3.7.2.1 Schedules | COMNET

Cooling Schedule
Applicability	All cooling systems
Definition	A schedule that represents the availability of cooling
Units	Data structure: schedule, on/off
Input Restrictions	Schedules should be typical of the proposed building type or as assumed for the building design. The schedules in Appendix C can be used as a default for cooling availability. The cooling availability schedule shall be consistent with the supply fan schedule and thermostat schedules to reduce the likelihood of unmet load hours.
Baseline Rules	Same as the proposed design

Heating Schedule
Applicability	All systems
Definition	A schedule that represents the availability of heating
Units	Data structure: schedule, on/off
Input Restrictions	Schedules should be typical of the proposed building type or as assumed for the building design. The schedules in Appendix C can be used as a default. The heating availability schedule shall be consistent with the supply fan schedule.
Baseline Rules	Same as the proposed design

Air-Handler Schedule
Applicability	All systems that do not cycle with loads
Definition	A schedule that indicates when the air handler operates continuously
Units	Data structure: schedule, on/off
Input Restrictions	Schedules should be typical of the proposed building type or as assumed for the building design. The schedules in Appendix C can be used as a default. When a fan system serves several occupancies, the fan schedule must remain ON to serve the operating hours of each occupancy.
Baseline Rules	Same as the proposed design

Air Handler Fan Cycling
Applicability	All fan systems
Definition	This building descriptor indicates whether the system supply fan operates continuously or cycles with building loads. The fan systems in most commercial buildings operate continuously.
Units	List: continuous or cycles with loads
Input Restrictions	Schedules for HVAC fans that provide outdoor air for ventilation shall run continuously whenever spaces are occupied and shall be cycled on and off to meet heating and cooling loads during unoccupied hours. Exceptions: Where no heating and/or cooling system is to be installed and a heating or cooling system is being simulated only to meet the requirements described in the 90.1 PRM, heating and/or cooling system fans shall not be simulated as running continuously during occupied hours but shall be cycled on and off to meet heating and cooling loads during all hours. HVAC fans shall remain on during occupied and unoccupied hours in spaces that have health and safety mandated minimum ventilation requirements during unoccupied hours. For hotel guest rooms and high-rise residential, continuous operation is the default, however, the option to let the fan cycle with loads may be used when the following conditions are met and documented: The spaces served by the system are located within 25 ft of an operable window. The openable window area is at least 4% of the floor space. Other requirements for natural ventilation specified in ASHRAE Standard 62.1-2016 are satisfied.
Baseline Rules	Same as proposed design, except if the proposed building has natural ventilation, in which case the baseline building fans will operate continuously when the space is occupied and cycle to meet the loads duing unoccupied periods. HVAC fans shall remain on during occupied and unoccupied hours in spaces that have health and safety mandated minimum ventilation requirements during unoccupied hours.

Optimal Start Control
Applicability	Systems with the control capability for flexible scheduling of system start time based on building loads.
Definition	Optimal start control adjusts the start time of the HVAC unit such that the space is brought to setpoint just prior to occupancy. This control strategy modifies the heating, cooling, and fan schedules.
Units	Boolean (Yes/No)
Input Restrictions	As designed
Baseline Rules	The baseline building shall have optimum start controls when the baseline building design supply airflow is greater than 10,000 cfm.

Night-Cycle HVAC Fan Control
Applicability	All systems
Definition	The control of an HVAC system that is triggered by the heating or cooling temperature setpoint for thermal blocks during periods when the heating, cooling and fan systems are scheduled to be off. Night cycle control is required for both baseline and proposed building in accordance to 90.1 2010 Section 6.4.3.3.2. For this control, the space is controlled to the setback or setup temperature only; this control is not equivalent to a night purge control. The choices are: Cycle on call from any zone Cycle on call from the primary control zone Stay off Cycle zone fans only (for systems with fan-powered boxes) for cooling. Cycle AHU fans for cooling Restart fans below given ambient temperature.
Units	None
Input Restrictions	Schedules for HVAC fans that provide outdoor air for ventilation shall run continuously whenever spaces are occupied and shall be cycled on and off to meet heating and cooling loads during unoccupied hours Exceptions: Where no heating and/or cooling system is to be installed and a heating or cooling system is being simulated only to meet the requirements described 90.1 2010 PRM, heating and/or cooling system fans shall not be simulated as running continuously during occupied hours but shall be cycled on and off to meet heating and cooling loads during all hours. HVAC fans shall remain on during occupied and unoccupied hours in spaces that have health and safety mandated minimum ventilation requirements during unoccupied hours.
Baseline Rules	Same as proposed design except if the proposed building has natural ventilation in which case the baseline building fans will operate continuously when the space is occupied and cycle to meet loads during unoccupied periods. HVAC fans shall remain on during occupied and unoccupied hours in spaces that have health and safety mandated minimum ventilation requirements during unoccupied hours.

90.1-2019

Cooling Schedule
Applicability	All cooling systems
Definition	A schedule that represents the availability of cooling
Units	Data structure: schedule, on/off
Input Restrictions	Schedules should be typical of the proposed building type or as assumed for the building design. The cooling availability schedule shall be consistent with the supply fan schedule and thermostat schedules to reduce the likelihood of UMLH. This schedule is not needed for all simulation tools. Other methods (outdoor conditions, zone conditions) may be used to control cooling availability in most systems. If cooling is truly not available during certain times (school vacations, weekends) the zone thermostat cooling setpoints need to be modified to reflect this and the HVAC availability schedule (see below), which defines fan operation based on occupancy, needs to be set to zero.
Baseline Building	Same as the proposed design. However, setpoints and schedules can differ between proposed and baseline design: For HVAC systems that automatically provide occupant thermal comfort via means other than directly controlling the air dry-bulb and wet-bulb temperature, provided that equivalent levels of occupant thermal comfort are demonstrated via the methodology in ASHRAE Standard 55, Section 5.3.3, “Elevated Air Speed,” or Standard 55, Appendix B, “Computer Program for Calculation of PMV-PPD.” When necessary to model nonstandard efficiency measures, provided that the revised schedules have been approved by the rating authority.

Heating Schedule
Applicability	All systems
Definition	A schedule that represents the availability of heating
Units	Data structure: schedule, on/off
Input Restrictions	Schedules should be typical of the proposed building type or assumed for the building design. COMNET Appendix C (COMNET 2017) can be used as a default. The heating availability schedule shall be consistent with the supply fan schedule.
Baseline Building	Same as the proposed design However, setpoints and schedules can differ between proposed and baseline design: For HVAC systems that automatically provide occupant thermal comfort via means other than directly controlling the air dry-bulb and wet-bulb temperature, provided that equivalent levels of occupant thermal comfort are demonstrated via the methodology in ASHRAE Standard 55, Section 5.3.3, “Elevated Air Speed,” or Standard 55, Appendix B, “Computer Program for Calculation of PMV-PPD.” When necessary to model nonstandard efficiency measures, provided that the revised schedules have been approved by the rating authority.

HVAC Availability Schedule
Applicability	All systems
Definition	A schedule that indicates when the air handler operates continuously
Units	Data structure: schedule, on/off
Input Restrictions	Schedules should be typical of the proposed building type or assumed for the building design. The fan schedule can be defaulted to the applicable schedule from COMNET Appendix C (COMNET 2017). Other schedules may be used when detailed information is known about the proposed design.
Baseline Building	Same as the proposed design unless one baseline HVAC system serves a combination of systems in the proposed design with varying HVAC availability schedules. For those systems the HVAC availability schedule is determined by the most inclusive schedule represented in the proposed building design. If the most inclusive schedule does not cover the full range of availability, a hybrid schedule that does shall be created.

Air Handler Fan Cycling
Applicability	All fan systems
Definition	This building descriptor indicates whether the system supply fan operates continuously or cycles with building loads. The fan systems in most commercial buildings operate continuously during occupied hours.
Units	List: Continuous or Cycles with Loads
Input Restrictions	Schedules for HVAC fans shall run continuously whenever HVAC zones are occupied and shall be cycled on and off to meet heating and cooling loads during unoccupied hours. Hours with occupancy >5% are considered to be occupied hours and require continuously operated fans. Exceptions: HVAC fans that do not provide outdoor air for ventilation shall cycle on and off to meet heating and/or cooling loads. This requires that outdoor air is introduced through some other approved means such as natural ventilation or another fan system. Where no heating and/or cooling system is to be installed and a heating or cooling system is being simulated only to meet the requirements described in Standard 90.1-2019 PRM, heating and/or cooling system fans shall not be simulated as running continuously during occupied hours but shall be cycled on and off to meet heating and cooling loads during all hours. HVAC fans shall remain on during occupied and unoccupied hours in HVAC zones that have health and safety mandated minimum ventilation requirements during unoccupied hours. HVAC fans shall remain on during occupied and unoccupied hours in systems primarily serving computer rooms For hotel guest rooms and high-rise residential, continuous operation is the default, however, the option to let the fan cycle with loads may be used when the following conditions are met and documented: – The spaces served by the system are located within 25 ft of an operable window. – The openable window area is at least 4% of the floor space. – Other requirements for natural ventilation specified in ASHRAE Standard 62.1-2016 are satisfied.
Baseline Building	HVAC fans shall run continuously whenever HVAC zones are occupied and shall be cycled on and off to meet heating and cooling loads during unoccupied hours. Except: HVAC fans shall remain on during occupied and unoccupied hours in systems primarily serving computer rooms HVAC fans shall remain on during occupied and unoccupied hours in HVAC Zones that have health and safety mandated minimum ventilation requirements during unoccupied hours. Fan schedules may be allowed to differ when Standard 90.1-2019 Section G₃.1.1(c) applies.

Optimal Start Control
Applicability	Systems with the control capability for flexible scheduling of system start time based on building loads
Definition	Optimal start control adjusts the start time of the HVAC unit such that the space is brought to setpoint just prior to occupancy. This control strategy modifies the heating, cooling, and fan schedules.
Units	Boolean (Yes/No)
Input Restrictions	As designed Heating and cooling systems with design air capacities greater than 10,000 cfm served by one or more supply fans are required to have optimum start controls.
Baseline Building	Heating and cooling systems with design air capacity greater than 10,000 cfm served by one or more supply fans are required to have optimum start controls.

Optimal Start Control: Control Zone
Applicability	Systems with optimal start controls that serve multiple zones
Definition	The zone that governs the start time for applying optimal start controls
Units	Boolean (Yes/No)
Input Restrictions	List: “Any Zone,” all zones served by the system
Baseline Building	Same as proposed If optimal start controls are not required by the proposed design, but required in the baseline building, then this input will be set to “Any Zone”