ASHRAE-90.1-2022- - Page 143
Extracted Content
Table 7.4-2 Minimum Piping Insulation Thickness for Service Water Heating Systems [ a,b]
| Service Hot-Water Temperature Range | Insulation Thermal Conductivity | Col3 | Nominal Pipe or Tube Size, in. | Col5 | Col6 | Col7 | Col8 |
|---|---|---|---|---|---|---|---|
| Service Hot-Water Temperature Range | Conductivity, Btu·in/h·ft2·°F | Mean Rating Temperature, °F | <1 | 1 to <1-1/2 | 1-1/2 to <4 | 4 to <8 | ≥8 |
| Service Hot-Water Temperature Range | Conductivity, Btu·in/h·ft2·°F | Mean Rating Temperature, °F | Insulation Thickness, in. | Insulation Thickness, in. | Insulation Thickness, in. | Insulation Thickness, in. | Insulation Thickness, in. |
Service Water Heating System Piping not Located in Partitions within Conditioned Spaces
| 105°F to 140°F | 0.22 to 0.28 | 100 | 1.0 | 1.0 | 1.5 | 2.0 | 2.0 |
|---|---|---|---|---|---|---|---|
| >140°F to 200°F | 0.25 to 0.29 | 125 | 1.5 | 1.5 | 2.5 | 2.5 | 2.5 |
| >200°F | 0.27 to 0.30 | 150 | 2.5 | 2.5 | 3.0 | 3.0 | 3.0 |
Service Water Heating System Piping Located in Partitions within Conditioned Spaces
| 105°F to 140°F | 0.22 to 0.28 | 100 | 1.0 | 1.0 | 1.5 | 1.5 | 1.5 |
|---|---|---|---|---|---|---|---|
| >140°F to 200°F | 0.25 to 0.29 | 125 | 1.0 | 1.0 | 2.0 | 2.0 | 2.0 |
| >200°F | 0.27 to 0.30 | 150 | 1.5 | 1.5 | 2.5 | 3.0 | 3.0 |
a. These thicknesses are based on energy efficiency considerations only. Additional insulation may be necessary for safety. b. For direct-buried service water heating system piping, reduction of these thicknesses by 1.5 in. shall be permitted (before thickness adjustment required in Section 7.4.3 but not
to thicknesses less than 1 in.).
7.4.4 Service Water-Heating System Controls Informative Note: Service water heating system control settings and operating temperatures should be determined in accordance with the ASHRAE Standard 188 building water systems water management program for the building, or with generally accepted engineering standards and guidance (e.g., ASHRAE Guideline 12).
7.4.4.1 Temperature Controls. 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 ther-
mostat setting to minimize condensation and resulting corrosion.
7.4.4.2 Temperature Maintenance Controls. Systems designed to maintain usage temperatures in hotwater 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.
7.4.4.3 Outlet Temperature Controls. Temperature controlling means shall be provided to limit the maximum temperature of water delivered from lavatory faucets in public facility restrooms to 110°F.
7.4.4.4 Circulating Pump Controls. 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.
7.4.5 Pools 7.4.5.1 Pool Heaters. 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.
7.4.5.2 Pool Covers. 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
on-site renewable energy .
7.4.5.3 Time Switches. Time switches shall be installed on swimming pool heaters and pumps . Exceptions to 7.4.5.3:
- Where public health standards require 24-hour pump operation.
- Where pumps are required to operate solar and waste heat recovery pool heating systems.
7.4.6 Heat Traps. 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
ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 141