ASHRAE-90.1-2022- - Page 140
Extracted Content
generally accepted engineering standards and handbooks acceptable to the adopting authority (e.g., ASHRAE Handbook—HVAC Applications ).
7.4.2 Equipment Efficiency. 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 7.4-1. 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 7.4-1 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 7.4-1 when
- the tank surface is thermally insulated to R-12.5,
- a standing pilot light is not installed, and
- gas- or oil-fired storage water heaters have a flue damper or fan-assisted combustion.
7.4.3 Service Water Heating System Piping Insulation. Service water heating system piping shall be surrounded by uncompressed insulation of the thickness shown in Table 7.4-2. When the insulation thermal conductivity is not within the range in the table, the following equation shall be used to calculate the minimum insulation thickness:
talt = r [(1 + ttable / r ) × kalt / kupper - 1]
where talt = minimum insulation thickness of the alternate material, in. r = actual outside radius of pipe, in. ttable = insulation thickness listed in Table 7.4-2 for applicable fluid temperature and pipe size kalt = thermal conductivity of the alternate material at mean rating temperature indicated for the applicable fluid temperature, Btu·in/h·ft [2] ·°F kupper = upper value of the thermal conductivity range listed in this table for the applicable fluid temperature, Btu·in/h·ft [2] ·°F Exception to 7.4.3: For nonmetallic piping thicker than Schedule 80 and having thermal resistance
greater than that of steel pipe, reduced insulation thicknesses are permitted if documentation is provided showing that the pipe with the proposed insulation has no more heat transfer per foot than a steel pipe of the same size with the insulation thickness shown in the table.
7.4.3.1 The following piping shall be insulated per the requirements of this section:
a. Recirculating system piping, including the supply and return piping b. The first 8 ft of outlet piping from
- storage water heaters,
- hot-water storage tanks, and
- any water heater and hot-water supply boiler containing 10 gal or more of water heated by a direct heat source, an indirect heat source, or both a direct heat source and an indirect heat source. c. The first 8 ft of branch piping connecting to recirculated, heat traced, or impedance heated piping. d. The make-up water inlet piping between heat traps (see Section 7.4.6) and the storage water heaters and
the storage tank they are serving, in a nonrecirculating service water heating system . e. Hot-water piping between multiple water heaters, between multiple hot-water storage tanks, and
between water heaters and hot-water storage tanks. f. Piping that is externally heated (such as heat trace or impedance heating).
Exceptions to 7.4.3.1:
- Factory-installed piping within water heaters and hot-water storage tanks tested and rated in accordance with Section 6.4.1.
- Piping that conveys hot water that has not been heated through the use of fossil fuels or electricity.
- For piping 1 in. or less, insulation is not required for valves or strainers.
- Piping in existing buildings where alterations are made to existing service water heating systems where there is insufficient space or access to meet the requirements.
- Insulation is not required at the point where piping passes through a framing member if it requires increasing the size of the framing member.
- Insulation is not required on piping at the point where a vertical support of the piping is installed.
138 ANSI/ASHRAE/IES Standard 90.1-2022 (I-P)