What is currently used for ducting with HPWHs?
    • For installers who have been called back to a site for HPWH issues, what have the issues been and how were they resolved?
      • Condensation in ducting?
      • Noise?
    • What commissioning steps can be required of installers to ensure performance?
  • Costs
    • What would be the incremental cost of ducting if the space in the DHW room was insufficient and could not otherwise be vented?
    • What are the costs associated with marking the minimum clearances for the HPWH on the floor around its installed location if installed in a room with a volume less than 700 cu. Ft.?

Central HPWH Clean-up

For the 2022 code cycle, the Statewide CASE Team developed an alternate compliance pathway for central HPWH systems. The prescriptive requirements include basic equipment, plumbing, control, and design documentation requirements. It provides prescriptive compliance pathway for a wide range of central HPWH design options. This measure would improve the current prescriptive requirement by:

  • Revise the existing prescriptive requirement to use single-pass HPWH as the primary HPWH equipment in DHW plant design. Additional revisions include removing primary storage tank plumbing configuration requirement to allow design flexibility, clean-up recirculation loop tank heater requirements.
  • Add alternative prescriptive pathway leveraging the Northwest Energy Efficiency Alliance (NEEA)’s Advanced Water Heating Specification V8.0 for commercial HPWH system to allow design flexibility, ensure system efficiency and reliability using prescriptive pathway.

Data Needs/Stakeholder Information Requests

  • What are the different design configurations that the code needs to address?
  • How does each central HPWH design configuration compare to each other in terms of cost and energy efficiency?

Central DHW Electric-Ready

The central DHW electric readiness mandatory measure would add electrical, space, ventilation, and condensate requirements at the time of construction to accommodate the future retrofit or replacement of fossil-fuel burning devices with electricity-powered devices. Specific requirements include:

  • Physical space to accommodate electric water heating equipment and storage requirements in the future;
  • Identification of ventilation access;
  • Installation of condensate drain lines;
  • Electrical system sizing and design to accommodate shifts to electric devices in the future; and
  • Design documentations that the building design meets the requirements, to be approved by certified professionals. .

Data Needs/Stakeholder Information Requests

  • During the new building design process, what planning needs to be done to make the central heat pump water heater electric ready?
  • What other infrastructure needs to be installed during new-construction to make the central water heater electric-ready?

Individual DHW Electric-Ready Clean-up

This mandatory measure would evaluate the current code language requirement for a “dedicated 125-volt, 20-amp electrical receptacle that is connected to the electric panel with a 120/240-volt 3 conductor, 10 AWG copper branch circuit”, considering the distance between the main panel and water heater location. The CASE Team proposes revising the size to be rated at 30A to accommodate concerns about the likely voltage drop in multifamily applications. In addition, the CASE Team proposes new requirements including minimum space requirements and minimum ventilation requirements.

Data Needs/Stakeholder Information Requests

  • What is the minimum space required for a future heat pump water heater? Is there a standard closet size that we should know of when developing minimum space requirements?

Data may be provided anonymously. To participate or provide information, please email Dove Feng ([email protected]) directly and CC [email protected]

Relevant Documents

CASE Report

Round Two Utility-Sponsored Stakeholder Meeting Materials

Round One Utility-Sponsored Stakeholder Meeting Materials

Provide Feedback

Submit feedback and view the Energy Commission's proceedings and available proposed code language by visiting their 2025 Building Energy Efficiency Standards page.

This measure page will be updated as the 2025 code cycle progresses. For questions or suggestions, email [email protected]. Please include the measure name in the subject line.

Give Us Your Feedback

The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.

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