5.3    Mandatory Requirements for Water Heating

5.3.1      Equipment Certification

§110.3(a)

Manufacturers must certify that their products comply with California’s Title 20 Appliance Efficiency Regulations, Section 1605.1(f) at the time of manufacture. Regulated equipment that applies to all of the aforementioned system types in Section 5.2 must be listed in the California Energy Commission Appliance Efficiency Database.

5.3.2      Equipment Efficiency

§110.3(b), §110.1

Water heaters are regulated under California’s Title 20 Appliance Efficiency Regulations, Section 1605.1(f). These regulations align with the federal efficiency standards for water heaters. Consumer water heaters and residential-duty commercial water heaters are both rated in Uniform Energy Factor (UEF). The draw pattern is based on the water heater’s design first hour rating for storage water heaters, or gallon per minute for instantaneous water heaters. The efficiency requirements for the most common consumer water heaters are given in Table 5-4 below. The efficiency requirements for the residential-duty commercial water heaters are given in Table 5-5 below.

The Energy Commission has developed a water heater efficiency guide to allow quick lookup of the minimum efficiency of the most common types and sizes of water heaters. It is available to download at https://www.energy.ca.gov/sites/default/files/2020-07/2019_WaterHeating_Guide.pdf.

Table 5-4: Minimum Federal UEF Requirements for Consumer Water Heaters

Source: U.S. Department of Energy

Table 5-5: Minimum Federal Uniform Energy Factor Requirements for Residential-Duty Commercial Water Heaters

Source: California Energy Commission, Title 20 Appliance Efficiency Regulations (2014)

5.3.3      Storage Tank Insulation

§110.3(c)3

Unfired water heater storage tanks and solar water heater backup tanks must have one of the following:

1. External insulation with an installed R-value of at least R-3.5

2. Internal and external insulation with a combined R-value of at least R-16

3. The heat loss of the tank based on an 80-degree F water-air temperature difference shall be less than 6.5 Btu per hour per sq ft. This corresponds to an effective resistance of R-12.3

5.3.4      Isolation Valves

§110.3(c)6

All newly installed instantaneous water heaters (minimum input of 6.8 kBTU/hr) shall have isolation valves on both the incoming cold water supply and the hot water pipe leaving the water heater. Isolation valves assist in the flushing of the heat exchanger and help prolong the life of instantaneous water heaters. Instantaneous water heater that has integrated drain ports for servicing are acceptable to meet the requirements of §110.3(c)6 and will not require additional isolation valves.

5.3.5      High-Efficiency Electric Ready for Gas Water Heater

§150.0(n)

To facilitate future installations of HPWH, the Energy Codes contain the following mandatory requirements for s gas or propane water heaters. When a gas or propane water heater is installed, the building must be made electric ready to minimize future retrofit costs when gas appliances are replaced with electric appliances. Dedicated space for a future HPWH, and wiring is required to be run to the designated location. Space must also be reserved at the electric panel to serve a future heat pump water heater, and a condensate drain must be installed

These requirements are for newly constructed buildings and additions (if a water heater is installed in the added floor area), and they are not applicable to alterations. Moreover, these requirements are not applicable when installing an electric water heater.

1.    A dedicated 125-volt (V) electrical receptacle that is within 3 feet of the water heater and accessible to the water heater with no obstructions, and be connected to a three conductor, 10 AWG branch circuit. In addition, the unused conductor must be labeled and electrically isolated and have a reserved circuit breaker space.

2.    A condensate drain that is no more than 2 inches higher than the base of the installed water heater and allows natural draining without pump assistance

These requirements make it easier for someone to retrofit HPWH in the future. Wiring during initial construction stage is much less costly than trying to retrofit it later.

5.3.5.1    Electrical Receptacle

The goal of this requirement is to allow easy installation of HPWH when the existing gas water heater needs to be replaced. HPWH typically requires a 240-volt circuit, and this requirement allows an electrician to easily convert the 120-volt circuit to a 240-volt circuit.

The electrical receptacle must be installed with 3 feet from the water heater. It should be connected to a dedicated circuit with a 10 AWG copper branch circuit. The ends of the unused conductor must be labeled as “spare” and be electrically isolated.

A reserved single-pole circuit breaker space must be placed in the electrical panel next to the circuit breaker for the branch circuit and labeled with the words “Future 240V Use.”

5.3.5.2    Condensate Drain

The requirement for the condensate drain being placed near the water heater and no higher than the base of the tank allows the condensate to be removed without relying on a sump pump.

5.3.6      Mandatory Requirements for Hot Water Distribution Systems

5.3.6.1    Pipe Insulation for All Buildings

§150.0(j)1

All domestic hot water piping shall be insulated as specified in Section 609.11 of the California Plumbing Code, which requires pipe insulation thickness equal to or more than the diameter of the pipe, up to 2 inches. Above pipe diameter of 2 inches, the insulation thickness must be at least 2 inches.

All domestic hot water pipes that are buried below grade must be installed in a waterproof and noncrushable casing or sleeve. The installation shown in Figure 5-4 below would not meet the installation requirements since it is not insulated. In addition, in Figure 5-4 the hot and cold water lines are not separated. Heat transfer will occur, resulting in energy loss and causing condensation on the cold water line.

Figure 5-4: Noncompliant Below-Grade Piping and Hot and Cold Water Lines Separation

Source: Davis Energy Group/Frontier Energy

A.    Piping Exempt From the Mandatory Insulation Includes:

1.    Factory-installed piping within space conditioning equipment.

2.    Piping that serves process loads, gas piping, cold domestic water piping (other than within 5 feet of the water heater), condensate drains, roof drains, vents, or waste piping.

3.    Piping that penetrates framing members. This piping is not required to have insulation where it penetrates the framing. However, if the framing is metal, then some insulating material must prevent contact between the pipe and the metal framing.

4.    Piping located within exterior walls that are installed so that piping is placed inside wall insulation. Wall insulation may be an acceptable alternative insulation method for sections of pipes that would otherwise need pipe insulation, as long as the wall insulation in the walls where the pipes are located meets the requirements of QII and the pipes are roughly centered in the wall cavity. (see Reference Appendix RA4.4.1).

5.    Piping surrounded with at least 1 inch of wall insulation, 2 inches of crawl space insulation, or 4 inches of ceiling insulation. For pipes buried in attic insulation, piping may not be placed directly in contact with sheetrock and then covered with insulation to meet this requirement.

B.    Other installation information:

1.    Insulation must be at least 6 inches away from the flue. If possible, bend the pipe away from the flue. Otherwise, it may be necessary to stop pipe insulation short of the storage tank. (See the current version of the California Mechanical Code.)

2.    All pipe insulation seams must be sealed.

3.    Installed piping may not be located in supply or return air plenums. (See the current version of the California Mechanical Code.)

4.    Hot and cold water piping, when installed in parallel runs, must be at least 2 inches apart. (See Reference Appendix RA4.)

5.    If a fire wall interrupts the first 5 feet of pipe, the insulation may be interrupted at the wall and continued on the other side.

6.    Insulation for pipe elbows should be mitered and insulation for tees should be notched. (See Reference Appendix RA4.)

Figure 5-5: Pipe Insulation Requirements First Five Feet From Water Heater

Source: California Energy Commission

Table 5-8: Pipe Insulation Thickness Requirements for Space Conditioning, Solar Water Heater Collector Loops, and Steam & Hydronic Heating Distribution

Insulation properties are given (inches and R-value) by fluid temperature (degrees Fahrenheit) and nominal pipe diameter (inches).

Source: Excerpt From Table 120.3-A|topic=Table 120.3-A PIPE INSULATION THICKNESS of the Energy Codes

5.3.6.2    Insulation Protection

§150.0(j)2

If hot water piping insulation is exposed to weather, it must be protected from physical damage, ultraviolet (UV) light deterioration, and moisture. Insulation is typically protected by aluminum, sheet metal, painted canvas, plastic cover, or a water-retardant coating that shields from solar radiation. Adhesive tape should not be used as insulation cover because removal of the tape will damage the integrity of the original insulation during preventive maintenance.