DDC shall be provided in the applications and qualifications in accordance with Table E503.4.6.12.1.
For SI units: 1000 British thermal units = 0.293 kW, 1 horsepower = 0.746 kW
Exception: DDC is not required for systems using the simplified approach to compliance in accordance with Section E503.3. [ASHRAE 90.1:220.127.116.11.1]
|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 or more|
|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 300000 Btu/h or more|
|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 300000 Btu/h or more|
|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-coil (s) 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 or more and supplying more than three zones and more than 75 percent of zones are new|
|Alteration or addition||New or upgraded chilled-water plant||Where all chillers are new and plant design cooling capacity is 300000 Btu/h or more|
|Alteration or addition||New or upgraded hot-water plant||Where all boilers are new and plant design heating capacity is 300000 Btu/h or more|
Where DDC is required by Section E503.4.6.12.1, the DDC system shall be capable of and configured with all of the following, as required, to provide the control logic required in Section E503.5:
- Monitoring zone and system demand for fan pressure, pump pressure, heating, and cooling.
- Transferring zone and system demand information from zones to air distribution system controllers and from air distribution systems to heating and cooling plant controllers.
- Automatically detecting those zones and systems that are capable of excessively driving the reset logic and generate an alarm or other indication to the system operator.
- Readily allowing operator removal of zone(s) from the reset algorithm. [ASHRAE 90.1:18.104.22.168.2]