Multifamily Domestic Hot Water

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.

• California Plumbing Code (CPC) Appendix M Pipe Sizing
• Pipe Insulation Enhancement
• Thermostatic Balancing Valves
• Master Mixing Valves
• Central HPWH Cleanup
• Individual HPWH Ventilation
• Individual DHW Electric Ready
• Central DHW Electric Ready

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 proposal recommends using pipe sizing methodology based on CPC Appendix M in lieu of the standard practice CPC Appendix A. Specifically, this measure would add a prescriptive requirement in Section 170.2(d) for sizing water pipes according to CPC Appendix M for central DHW systems in multifamily buildings. This measure would apply only to newly constructed multifamily buildings. The proposal would require minor updates to the compliance software. This measure would not add field verification or acceptance tests. Sizing water pipes according to CPC Appendix M is currently a compliance credit in California Building Energy Code Compliance (CBECC) 2022.

Pipe Insulation Enhancement

Pipe insulation enhancement is a combination of two measures including field verification and code language cleanup. The first component investigates the mandatory pipe insulation requirements contained under Title 24, Part 6, Section 160.4 for possible cleanup. The second component is a proposed mandatory requirement for field verification that would confirm installation of code required pipe insulation and overall insulation installation quality. This proposed mandatory measure would apply to newly constructed buildings only. The measure would add field verification, but no acceptance tests. The proposal would require minor updates to the compliance software.

Thermostatic Balancing Valves

The proposal would add a new compliance option for smaller recirculation systems serving multi-riser central DHW systems in multifamily buildings. For additions and alterations projects the same criteria apply. The project would be applicable for the compliance credit if the design team works to meet the criteria and document that the criteria is met.

To receive the compliance credit the project must include:

1. More than one DHW supply riser
2. Each DHW supply riser shall have an accessible thermostatic balancing valve (TBV)
   1. Located after the last supply branch from the supply riser, in the direction of flow.
   2. Set to a maximum temperature of 120 °F. 3.
3. Variable speed hot water return circulating pumps specified to operate with differential pressure control.
4. For systems with one return pipe loop, hot water return piping that does not exceed 225 feet developed length.
5. For systems with multiple recirculation return pipe loops, no return pipe may exceed 225 feet developed length.

The compliance option would apply for new construction, and to additions and alterations. For additions and alterations, the compliance option would be most feasible when the scope of work includes:

1. Replacement of the existing water heater
2. Addition of new plumbing fixtures that require hot water.

Master Mixing Valves

This prescriptive measure would require the installation of a thermostatic master mixing valve (MMV) that conforms to the American Society of Sanitation Engineers (ASSE) 1017-2009 standard, Performance Requirements for Temperature Actuated Mixing Valves for Hot Water Distribution Systems.

The proposed code change would impact Section 170.2(d) – Prescriptive Approach for Water Heating Systems. The MMV must be installed on the central heating plant hot water supply outlet header leading to the recirculation loop. The MMV shall be installed and commissioned in accordance with manufacturer’s instructions and applicable reference appendix. The plumbing plans shall provide MMV installation details and specifications indicating water mixing parameters, if this exceeds the mixing capability of the specified MMV, the designer shall provide valve commissioning instructions to prevent temperature creep.

Central HPWH Clean-up

This proposal suggests revising the prescriptive pathway(s) for alternative DHW plant design and control approaches as well as adding an alternative prescriptive pathway leveraging NEEA’s Advanced Water Heating Specification V8.0 for commercial HPWH system.

This measure would include the following prescriptive requirement for new construction multifamily buildings:

• Revise the existing prescriptive requirement to use single-pass HPWH as the primary HPWH equipment in DHW plant design, remove primary storage tank plumbing configuration requirement to allow design flexibility for HPWH, and cleanup recirculation loop tank heater requirements.
• Add alternative prescriptive pathway leveraging NEEA’s Advanced Water Heating Specification V8.0 for commercial HPWH system to allow design flexibility, ensure system efficiency and reliability using prescriptive pathway. The alternative prescriptive requirement would require HPWH systems meeting NEEA AWHS V8.0 Tier 2.

Individual HPWH Ventilation

This proposal suggests adding mandatory requirements to provide adequate ventilation for integrated HPWHs.

This measure would include the following code changes:

• Add and adjust existing definitions in Section 100.1(b) to better differentiate HPWH types, so that the proposed ventilation air requirements do not impact HPWHs that do not need ventilation air.
• Add a “Heat pump water heater” section to the end of Section 110.3(c)I.
  • Language is based on ventilation air for gas appliances requirements from the California Plumbing and Mechanical codes.
  • Proposed code change provides for four basic HPWH ventilation paths: large unvented room/closet, small vented room/closet, directly ducted to the HPWH inlet or outlet in any size room/closet, and ventilation methods approved by the manufacturer and included in the permit application for approval from the building department.
  • Proposed code prohibits using outdoor air for ventilation air without backup heat if compressor cutout is above the Winter Median of Extremes in JA2.2, Table 2-3.

Individual DHW Electric-Ready Clean-up

This measure would clean up and add to the existing mandatory requirements of Title 24, Part 6 Section 160.4 for all new construction multifamily buildings constructed with gas or propane individual water heaters. This measure moves the language to section 160.9, which is the multifamily mandatory requirements for electric ready buildings section, and adds or updates the following electric ready requirements:

• Electrical system components including the building main service entrance conduit, meter panel, main service disconnect, and main distribution panel must be sized and installed to accommodate the future HPWH.
• The branch conductor size requirement is updated from requiring “a 120/240-volt 3 conductor, 10 AWG branch circuit” to requiring a 120/240-volt 3 conductor branch circuit rated to 30 amps.
• Adequate physical space to accommodate the future HPWH.
• Adequate planning to meet the future HPWH ventilation needs, by reserving a future HPWH location with adequate volume as defined by the proposed code language, installing fixed openings, or by planning for future ducting to serve the HPWH.

Based on the findings from the multifamily research and stakeholder feedback, the Statewide CASE Team also proposes to improve the single family code language in Section 150.0(n). The Statewide CASE Team proposes to update the branch conductor size requirement, when the future HPWH would be within 3 feet from the water heater, from requiring “a 120/240-volt 3 conductor, 10 AWG branch circuit” to requiring a 120/240-volt 3 conductor branch circuit rated to 30 amps minimum.

Central DHW Electric-Ready

This measure would include mandatory requirements for all new construction multifamily buildings constructed with gas or propane central water heating equipment to provide planning and infrastructure for future electric equipment. For the purposes of this measure, HPWH equipment includes the heat pump, storage tanks, and temperature maintenance tanks. This measure would require planning for the following electric ready components:

• Electrical system components including the building service entrance conduit, meter panel, main service disconnect, main distribution panel, and dedicated conduit from the panel to the planned location of the future HPWH. Equipment must be sized and installed to accommodate the future HPWH equipment.
• Installation of condensate drainage piping from the location of the future heat pump to an acceptable termination point, in accordance with the California Plumbing Code, to serve the future HPWH.
• Adequate physical space to accommodate the future HPWH equipment and required service clearance.
• Adequate planning to meet the future heat pump ventilation needs.

The measure includes two pathways for the new construction to comply with the proposed requirements: the design team can meet the electric ready requirements using code prescribed sizing factors, or the design team can meet the electric ready requirements by planning for a specific product if sufficient documentation of the design is provided.

Relevant Documents

CASE Report

• Final CASE Report – Multifamily Domestic Hot Water
• Draft CASE Report – Multifamily Domestic Hot Water

Round Two Utility-Sponsored Stakeholder Meeting Materials

• Presentation – Introduction, Round Two Stakeholder Meetings
• Presentation – Multifamily Domestic Hot Water, Part 1 (May 1, 2023)
• Presentation – Multifamily Domestic Hot Water, Part 2 ( (May 1, 2023)
• Multifamily Domestic Hot Water – Proposal Summary
• May 1, 2023 Meeting Notes

Round One Utility-Sponsored Stakeholder Meeting Materials

• Stakeholder Meetings Introduction
• Multifamily Domestic Hot Water – Presentation
• Multifamily Domestic Hot Water – Proposal Summary
• February 17, 2023 Meeting Notes