ASHRAE-90.1-2022- - Page 083
Extracted Content
Table 6.4.3.10.1 DDC Applications and Qualifications
| Building Status | Application | Qualifications |
|---|---|---|
| New_building_ | Air-handling_system_ and all zones served by the_system_ | Individual_systems_ supplying more than three zones and with_fan system bhp of 10_hp and larger |
| New_building_ | Chilled-water plant and all coils and_terminal_ units served by the_system_ | Individual plants supplying more than three zones and with design cooling capacity of 300,000 Btu/h and larger |
| New_building_ | Hot-water plant and all coils and_terminal_ units served by the_system_ | Individual plants supplying more than three zones and with design heating capacity of 300,000 Btu/h and larger |
| Alteration or addition | Zone_terminal_ unit such as_VAV_ box | Where existing zones served by the same air-handling, chilled-water, or hot-water_system_ have_DDC_ |
| Alteration or addition | Air-handling_system_ or fan coil | Where existing air-handling_system_s and fan coils served by the same chilled- or hot-water plant have_DDC_ |
| Alteration or addition | New air-handling_system_ and all new zones served by the_system_ | Individual_systems_ with_fan system bhp_ of 10 hp and larger and supplying more than three zones and more than 75% of zones are new |
| Alteration or addition | New or upgraded chilled-water plant | Where all chillers are new and plant design cooling capacity is 300,000 Btu/h and larger |
| Alteration or addition | New or upgraded hot-water plant | Where all_boilers_ are new and plant design heating capacity is 300,000 Btu/h and larger |
6.4.3.9 Heated or Cooled Vestibules or Air Curtains with Integral Heating. Heating systems for vestibules and air curtain units with integral heating shall include automatic controls capable of and configured to shut off the heating system when outdoor air temperatures are above 45°F. Vestibule heating and cooling systems shall be controlled by a thermostat in the vestibule capable of and configured to limit heating to a maximum of 60°F and cooling to a minimum of 85°F.
Exception to 6.4.3.9: Heating or cooling provided by site-recovered energy or by transfer air that
would otherwise be exhausted.
6.4.3.10 Direct Digital Control (DDC) Requirements. Direct digital control shall be required as follows.
6.4.3.10.1 DDC Applications. DDC shall be provided in the applications and qualifications listed in Table 6.4.3.10.1.
Exception to 6.4.3.10.1: DDC is not required for systems using the simplified approach to compliance
in accordance with Section 6.3.
6.4.3.10.2 DDC Controls. Where DDC is required by Section 6.4.3.10.1, the DDC system shall be capable of and configured with all of the following, as required, to provide the control logic required in Section 6.5:
a. Monitoring zone and system demand for fan pressure, pump pressure, heating, and cooling b. Transferring zone and system demand information from zones to air distribution system controllers and
from air distribution systems to heating and cooling plant controllers c. Automatically detecting those zones and systems that may be excessively driving the reset logic and gen erate an alarm or other indication to the system operator d. Readily allowing operator removal of zones from the reset algorithm
Informative Note: ASHRAE Guideline 36 includes detailed sequences of control for monitoring zone and system demand, automatically detecting and alarming zones that are excessively driving reset logic, and readily excluding those zones from reset logic.
6.4.3.10.3 DDC Display. Where DDC is required by Section 6.4.3.10.1 for new buildings, the DDC system shall be capable of trending and graphically displaying input and output points.
6.4.3.11 Chilled-Water Plant Monitoring
6.4.3.11.1 Monitoring. For electric-motor-driven chilled-water plants in new buildings, or for new plants in existing buildings, measurement devices shall be installed and shall measure the electric energy use and efficiency of the chilled-water plant for
ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 81