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Service water-heating systems and equipment shall comply with the requirements of this section as described in Section 7.2.

Service water-heating systems and equipment shall comply with the requirements of this section.

Exception to 7.1.1.2

When the service water heating to an addition is provided by existing service water-heating systems and equipment, such systems and equipment shall not be required to comply with this standard. However, any new systems or equipment installed must comply with specific requirements applicable to those systems and equipment.

Building service water-heating equipment installed as a direct replacement for existing building service water-heating equipment shall comply with the requirements of Section 7 applicable to the equipment being replaced. New and replacement piping shall comply with Section 7.4.3.

Exception to 7.1.1.3

Compliance shall not be required where there is insufficient space or access to meet these requirements.

Compliance shall be achieved by meeting the requirements of Section 7.1, "General"; Section 7.4, "Mandatory Provisions"; Section 7.5, "Prescriptive Path"; Section 7.7, "Submittals"; and Section 7.8, "Product Information."

Projects using the Energy Cost Budget Method (Section 11) for demonstrating compliance with the standard shall meet the requirements of Section 7.4, "Mandatory Provisions," in conjunction with Section 11, "Energy Cost Budget Method."

Service water-heating system design loads for the purpose of sizing systems and equipment shall be determined in accordance with manufacturers' published sizing guidelines or generally accepted engineering standards and handbooks acceptable to the adopting authority (e.g., ASHRAE Handbook—HVAC Applications).

All water-heating equipment, hot-water supply boilers used solely for heating potable water, pool heaters, and hot-water storage tanks shall meet the criteria listed in Table 7.8. Where multiple criteria are listed, all criteria shall be met. Omission of minimum performance requirements for certain classes of equipment does not preclude use of such equipment where appropriate. Equipment not listed in Table 7.8 has no minimum performance requirements.

Exceptions to 7.4.2

All water heaters and hot-water supply boilers having more than 140 gal of storage capacity are not required to meet the standby loss (SL) requirements of Table 7.8 when

  1. the tank surface is thermally insulated to R-12.5,
  2. a standing pilot light is not installed, and
  3. gas- or oil-fired storage water heaters have a flue damper or fan-assisted combustion.

The following piping shall be insulated to levels shown in Section 6, Table 6.8.3-1:

  1. Recirculating system piping, including the supply and return piping of a circulating tank type water heater.
  2. The first 8 ft of outlet piping for a constant-temperature nonrecirculating storage system.
  3. The first 8 ft of branch piping connecting to recirculated, heat-traced, or impedance heated piping.
  4. The inlet piping between the storage tank and a heat trap in a nonrecirculating storage system.
  5. Piping that is externally heated (such as heat trace or impedance heating).

Temperature controls shall be provided that allow for storage temperature adjustment from 120°F or lower to a maximum temperature compatible with the intended use.

Exception to 7.4.4.1

When the manufacturers' installation instructions specify a higher minimum thermostat setting to minimize condensation and resulting corrosion.

Systems designed to maintain usage temperatures in hot-water pipes, such as recirculating hot-water systems or heat trace, shall be equipped with automatic time switches or other controls that can be set to switch off the usage temperature maintenance system during extended periods when hot water is not required.

Temperature controlling means shall be provided to limit the maximum temperature of water delivered from lavatory faucets in public facility restrooms to 110°F.

When used to maintain storage tank water temperature, recirculating pumps shall be equipped with controls limiting operation to a period from the start of the heating cycle to a maximum of five minutes after the end of the heating cycle.

Pool heaters shall be equipped with a readily accessible on/off switch to allow shutting off the heater without adjusting the thermostat setting. Pool heaters fired by natural gas shall not have continuously burning pilot lights.

Heated pools shall be equipped with a vapor retardant pool cover on or at the water surface. Pools heated to more than 90°F shall have a pool cover with a minimum insulation value of R-12.

Exception to 7.4.5.2

Pools deriving over 60% of the energy for heating from site-recovered energy or site-solar energy.

Time switches shall be installed on swimming pool heaters and pumps.

Exceptions to 7.4.5.3

  1. Where public health standards require 24-hour pump operation.
  2. Where pumps are required to operate solar and waste heat recovery pool heating systems.

Vertical pipe risers serving storage water heaters and storage tanks not having integral heat traps and serving a nonrecirculating system shall have heat traps on both the inlet and outlet piping as close as practical to the storage tank. A heat trap is a means to counteract the natural convection of heated water in a vertical pipe run. The means is either (a) a device specifically designed for the purpose or an arrangement of tubing that forms a loop of 360 degrees, or (b) piping that from the point of connection to the water healer (inlet or outlet) includes a length of piping directed downward before connection to the vertical piping of the supply water or hot-water distribution system, as applicable.

The use of a gas-fired or oil-fired space-heating boiler system otherwise complying with Section 6 to provide the total space heating and service water heating for a building is allowed when one of the following conditions is met:

  1. The single space-heating boiler, or the component of a modular or multiple boiler system that is heating the service water, has a standby loss in Btu/h not exceeding

    (13.3 × pmd + 400)/n

    where pmd is the probable maximum demand in gal/h determined in accordance with the procedures described in generally accepted engineering standards and handbooks, and n is the fraction of the year when the outdoor daily mean temperature is greater than 64.9°F.

    The standby loss is to be determined for a test period of 24 hours duration while maintaining a boiler water temperature of at least 90°F above ambient, with an ambient temperature between 60°F and 90°F. For a boiler with a modulating burner, this test shall be conducted at the lowest input.

  2. It is demonstrated to the satisfaction of the authority having jurisdiction that the use of a single heat source will consume less energy than separate units.
  3. The energy input of the combined boiler and water heater system is less than 150,000 Btu/h.

Service water-heating equipment used to provide the additional function of space heating as part of a combination (integrated) system shall satisfy all stated requirements for the service water-heating equipment.

New buildings with gas service water-heating systems with a total installed gas water-heating input capacity of 1,000,000 Btu/h or greater, shall have gas service water-heating equipment with a minimum thermal efficiency (Et) of 90%. Multiple units of gas water-heating equipment are allowed to meet this requirement if the water-heating input provided by equipment with thermal efficiency (Et) above and below 90% provides an input capacity-weighted average thermal efficiency of at least 90%.

Exceptions to 7.5.3

  1. Where 25% of the annual service water-heating requirement is provided by site-solar energy or site-recovered energy.
  2. Water heaters installed in individual dwelling units.
  3. Individual gas water heaters with input capacity not greater than 100,000 Btu/h.

The authority having jurisdiction may require submittal of compliance documentation and supplemental information in accord with Section 4.2.2 of this standard.

Table 7.8 Performance Requirements for Water-Heating Equipment—Minimum Efficiency Requirements

Equipment Type Size Category (Input) Subcategory or Rating Condition Performance Requireda Test Procedureb,c
Electric table-top water heaters ≥12 kW Resistance ≥20 gal See footnote (g).  
Electric water heaters ≥12 kWe Resistance ≥20 gal See footnote (g). Section G.2 of ANSI Z21.10.3
>12 kWe Resistance ≥20 gal 0.3 + 27/Vm %/h
≥24 Amps and
≥250 Volts
Heat Pump See footnote (g).
Gas storage water heaters ≤75,000 Btu/h ≥20 gal See footnote (g).  
>75,000 Btu/hf <4000 (Btu/h)/gal 80% Et (Q/800 + 110√V)
SL, Btu/h
Sections G.1 and G.2 of ANSI Z21.10.3
Gas instantaneous water heaters >50,000 Btu/h and <200,000 Btu/h ≥4000 (Btu/h)/gal and <2 gal See footnote (g).  
≥200,000 Btu/hd,f ≥4000 (Btu/h)/gal and <10 gal 80% Et Sections G.1 and G.2 of ANSI Z21.10.3
≥200,000 Btu/hf ≥4000 (Btu/h)/gal and ≥10 gal 80% Et (Q/800 + 110√V)
SL, Btu/h
 
Oil storage water heaters ≤105,000 Btu/h ≥20 gal See footnote (g).  
>105,000 Btu/h <4000 (Btu/h)/gal 80% Et (Q/800 + 110√V)
SL, Btu/h
Sections G.1 and G.2 of ANSI Z21.10.3
Oil instantaneous water heaters ≤210,000 Btu/h ≥4000 (Btu/h)/gal and <2 gal See footnote (g).  
>210,000 Btu/h ≥4000 (Btu/h)/gal and <10 gal 80% Et Sections G.1 and G.2 of ANSI Z21.10.3
>210,000 Btu/h ≥4000 (Btu/h)/gal and ≥10 gal 78% Et (Q/800 + 110√V)
SL, Btu/h
 
Hot-water supply boilers, gas and oilf ≥300,000 Btu/h and <12,500,000 Btu/h ≥4000 (Btu/h)/gal and <10 gal 80% Et Sections G.1 and G.2 of ANSI Z21.10.3
Hot-water supply boilers, gasf   ≥4000 (Btu/h)/gal and ≥10 gal 80% Et (Q/800 + 110√V)
SL, Btu/h
Sections G.1 and G.2 of ANSI Z21.10.3
Hot-water supply boilers, oil   ≥4000 (Btu/h)/gal and ≥10 gal 78% Et (Q/800 + 110√V)
SL, Btu/h
Sections G.1 and G.2 of ANSI Z21.10.3
Pool heaters, oil and gas All   See footnote (g). ASHRAE 146
Heat pump pool heaters All 50°F db 44.2°F wb Outdoor air
80.0°F entering water
4.0 COP AHRI 1160
Unfired storage tanks All   R-12.5 (none)
  1. Thermal efficiency (Et) is a minimum requirement, while standby loss (SL) is maximum Btu/h based on a 70°F temperature difference between stored water and ambient requirements. In the SL equation, V is the rated volume in gallons and Q is the nameplate input rate in Btu/h. Vm is the measured volume in the tank in gallons.
  2. Section 12 contains a complete specification, including the year version, of the referenced test procedure.
  3. Section G.1 is titled "Test Method for Measuring Thermal Efficiency and Section G.2 is titled "Test Method for Measuring Standby Loss."
  4. Instantaneous water heaters with input rates below 200,000 Btu/h must comply with these requirements if the water heater is designed to heat water to temperatures of 180°F or higher.
  5. Electric water heaters with input rates below 12 kW must comply with these requirements if the water heater is designed to heat water to temperatures of 180°F or higher.
  6. Refer to Section 7.5.3 for additional requirements for gas storage and instantaneous water heaters and gas hot-water supply boilers.
  7. In the U.S., the efficiency requirements for water heaters or gas pool heaters in this category or subcategory are specified by the U.S. Department of Energy. Those requirements and applicable test procedures are found in the Code of Federal Regulations 10 CFR Part 430.
Those requirements and applicable test procedures are found in the Code of Federal Regulations 10 CFR Part 430.
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